Ron Swelter's Tropical Cool Blog

Keeping cool without sweat

2007-12-31T23:56:00.000-08:00

Note for new readers: this blog presents a rather technical approach to the subject of living comfortably in the tropics. It aims to teach you about tropical comfort and discomfort. Don't read this blog unless you got a "B" or better in high school physics or are an architect/builder who needs to understand heat transfer! If you're more interested in tropical lifestyle matters, the ups and downs of living in paradise, you can check out the blog by my brother Jack at:

http://www.nationmultimedia.com/webblog/home.php?uid=361

One of our readers, reflecting on the pleasures of keeping cool using one of those "mist fan" machines while struggling to enjoy a good cigar, raises the following question:

There has to be some balance point here, where body cooling by external evaporation is such that the body does not need to sweat heavily and so is happy in a high humidity atmosphere. These machines do work, the only problem I have with them is keeping my cigar alight...........

Yao Bar at sundown, your author making the sketch that you see here

Appropriate meditiation on this matter requires a proper setting, and I write here from one of my favorite streetside venues, the Yao Bar off Ekamai, where the sun is setting in a tawny sky at the end of a day warm enough to raise a slight sweat as I was walking here. Now the waitress is serving a large (22 oz) bottle of cold Chang beer, 70 baht, over a large glass of ice cubes (3 degrees C, but my radiant thermometer is probably mistaken here because it's mosquito brain does not really know the exact emssivivity of ice, or as you can see, of the sky which of course is not 6 degrees but closer to 30 degrees, only emitting like a 6 degree object). Here, carressed by a gentle breeze, watching life, much of it casually and lightly clothed as tends to be on these sois, I am comfortable enough, not sweating at all, though I am continuing to produce, as we all do while engaged in these indolent activities -- and subsisting on a healthy Thai diet of fish and rice, not fatty British pub food simultaneously engaged in heated discusion of such matters as cricket and motor racing-- heat. And my heat production is likely to be around 50 watts.

Now sitting here I perceive that I am comfortable but on the verge of sweating. (At this point I can only appeal to the reader's intuition when I say comfortable, since I can neither define that term or conversely define its opposite, uncomfortable, though in the future we will necessarily have to face this definitional task, not as simple as it might first appear).

Let us now proceed to make some estimates of the transfer of heat that is occurring at my bodily envelope (having disposed of the problem of dealing with transfer of moisture, since I'm not sweating, though almost sweating).

Since I am warmer than the air around me by about 3 degrees, and the transfer of heat being a linear function of temperature difference with a constant of proportionality of about 10 (for a pleasant breeze) my transfer via convection to the air will be in watts

W=10*(34-31)=30 watts

I am also radiating heat directly to both the "cold" sky at 6 degrees and my other surroundings, and without going through l the tiresome arithmetic, Stefan Boltzmann constants and so forth (unless I later add an appendix to this chapter), my estimate for radiant loss is a minor 10-15 watts.

The 22 ounce bottle of Chang beer which by ingesting I am raising from 18 to 37 degrees over a time period of 20 minutes provides further cooling of about 5 watts, not counting the vasodilative impact of alcohol on improving the blood supply to my nose. I neglect my cigar, and I am now too weary with these exertions to account for respiratory loss, either sensible or latent, though I think it might be as much as a few watts.

Observation of surroundings: the waitress is hacking at a mango in the course of making herself som tam dinner; though lightly dressed her skinny brown legs to which my eyes are drawn are doubtless more effective in transferring heat to the air than my ham-like euro limbs. The bartender, who has a large belly, is engaged in mild activities, and has elected for his comfort to be shirtless. Altogether, we represent a sample of three varied non-sweating bodies, with heat production approximately equal to the rate of heat being lost to our environment. Therefore we meet a working definition of comfort with sweating:

Energy produced sweatlessly=energy lost without need for sweat.

On this basis, I propose that for a typical fahlang, sweating will not be necessary for sedentary activity with surrounding temperature (e.g. air temperature but also consider surrounding radiant temperatures) of about 30 degrees or a little less. Under these or cooler conditions, we do not call on any heat dissipative mechanism that is sensitive to humidity, so we may say in a gross sense that humidity is not a factor in our comfort. If however our level of effort should increase to say 100 watts, we will not be able to throw off enough heat to the surroundings and after a few minutes our body and skin temperature will begin to rise and our sweat system will activate, with the rate of cooling being very sensitive to humidity (more on this later). And we will begin to say that we are too warm (suggesting that sweat = thermal discomfort.)

So my answer is this: humidity doesn't matter too much (except in relation to such issues as keeping cigars lit and beers cool) as long as we are not sweating, ie at a temprature of roughly 30 degrees in sedentary mode.

Thin Roofs...and foil

2007-12-29T22:31:00.000-08:00

Even now at the winter solstice, with the noon solar radiation reduced some 20 percent, any thin darkish thin surface (such as a metal roof or a tile roof) heats up to 50 degrees C or more, with the heat being almost immediately transferred undiminished to the underside, as you can see from the temp reading of the underside of this rubberized canvas tent which is supposed to provide cooling shade but really provides heating shade which will radiate on the order of (52-32)*5=100 watts per square meter to my balding head, plus perhaps as much again convected to the air below. Not as bad as the 700 watt sun, you might say, but not comfortable either – and suffocating if the underside of the roof is not radically ventilated. So next time you are sitting under one of these tents at a Thai wedding or funeral, be warned -- it's the heat, not your emotions, that is causing you to feel like you are going to faint.

Here is an excerpt from the manual of the Australian company Bluescope Steel who make (and promote) steel roofing in Thailand. This indicates a good reduction in heat transmission through thin roofs (steel, cement tile, etc) with foil insulation, properly installed (air space above and below foil, and foil with shiny side down.) For a dark roof, the thermal transmission is said to drop from 165 to 22 watts, almost 90 percent.

Foil sales folks must be delighted with this conclusion. But be aware that it contains at least one hidden but important assumption -- very low convective transfer from the roof to the room below because the air beneath the foil is taken to be perfectly still. But this is not true in any case for many reasons. Convective cells develop even in sealed spaces, desirable fans move air, and required ventilation to replace that air which will otherwise heat at about 2 degrees per minute (ventilation rate of approx one room air change per minute--that's right, not one or two air changes per hour, as in most attic spaces even with vents) so there is in fact much more downward convective transfer from the roof than this chart suggests.

My estimates do not yield quite such promising results – my 1935 Eshbach Engineers Manual (college edition) indicates an R value bonus of only about 2 or so for a single layer of foil. And a direct measure of the efficacy of shiny vs. black spray paint surface on the foil which can be seen in the simple room simulation which I performed last month yields a reduction of about 50 percent in heat transmission. This implies that the heat flux from downward radiation and convection are about the same. Th foil brigade will try to tell you that here is not convective transfer downward at all, and this just ain't true.

Want to know the exact ruth? The fact is that the physics of downward heat flow in roofs is extremely complex, the stuff of learned papers by mathematically oriented professors.

But I don't question that properly installed foil will improve matters-- from very bad to not as bad--in the case of a thin tile, cement, or metal roof. Studies such as those done in Florida suggest aircon energy savings of perhaps 15 percent with the addition of foil. My caveat is that in most practical situations one cannot rely on foil alone to prevent uncomfortable heat buildup from a foil-insulated roof.

Some reasonably unbiased web sites describing use of foil insulation are:

Florida studies indicating reduction of energy 25 percent and temp 6 deg:

http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1231-01/index.htm

Wikipedia:

http://en.wikipedia.org/wiki/Building_insulation

Q&A on foil insulation by experienced researchers:

http://www.fsec.ucf.edu/en/publications/html/FSEC-EN-15/index.htm

Night before Christmas

2007-12-24T22:34:00.000-08:00

Some think of Santa. I dream of Planck's Constant.

I put a steel bar outside on the roof at night, facing upward into the relatively clear sky (stars visible), compare its temp with the temp of a shielded sensor; you see, on December 23-24, 2007, a temp suppression of the bar of only about one degree. This is with a sky radiant temp (Radioshack sensor) of about 5 degrees and relatively high dew point of about 21 degrees. Notice the wave of humidity at about 2 to 4 am, dew point reaches close to air temp, so RH is close to 100 percent and the temp suppression becomes much less (in part because water begins to condense on the steel surface, creating heat.). Therefore we cannot get much radiant cooling under these circumstances of high air saturation.

It happens that I did not in my bed dreaming of sugar plums notice any suffocating wave of humidity at 2-4 am, perhaps it did not arise in the indoor environment. Why? Or was it the low temp, not over 23 degrees, that kept my body well below the point of perspiration? All worth investigating as the hot season approaches and the night temps hover up at around 30 rather than this month's more comfortable mid twenties.

Shortest day

2007-12-23T22:30:00.000-08:00

For millenia we northern folk have been mighty nervous about these shortening days of winter and have invented all kinds of potions and ceremonies to ward off the fear that the days were going to get shorter…and shorter.. and God know what then. So we have mulled wine and moldy grain (which is what Tacitus described as the favored beverage of the barbarians of the north) and those big stone henges in Ireland and even Peru where the priests coax the sun back from wherever it has wandered off to, and nowadays Prozac for Seasonal Affective Disorder and doubled up holiday AA meetings for those who overdid it in Christmases past. Here in Thailand it was April, not Decmber, that was the big deal in the old days, but this hasn’t prevented the Thai from going mad with joy over Christmas and New Years as you can see from this little video clip I took last night in the Emporium. Notice at the end that it is against the law to photograph Santa Claus here in the land of smiles, leaving poor Santa looking like some kind of frightened and much overdressed hostage imprisoned here far from his native latitudes.

With the sun vacationing somewhere down in Australia some 36 to the south, solar radiation, as you can see from the readings of a solar radiometer at Bnagkok's Mahidol University is now peaking at about 750 watts per square meter.

http://nanotech.sc.mahidol.ac.th/weather/Weather_Soil_Experiment.htm

As always you correspondent finds the season an emotional challenge, taking comfort that though the days are a little shorter they aren’t a lot shorter. This morning, in fact, the sun rose over Bangkok at 6:30 am, and tonight setting at 6:00, as I make my way to the pub for what I hope will be a modest pint or two, leaving the sky over Sukhumvit washed with a smoky plum, when I take this photo thirteen minutes later.

But where are those refreshing cold snaps that are supposed to be blowing down from the north? This year you hear Thai complaining of the heat and muttering about global warming, with the wind even now backing around to the south and the temps creeping up into the low thirties, a preview of the coming hot season.

Red wine in them hills

2007-12-18T23:16:00.000-08:00

Jack and Dah had me over for dinner, quite a nice pasta with little sea clams, plus a red wine that Jack said was a local Thai wine, 600 baht a bottle.

It was certainly drinkable. We did a second bottle. I thought about this. "Don't wine grapes have to grow in a cool place?"

"That's it, this stuff is only 100 clicks from Bangkok, it's a kind of hill station. Look at the bottle."

"Fourteen degrees latitude, that's not far."

Jack said "About three hundred meters above sea level. Cool nights, not far from our village. We're at two hundred." Jack and Dah were building another house in this little Isan village they had discovered, four hours from Bangkok.

Now after the second bottle Jack was mad to grow wine grapes. He wanted to know all about the climate there, he wanted me to compare Bangkok, and the PB wine growing place near Khao Yai, and his new village at the foot of the same hills a little to the west of Khao Yai. The next week, mid December, we took the bus to a little place south of Korat called Pak Tong Chai, near where Jack and Dah were building their house. An uncle picked us up and drove us around, we stayed a couple of days. The mornings were delightful, dew on the grass and nice little jungly tropical mists over the patches of rice paddy.

I took temp measurements with my roving Hobo, compared them with Bangkok. Here they are.

Cool nights indeed, you can see the difference at night, I shaded it blue. Sundown the temp dropped a lot up there, much more than Bangkok. You could se stars at night.

Sunday roast

2007-12-02T18:16:00.000-08:00

This Sunday afternoon I was alone and I took to the streets walking, no more than a slight film of sweat on the brow on this fine California-like afternoon, then sitting in the park for a while then consumed a giant roast pork dinner and the Financial Times in the Robin Hood.

The steady graphed points are a recording of the temp and dew point on my deck at home, beneath a large mango tree. The irregular traces are a recorder that I carried with me, you can see every time I go into an air conditioned space where the temp and dew point both drop a few degrees. Consultation with Carrier's chart indicates that each cubic meter of conditioned air has been subjected to about 10 KJ of enthalpy reduction--at considerable energy cost.

Sunday afternoons bring a few families out and into the pubs, you can see this sixty-something guy with his thirty-something Thai wife and "half child", the dream of many a Thai girl. Some of the foreign-Thai relationships are disastrous for the man, but this one looks pretty pleasant for all, arguably more interesting than playing golf and visiting prospective nursing homes back in the old country (or obsessively recording temps in the new), and certainly a step up in comfort and respectability for the girl from an poor Isan village.

Interesting stuff blows in from Isan

2007-12-01T01:26:00.000-08:00

Sometimes for relaxation in the cooler evenings now I like to go down to Soi Cowboy and watch the world go by, just sitting at a little bar by the side of the road, watching tourists and bar girls, I try to figure the girls that are fresh from upcountry from the ones who say they are fresh from upcountry. They blow into Bangkok, the prettiest girls from the villages, dozens a day, on buses to Mo Chit and trains to Hua Long Pong, and a lot of them drift over to this street and the other two or three venues that cater to the tourists looking to see Bangkok's notorious sex scene. There they wait by the side of the road, in front of their clubs, like trout waiting under the banks of a stream for passing grubs.

This time of year the wind is from the north to northeast too, and along with the girls comes the cool air of the north, equally delightful, the air warming like the girls themselves as it blows out of Udorn and Korat and Surin, down from the hills, across the plain, and into the wicked concrete alleys of the town. The journey takes about a day, and you can see from the twin pictures here of parallel temp and dew point of November air in Bangkok and Korat, 165 to the north. The air moisture stays pretty much the same, but you can see the arrival of the air in the big city heats it up by about 4 degrees C. Even so, most Bangkokians will be complaining of the cold, and if they venure to the northeast, they will make special purchases in fahlang thrift shops or expensive department store, depending on their situation in life, of "winter" clothes.

Oh, I should note that not all of them are girls.

Change your perception of, and attitude toward, discomfort

2007-11-16T21:42:00.000-08:00

The prospect of staying longer in the house of Jack and Dah, on the occasion of their travels in the country, seemed agreeable to a degree that was even enhanced as the dew point declined during this week, and I found myself spending less time in the pub and looking forward, as a man might in the morning shower look forward to an anticipated departure or an encounter with a certain lady that promised to end in a pleasant conclusion, to my evening cigar and a cold bottle of Singh, and a profitable review of the basic equations of gaseous heat transimission. And yet, as the week went on, I found myself to an increasing degree drawn to reading Swann's Way, from which I began to learn slowly a new manner of perceiving everyday events, as in reading the passage in which Proust's father, remarks to his son's visiting friend, who is visibly wet on the occasion of his visit to the house at Combray: "Why, Mr. Bloch, is there a change in the weather? Has it been raining?" Which drew from Bloch nothing more instructive than: "Sir, I am absolutely incapable of telling you whether it has rained. I live so resolutely apart from physical contingencies that my senses no longer trouble to inform me of them." This bringing to mind the teachings of the eminent Thai monk Buddhasa Bhikkhu who told of his many solitary months living in the forest near the current monastery of Suan Mokh, in the province of Surat Thani, and his conquest of mosquito bites in the evening by strict adherence to the precepts of the Dhamma. "Not using mosquito nets...was very beneficial. It helped us xpand our thinking, to feel unburdened, to wake up better, and to consider sleep as a temporary rest rather than a pursuit of or indulgence in comfort. It also helped us practice wakefulness to the best."

Cool night sky

2007-11-12T19:21:00.000-08:00

I got a giant case of ptomaine from eating a giant hot dog at the Robin Hood and while bedridden began to read a copy of Proust that I found at Jack's place, he and Dah were upcountry. A few days in the world of Combray put me in a contrarian frame of mind and I began to imagine that much of what I believed about roof insulation could be wrong, that rusty tin roofs might be the best of all. Thai country folk lived under them. They just stayed under the house, not in the house, in the daytime when the uninsulated roof created oven-like heat in the room. But at night maybe the outward radiation would cool the simple metal roof below air temperature.

An email from technology innovator Steve Baer reminded me of work by the solar master Harold Hay who invented and promoted a roof pond concept in California that relied on night radiative cooling to store "coolness" for the day use.

I built a "upcountry" room with a metal roof and zero ventilation and let it sit on my roof for a couple of days. Of course not a real room, but one of about a cubic foot size with a sheet of mat black aluminum foil for a roof and the room itself a foam picnic box that I bought for a buck at the Chinese shop down the street. Into which I put a brick for thermal mass and a hobo to measure temp and dew point.

You can see the temp history of the country room in red and the temps of Jack's bedroom and the outside temp (last two almost the same) over several days. The country room is impossible in the daytime but gets really cool at night. At least toward the end of the test period when the dew point got fairly low and the night sky temp fell to as low as -5 degrees C. So you might be very happy with a simple tin roof at night -- though not at day. And, this being a dryish night, note that the suppresssed temp is still way above the dew point, so there will be no problematical condensation. The question being, how about during the hot season, when the dew points are a lot higher, maybe 18 C instead of 10 C? Would you get any radiative night cooling then? If so, would water start to drip from the ceiling?

By the way, I say test boxes--there were two of them. One had foil with shiny side down (the blue line) the other had the bottom surface of the foil spray painted mat black (red line). The shiny foil reduces the peak heat of the day but also slightly reduces the cooling effect of night radiation.

In the cool of the pub

2007-11-03T21:59:00.001-07:00

Sometimes the only place that seemd tolerable was a pub, so I spent time working in those fine places sipping Heinekens and sketching out my ideas on paper napkins. Sometimes I'd lose interest in thermodynamics -- I did poorly in it at college --and then I'd draw little pictures of the action around me, older guys like myself thinking and drinking or watching TV with their bored girlfriends picking at the fahlang food or patiently waiting, like rice farmers waiting for the rains.

I noticed that many of these girls had remarkably large hands.

A one-watt air conditioner

2007-11-03T21:40:00.000-07:00

Air conditioning for your pet mouse

Jack and Dah have a goal: no house air conditioning.

Air conditioning is notoriusly inefficient in Thailand, with typical split room-size air conditioners churning out 12000 BTU per hour (3000 watts) of cooling per room, mainly energy spent on cooling sun-heated walls and vaporizing moisture that freely enters the room from outside sources, all at a cost equal to 35 percent of a Thai college graduate's salary. Tankers of oil steam into the Gulf to meet this wasteful demand.

And of course with the light, leaky construction of a traditional Thai house an off-the-shelf machine would be even more inefficient.

So...while hanging around the pub one day I set out to reinvent the air conditioner.

Let's start not with a 3000 watt machine, or even a (say) 300 watt machine that would be arguably sufficient to cool Jack and Dah when they are sleeping. Let's start with the bench machine above, which I built for a couple of hundred baht, a one-watt air conditioner, which meets the following specifications:

cooling capacity (mostly latent): 1 watt
condensate, cc/hr: 1
unconditioned air water vapor entering machine: 20 g/cubic meter
conditioned air water vapor exiting machine: 8 g/cubic meter

Operation of this machine requires about 3600 joules of energy per hour, which can be easily provided by only about 10 grams of ice.

The question: can we effectively scale up, say by a factor of about 300? This would require about 3 kg of ice per hour--seems doable.

Aircon fantasies

2007-11-02T21:52:00.000-07:00

In times of general retreat I spent hours fiddling with air-conditioning ideas. Solar powered desiccants. Micro air conditioners like they used to cool yachts and space men and NASCAR racing drivers. I went to the annual southeast Asian air conditioning trade show at the Sirikit convention center. Eager Chinese salesmen filled my arms with lavish brochures. The brochures showed their company president, tan, fit, and shrewd, perfecting his golf swing. China was clearly the future of air-conditioning manufacture.

But what I wantedI couldn't find. That was, a device that would condition air for a couple of people, not cool a big leaky overheated Thai room that delivered 2000 watts of heat from walls heated by the afternoon sun and steamy outside filthy air through window framwes that didn’t fit right. I knew he was on the right track when I went to visit the Carrier office in Bangkok. They somewhat reluctantly sent an engineer out to talk to this fahlang with the short pants milling around the front desk. Could they offer small units, maybe 5000 btus or less, asked I?

"What you want for?" the engineer asked, his eyes narrowing suspiciously.

“For small room, maybe twenty, twenty five square meters.”

The engineer whipped out a calculator and pecked in some numbers. Multiplying something by twenty five. No wonder people are annoyed by engineers, I thought to himself.

"Twelve thousand. "

"Twelve thousand what, for what."

" BTU for room."

I said that I was amazed, amazing thailand, I said, that he could do this so quickly. He must have a very good college degree. I thanked him for his time in a rather exaggerated way that he hoped conveyed the general idea. This was a Thai trick he had learned.

*********************************

I thought some more on this subject that I was clearly thinking about too much.. This is what I am looking for, I thought:

The system would cool a large fahlang body, and maybe Dah too if Jack could ever get it together with her. It would cull a small space that was reasonably protected against radiant, convective heat transfer and moisture infiltration, either convective or diffusive. Maybe like a tent. I drew a sketch.

The air within would be dry, say 40 percent RH but not too cold, so maybe there would be some heat transfer between the incoming and outgoing air. The capacity would be only say 500 watts or 2000 BTUs per hour, half the size of a small US style window unit, 20 percent of the one that Mr. Wonton said was necessary because it was the smallest the Carrier company made. The electrical savings for say six hours of operation of a 2000 btu unit would be a dollar fifty a day. Half a million air conditioners were bought in Thailand every year. The space to be cooled would be small, maybe 25 cubic meters altogether, and the envelope would serve as a mosquito barrier as well. The air would be conditioned air would be ducted into the space silently.

And wouldn’t it be nice to power the whole thing with exactly that dreadful stuff that was causing the whole problem, the 1000 watts per square meter, that would be 36 kw of power, of sun power burning down on that hot red roof? Maybe putting all that heat into the ground or say a lithium salt solution or some ammonia like the old days under the house or hidden away in the garden and some of it into the cool 26 degree water that came in off the street so the shower would be nice in warm in the cool season when the sky is clear and the solar at a maximum?

They would call it the "Ron Swelters Quarter Ton Aircon Machine", dedicated to His Majesty the King who had shown a keen interest in energy savings, and also to Doctor Carrier who invented the first air conditioner to cool the fevered brows of malaria victims but who had been swindled out of his rewards by John "Ice King" Tudor. In the year 1831, it was.

This was getting good. I ordered another pint, it was three minutes before seven and the price would double if I didn’t, the waitress told me so.

***************

The following night I had dinner with Jack and Dah. I told them all about my air conditioning ideas.

"Oh, Khun Jack, that very good. "

Jack thought this would be a good time to sort of pop a question.

"You know, Dah", he said, "we have to make an important decision. W can do it with only 1000 btu. But maybe I should get extra, maybe 2000 btu. Just in case maybe things different in the future."

Dah considered this.

"I think you and Ron know best about this. We need more money in account."

End of the rains?

2007-10-25T02:50:00.000-07:00

Could this be it, the end of the rains?

Last weekend a great flood in our neighborhood, a day confined to home with two feet of dirty water in the streets, local kids swimming happily in the sewage. Dek Sa-lum, says Auntie Porn, our Isan cleaning lady.

Now this week the days feeling cooler in the morning, no more than a few weak drops of rain in the late afternoon. It just feels different. Notice the wind heading from the west to east, then changing to the north, this was the beginning of the different feel. Dah says that winter has come. (Though the night temperature of close to thirty is still a little warm for this fahlang.)

Index of pages

2007-10-01T01:49:00.000-07:00

A long way from home	1/1/2007
black hole	1/1/2007
Greasy black dust	1/7/2007
2007/07/first-night-tropical-paradise.html>	1/10/2007
by Ron Swelters " align="left" height="17"> 2007/07/that-april-thrill.html#comments> by Ron Swelters	1/10/2007
2007/06/here-is-my-story_25.html>	2/28/2007
2007/06/same-heat-every-year.html>	3/1/2007
Tropical Cool: How was it for you?	3/6/2007
Tropical Cool: Hot roof unmitigated(revised)	3/9/2007
Tropical Cool: Solar-heated concrete roofs	3/10/2007
Tropical Cool: Foiled by the foil	3/11/2007
Tropical Cool: Carrier's magic chart	3/12/2007
Tropical Cool: Tour the world's most uncomfortable cities!	3/15/2007
Tropical Cool: Why so hot at Don Muang?	3/17/2007
Tropical Cool: Keeping cool without sweat	3/22/2007
Topical Cool: Bangkok 's lovely breezes	3/23/2007
Tropical Cool: You probably don't vent enough	3/27/2007
Tropical Cool: Big open windows	3/28/2007
Tropical Cool: Fans and turbines for a hot afternoon	3/29/2007
Tropical Cool: A hat for her apartment	4/1/2007
Tropical Cool: When will the heat break?	4/3/2007
Tropical Cool: An escape from romance	4/8/2007
Tropical Cool: Worst night yet	4/8/2007
Tropical Cool: A two-hundred foot tree	4/15/2007
Tropical Cool: Local wisdom, upstairs/downstairs	4/20/2007
Tropical Cool: How cold that night sky	4/22/2007
Tropical Cool: Regional heat agony today	4/24/2007
Tropical Cool: My fan's fan Apr 27, 2007 352	4/27/2007
Tropical Cool: Cold exceptions prove the hot rule Apr 30, 2007 298	4/30/2007
Tropical Cool: Banish unsightly necksweat! May 08, 2007 320	5/8/2007
Tropical Cool: Hungarian attack on US hegemony May 11, 2007 316	5/11/2007
Tropical Cool: Are the Thai really different? May 13, 2007 508	5/13/2007
Tropical Cool: Enter humidity May 21, 2007 308	5/21/2007
Tropical Cool: Thai comfort II (the mysterious orient) May 25, 2007 297	5/25/2007
Tropical Cool: Is a hot tin roof cooler? Jun 10, 2007 249	6/10/2007
2007/07/hatless-in-bangkok.html>	7/30/2007
2007/07/waning-heat-of-summer.html>	7/31/2007
2007/08/hot-tin-roof.html>	8/1/2007
" align="left" height="17"> 2007/09/old-spice.html#comments>	9/24/2007
2007/09/normal-year.html>	9/24/2007
one watt aircon	11/3/2007
aircon fanatasies	11/3/2007
IN the cool of the pub	11/4/2007
Cool night roof	11/12/2007
Would you mosquitoes mind leabving	to add from thaivisa
Out of Africa	to add from thaivisa
Rain and the mud	to add from thaivisa
Tropical Cool: The dream and the dread	x
Tropical Cool: That April thrill	x
Tropical Cool: Hot tin roofs and fahlang sweat	x
Tropical Cool: Night heat in June Jun 15, 2007 257
the air from Isan--november	12/1/2007
change your perception of (proust)	11/26/2007
index	10/1/2007

Old Spice

2007-09-24T03:09:00.001-07:00

Last year the makers of "Old Spice" deodorant for men published the results of a study of the "sweat rankings" of American cities. The winner was Phoenix Arizona but Texas cities like Dallas and Houston and several Florida cities were right up there and since I've always had a bad memory of Houston I'm going to use that place as a kind of bench mark, to compare Boston and Bangkok.

Take a look at the "march of temperature" through the seasons in three cities: Boston, which had a famous heat wave the first few days in August, 2006 (pink circle), a hundred thirty six people died including one woman sitting inthe bleachers at Fenway Park; Houston, which as I said seemed to me to be really awful, and Bangkok, awfuller yet. The red points are the highest temperature of the day, the green the highest dew point temperature of the day (more on that later). When the temperture is more than 30, you will begin to sweat, even if you are just sitting looking at this blog.

As you can see, that's most afternoons in Bangkok (the daily high is usually at about three o'clock).

You might say that Boston heat wave got up as high as Bangkok, but even thoughthey were passing out cold water on the half deserted Boston streets you could still sweat pretty effectively there because the dew point temperature was low, down around 24. In Bangkok, in contrast, the dew point hardly gets below 26 most of the year, so all that sweat just soaks your shirt and hardly cools a body at all.

Normal Year?

2007-09-24T02:53:00.000-07:00

A couple of weeks ago a Thai lady said to me "The heat hasn't been bad this year, a couple of weeks in March or April, then the rains cooled things down and it hasn't been bad since."

This lady happened to be an experienced architect, and my sense of the year agreed with her comment, but as a "quant" I felt compelled to look at the data, so I loaded Don Muang daily highs (temp and dew point) and superimposed on the hottest year I've found, which happens to be 1983. To my surprise this suggested that 1983 wasn't really so bad after all, except that the hot season got a little prolonged (so it just kept getting hotter) and then finally broke with the rain which (if I am right in my thinking) came a little late. I also believe that 1983 was a bad flood year, so now I wonder wheher al these things are tied together.

Hatless in bangkok

2007-07-30T18:50:00.000-07:00

It was getting into late July now and to my delight the weather had become tolerable and even pleasant. I had feared the sun and brought from California an excellent straw hat, designed and branded in Australia, made in China, and bought by me in a sporting goods store for five dollars and ninety eight cents. The shading and ventilative features of this hat were excellent, but it was more than a nuisance to carry, and I began to notice that I really needed it only a few minutes every day. I had, for one, found that I was not venturing abroad for vigorous midafternoon walks as I might in America, and even then the sun did not shine much of the day, the sky filled with rapidly changing clouds, now mild and oyster colored, now blackish and turbulent. Soon enough I left the hat somewhere, I think in a movie theatre in Siam Square where they occasionally showed films that met my discriminating tastes.

I determined to design a better hat, since all that I was able to find in the markets were intolerably hot except during those very occasional and fleeting moments of fierce overhead solar radiation, for the Bangkok sun since April and until August was almost directly overhead. Extreme portability and low value were the principal design criteria for my hat; I thought that a small napkin-like folded paper disposable might do the trick, but I grew weary of trying to find the right materials and one day stumbled in desperation on the expedient of cutting a sleeve from an old T-shirt and gluing the end opening with ordinary carpenters glue. This worked well, I eventually made half a dozen, and though it might be said to have created a somewhat odd appearance I reasoned that foreigners were universally taken by the natives to be both odd and correct. I have never noticed even when shooting my most darting looks at the locals passing on the streets the slightest hint of derision from anyone.

But were it not for the impractical bulkiness for city wear, the traditional Thai farm hat, or muak, is clearly the winner, allowing for full shade and full circulation of air on your sweaty head.

Waning Heat of Summer

2007-07-30T18:32:00.000-07:00

To my delight, the temperature moderated over the summer because of the rains, not at all unpleasant, crackling thunderstorms that might appear at any time, dawn, mid-day, most often in the late afternoon, everyone scurrying for shelter where girls had plenty of time to give you a lookover, then the black clouds would open and the dazzle would come back.

I downloaded the daily high temps for the year so far(blue), superimposed them on a speciment year fro the past (red) and it became clear that thought the sun was still hovering around in the middle of the sky, the cooling bath of rains was causing the temp to drop over the summer months. For that matter, it appeared that if you hated heat, the time to avoid in Bangkok was March through June.

That April Thrill

2007-07-16T21:55:00.001-07:00

So my brother calls me on my new Thai cellphone.

"That's fine, your first effort, but what are you talking about women for? You're supposed to be writing about the tropical weather, how foreigners can learn to live with it, help me figure out how to stay comfortable in this house, not about going to bars and women, for God's sake. Try thinking like the M.I.T. student you once were, not like an adolescent."

He's talking about my new blog, he doesn't like the way I'm going on this thing. Annoying, but he did help with my ticket here. I'll try to get back on topic.

The sun. That's a good place to start, our ancient enemy, the sun.

The Sun

Most people don't know it, but down here in the tropics we've got two "hottest" days of the year, not one like back up north. Wintertime, the sun is down there in Australia, giving skin cancers to all those pale blokes who live at the tropic of Capricorn, 23 degrees below the equator. Around the end of the year, even at noon the sun is fairly far off vertical in Bangkok, in fact this picture of a lady at Asoke BTS station (a burning hell of a place in general) at noon shows that the sun is at 53 degrees. Makes sense, when you think that Bangkok is about 13 degrees above the equator, so

90-(23+13)=54 degrees (OK, it's not exact)

Notice something else about this picture, that lady is carrying an umbrella. In winter. She doesn't want any part of the sun, she's even holding up her shopping bag to keep out any little slivers of sunlight.

This is typical of the people here, Thailand, Malaya. They hold up their arm to show you," I very black skin," they say. You say "O I think beautiful skin, I wish I had the same." They smile, thinking "fahlang very polite, they always say this but not believe." That night they put on extra skin whitener, which is about as effective as "anti-aging cream."

Tons of the stuff sold in Bangkok every day.

It's a system, the old Khmers had it all figured out nine hundred years ago, they learned it from the Indians.works like this, the sun gets to be right overhead in April, starts to decline a bit to the north over the summer, then in August back again. On April 29 and again on August 13, you throw no shadow at noon.

You can make a graph of the relative intensity of the sun on a flat surface at noon, it gets up near 1000 watts a square meter in april and August. You can compare the relative intensity with other places, like Miami and Boston, as I've done above.

Now I got my hands on a large set of data for Bangkok weather, must be from the old Don Muang airport, and I made a chart showing the daily high temperature and dew point for the years 1982 to 1985. And the yellow line is an accurate plot of the graph above, the relative noon intensity of sunlight falling on the unshaded ground at noon on the same day.

You'll not be surprised to see that the daily high temperature starts out nicely in the beginning of the year and then as the sun gets progressively higher in the sky, the dawn heat builds with it month by month, now in the beginning of March it's getter pretty sweaty even when I get up to walk to Starbucks early, and it's going to get worse, maybe a lot worse, some people say that this will be the big one this year in April, toward the end of the month.

But then, look, there in late April or early May, when the hot tension has built to a peak, and the people are dancing around and throwing water on each other but especially on fahlangs, and they used to have these wonderful rites with lingas -- you know what they are, don't you? -- the lingas spurting water and everyone is saying "Ahhh..." or as they say in Thai "Ooooiiiiyy........"

And then everybody gets this terrific little kiss from the gods.....

Or at least it seems terrific to them. As far as the folks from Boston are concerned, it's still one helleva big heat wave for the next six months, til November.

Same heat every year?

2007-06-28T23:06:00.000-07:00

Brother jack let it be know that Bangkok's horrible heat and humidity was the game, and that he expected solutions from me. "You're the guy from MIT," he said.

I had a couple of days before leaving and instead of buying gift chocolate figurines of Mickey Mouse or Parodi cigars as gifts for all the people I was going to meet I went for the UCLA library and loaded up on data. I found a huge collection of Bangkok weather data from some American military spy agency and almost missed my flight transferring all the files to a CD.

Our ultimate concern here is the weather within a room, or between your shirt and your skin, not the world at large. Although we are not particularly interested in grand questions such as global warming or pressure ridges in China -- I know nothing of these matters -- one of the first things that I asked myself was whether the weather, or more specifically the heat, which is my enemy here, is always the same in Bangkok, year by miserable year.

This extract from my massive data file (which you can have, for free, if you have some good purpose)gives a quick answer to this question. It shows the daily mid afternoon temperature, which is almost always the hottest temperature of the day, for fifteen years, starting in 1982.

Given that you are going to start to sweat at 30 degrees even at rest, you can see that a brisk walk at three pm is not going to be enjoyable.

Especially if it happens to be 1983.

But will jogging be more pleasant at six in the morning?

Night heat in June

2007-06-15T21:24:00.000-07:00

We saw the other day that in theory the roof on brother Jack's house retains a critical amount of heat resulting in a room temperature that is two or three degrees higher than the outside temperature -- enough to make the difference between a good and miserable sleep.

How does this check out in practice?

Here you can see my notes from a recent stay at the house. I measured the temp of the interior wall surface with a radiant thermometer until about 3 am, at which time the outside air temp was about 29 and the interior temp hanging up at 31 -- too warm for comfort (the orange colored zone). This was a pretty typical June night (June 8, 2007) ending with a dawn temperature of 27 to 29, (dawn temp also happens in almost all cases to be the daily minimum.). This matches the experience that Jack has been reporting, too hot in room in the middle of the night many nights in June. (It doesn't help that Dah insists on closing the windows at night for fear of intruders).

The interesting thing here is that the the discomfort comes from only a small amount of temp elevation. If we can drag the temp down just a couple of degrees, we will be as happy as the farmer sleeping under a cool nighttime tin roof. The challenge is this-- how can we get this modest amount of cooling without resorting to the overkill of air conditioning?

Is a hot tin roof cooler?

2007-06-10T21:22:00.000-07:00

Interestingly enough, the answer might be yes if we are talking about the time that matters most to many folks, that being at night when the outside temperature is slowly falling from the low thirties (too hot!) to the upper twenties (reasonably cool for sleeping). A "tin" (galvanized iron) roof is fairly light, perhaps a kilogram per square meter and has a very low "R" value. So hot as it might be even at sundown, it quickly cools to the ambient air temperature, even two or three degrees below if the humidity is not too high and the effective sky temperature is low, say 5 degrees or so. So you may even get some free radiative air conditioning from such a roof at night.

Lets look at Brother Jack's roof:

This roof weighs about 10 kg/sm and has an "R" value of about 5, and each square meter retains perhaps 10,000 joules of heat per degree. If you want it to cool as fast as the outside air, say 1 degree per hour, you've got to make it discharge 10,000 joules per hour per sm, or 3 watts/sm. If the "R" value is 5, this will require a temperature gradient across the roof from inside to outside of about 3 degrees. In other words the interior temperature will be 3 degrees higher than the outside air temperature--which is what we saw earlier on our April 3 measurements (vertical difference between red and blue lines). Therefore even when the outside air dips to a nice 29 degrees, the inside of the room will still be a sweaty 32 -- too warm for sleeping. And if in your desperation to keep cool in the daytime you had installed some bulk insulation instead of the foil insulation, the "R" value might be double, and the required temperature to push 3 watts out through the roof even more, maybe 5 degrees, an even worse situation! Meanwhile the poor farmer next door will be happily snoozing with his tin roof at or below outside air temperature! His red line will closely track the blue line, maybe be even lower.

So the joke is on you, Mister high-tech fahlang--you tricked nature in the afternoon, but she got back at you when you were trying to sleep!

Thai comfort II (the mysterious orient)

2007-05-25T21:21:00.000-07:00

Ron: So Dah, do you think Thai people feel the heat the same as fahlang? Sometimes when I feel very hot my girlfriend also says "very hot" too.

Dah: Thai people say "Oh very hot" but just start the conversation, that all. It not about real hot. Actually it not bother them. It just the way it is. After you born it like this, no one can change. Even you go to hospital and doctor there make mistake, you have to think maybe I do bad last life, that's why I get. In America if someone do something bad, you have to sue him to get something back. But in Thai they think maybe last life I do something bad to them.

Ron: I see. But Jack told me last few days you were complaining about the heat at night. Were you just making conversation?

Dah: No, it about the flea, that bug, I don't know if flea or not. It bother me. Not the heat.

A long way from home

2007-05-25T21:17:00.000-07:00

Enter humidity

2007-05-21T21:21:00.000-07:00

My mother called it "sticky", and it's a subject that we've been avoiding here, hoping that the weather would just stay cool enough. But when the Don Muang temp hits 29.5 as it did the last couple of nights we just can't seem to convect and radiate that heat away, and the dreaded sweat begins to bubble from our pores and we have to get our hard little pillow, however full of mold it may be (according to our faithful correspondent wch). The other day I took a wet washcloth out on the deck in the shade with a nice breeze and let it dry a bit. It was ten inches square and after an hour it had lost 8 grams of moisture, that's about 5 watts of cooling power, equivalent to 80 watts per square meter.

Depends on wind and humidity, you're thinking, so here's a formula to figure it for whatever you like:

Evaporation in tropics, grams

E=(25+19V)(30(1-RH)/3.6/1000)A*T

E=evaporation, grams
V=wind, m/s
RH=relative humidity
A=area, sm
T=time, sec

And here is a handy little graph of that formula:

Now you might have the same problem that I do here, because when I try to find a rate of 80 watts per square meter on this grpah, I don't. So maybe I'm a lousy experimentalist, or the formula, which is supposed to be for open pan evaporation, doesn't work for wet washcloths. I'll have to look into it. But what you can see in general here is what you know already, that is, when you begin to sweat to the point where half of your boys is soaked, and you're in a good breeze on a hot dryish day, you get a lot of cooling power, enough to take care of the 200 watts or so that you generate when excercising.

Are the Thai really different?

2007-05-13T21:18:00.000-07:00

For some years academics have been debating whether thermal comfort varies among different enthnicities, with the balance of opinion seeming to shift in these days of multicultural pride toward discoveries of ethnic difference. A recent study by a Thai professor at the excellent Silpakorn University follows thsi view by concluding, based on a field survey of many Thai people in their own settings, that Thai prefer much warmer and more humid environments than fahlang. Based on my experience giving bedtime thermal comfort questionnaires to my girlfriend (is that why she is mad at me?), I half believe this, and when I read the paper by the professor I knew that I was supposed to believe it without question.

You saw the Olgyay chart in the last posting here, and now you can see the results of the survey here.

Do you believe it?

I've superimposed the zone of favored conditions for Thai people on top of the Olgyay bioclimatic zone diagram shown last post. Do you think the Thai are most comfortable in their ordinary lives and activities at a temperature of 30 and RH of 80 percent? The warmer days and nights of last month (April 2007)? This is certainly enough to make me miserable.

I wonder. I have some methodological issues with the research, but I'm going to give you the link to the paper below so you can make up your own mind. We'll talk more about his later, meanwhile I look forward to your views.

http://www.unige.ch/cuepe/html/plea2006/Vol2/PLEA2006_PAPER842.pdf

Hungarian attack on US hegemony

2007-05-11T21:17:00.000-07:00

The reader has been introduced to the famous Carrier psychrometric chart which will be easly recognized as an attempt to confuse and perplex ordinary people with the goal of herding them like sheep into the corrals of air conditioning salesmen. Air conditioning engineers, whomever they may be, love this Carrier chart with its arcane title, its Cal Tech terminology ("enthalpy", etc). Internationals hate it because it is just one more attempt to foist American hegemony on the world. Architects despair at knowing which is up and which is down and which is sideways on the chart, the French hate it because it spelled the death of Scientific French as surely as McDonalds has proven to be Vichy regime of French cuisine, and Freudians consider "psychrometric" an invasion of their stranglehold on epistemology.

Along comes this Hungarian, Victor Olgyay, and saves us by making another kind of thermal comfort chart, as shown above. Notice that it is written in Spanish, so it will not be understand by Americans. I've plotted a couple months of Bangkok weather on it, so you can see how justified you are in just turning on the fan and relaxing, because you are at the limite de trabajo while still safe from a golpe de color.

Banish unsightly necksweat!

2007-05-08T21:14:00.000-07:00

One of the thermal challenges in hot-season Bangkok is sleeping comfortably without air conditioning between bedtime and about 2 am, when things finally begin to cool off. With temperatures remaining in the low 30s, the body cannot pass off its 100 watts of heat to the environment by convection, especially if one is sleeping on a fahlang-style mattress and using a fahlang-style pillow. So sweat begins, and soon enough you are lying on a disgusting wet pillow that is hard to dry. Your head, with its ample blood supply, becomes especially sweaty.

It never would have occurred to me, even after watching the natives, but a guy on Soi Cowboy told me that fahlangs are overly attached to their sleeping apparatus, fluffy pillows and soft mattresses, but the fact was that in a few nights they could get used to the local way, hard pillows and sleeping on concrete was no serious inconveneince once you got used to it.

So I replaced the fahlang pillow for a few nights with this smaller hard thing. He was right, I was more comfortable the first night, with air circulating nicely around my neck. Assuming that I am evaporating half a can of Singh every hour, 90 grams at 2500 joules per gram heat of vaporization, I'm picking up 60 watts of cooling. Good for my blood pressure, too!

Next challenge: go all the way, sleep on a wooden pallet which is the Thai tradition.

Cold exceptions prove the hot rule

2007-04-30T21:13:00.000-07:00

Now considering solar declination alone the 29th of April should be the hottest day of the year in Bangkok, latitude 13.9, for that is the day when the sun passes directly overhead and there is no shadow at noon. But saturday there were no shadows at noon, and in fact the past few days have been downright cold. When I stopped by Jack and Dah's place after a thunderstorm several of the tall willowy trees that have sprung up in their garden had bent all the way over so the crowns of the trees were splayed out in the garden. Evidently the wind had got the water-soaked tree swinging back and forth until it reached a point of instability and collapsed, though Jack told me later that he was able to put them right again without permanent damage.

Young willowy trees, as unstable as young men.

Now when I first came to Thailand I thought the hot season was going to be a relentlessly increasing tide of heat peaking in April and agian in September. But this is not how things have behaved at all the past few weeks, and if you look at the march of temperature and wind as we do here you get a picture that looks a little like those trees in Jack's yard. "Normal" hot weather (orange zones) with steady breeze from the south, punctuated by unstable wind directions accompanied by storms and cool weather.

Cold strokes in the hot season or the other way around?

I don't know anything about meteorology, low pressures and the South China Sea, but the behavior of the wind and the level of comfort looks more like the stock market or my girlfriend's moods than some orderly sun-driven cosine thing.

I guess I'm going to have to start reading a little Mandelbrot if I'm ever going to survive in this place.

My fan's fan

2007-04-27T21:13:00.000-07:00

I am ashamed to admit this, but one time when my girlfriend fell asleep I crept into her room and took a picture of her fan. I was really impressed with its clean design and checked out the price at Lotus, only 750 baht. It comes in a little box and you can pretty much put it up by yourself. It's a Thai product, a good one.

Overhead fans are great, even when you have aircon.

Anyway, who wouldn't want an overhead fan? Romance, Humphrey Bogart, plot your own revolution. And they work, too, the one above provides a nice efficient and smooth flow of air.

Brother Jack decided he had to have a fan under his mosquito net, and he loved to talk about this Honeywell model, which I admit seems to work pretty well, though it's airstream is choppy, narrow, and turbulent. Dah says it doesn't keep her cool. Maybe because jack points it at himself.

Dah sleeps on a wood bed when it gets hot (more on that tommorrow) and she put up this large overhead model which she says cost 3000 baht. I'll admit it looks pretty nice in her and Jack's place, but it is also very quiet and seems to provide the largest and least turbulent flow of the three models. I know that "turbulence" isn't on the list of things people usually consider in buying overhead fans, but I've come to the conclusion that it is important.

Regional heat agony today

2007-04-24T21:11:00.000-07:00

This dreadful day I made the mistake of getting my girlfriend to accompany me to Klongtoei, where I wanted to idle away the afternoon browsing machine shops.

My idea of a date.

After almost fainting in the heat (both of us) they we took refuge in the huge Lotus, collapsing on a wood bench from which we could listen to American country music and watch a Charlie Chaplin VCD and eat a McDonalds ice cream cone. My numb mind filled with happiness at the cold air.

Is there any hiding from it? See for yourself, here are the 1 pm temps all over SE Asia on what must be the hottest day yet this year. The folks in Udorn have my heartfelt sympathy.

How cold that night sky

2007-04-22T02:12:00.000-07:00

People who write learned papers and books about tropical architecture and comfort --Floridians, Singaporeans, Australians, and, God knows why, even some Norwegians -- talk of "dumping" building heat, ie trying to find places where the enthalpy is low to which unwanted building heat can be efficiently transferred.

Alas, this is not easily done in Thailand because there aren't any cool places to be found. With a mean temp over the year of nearly 28 degrees, the earth itself is warm -- about 28 degrees, which does not provide much of a "sink" for heat. (One night I walked into a bar in Pnom Penh and started taking the radiant temperature of the palms of all the girls in the bar. I told them that I was measuring what kind of a wife they would be. I leave what one girl did it to the reader's imagination )

The sky, which cools the overheated brow and roof in the night desert (or in places like Hollywood, where I lived a rather disappointing life, but for other reasons than heat, until recently) is fairly warm, and efforts to radiate heat into the sky from buildings are not usually considered to yield much benefit, especially in the hot season.

But since we have recently seen that we are not asking for much cooling, just a few degrees, I've been taking some night sky temperature measurements* with my little radio Shack radiant thermometer. Here are the results on the left. Evidently the night sky temperature is a function of sky moisture, or dew point. And in the hot season, when there is a lot of moisture in the air, the night sky becomes less effective as a heat sink.

But still. How much can we get from a night sky of 15 degrees?

According to radiant heat theory, we should be able to transfer about

k*(Troof^4-Tsky^4) watts/m2

where k= 5.6697xlO-8 w/m2-°K. T

which comes to about 50 to 80 watts per square meter of roof. This is enough to lower the roof temperture, suppress it as we say, by two or three degrees.

Can we use this natural cooling to some good end?

-------------------------------

* I know that this instrument is not really measuring the temperature of anything in the sense of say a thermometer, rather it is feeling how much radiation is being emitted by whatever you point it at. Or whatever you point it's 30 degree "eye" at. It thinks that the emittance of everything is the same, maybe 0.9, which is not true or things like aluminum and skies. But since radiation is what we are talking about here, I'm just going to go ahead and figure the heat transfer as if the "temperature" of the sky was what the radiant thermometer says it is.

Local wisdom, upstairs/downstairs

2007-04-20T02:09:00.000-07:00

There's a lot to be learned from the natives.

Here I am going on about how terrible hot tin roofs are, and then I discover, from reading my own blog, that if it's a good sleep you're wanting, you might be best off under a hot tin roof.

Here's the idea: even though the night sky in the tropics is fairly "warm", that is, its temperature as measured by a radiant themometer is not close to freezing as it would be in the desert (so don't try to build a heavy masonry building in Thailand and expect it to be cool like a Mexican church), but rather closer to 12 deg C, owing to the high moisture content of the air. But the sky still does does manage to pull off some heat by radiation, so that the temperature of, say, a roof surface will be suppressed by perhaps 2 degrees. With the outside night air in the hot season remaining at a sweaty 30 degrees, the roof temp might fall to say 28 degrees. In the case of a roof with no insulation, say a metal roof or cement tile roof, this cooling would carry through to the underside of the roof--where it might be a big help to sleepers below, happy to be able to radiate from their hot 35 degree brows to a 28 deg surface above, maybe pick up some convective air cooling as well.

Result: the Thai family that avoids the upper floor during the day, but sleeps there at night, would do best without any roof insulation!

So what does this family do in the day?

Everyone knows that they spend their time under the house. Because it's cooler there.

How much cooler?

Here are the measurements above for three hottish days in early march 2007. And we can see that Jack and Dah's house is about 4 degrees cooler downstairs during the day.

Note that the upstairs remains a little warmer throughout the night as well. The moderate insulation of the roof (R=4) doesn not encourage the sky radiant temperature suppression we discussed above.

Worst night yet

2007-04-18T01:36:00.000-07:00

Yes, last night was serious challenge.

After several days of cooler disturbed weather that seemed to bring the hot season to a close, the heat came back yesterday, with daytime temps around 38, temperature in Jack and Dah's bedroom (where I am temporarily staying to hide from my girlfriend) still at 33 in the evening, slowly declining over the night to 30. Since the maximum sweat free sleeping temperature under the best of conditions (good overhead fan and nude sleeping) is 29 as shown above, it was a sweaty night without aircon, only barely comfortable even at dawn. Looks like more punishment may be on the way, with the solar intensity not peaking for another 11 days.

The dawn air temperature in Bangkok according to Weather Underground was 29 degrees this morning, a high for this year. Dew point was only a little less, 26 degrees. Even though the (apparent, measured by radiation thermometer) dawn sky temperature was 12.5 degrees allowing for a slight suppression of the surface roof temperature to about 26.5 degrees, a couple of degrees below air temperature. Little of this carried through to the underside of the roof. The wee hours of the morning are a time when a roof minimum R-value would actually be a benefit, allowing more of the radiative heat loss to carry through to the rooms beneath. As it is, the room temperature even in this light house stubbornly remains about 2 degrees above the air temperature throughout the night. This is a two degrees that could make a difference in comfort.

A two-hundred foot tree

2007-04-15T01:28:00.000-07:00

After lving in the house and accruing a few days of hobo measurements I had a pretty good record of how the house behaved during a typical day in the hot season, April 3-5 in this instance. April 3 turns out to be the second hottest day of the year so far, with temperature on the house deck and bedroom peaking in the afternoon at close to the Don Muang maximum of 37 degrees. Note the circled part of the record, where the bedroom temperature seems to have a little "kick" starting at about 3 or 4 pm. This is caused by the sun striking the dark wood wall panels in the late afternoon, when the sun angle is low enough to slip beneath he roof overhang.

From this and other data we derive the following basic principle: Shade from the fahlang's ancient enemy, the sun, is the first defence against heat in Bangkok.

Though Jack might have done better, in theory, by orienting the house so the long axis was east-west, thereby reducing the exposure to the direct sun, especially in the afternoon (hottest time of day is about 3 pm), other siting conditions governed (as they usually do) so that the roof and wall of the house, the bedroom wall, were exposed to late afternoon sun. Fortunately the light construction of the house does not allow for much storage of heat, so that the roof and wall would cool soon after sunset (not like concrete walls and roofs, which stay warm well into the evening). Note however that the bedroom temperature persists at about 2 degrees higher than the outside air. This may seem like a small amount but it is important when we consider that the threshold of sweaty discomfortfor a well-fanned sleeper is around 28 to 30 degrees.

But Jack and Dah have enjoyed a stroke of luck.

A tall apartment building stood to the west of the house, so that during the hottest part of the year, mid-April to September, the building throws a shadow that arrived at just abouot 4:30 pm! (Yep, when you are site planning you can check all this out yourself on Google)

Two hundred foot tree

An escape from romance

2007-04-08T01:45:00.000-07:00

"The mosquitoes are eating us up, my pillow is soaked with sweat, and Dah, last night she was up and down all night, this morning she is in a terrible mood. I see by your blog that it's just going to get worse for the next month, I can't stand it, I'm taking her to Singapore for a couple of days." Jack called me and suggested I might like to stay at his place for a bit, maybe come up with some practical solutions. "Practical" is the word he used, meaning that my research on tropical comfort was somehow lacking in that regard.

"I'm thinking of changing the blog to "Tropical Comfort Hacks", what do you think?"

"I don't care what you call your blog, Ron, just try to help me out on this, would you please?"

My girlfriend had started to talk about a "salary" which was a new and unwelcome idea to me, so maybe it might be a good idea to take a little vacation from our relationship.

Jack and Dah's place wasn't bad, in an old fashioned sort of way. Dah fixed up the guest bedroom pretty nice and Jack slipped me 5000 baht on his way out. I was a little tired. I walked around the corner to a little shop and bought two bottles of Singh, a plastic bag of what looked like little sugar-coated donuts, and two plastic bags of ice, then I went back to the house and sat in the room and smoked a nice cigar that I had found on Sukhumvit, 400 baht for a box of ten, and settled in for some pleasant reading. It was still a little warm inside the room at 8 o'clock, 31 degrees and the ceiling about 33. Outside the world was 28 and the sky about 11. I couldn't figure why the roof wasn't losing more heat to the sky but I was too lazy to climb up on something to check the roof temperature. I fell asleep reading about the origins of the Stefan Boltzmann radiation constant, it was another one of those scientific ties, like Newton and that german guy with the calculus.

------------------------------------------

The next morning I woke up early and made some coffee in this cool little french coffee machine that they had and then offloaded data from the two Hobos that I had given Jack, one to put in the bedroom and the other out on the deck. During the night it had been on the warm side under the mosquito net and I was sweating even with no clothes. But it cooled down and by the next morning it seemed just about right, you didn't wish you had aircon at all.

First thing I wanted was to compare the temp at the house with the Wundergound temps at Don Muang and Asoke. After and hour or so I had the little comparative graph you see here. This confirmed my sense that you couldn't say what the "real" temperature was at Bangkok, it wasn't something you could find like that gold meter bar with two little scratches on it that the french said they had in a museum in Paris. They said that it was the "real" meter. I remembered reading that in a book in a course called "scientific french", that's how old I was getting to be these days to remember ancient history like that.

So temperature in Thailand is a little like morality nowadays. It depends on your local situation. After all, the sun can't heat the air, you can't do anything to air with radiation (almost true, anyway) you had to heat it by convective transfer from local things. Don Muang was pretty hot maybe because of all those asphalt taxiways soaking up the sun. Jack's deck was better, it was partly shaded by a nice big mango tree, though the other part was shaded by the roof overhang, which most likely a warm underside. Asoke I couldn't figure, maybe it was on the cool side of a building. Who knows, it might give readings that were tow high in one season, two low in another. My bedroom wasn't too bad, it lagged the deck by a couple of hours, but at night as I had discovered it stayed two or three degrees warmer than most earthly things in the neighborhood outside. So here was a good problem: could I figure a way to drop the bedroom temp a little. so it was more like the outside? Or maybe was I myself helping to raise the bedroom temp, the observer interfering with the observed?

When will the heat break?

2007-04-03T01:22:00.000-07:00

The chart below shows the 2007 season data, increasing heat and dew point, through March. It conforms to our recent experience of increasing discomfort as the hot season approaches. It follows the pattern you can see in the background of the major El Nino year of 1983. (However the 2007 data are from a new weather station downtown Bangkok, at Asoke, while the 1983 data (white points) are for Don Muang which for various reasons is consistently warmer than downtown.) The intensity of solar radiation for cleart weather is shown as a yellow line, you can see that the heat pattern so far follows solar intensity.

It is evident that we are on the same track as in the past, and that we can expect a "break" in the heat during the next month or two. The Thai say that Songran is the hottest day of the year and there appears to be good reason for this. If Bangkok were located at latitude 8 instead of latitude 15, April 15, Songran, would also be the longest day, the day of no noon shadow as well. Latitude 8 conforms to the location of southern Thailand, perhaps the early calendars were devised there.

Other years, not major El Nino years, show a break in heat earlier than 1983, which is extreme. Since 2007 is not a major El Nino year, we may expect an earlier break as in the the years 1984 and 1985, shown below.

A hat for her apartment

2007-04-01T01:08:00.000-07:00

After a few weeks in Bangkok I met a nice lady. I told her I'd like to cook a meal and she invited me to her apartment. I stopped at Villa supermarket and bought too much capelloni and fifteem tasty looking Australian scallops for 150 baht and some buttterhead lettuce and a bottle of Shiraz, a little expensive but not too bad at 550 baht. Excellent bread, too.

I arrived at the lady's apartment at about seven o'clock and it was like an oven. The place was on the top floor and there was a 4 inch concrete slab between her and the sun, the slab was still glowering away in the night, about 40 degrees sti;; even after sundown. "This will never do," I said.

The next week I made a model of the daily heat budget of the roof and room, you can see a two day run in the illustration. The top of the roof gets up to about 60 degrees but the underside gets pretty warm too, a little later in the afternoon.

I figured a nice black net would prevent that big heat buildup during the day.

My lady friend had a contractor who owed her a favor and I showed him how to build a tent on top of the roof, using that net-like stuff that they put over plant nurseries and fish markets. I got the idea from watching fisherfolk on the Mekong River near Vientiane.

I took temperature measurements later, of course. The bedroom was much more comfortable with the net.

Here I am standing on the roof next to the net.

Funny thing is, turned the contractor owed here a favor but not that big a favor, so I loaned here the money to make up the diffrence, a couple of thousand baht. Funny thing is, she hasn't given me the money yet, but I'm very proud of the accomplishment.

Fans and turbines for a hot afternoon

2007-03-29T00:54:00.000-07:00

Now children, if you are going to learn science, sometimes you just have to do some things that might seem a little boring, we can't be making gunpowder and coating your coins with mercury and dripping acid on your friends homework every day!

So today we practically fell asleep looking up the capacities of wind turbines and fans on the web. It wasn't easy, and then we converted them all into the same units! Then we climbed all the way up to the Asoke BTS and took this picture of all those turbines whizzing away in the stiff afternoon breeze! Then we went to get a beer in the pub!

Here they are, diameter in inches and manufacturers rated capacity (cubic meter per second) for various wind velocities.

Performance Data

	diam inch	wind vel, km/hr	cm/sec
axial fan	9		0.15
axial fan	16		0.90
axial fan	14		0.63
turbine	32	6	0.58
turbine	18	6	0.23
turbine	12	8	0.16
turbine	32	16	1.29
turbine	6	6	0.05
turbine	18	16	0.47
turbine	24	10	0.94
turbine	20	6.4	0.80
turbine	20	15	1.25
turbine	6	16	0.13

Now here is your homework:

What would you rather have if the wind velocity is 1 meter per second: a one square meter open window on each side of the room (assuming it has two sides) or eight 12 inch turbines as shown?

Big open windows

2007-03-28T22:15:00.000-07:00

We talked last time about the need for major ventilation. If we hope to cool spaces under roofs that a lightly insulated with "passive" openings, say windows or grill vents we will need very large openings to keep the temperature rise less than about one degree C. when the roof gets hot. Here you can see an example, a high roof vent that provides about a square meter of open ventitlation at the peak of both ends of a traditional Thai house.The house is oriented N-S, so it presumably does well at catching the southerly breezes characteristic to the hot season.

In addition in this view you can see that the open windows with curtain billowing into the bedroom provides cross ventilation in the other direction as well.

The result in this case is a room that does not become much hotter than the outside air (maybe a degree or two at most) even though the roof, which is only lightly insulated, gets up to about 70 degrees on the outside in mid afternoon, late march.

In this case, there is no dropped ceiling or loft/attic space. but the same principle jolds if you have such space in your house and don't want a 40-degree dropped ceiling over your head when you nap, or (if your roof is concete and retains the heat) when you sleep at night. If you are goinng to cool space by ventilateing poorly insulated areas, you've got to have strong ventilation through big openings.

You probably don't vent enough

2007-03-27T22:09:00.000-07:00

We come now to a problem that is in my experience the most misunderstood thermal building issue in the tropics, the source of more than half of the discomfort in non-air conditioned buildings, that being the lack of understanding of cooling ventilation. By cooling ventilation I mean ventilation that aims to reduce the temperature of the air of building materials within the building or within any space (such a an attic) that is subject to heating from an overlying roof.

When I was a kid growing up in Boston, Massachusetts during the "dog days of August" when the heat and humidity would sometimes reach the levels of Bangkok in March, my mother would leave the shades dawn and windows closed in the morning, then in the late afternoon when the inside of the house would get too warm, she would open everything and then in the evening turn on a big attic fan, that would roar away all night supposedly pulling cool outside air through the house.* The afternoon-evening ventilation was meant to cool the house -- which was probably 30-35 degrees, with outside air that by late afternoon might be cooler than the interior temperature.

Now times have changed and in the US people are trying to build airtight houses with central air conditioning which is considered a sort of basic right similar to the right to own a big gas guzzling SUV, with much the same wasteful effect, in my humble opinion. As a result the defintion of ventilation has undergone a drastic change, it now being something like "providing just enough replacement air to prevent the house from stinking of cabbage or cigarette smoke or poisonous off-gassing of all the crappy modern furniture and devices people put in their houses these days." This means only a tiny amount of air, not enough to cool anything. Anything more than this minimum to prevent you from getting nauseous is considered wasting energy and bringing in outside pollution (presumably from the SUVs).

Yes, the modern world and it's lobbyists have really created some big unsolvable problems that they then propose to tackle with even more ridiculous ideas like wind farms. Fortunately Thailand has not yet copied these bad ideas and is still pursuing old-fashioned bad ideas by burning cubic miles of coal (with associated planetary detriment) in order to cool leaky concrete structures.

But let's say you want to go back to the real old days, like my brother Jack and his partner Dah, and live in country-style house with low thermal mass (e.g. wood) and a lotta ventilation, enough to keep the house from getting too hot. Then you 've got the same problem, providing enough ventilation to exhaust any heat buildup either in the house or in the "attic" espcially in the mid-late afternoon when you want to realx with a big bottle of Singh beer and a ciager. The real problem where almost everyone goes wrong is getting sufficient ventilation, which is a lot of ventilation, not the amount of ventilation you'd find recommended in any fahlang websites or literature, since this is all aimed at the new paradigm of sealed houses.

We touched on this topic earlier when we noted the oven effect that you usually find with a dropped ceiling, as shown on the sketch and previously discussed:

Now what a lot of people do is put in some kind of a dropped ceiling, which of course intercepts the radiant heat from the underside of the roof. But even though you can turn off the radiant heat, but the convective transfer will soon enough heat up the air in the "attic", maybe all the way up to the high 40s. Then the gypsum ceiling will heat up, then....you are right back where you started, a hot gypsum ceiling instead of a roof. Sure, there is a little time factor here, each square meter of hot roof has to heat up a couple of cubic meters of air and a little bit of gypsum, but that may be as little as a few minutes, since the hot roof with an R value of less than 1 will deliver about 100 watts per square meter of heat.

But how much in the way of openings for ventilation is enough?

To find the answer in a proper engineering way you've got to know the R value for the roof, from which you can determine how much heat is going to flow through the roof into the space below. Given the rate of air heating, you then need to reckon the air replacement rate necessary to prevent the temperature from rising more than a nominal amount, say 1 degree C. Then you've got to figure the sizes of openings (we'll save fans and turbines until next time) necessary to deliver this amount of air to the space under normal conditions -- let's say a breeze of 1 meter per second, typical for hot weather in Bangkok.

Now I have done this for you generically (and will post the derivation here some time for your criticism) but am going to summarize my results below to save you the pain (while meanwhile adding to your suffering when you realize that your vent area probably doesn't meet the standard).

Standard for wall openings to prevent interior heating significantly above outside air temperature**

1. No roof insulation, eg metal or thin tile roofs only: Not recommended because underside of roof will get very hot and radiate onto your head, and wall openings will have to be 20 percent or more of the wall area. Better just lie under a grass rood with no walls.

2. "The usual" roof insulation -- a layer or two of air, maybe a sheet of aluminum, plus a wood or gypsum dropped ceiling. R value on the order of 5: vent must be 10 percent of wall area. For example for a 4 m high by 5 m long bedroom wall, you will need 2 square meters of open windows on opposing walls (ie full cross ventilation) to maintain temp at 1 degree above outside air temperature.

3. Good roof insulation, eg at least 3 inches of fiberglass or equivalent foam material, R value of 15: Same as 2 above, except area can be reduced to 2 percent of wall area, eg a grill with about 0.5 square meter opening area.

------------------------------------

* In retrospect I remember the fan as being about 15 inches diameter, which would move about one-half cubic meter a second -- not enough to cool several rooms very quickly. But the R value of the roof was probably pretty good, there was about 6 inches of fluffy stuff -probably asbestos, now that I think of it, over the ceiling.

** Don't ever forget, you're not going to "cool by ventilation" anything to below outside air temperature, which may be pretty unbearable on April afternoons. (Then it's time to go under the house...you do have an underhouse, don't you?) True, as we shall see, you can cool surfaces like nightime roof surfaces, to below air temperature, more on this disappointing topic later.

Bangkok 's lovely breezes

2007-03-24T23:57:00.000-07:00

Preparing now to take on the grim subject that in my experience leads to the greatest thermal suffering and disappointment, namely the lack of ventilation/insulation of enclosed subroof spaces (ie "attic" spaces), we need to tarry a bit blathering on some about the happy existence of tropical breezes here in Thailand.

First, some data:

Bangkok is fortunate in this regard, enjoying a hot season breeze that typically ranges from 1 to 2 meters per second (4 to 8 km/hr), as you can see from both the annual history for 2005-2006 at Don Muang, and also from the history of the last few days. (Both of these graphs are readily available from Weather Underground)

I include the temperature history on both graphs because it is quite lovely if you are a scientifically oriented person to sit and look at the season pass in this little data-world, the moment of pneumatic confusion followed by the decisive reassertion of the wind from south to north at the end of the rainy season, etcetera. Christians will rejoice at the miraculous plunge of the dew point to create, as best as Thailand can do, a starry windless Christmas eve, others will doubtless enjoy finding their own divine interventions, Tuesday's predawn tussle between Boreas and Notus, and so on.

But let's stop fooling around here, what we want is comfort, and we rejoice that Bangkok fairly consistently delivers a breeze of about 8 km/hr, which is about 2 meters per second, which you can compare with the general standards used as follows:

0.5 m/s: pleasant breeze. Lowers apparent temperature by about 3 degrees C (mainly by improving convective transfer from body to air)

1.0 m/s: desirable indoor upper limit in USA, according to various authorities in that country. Enough to feel on face, move hair and papers slightly.

2.0 m/s: further cooling effect, but felt as unpleasant or gusty by fussy people. Recommended as permissive upper limit for indoor by tropophiles.

It would appear, then, that if a substantial portion of wind can be brought into the indoors, our thermal felicity will be well served. So our general aim here is to put this windy energy to work in improving our indoor environment, which we propose to do in the next chapter.

Why so hot at Don Muang?

2007-03-17T23:54:00.000-07:00

For years climate control specialists have relied on weather data from the Don Muang airport about 20 minutes drive north of downtown. But now new weather stations have been established in various parts of the city, and indicate significantly cooler temperatures and dew points downtown as indicated on the graph for this summer. My local readings in the Sukhumvit area closely match the red data, not the Don Muang data.

Blue, Don Muang. Red, downtown

As I will try to prove elsewhere, "dew point" is probably a better measure of comfort that temperature. You can see that by that measure Don Muang should be significantly less comfortable than the Sukhumvit area.

How can this be? At this point I offer no more than speculation. Maybe more heat-absorbing concrete, hence higher enthalpy. Maybe the sensor at Don Muang is defective.

Strange too, that Bangkok is said to be an urban "heat island", with temperatures about 5 degrees C higher than the adjoining countryside.

One of these days I am just going to have to take one of my "Hobo" recorders on a taxi ride to the airport and leave its brother at my brother's house downtown.

Anyone have any theories?

Adventure tour the world's most uncomfortable cities!

2007-03-15T23:53:00.000-07:00

Why go along with the crowd in a vain, un-Buddhist quest to find luxury and comfort? Wouldn't you like to spend a month touring unforgettable places like the diamond mines from Blood Diamond, evenings visiting local villages with the boy soldiers? Or spend an idyllic week at the site of the Reverend Jim Jones massacre? Or join a session of aerobics followed by a fun run through the stalls at Jatujak market, Sunday at 3 pm in mid April?

To aid you in planning your trip I have brought you yesterday's global dew point map from weather underground (showing a possible itinerary), along with the latest surface sea temperature record from satellites. Note that these valuable maps will not, like inferior imitations, just show you places with sauna-like heat -- those are a dime a dozen -- but allow you to select locales where you can be assured that you will be immediately soaked in healthy sweat even before you finish dealing with the scowling customs agent with the automatic weapon.

(Whoops, what's that missing square in he middle of Africa? Maybe the boy soldiers just paid a visit to the weather station!)

And remember, you can find a few places in the world (at least this week) where the comfort level is even less than Bangkok!

Any suggestions from Ian out there for special events?

Happy travels!

Foiled by the foil

2007-03-11T03:25:00.000-07:00

Now I'm not supposed to show you this, but my brother Jack is building this house, he's very proud of it, but he's made a couple of mistakes and this is one of them. It's a common enough mistake in Thailand, you might say that the Thai building industry is commited to making it, because you see it everywhere. Aware of all the problems we've been discussing here in regard to tin, tile, and concrete roofs, the futility of dropped ceilings as insulators, and so on, they have turned to the use of insulation, which is all to the good. Unortunately they've all been conned into one of the great snake-oil building techniques of the 20the century, aluminum foil insulation.

The type of roof my brother Jack had in mind was cement tile underlain with teak planking ceiling, with a little space in between. Anyone who has observed Thai construction practices knows that the usual heat protection with this arrangement is the addition of a sheet of reflective foil insulation between the two materials (the space is about two inches.) The purveyors of the foil will tell you, while catching their breathe in the course of praising their product, that you only have to leave a little space between the foil and the next layer in the sandwich, then you will be rewarded with a reduction in heat of more than 50%, etc etc

Jack succumbed aboriginally to the magical promises of aluminum, and decided to use foil insulation.

This was a mistake.

We see above the guys putting on the roof panels, over the foil which (shiny side down) is in turn over the teak panels. And you can see from the picture that there is not going to be much space, maybe very little space at all, between the bottom of the foil and the teak ceiling. And very thin or irregular spaces are not very effective at interrupting the flow of heat from the roof tile, which as we've seen may reach 60 degrees on a sunny day.

So Jack thought to himself (after I toldf him about the importnace of the space) , should I start shouting at those guys not to walk on that foil when they are putting on those roof panels? What do you think? Jack thought not.

Let's see what theory tells us about the effectiveness of foil like this, whether applied correctly or not.

The first little sketch below shows the R value for the roof "sandwich" without any foil at all. We assume the roof temp is 50 C, the room temp is 36 C in each case. The foil-less sandwich delivers an R value of 2.7 altogether, and the estimated temp of the underside of the teak roof is 40 C--much too warm. Moreover, the heat transfer into the room is 28 watts per square meter, or in excess of 500 watts for a room. Not as bad as a simple tin roof, but not what we'd like.

Now suppose wwe add foil. First, we do it badly, the way Jack did it, so the foil is mostly resting its shiny side on the top of the teak. No surprise here, the foil is not very effective, as shown on the third of the little sketches.

Now suppose we do it right, we leave a space of an inch or more beneath the foil. That's the middle sketch. This time the R value is 3.85, a littlle improvment over the no-foil case(R=2.8), bringing down the underside of the roof to 38.5 C. The heat flow drops from 28 watts to about 20 watts -- hardly the "more than 50 percent" claimed by the aluminum salesmen.

What you get from the theory is that the correct spacing would improve things a little, but not much.

One other conclusion here: whether we use foil or not, the fact that we've got a roof "sandwich" has reduced our heat flow from more than 100 watts per square meter (the hot tin or tile roof) by about 75 percent. This eases our ventilation problem a bit, we don't need a howling wind blowing through the room to blow away the heat seepage like we did with the tin roof. As to how much ventilation, we'll develop some guidelines in a future posting.

Conclusion: foil may have it's uses (more on that later) but the way it's used in Thailand does not do very much to improve either ceiling temperatures or heat flow through a roof.

But let's ask this: what constitutes "improvement" anyway?

The simple answer is: "a cooler room below". But what is cool? The answer is "not just air temperature", but also a cooler underside to the roof, because the heat you feel in a room is about fifty percent air temperature and fifty percent radiant temperature, ie the temperature of surrounding surfaces. And as long as you leave the windows open so the place doesn't heat up like an oven, the air temperature will not rise much. But if the ceiling is say 37 or 40 degrees, you are going to wish you were back in misty England or foggy San Francisco, that ceiling will deliver maybe 35 unwanted watts per square meter to your suffering fahlang head.

So how did Jack's roof turn out?

Pretty much as predicted by theory. With outside temps about 32, the interior surfaces got up to a somewhat uncomfortable high 30s, but as long as the windows were open and the breeze was good, the place was bearable, even in the afternoon, or at least not much worse than a shady spot outside where you would have to live with a slightly sweat-inducing 32 C.

Warm but bearable all around. The temperatures shown around the room are temperatures of the wood interior surfaces, which radiate heat
to all objects of lower temperature within the room. Such as Jacks's 34 degree bald head.This accounts for about half of the perceived heat, the rest being related to air temperature, which with good ventilation would reach 32-33 C, as you can see from the floor and shady wall temps.

But here is the big question: what would have been better than foil?

Carrier's Magic Chart

2007-03-10T03:35:00.000-08:00

Air Conditioning engineers trace the decline of US-French relations to the popularity of the chart which was invented by the American patron saint of aircon, Willis H. Carrier. Carrier's so-called psychrometric chart replaced the beloved French Mollier diagram, marking the end of French superiority in science. Sigmund Freud was fascinated by the chart, which he mistakenly thought quantified the human psyche (misreading psychrometrics as psychometrics). However, after discovering his mistake he thought it soounded like a good idea anyway, and went on to develop his concepts wherein he substituted libidinous pressures (The "Id") for vapor pressures.

For those readers who are seeking a little more rigorous discussion of Bangkok weather, I am taking a break from roofs and such to put the recent weather, which we see here as red and green points, in the context of the Carrier chart (basics of which you can look up in Wikipedia if you are really curious).

What I do here is trace the natural history of a cubic meter of Bangkok air which you might find around, say, Benjasiri Park at 6 am when folks are out there doing Tai-Chi and aerobics. The moisture, temperature, dew point, and enthalpy of the air at 6 am is shown as the starting point of the day's oddyssey. The wet bulb temp, ie the temperature of all those dewy flowers across the street at Villa supermarket, is about 24 C, and the enthalpy (ie energy) is a little over 70 KJ per cubic meter. With a relative humidity of about 80 percent, those joggers are going to start to sweat pretty quickly.

It always struck me as curious that the Bangkok air does not change its energy content much over the day, by afternoon it's a lot hotter but a little drier so energy is much the same. But look what happens to that air if it is lucky enough to get sucked up in the Emporium air con engines which blast off at about 10 am. This air will be cooled down to its saturation point (ie the dew point) and then with further cooling dump about half of it's moisture, so that the nice icy feeling you get when you go into the mall is your own dear sweat getting sucked up by this dry hungry air. It's not the air that's so cold, it's your own vaporizing sweat!

We can look ahead with delicious dread at the daily cycle at the peak of the hot season in early May, shown in red away up on the diagram. For all those Buddhists out there, lots more suffering to come!

The colored zones on the chart are so-called comfort zones, green where everyone is happy, yellow where some fahlng experts say folks in "undeveloped" tropical countries should be happy (so they don't use so much of that fuel meant to fire up big SUVs). Everyone is unhappy in the red zone.

Nice going, Emporium, I think we'll all go shopping!

Solar-heated concrete roofs

2007-03-10T03:14:00.000-08:00

Now we noted and you might recall that those big churches in Spain or Mexico are pretty cool inside and imagine that thick masonry walls or roof would do the trick of keeping you cool in your house. So let's exchange the thin hot roof (metal or cement tile) which we discussed last time for a nice typical 4 inch concrete roof slab. What happens?

Not only does the 4 inch concrete not slow the heat penetration down much (R= about 0.5 which is still a long way from the 10 or so we would like*) but the heavy concrete stores much of the afternoon heat about (10 kilowatt hours for a 25 square meter room), then releases it back into your room in the evening until 9 or 10 o'clock. This is not the time when you want a lot of heat!

And if you deal with this by turning on an overhead fan, you just accelerate the rate of heat transfer from the warm underside of the roof to the lower part of the room--and yourself. Sure, you can turn on an air conditioner, but what kind of "green" living is that? First you go and use solar heating to store unwanted heat in your concrete roof, now you use fossil fuel to suck it into the room, pump it back out in the form of vaporized refrigerant gas, then blow it on your neighbors, just like that hi-so Italian restaurant does on Soi 23, blowing hot air from its battleship array of compressors on lowly pedestrians.

Increase global warming! What a waste!

But wait. Why do thick walls work for those cool churches?

First, the walls are truly massive, maybe several of feet thick, so the heat takes a long time to penetrate (just as the ground deeper than a few feet is not heated much by the day's sun). Second, the dry desert regions have night sky radiant temperatures that are very low, maybe even below freezing, and whatever heat collects in the masonry bleeds back out to the outside sky at night, not into the church. Solar heating is offset by effective nocturnal cooling. But in the humid tropics the night sky temperature drops to only only 15-20 degrees. So there may be a little bit of night cooling (maybe 50 watts per square meter), but not enough to offset the effect of strong daytime heating (which is closer to 500 watts per square meter).

So if you are unforunate enough to be living in the top floor of a house or an apartment I have a two ideas that I think are better than blowing your budget on ai rconditoners that (like most in Bangkok) mainly cool solar-heated concrete.

First, you can create what I call an "artificial tree," which is almost as good as a real shade tree over the roof ( which would be the best of all solutions to the problem). I first noticed this technique at fish markets on the Mekong River in Laos, where the market folk created shade nets made from the plastic netting sold for use to cover plant nurseries. The netting, usually either green or black-- both seem work as well-- is suspended like a Berber tent a meter ot two above the roof, absorbs most of the solar heat and allows it to dissipate away into the air, so that the netting material itself (amazingly) doesn't get very warm. Two layers work better than one, but you don't want to use an unperforated fabric or plastic or canvas cover, because this will immediately heat up to 50 C or more and radiate this too the roof, just as bad as the dreaded tin roof we discussed yesterday. This all requires some effort because suspending a net big enough to cover several rooms requires some support structure. I did it at both his top floor apartment and a top floor office, each 150 square meters area, at a cost of about 6000 baht each for installation. The comfort level was immediately improved, and much cooling money saved (though some air conditioning was still necessary to reduce humidity). In both cases the results were worth the effort.

Second, you can paint the surface of the roof bright white to reflect half or more of the solar radiation back into the sky. This is what governement energy folks in both Australia and Florida have been recommending for years, and several readers brought up this idea in my last entry. I have not tried this but it makes sense and the improvements are well documented. There are special paints for this, they appear to be more effective than ordinary white paint.

But what about a new house that aims to have a bit of architectural style? Nets and white paint?

Neither of these approaches may be acceptable on esthetic grounds. A white roof would look wrong, and be an annoyance to neighbors as well--they don't want our glare and heat. And a traditionalThai house covered by a black net?

I don't think Jim Thompson's ghost would stand for it.

So another approach is required here: insulation . We'll get into that, and all the ways you go wrong with it too, next time.

----------------------------

Just for handy reference, here are the R values, English units (Btu/hr/sq ft/deg F) for the common building materials in roofs and walls:

concrete 0.1 (per inch thickess)

wood 1 (per inch thickess)

foam 7 (per inch thickess)

material/air interface 0.6 (still air)

material/air interface 0.2 (15 mph breeze)

to figure heat transmission you can use the following:

Watts/square meter=5.6*(temp difference C) /R

So a 4 inch concrete slab is

R=4*.1+0.2=0.6,

and heat transmission for say a temp drop across the slab of 50 to 30 deg is

Watts/square meter=5.6*(50-30)/0.6=200 watts.

Which is A LOT!

Tropical Cool: Hot roof unmitigated

2007-03-09T20:32:00.000-08:00

Yesterday we looked at hot tin roofs, today we will see some ways folks try to reduce the heat from same.

First, just to show that I'm not joking about hot roofs, I just took the temp of a piece of roofing which has been sitting in the mild morning sun with a nice cooling breeze for a while. Almost 50 C, as you can see. And guess what, when I check the temperature under the tile, it is within a tenth of a degree of the top temperature. This afternoon the reading will be more than 60 C. (Night time is a different story, and an improtant one from the standpoint of human comfort, but more on that subject later.)

If you were sitting under this roof, and had no hair, you would be suffering, even if the air in the room were cooled, as by an air conditioner or by strong ventilation. This is because the 50 degree underside of the roof radiates about 100 watts per square meter on objects below, regardleess of the air temperature in the room. If the iar temp is say 30, you will feel 40 on your head.

If there is not strong ventilation the air will quickly heat, as much as 5 degrees in a few minutes, and you will suffer from high air temperature as well. With no ventilation you could easily die. (Remember the sorry case of the prisoners loaded into hot trucks?)

But what you can do, is try to get rid of that heat -- 100 watts per square meter over a 5 meter square room is 2500 watts -- but to do this by ventilation you will need about 60 air changes per hour in the room, a change every minute. The requires a pretty good wind moving through the room (or attic). And if there is no wind outside, or you don't have huge openings, and if you don't dela with the radiant heat as well, you are still mighty uncomfortable. (I know, everyone raises their hand and wants to talk wind turbines and fans, but that's for next time.)

Ah, but hasn't the building industry come up with a magic solution, aluminum foil?

Hot Tin Roof

2007-03-07T22:02:00.000-08:00

My responsibility here being to show you how to beat the heat in Bangkok, and having displayed a bit of information on the annual weather cycle, I plan now to talk a bit about how the buildings we live in repsond to the weather, particularly how they respond the dreaded sun.

I claim that of the principal elements of foreigner felicity in Thailand is the achievment of thermal comfort. One of the principal enemies of thermal comfort is a hot roof.

Why?

Because our comfort in what Jack calls the sub sweat stage is sometimes determined more by the radiant temperature around us than by the temperature of the air. Thus, if the air temperature is a pleasant 27 C (80 F) and the wall or roof temperature is 39 C (ie 102 F) which it often is in these parts, we are going to "feel" as if the temperature is in the nineties (ie aboout 33 C) Since this is virtually the same as our skin temperature, we cannot dump any of our body heat into our surroundings, and that is not pleasant and we will soon enter the sweating stage, which is our body response to inadequate cooling by convection*.

If the underside of our thin metal or cement tile corrugated roof is say 43 C (110 F), which is typical midday, we are going to miserable no matter how cool the air is.

The reason the underside of the roof gets hot is that the outside of the roof on a sunny or partly cloudy day in bangkok is typically 45 C, and that heat is easily transmitted through the thin conductive material (R is only say .05, vs the 10 or more that is desirable for a roof). Because the layer of air against the bottom of the roof is a fair insulator, say R= 2 to 5, most of the temperature drop is going to be in the air, not the thin roof, so the radiant temperature of the underside is going to be almost as high as the outside temperature. A temperature of 45 degrees, by the way, is enough to cause medical-class burns to the skin.

And this, remarkably, is the usual state of Thai buildings, especially in the countryside. And if you ask the Thai about this, they will act as if the problem never occurred to them, they don't pay any notice to it, or who knows what they think or feel, I have been unable to get a clear answer to that question. It must be like asking an Eskimo whether he objects to the color white, it's so ordinary it's just a little outside the range of notice, maybe like asking a person how they feel about nitrogen.

But we, as rational heat-sensitive westerners, feel compelled to take action to increase our thermal happiness. So what can we do about this problem?

--------------------
*Convective heat loss (body to air) for typical conditions is about 8 watts per square meter per degree difference temperature (Centigrade). Hence, a half naked fellow, with an exposed skin area of about one square meter and a skin temperature of 34 deg, will convect about 32 watts of heat into surroundings that have a warmish 30 degree temperature (8*(34-30)=32). This is not enough because his body is producing about 50 watts of heat even when he is quietly gazing at his Thai girlfriend. (We are assuming here that radiant surroundings, walls and ceiling and suchlike, are at body temp, so there is no loss by radiation. If he were say praying in a Mexican cathedral with cool walls at say 25 degrees, he would lose an additional 40 or so watts by radiation.) So a bit of what my mother used to call "stickiness" will develop, maybe even a bead or two of perspiration. Perspiration will supercharge the heat loss, depending on how hot and humid it is, and whter a breeze blows. More on this advanced but very important topic of evaporative heat loss later.)

But the Thai lady will almost always have a lower body weight to skin area ratio, less heat-producing kilos of meat per square meter of skinny arms and legs, therefore she doesn't need to dump 50 watts of heat per square meter, maybe only 25 or so, so she will not be sweating but thinking "fahlang get too hot here in Thailand."

Commetrs
Timothy Pellissier 25/04/2007 09:59 IP: 58.9.39.243

Hey all you comedians... Cut the crap and add some usefull information on creating sustainable comfort in the Thai home: like materials, methods, sources of materials, costs, and results. I'm on my way to HomePro to see what I can find for myself.
________________________________________

Ian 08/03/2007 10:33 IP: 124.121.71.46

Ggrass, thanks for the info, who sells it? Do you think it might be an idea to start a blog just to exchange info like this, where things can be bought which are not normal to Thailand? I am sure many newcomers struggle to find the things they need to make life here more comfortable. A simple example is it took me 3 months to track down an importer of my favourite cigar:-) Incidentally "staycool" and other loft/roof type insulation is on sale at Homepro, which is also where I managed to buy a RCCB (residual current circuit breaker), ELCBs which are the norm here are actually illegal in the UK:-)
________________________________________

GGrass 08/03/2007 10:10 IP: 203.113.15.234

bagger (it's pronounced baYer) cool paint <-- the new innovative paint that's currently on advertisements. it's supposed to contain some ceramic stuff, that reflects sun's heat upto 90% or something like that. they say it's the technology used in space-shuttles. ________________________________________

Ian 07/03/2007 19:01 IP: 124.121.72.124 Ron, my neighbours complained of dazzle when I painted th e walls white, however they shut up when I pointed out they never ventured outside until after sunset. The white paint you mention is I suspect the same or similar to the paint used for reflective street signs and marking, it contains microspheres of glass. Regarding your Thai lady and sweating, apart from when in the shade her brown skin is a better radiator, if you examine her skin carefully you will find she has less sweat glands per square cm than you do:-) ________________________________________

Ron Swelters 07/03/2007 18:23 IP: 58.8.69.43 In regard to the white paint, there is a special heat reflective kind that is even better than normal white (your eyes can't tell the difference.) The Australians promote this solution, reflects maybe 25 percent more of the sun's heat. But your neighbors might not like it, if that matters to you. We will compare some other solutions son. Thanks for the other excellent ideas. ________________________________________

Ian 07/03/2007 16:51 IP: 124.121.74.247 energy watch, 15% of body heat is lost through the head, yet your genitals which are much smaller lose 10% of body heat, this is why you should wear very loose briefs or better none when at home. If you are outside and want to cool fast wet your wrists as the blood vessels are closest to the surface here. Diet is another factor in keeping cool, have a word with a local Chinese about "heating and cooling" foods. ________________________________________

EnergyWatch 07/03/2007 16:29 IP: 58.136.227.174 Ron Swelters>>>> Your body is like 4000 cc jaguar but your wife is 1300 cc corollar. When you both sit in the tin-roofed room (idle condition) your jaguar engine consume more gasoline to keep it idle than her idle condition. Heat has speed. If the gap between your body and room temperature is more, your body lose more heat at more speed. In this theory, I may advise you, that, take a bath to make your body wet, then lie on the tile floor with fan, your body heat runs out quickly. The tile is a secret how Thais cool their body. Tile conduct heat very fast, here from your boiling body to tile floor. Baked Tile is good conductor of heat. >>>> If you can 'hole' in the roof, the air is afloat and leak over as hot air always flows up. I put roof 'natural fan' that pump out the 'under roof hot air insulation, and keep the room in natural ventilation, of course wet my body and lie on clean tile floor in only brief, under standing fan (absolutely not ceiling fan !) and tease my wife,,, Cool !,,,,HaHaHa !
________________________________________

n 07/03/2007 15:04 IP: 124.121.71.98

I yesterday asked one of my local builders to paint my roof white, he was horrified:-) He produced many reasons against this, the paint would only last a year, the accepted colours are red, blue, green or cement, paint is expensive and would not survive the rain. I pointed out that my walls were white using an exterior grade cement paint, he said that ok as they vertical so not get wet! I said I want the same paint on my roof, he said no way much too expensive. I said 700 Baht for 10 litres not expensive. He said have to paint every year, I said if so it will be worth it. I think I will have to paint it myself, you cannot alter the way a Thai thinks.
________________________________________

Ron Swelters 07/03/2007 14:30 IP: 61.90.146.66

Why sure, steal whatever you want. Is being under your ass better than being under the dust that is under your shoes? I'm new to Thailand.
________________________________________

EnergyWatch 07/03/2007 14:13 IP: 58.136.227.249

Ronswelters !

Can I steal your 'scatch under tin'. I am your neighbor. You are under my ass.
________________________________________

Tropical Cool: How was it for you?

2007-03-06T19:58:00.000-08:00

Well for me it wasn't too bad, , the first part of the year, I think I'm getting used to the heat and humidity a little. But they say that this year is going to be a bad one. The question is, how much worse is it going to get?

I took the worst year I could find, the big El Nino year of 1983, when the Pacific practically started boiling. (You saw that sequence of years in my last posting, years 1982-1985). Then I superimposed the daily high temperature and dew point for the Asoke station* right down the road from where I am now writing this. The 83 data are in white, the 2007 data, right up to this morning, are in red and green.

What you can see here is how it began to warm up in January, then took a refreshing little dive in the beginning of February, now it's back on track again, with even the Thai beginning to comment a little on how hot it is, and now it's heading for the big peak usually around mid to late April or even May. The graph suggests it may be a little cooler than 1983, but the 83 data are from Don Muang, not downtown, it may be a little hotter up there with all those hot (but uncracked) taxiways. But the dew point -- I will argue later that dew point is probably a better all-round indicator of thermal discomfort -- looks about the same this year as 83.

AND, by the way, the weather the last few days has been almost exactly the same as the weather in Boston, last year in July, (2006), the dreaded heat wave of '06 (see my first posting), when the streets were deserted and water was being passed out and they made one hundered fifty thousand phone calls to warn people that it was hot!

Stay tuned!

First night , tropical paradise

2007-01-10T02:49:00.000-08:00

It was California summer when I arrived in Bangkok, the Thai Airways flight gets in late and when I stepped out into the Asian night I expected a blast of tropical heat and was a little disappointed, it was cool and cloudy and I couldn't figure what the big fuss was about, Jack paying me to come over here to save him and his marriage from the dreaded climate. In fact it seemed a lot nicer than my place inHollywood, my little apartment on the top floor of an old LA style wood apartment that heated up like an oven in the middle of the afternoon with the sun blasting down on the tar roof, it was miserable well into the evening when the coastal fog finally moved in. West Coast marine, they called that climate, I remembered that from my junior high geography class.

He and Dah couldn't meet me, they had to go to a funeral in her village but they set me up with a room in this middlebrow hotel, the Taipan, on Soi 23 in this lively neighborhood. Everyone seemed pretty nice at the desk, the girls smiling all the time, Even with some old geezers walking in to the hotel with some surprising looking ladiies. I started walking around the streets around midnight and these girls sitting at bars said Welcome and I saw these massage places where they actually publically advertised on big signs with flashing lights that teen girls would rub your testicles with gel, I couldn't quite believe that, but a guy in a place called the Ship Inn told me that the place was full of Japanese and they went for that kind of thing.

Back at the hotel I couldn't sleep for the jet lag and I started to fool around with some ideas, why my Hollywood place got so hot and so forth, and where I was now in the big picture, down at latitude 13 instead of up around 40 or so in California.

I had found it almost impossible to meet women in Hollywood, no one was interested in a broken down MIT guy there. This seemed like a different world. I fell asleep thinking of Boston Hollywood Bangkok, Boston Hollywood Bangkok. I has a dream of the Puritan days back in Boston, where they hanged a woman, Anne Dyer was her name, because she talked too much about the Quaker religion.

Bangkok looked like a different kind of venue, I wondered what the Puritans would think of this place.

Greasy black dust

2007-01-07T21:44:00.000-08:00

Saturday morning inspection

Greasy black dust.

What is the catalogue number for this annoyance in Bangkok's registry of invasions, threats and assorted hazards? All those things that are going to make it impossble to live in an old wood Thai house?

No question, after a few weeks of neglect there is a black film on everything.

But lets not get hysterical here! Jack pops open a Singh, lights a cigar, and meditates on World War Two years in Boston, USA, when he used to visit his grandmothers old house in the city. Wasn't everything covered with soot, including the snow? They burned coal. Not an unpleasant smell (it comes back to Jack when he has another beer and concentrates on it).

But dirty nonetheless.

Herald Tribune has an article about pollution in Asian cities.

Better Bangkok than Beijing

Wait a minute, Bangkok doesn't look so bad! Not any worse than LA or Chicago.

For more on Bangkok air:
http://www.aqnis.pcd.go.th/news/health_effects.html

Coldest day in bangkok, 2007?

2007-01-03T20:55:00.000-08:00

Up this morning at dawn, one of the coldest days of the year here in Bangkok, no fan last night and a quilty cover needed for warmth. How luxurious to be cold! At 5:48 it's two minutes before nautical twilight and the first prayer cries form the mosque half a mile away float scratchily through the dawn air and are picked up by a not unpleasing wave of dog howlings. One of these mornings I must make a catalog of "dawn sounds from Bangkok", add them to this blog. I make a few myself, throwing latches and carefully working my way out on to the deck so I don't stumble on the many levels we've built into this house, then climbing shakily up on a chair to measure the roof temperature.

One of the first steps in engineering a solution to Bangkok's heat problem is to make an inventory of possible heat sinks, cool places to which unwanted heat might be transferred. For example: practitioners of alternative thermal climate control in temperate regions of the world usually think of a presumably cooler underground where the temperature is likely to hover at somewhere near the mean annual temperature in that region. For example, a considerable quantity of 98 degree air can be cooled to a pleasant 75 degrees if a source of 60 degree heat sink is conveniently available. A cubic meter of earth at a depth of three meters , where the ground temperature will be, in say northern Europe, about 15C (60F), will pull the required 22 degrees of summer heat from a houseful of august air. Alas at the latitude of Bangkok, with a mean annual temperature of about 28, relatively cold earth is not found at any depth; in fact, the earth begins to warm to about 30 degrees fifty meters down. (In fact a recent analysis of subsurface temperatures beneath BKK indicate a 1.7 C increase in earth temperatures during the past fifty years in the inner city due apparently to urban heat island effects, over and above global warming effects). Annual variation in subsurface temperature at a depth of 3 meters is only one degree or so.

So we can forget about earth cooling, we've got to find some other cool place.

Here is my measuring instrument, about fifty bucks form Radio Shack.

You can see here that the roof temperature which I took yesterday in a test run is 20 degrees, the sky temperature -2 degrees.

But this morning I measure as follows:

Roof temperature: 16 degrees C
Air temperature: 20 degrees C

But how can this be? This is the same question I used to ask myself about the frost on the pumpkin. How can the frosty pumpkin be colder than the air, which is above freezing temperature?

Here is he answer: when I turn the thermometer upward to the sky the temperature reads -7 degrees.

Sky temperature: -7 deg C!!!

In other words, here at latitude 13 the sky is seven degrees below zero, more or less the same temperature of the air today in Wisconsin where

The bitter frostes, with the sleet and reyn,
Destroyed hath the grene in every yerd;

So the sky is very cold, even here in tropical Bangkok, and this -- in spite of the warmth of the air-- is sucking heat out of the roof to the extent that the temperature is supressed 4 degrees below air temperature. Can I use this to my advantage when the dreaded hot season arrives three months from now?

A long way from home

2007-01-01T21:44:00.000-08:00

I grew up in New England.

The summers, especially the "Dog Days of August" were sultry; the fall was crisp and delicious, and then the "frost was on the pumpkin" and the rains came and then the howling "Nor' Easter" storms that closed all schools, we heard the good news on the radio in the morning. Serious businessmen like my father trekked through the drifts to work anyway, never missed a day.

Boston as always thought the best of itself and everyone said that the vigorating seasons were what made people alert and industrious, compared, for example, to Mexico, where everyone slept away the day, and Havana, God knows what they did down there. But then you'd think about that, whatever they did do down there, maybe it wouldn't be so bad after all, the warm wind on the Malecon and the bar lights twinkling and one night when I finally went there to see what was going on I went into one the bars and there was a juke box playing Nat King Cole and a couple of girls sitting at the bar and...well that's another story. The funny thing is, my father, the serious businessman, once had a Cuban girlfriend. But this was the tropics, people ran away to places like that, it was hot and sticky and sweating far into the night, the weather just did things to you. Made you irresponsible.

But getting back to Boston, as soon as the days that my mother called the "dog days of August" were over, bright and sparkling September came along and I walked to school kicking the yellow and orange maple leaves. I loved that weather, the smell of those leaves burning in the fall. Halloween was just around the corner, and then soon enough the "frost would be on the pumpkin."

But all of that was half century ago at latitude 42, and aside from my nightly film festival of dreams of those sparkling times and those Kodachrome neighborhoods, my days now, and probably all my future days, will be at a very different latitude, latitude 13. Think Djibouti, or Cape Verde, or the Marshall Islands, or who knows where in Africa.

Now I live a long way from home.

Think heat.

Think humidity.

Or think Bangkok, Thailand, where I am writing this entry, waiting for the sun to go down, then I'm going out into this traffic you see here, and do some things I'll discuss later in this blog.

************************************************

Last year the makers of "Old Spice" deodorant for men published the results of a study of the "sweat rankings" of American cities. The winner was Phoenix Arizona but Texas cities like Dallas and Houston and several Florida cities were right up there and since I've always had a bad memory of Houston I'm going to use that place as a kind of bench mark, to compare Boston and Bangkok.

Take a look at the "march of temperature" through the seasons in three cities: Boston, which had a famous heat wave the first few days in August, 2006 (pink circle), a hundred thirty six people died including one woman sitting inthe bleachers at Fenway Park; Houston, which as I said seemed to me to be really awful, and Bangkok, awfuller yet. The red points are the highest temperature of the day, the green the highest dew point temperature of the day (more on that later). When the temperture is more than 30, you will begin to sweat, even if you are just sitting looking at this blog.

As you can see, that's most afternoons in Bangkok (the daily high is usually at about three o'clock).

You might say that Boston heat wave got up as high as Bangkok, but even thoughthey were passing out cold water on the half deserted Boston streets you could still sweat pretty effectively there because the dew point temperature was low, down around 24. In Bangkok, in contrast, the dew point hardly gets below 26 most of the year, so all that sweat just soaks your shirt and hardly cools a body at all.

Black hole

2007-01-01T21:42:00.000-08:00

The "Black Hole" mosquito trap that attracted so much of Dah's mirth ("What you pay for that thing?") turned out to be a fine thing after all.

Jack's morning job was to empty the trap, which had hummed away the night on the floor of the bedroom. He was very Buddhist about it, sealing and placing the trap outside on the deck. Many of the mosquitos seemed to expire or go to sleep on the floor of the trap, with their feet sticking up. The several selected by destiny or will continued to fly around the trap batting themselves against the screen walls. When the number of "actives" had fallen to a countable number Jack opened the trap. The actives flew away (Dah suspected back to the bedroom) and the rest Jack dumped onto the deck for a count (some of these had been bluffing and flew away too.)

Jack made a graph of the count, combined with some weather data.

Question: What is the cause of the dramatic increase in January?