Complex thermal comfort data needs colorful solutions!

Operating a bedroom air conditioner to get the best comfort at the least cost is a lot more complicated and non-intuitive than most of us (including me) have imagined. Netatmo plus the visual SQL display tools from Tableau are the only way to really understand what is going on here in this "simple" display of thermal comfort data in a single night in steamy Bangkok March 2017 which we will examine in more detail later.

We thought that keeping the bedroom door closed to "keep the heat out" and "not waste electricity" was the best policy but the data here suggest otherwise!

Truly, the delight is in the detail!

Bangkok destined to be unliveable? Ominous trend from Netatmo

I am neither a "warmist" or a "denier" as they call those who are inclined to a group ideological approach to the subject of global warming. And I know from paleoclimatic studies that global changes occur naturally and plausibly via contemporary and excess human energy use. But I find reason for worry with the data shown here. Notice the daily high temperatures for the hot season (April and May) do not seem to have increased much if at all over the past 60 years of record from the Don Muang airport. But I have never thought that daily highs are of great significance. after all, Tucson gets a lot hotter in the day.

But look at daily Bangkok low temperature, usually at or about dawn, over the span of the last sixty years. In contrast to maximum daily hot season temperatures which everyone talks about, daily minima are not much recognized as being of importance, though I claim that these daily low numbers represent, at least in the tropics, the best index of thermal stress on human and perhaps other life. The coincidence of high dew point temp, surface sea temp in the Gulf of Thailand, and thermal comfort level through the day really determine the level of discomfort and danger, and these indices follow closely the daily Tmin during the hot season (April and May) in Bangkok. We see here a marked trend for hot season Tmin (only April and May data shown here) with values rarely exceeding 26-27 back in the fifties, but now commonly at 30 or more. Big difference!

As I write, Bangkok residents, Thai and non-Thai, have found conditions barely tolerable in the past few weeks of early May, 2016, many people remarking that it has been "the worst ever". Those of us who have lived through it would not disagree with my claim, backed by theory and experience,  that a daily morning min of about 35 degrees would be intolerable to human life without some kind of air conditioning. So our thinning margin of safety might be said to be half of what it was when I first came to Thailand in the 1960s.

But we should not rush to claim that this is due mostly to greenhouse gasses. Temperatures here and many places are airport temps, and airports have progressively become embedded in hundreds of square miles of mostly concrete, creating the well-understood effect of urban heating. The other morning, with 7 am temps of the pavement of 34 degrees in my neighborhood on Thonglor, you might say we were already having a local doomsday, though the minimum official airport temp for that day did not exceed 31.

How to distinguish between heating from urbanization and from global warming? I think I see away to do that and will make a project of it.

Temporary heat blips from direct sun

You probably don't want to place your Netatmo outdoor module where it will get direct sun. This yellow anomaly below is caused by direct morning sun for and hour or two on the outdoor module, and probably to a lesser degree from heating of the dark brown soil on which the module is set in this case. 



Poor location! Better put the module out of the sun and on a less heat absorbing surface.

Radiant heat: invisible but deadly

On a warm afternoon with full sun a 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 your 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 reduction in heat transmission through thin roofs (steel, cement tile, etc) if they have 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. But I can say from my own experience that there are many qualifications to this supposed effectiveness of thin foil, more specifically that bubble-backed foil that comes in rolls, to be discussed later with a real example.

Hot Season brings miserable hot wet wind from the sea

Much like the Texas Gulf, onshore hot season wind smothers Bangkok with heat and humidity. Even at the coolest time of the day the saturated air from the gulf to the south is close to 29C (surface sea temp, red), so sweat at body temperature will provide little cooling.

Old time hot days in Boston

From the free download chapter

We are much inclined to think that air conditioning is a necessity, but I have to wonder these days whether this and much of the other technology said to be so wonderful is really important at all. I think of the days old people in Boston used to call scorchers, though my mother preferred the ancient term dog days. On those canicules my grandmother would take me on the streetcar from her walk-up South Huntington Avenue apartment in Jamaica Plain downtown to the Boston Common. I still enjoy looking at the details in this photo, the necktie, the newspaper. Was this man a bum? An unemployed veteran? If so, he made an effort to dress properly. Or was he just a lower paid adjuster from one of the insurance companies that dominated the skyline, lacking in those days even the first John Hancock building behind the Boston Common? 

My Thai wife in her bedroom not minding 29 C (84F)

Generally I have not put much credibility on theories of racial differences for thermal comfort. My Thai wife's comments, sweat thresholds, and complaints are very close to my own. But as the hot season closes this year in I notice that I am turning on the aircon every night when the temp hits about 29 C (84F). She is not. Be interesting to see when she does.

My Netatmo readying for the coming blast of heat

With seriously high temperatures last week forcing me to turn on the aircon for sleeping, I ready my Netatmo system for the expected record blast of heat next month.

Hot season relentlessly moving in. New records for Bangkok?

@Netatmo @dickmeehan Checking out my Netatmo gear for the coming heat. Perfect performance to date, looking forward to recording rich data in and outside my Bangkok condo tropicalcool.com