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

Fire up the Netatmo, the heat is coming!

Weather unsettled of late, Bangkok breaking free of the cool northerly breezes and succumbing to the steady southern winds off the steamy Gulf of Thailand (once known as the Gulf of Siam). A bit of rain of late.


Thai wife turns on the aircon last night. Muttering on the streets of hot weather. Must fire up Netatmo and buy another module for the coming heat. 


If this usually reliable guy is right, could be an interesting year.