AC myths 6: Metabolism doesn’t count, not really

Thursday 15 September 2011, 2.30pm HKT

<< Part 5 << || >> Part 7 >>

(Continued from Part 5)

In this sixth instalment of the series, we’ll blow the myth about metabolic differences between individuals being relevant to AC settings that people still fall for — unless you’re comparing yourself to a pet animal.

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Bullshit #9
Room temperature should be in the range of 20°C to 26°C to best match human metabolism.

People love clutching at straws.

I happen to know something about metabolism. My first-ever job was a medical laboratory officer at a London hospital, and I quit after seven months because of the criminally poor pay — but that’s for another blogpost.

Mammals, my biology tutor once said, in many respects have a permanent fever. O rly? Mammalian metabolism always produce heat. The human body needs to maintain a constant 37°C (98.6°F). To dissipate the extra heat (generated by metabolism, movement, etc), the surrounding temperature needs to be lower.

FACT: Human body temperature is 37°C (98.6°F). As the ambient temperature rises to our body temperature or more, the less adaptable we become. The reason is that, as temperature rises, the protein molecules in our cells become increasingly denatured, thereby inhibiting our overall ability to produce somatic cells properly.

Sooner or later you’ll run into this kind of longwinded, scientific-sounding explanation (source forgotten):

“How much lower the environmental temperature needs to be for heat dissipation depends on the metabolic rate of each individual. Everybody has a different metabolic rate and these rates fluctuate according to the individual performing certain activities or under certain environmental conditions. Therefore, even people in the same room can feel differences of the same ambient temperature due to their different metabolic rates. That makes it very hard to find an optimal temperature in any given location. Body shape, height, weight, eating and drinking habits, etc, will affect thermal comfort, so generally the temperature for human thermal comfort is between 20°C and 26°C [68°F and 78°F].”

That’s a longwinded way of saying 20°C to 26°C is the temperature range for optimal human thermal comfort because human metabolic rates differ between individuals since each individual senses ambient temperatures differently.

Actually, that’s kind of crap. And coming from an online discussion board, you’ll know the person posting it was showing off.

You could churn out drivel like that only if you’re comparing yourself to a dog or a cat or gecko. Our metabolic rates are not wildly different between individuals — after all, we belong to the same species (although sometimes we must have wondered about that).

FACT: The human body works most comfortably with the least amount of physical stress at temperatures of 19°C to 21°C (66°F to 69°F).

You can check this fact against any university physiology textbook or lab manual.

These must be human beings … like you and me

Although my general appearance might suggest otherwise, I am in fact a highly consistent person in many things. One of my more highly consistent habits is about room temperature — 20°C (68°F) all year round, anywhere in the world, in hot or cold climes, come rain, shine and thunder, summer or winter.

Not only is 20°C something I’ve gotten used to, I’ve also seen with my own eyes (as an employer) that employees tend to work more efficiently at 20°C than at any other temperature.

Some might disagree, but they can go to hell and don’t come back — mainly because I don’t think people who say otherwise have actually taken the effort to check or test things out physically or information-wise, and just talk out of their backsides.

Human thermal comfort being 20°C to 26°C is nonsense and 10 degrees too wide. That’s only the temperature range in which human thermal comfort can tolerate; it’s not the same as actual human thermal comfort.

Now, we could get pretentiously scientific and talk about factors like air velocity, clothing, insulation, gender differences, thermal sensitivity, adjustment mechanisms of individuals, etc, also playing a part in thermal comfort. In the end, comparing human to human, the differences are of small enough scale that they don’t amount to a hill of beans.

FACT: Human metabolism operate within a rather narrow temperature range (± 2 degrees centigrade), otherwise our enzymes (the protein molecules that assist metabolic reactions) will start to become denatured and affect (or even halt) metabolism.

The pseudo-biologists forgot to tell you is this: Our bodies operate optimally when the surrounding temperature is 15 to 17 degrees lower than the body temperature (on the Celsius scale).

Then, our enzymes are more fully subject to internal body temperature (constant anyway) rather than be additionally influenced by high or low surrounding temperatures. At 15 to 17 degrees lower, that means the surrounding temperature has to be in the 3-degree band of 20°C to 22°C (68°F to 71°F). Please learn basic arithmetic, please.

And what coincidence: AC makers use 21/22°C as the preset temperature setting for ACs.

You can stand 20°C to 26°C pretty well and for a long time, but it doesn’t necessarily mean it’s comfortable. Of course, everyone considers comfort differently, but I would argue it’s more a psychological or psychosomatic preference — and nothing to do with metabolism.

But some people just can’t take ‘no’ for answer and argue endlessly. Then go bloody ask NASA for the figures — after all, they got the data from the Nazis, who got theirs from horrendous little experiments on innocent victims.

Like I said before, if 20°C/68°F is too cold, you must be one helluva effing physical wreck. You’re either not eating enough or not getting enough exercise or sex or something. In other words, you’re a dillweed.

* * *


Temperature vs. humidity vs. your propensity to be blindsided

<< Part 5 << || >> Part 7 >>

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© The Naked Listener’s Weblog, 2011.

Images: Right to Own Onion meme via c4c ♦ Guinea pigs on terracotta tiles via Coimbatore.

2 Responses to “AC myths 6: Metabolism doesn’t count, not really”

  1. Ed Hurst said

    I’m enjoying this, so far. I use a different metric entirely, though. I note simply that I enjoy a wide range of ambient temperatures due to my long experience in the military and because I grew up in Alaska. It’s totally subjective. I’ll take long rides in heat waves, and hike in shorts with snow on the ground (until it gets cold enough to crunch under foot).

    Meanwhile, computers are much more sensitive to heat than I, so I keep the computer office in my home as cool as I can. Having a wife in menopause makes this even more urgent.


  2. That’s it – nobody talks about the heat sensitivity of those bloody things (computers, radio, TV, dialysis machines, tape recorders, etc). And what about those nice pictures of ancestors? They just go to crap in the heat and humidity – which is fast happening in my home right now without the AC.


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