AC myths 7: Temperature and humidity for all and sundry

Thursday 15 September 2011, 3.05pm HKT

<< Part 6 << || >> Part 8 >>

(Continued from Part 6)

This is Part 7 of the series and we’ll look at the myth about correct temperature vs. correct humidity.

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Bullshit # 10
Temperature and humidity apply to men and women alike.

Interesting, but wrong — on a level you’d probably not considered before (unless you’ve read Dad’s books on HVAC).

Wear a jumper if you’re cold

In the heated debate about air conditioning, the biggest problem is that women get cold quicker than men. Ladies are cold, gents get hot.

In the home, he (or she) who cries the loudest, wins. In an open office, we need to agree somehow.

I can’t answer for other people, but I find even fat ladies get cold quicker than skinny guys. Some bitches turn up the heat, but mostly they turn up your temper. Maybe it’s the crowd I run with. Your mileage may vary.

There’s almost no research on difference in temperature preferences between men and women.

What’s the correct humidity?

Humidity (or relative humidity) comes under the general heading of thermal comfort. It makes a big impact on our perceptions of temperature and thermal comfort.

The commonly recommended indoor humidity level is 30% to 60% — and that sounds about right.

But nothing’s correct, really. There are no hard statistics on optimal humidity.

If you live in a dryish city like Johannesburg (59% relative humidity generally), then a cold AC can dry out the air quite a bit more than people would have liked and people sometimes become ill because of it.

If you live in a region where temperatures are never likely to go higher than the mid- to high 20s Celsius (high 70s to low 80s Fahrenheit), the AC is an option, not an essential. Instead, you need a standalone dehumidifier, which does the job much more efficiently.

Protip: Just so you know, a standalone dehumidifier creates a lot of heat. Don’t use the AC together with a standalone dehumidifier, otherwise you’re busting your AC and bills.

But if you live in a high-heat, high-humidity region (such as Central America, the Middle East, and the equatorial, tropical and subtropical regions), you couldn’t get enough dehumidifiers and ‘dehum’ ACs to stop yourself from drowning in the wet air.

Okay, I gotcha, you don’t mind perspiration

Humidity in the sense of comfort is about how fast body perspiration evaporates and gives a cooling effect. Our perception of a dry or damp indoor environment comes from relative humidity (an objective fact) and how our body sensors detect humidity (a subjective fact, but a fact no less).

Evaporation requires energy for it to take place. Water evaporating from a body draws heat energy from that body. Which is why we feel cooler coming out of the swimming pool, and also why water in porous earthen pots is found to be cooler than water in non-porous metal vessels.

Relative humidity creates the perception in us of an dry or damp environment. High relative humidity (i.e. high moisture content in the surrounding air) prevents evaporation from taking place. Which is why you and everything else are sopping wet in the rainforest because the high relative humidity there (99% or 100%) just stops any evaporation from happening.

Protip: If you live in a nice, drowningly humid and hot place (as I do), wear home clothes that allow you to perspire. Forget T-shirts — they’re hot and bothering. Wear shirts, preferably a cheapo silk shirt from a stocklot outlet.

Or do what I do — a unisex-looking woman’s silk gown around the house. It’s for comfort, not kinkiness. C’mon, you’re at home! Who’s looking?

Sensors in our bodies are fairly efficient at sensing heat and cold, but crap at detecting relative humidity. Which is why there is so much more subjectivity (and arguments) about humidity preferences.

I’m over the moon when and wherever relative humidity is 50% or anything lower. Others think I’m insane because they think it’s like living in a dehydration chamber. I also like really cold environments, which makes friends think I should live inside a freeze-drying unit. It’s a shame that Hong Kong is so opposite of what I like.

* * *


Insulation is okay for some places, but kinda daft for others.

<< Part 6 << || >> Part 8 >>

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© The Naked Listener’s Weblog, 2011. All images via c4c.

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