20100902

Thermal Comfort

One important important environmental criterion to be satisfied is thermal comfort.  Often this would mean indoors, but it could also mean outdoors.  After all, what happens outdoors sort of dictates what happens indoors.

Let's say you own a business, like say Tiendesitas in the Philippines, where you have a big roof over everything (i.e. you provide protection from solar radiation) but you do not have any air-conditioning and use only huge electric fans, do you think customers will be coming back?  It is very humid in the Philippines and under those circumstances, even with fans, the air blowing will feel like hot air because of said humidity.

It is likewise the same here in Japan during summer, but most specially this year when we have had so many days of daytime highs above 35 degrees Celsius, and for more than a month now, the average daytime high is 33 degrees.  It is also very humid, probably even with higher humidity than what I can remember in the Philippines, or at least in Manila.  Humidity is as much a factor as temperature when it comes to thermal comfort.  Air velocity is another.  There are places where they could have very high temperatures but relatively low humidity, so for as long as you are under the shade, it wouldn't feel so hot.  I've experienced this in San Francisco, California, whereby when you step under the sun, it is scorching hot, you feel your skin burning.  But step into the shade of a tall building and immediately you need to wear a sweater or to brave the much cooler air.

Anyway, in the case above, what Tiendesitas did was to not just use any kind of electric fan, but instead they used evaporative coolers which provide less "cool" than air-conditioning systems but use much less energy consumption per square meter of area that needs to be ventilated.  Ventilation (or air movement) after all helps alleviate the effects of humidity on thermal comfort.  Another thing they did was to spray mist using some of their huge electric fans.  The mist - relatively cool water - made it more comfortable there than if there weren't..

Talking about indoors, there is a standard temperature to be met, at least for offices or government institutions, according to the National Building Code of the Philippines (NBCP).  It says that the temperature should be between 23 and 26 degrees Celsius.  I think this is just appropriate.  Coincidentally, it is the law.

Years ago, I worked at a small firm with a small, 40 square meter office.  We had the air-conditioning at around 25 degrees most of the time, but probably had it between 21 and 25 degrees depending on the weather outside.  When some new employees came in, they were less tolerant to even such "standard" temperatures, and so upon encouragement from management to lower costs, we had the temperature at 27 degrees.  The standard-temperature-intolerant employees felt more comfortable.  As for me and some of my other colleagues, it felt quite uncomfortable.  It just didn't feel right for an office setting.  I felt less productive because I had to mind the uneasyness that that temperature setting gave me.  Plus I had to fan myself and so my other hand needed to do other things than just hold on to the mouse and type on the keyboard.

I agreed to have the temperature to 26 degrees, but no, they said it was still too cold for them.  We were all wearing typical Philippine/summer office clothing.  I argued that I can't take off any more clothes (I was already wearing very light clothing), but they can put on a jacket or sweater!

Later on, we were given an electric fan.  It made the 27 degree temperature a little more tolerable.  Anyways, it was during this time that I started looking up the NBCP for temperature standards.  And I came across that 23-26C prescribed range.

Of course, I thought that prescription was based on a US building code or standard, and apparently it is so.  If you look at documents from the Canadian Centre for Occupational Health and Safety, as well as the ASHRAE, they basically say the same thing: 23-26C for conditions where people are wearing light (summer) clothing, and the relative humidity is at 60%.  You can find that information here: http://www.ccohs.ca/oshanswers/phys_agents/thermal_comfort.html#_1_4.

Which brings me to my main point.  The relative humidity right now, during summer here in Japan is probably around 80% or more.  It is likewise so for most days in the Philippines.  But here in Japan, they prescribe that the temperature should be at 28C indoors!  It is very uncomfortable.  I don't think it is right as well, because people would have to get used to the hot weather, but just 6 months later the temperature drops down by 25 degrees.  Then people have to adjust again to the cold weather.  Or maybe it is just me, being from a tropical country where the temperature ranges only from 23-35 degrees, year round, versus 0-35 degrees here.  Maybe that 28C "standard" temperature is tolerable by people here; i.e. they can easily adjust to when the temperature is 0 degrees upto when the temperature is 40 degrees.

I would appreciate if anyone can point me to the basis for such a 28C "standard" temperature here in Japan.  Hopefully, it is a very logical and rational one.

2 comments:

Michelle said...

Your article intrigued me because I believe that thermal comfort is very relative. But going into it a bit deeper - I'm sure there is a technical basis to it as well. I am based in Boston and with the extreme changes in weather here from winter to summer can really be mind boggling for someone who comes from a tropical country as well. It is difficult to get used to it. And I find that every person has a different tolerance to temperature - or thermal comfort levels. So I searched online and found this information on Wikipedia: http://en.wikipedia.org/wiki/Thermal_comfort
It mentions a few factors for Thermal Comfort that are quite interesting including "Thermal Sensitivity of Individuals" to "Gender Differences". I'm sorry though that I have no answer to your last question about the 28C standard in Japan.

Ronjie Aquino said...

Thanks for reading and commenting.

I agree with you, thermal comfort is very relative. My current department also has a group that has conducted research showing a little bit of that tendency to be relative. Aside from temperature, as I mentioned, there are other factors that affect thermal comfort: humidity and air velocity, and as you pointed out, individual tolerance levels.

Here's an interesting read: http://goo.gl/ERiFN

Apparently, there is no technical or social basis for the 28 degree minimum air-conditioning temperature during summer here. Apparently, it's purely for... environmental? political? or (forward-looking) economic? reasons.

Even Japanese people themselves feel comfortable at 25 degrees and feel 28 degrees is too high. Basically, the Japanese government wants to drastically cut its GHG emissions. In that sense, setting air-conditioners indoors to 28 degrees (that's 82 degrees Fahrenheit, by the way) during summer, so as to help address climate change is the scientific basis.

I still really think it should not be imposed suddenly. Or if they want to do that, there are other ways. Because there has to be a balance with productivity. Like, it's autumn now (temperature ranging from 7 to 18 degrees) but the temperature indoors is still set to 28 degrees in the office and it's running 24/7 (it's centrally controlled). I think 28 degrees is fine but provide sufficient air movement at least, or dehumidifiers. As it is, I have to spend money to buy an electric fan that I will only use 2 months in a year so that I can be my normal, productive self for that duration, when supposedly the building should have already the proper HVAC system.