Physics Behind the Indoor Chills

Today's weather: High = 2 Low = -3
Chilly and hopeless

First off the bad news, the ongoing chills are going to remain for all of January. As the forecasters predicted way back in summer time, they warned that South China would again be facing this kind of a winter. At the time, that was adding insult to injury, as they had just recovered from the most severe summer flood season on record. As summer turned into fall, we got lucky with a great November and early December, but now the seemingly hopeless cold weather winter forecast has come true. Latest news reports, for example, show ice storms in the deep south (Guangxi province) and damaged crops.

The good news is that in two weeks time I'll be on a flight to Thailand and away from all this. It's just a matter of waiting it out.

For a Canadian like me, this would seem like child's play, but every year the same problem happens time after time. Indoor chills due to shitty building construction, end-of-semester work stress, and students / teachers alike dropping like flies from illness. As any seasoned teacher would agree in China, the short period between Western New Year and Chinese New year is an extremely miserable period of time. But the good news: things do recover nicely after that.

After hearing and vocing the same complaints year-after-year about the cold weather and the supposed reasons for it, I figured it was high time to get to the bottom of this and research the Physics for why it feels so damn cold indoors here, and, in some cases -- it's actually warmer outside.

It boils down to two factors: very low specific heat of concrete, and very low indoor humidity.

Specific heat basically means the capacity of a material to "hold" heat, or retain it. Water and air have high specific heats, as they can hold the heat well, and act as good insulators. Materials like concrete with a low specific heat cannot hold the heat.

During the hot summer day, the concrete blasts out the heat into the air and warms the air (which does retain heat well), making the air temperature very uncomfortable. In the winter time, the concrete sucks the heat out of the air, and so the air gets cold and it takes a lot of work to re-heat the air (if any success at all)

Regarding the humidity, we all know that hot air plus water vapor acts to make the air feel hotter in summer. But in winter, everyone says that the cold + humid air feels colder. That supposedly explains why places like Shanghai and Wuhan feel bone-chilly and you can never really warm up. This is somewhat true, but I stumbled on a more complete explanation this morning by accident.

While rushing to work, I jumped out of the shower and my hair wasn't completely dry. As I rode my bicycle, I felt like my head was submerged in an ice block. Then it made sense: the evaporating water from my head caused the body to feel much colder, basically the same effect as when we sweat.

On cold humid days, the humidity in the air makes contact with the skin and quickly evaporates, thus causing the chills. It's a never-ending process of torture.

Meanwhile, this same parcel of air is then de-humidified as it is brought into the house and becomes even colder due to the concrete walls. The chilly air inside the house is basically due to low humidity, not high humidity.

So the solution to Part I of the problem is rather simple: find a way to humidify the inside air as well as heat it. I'm going to experiment by purchasing some humidifiers on the weekend at the supermarket, and then combine that with the warm air-con heater.

Solving the other part is nowhere near as simple. The concrete buildings are basically a heat sink, and there is no getting around that. Unless there is a way to insulate the walls or the floor, among other things, the energy is more or less wasted. The only viable solution is to close off a particular room and try to heat that smaller area up, using the humidifier, a floor heater, an electric blanked, and then count down the days until Thailand.