Free air conditioning sounds like a deal you can’t pass up. Actually, it requires some up-front costs to install. But after that, there is no cost to run it.

I’m talking about a solar chimney. This is a system that can effectively cool your house if you live in a dry climate. A solar chimney utilizes the physics of warm air rising. The “chimney” is a vertical shaft that rises above the roof. The sunny side of the shaft is glass. The inside of the shaft is painted a dark color. When the sun pours into the shaft, it hits the dark interior surfaces and warms the air in the shaft. The warm air then rises and is allowed to vent out through the top through operable vents.


At the bottom of the shaft is another vent that allows the air in the house to enter the shaft and replace the rising air that is venting out the top. The house air is replaced by outdoor air that comes into the house through an underground piping system. The intake for this air is located on the cooler, shady side of the house. The air travels through underground pipes and is cooled by the earth. Because of the earth’s cooling effect, when the air enters the house, it is cooler than the outdoor air.

This kind of system create a convective flow of air. That is what rising hot air and falling cool air is called. The air flows without any mechanical fan and the air is cooled without any air conditioning compressor. A solar chimney is all natural and all free of electricity.  Your house, air conditioned for free!

For more ideas about Green and Sustainable Design tips, see Bill’s articles on About Home Design