Do Thermal Chimneys Work in Cold Climates?

How Thermal Chimneys Work

• Thermal chimneys function because heat rises. Warm air in your home escapes up the thermal chimney and out of vents at the top while keeping windows open on the lowest level of your home brings cooler air into the bottom of your home to help push the hot air out of your home. If the thermal chimney is on the south side of your home, the sun warms the chimney, heating the air inside. The hotter the air becomes, the faster it will rise up the chimney and out of your home.

Best Conditions for Thermal Chimneys

• Thermal chimneys are used in warm, dry areas where the dehumidification of an air conditioner is not needed, but cooling is. If you live in a humid environment, a thermal chimney will not reduce the moisture in the air like an air conditioner. The taller a thermal chimney you have, the more of a cooling effect you can get. Even in a two-story house with a 12-foot thermal chimney you could see up to 9 degrees Fahrenheit drop in temperature, according to "Passive Solar Architecture: Heating, Cooling, Ventilation, Daylighting and More Using Natural Flows."

Why Thermal Chimneys Do Not Work

• Cold weather conditions will cause a home to lose heat if you have a passive thermal chimney. During the winter, the thermal chimneys will continue to work as they did during the summer, drawing warm air up and expelling it through the vents and out of the house. Closing off the vents will stop the heat from leaving the house, but it will remain at the top of the thermal chimney until it cools and sinks again. You will need to make seasonal adjustments to your thermal chimney if you want to use it in a cold climate.

Making a Thermal Chimney Work in the Winter

• Add a fan to the top of the thermal chimney to make it useful all year long. During the summer, adjust the blades so they draw hot air up the thermal chimney and out of the house. When winter comes, switch the direction of the blades so hot air rising through the thermal chimney will be directed back down into your home. This retains heat in your home, keeping you warmer in a cold climate. The vents at the top of the thermal chimney should also be closed off in winter to keep hot air from leaking out.