The Basics of Cooling your home the "GREEN" way #2 … the chimney effect

You can take advantage of the chimney effect to cool your home without using an air conditioner. Using natural ventilation is an easy way to green up your lifestyle and save you money by reducing your cooling bills in the summer.

​In a closed room, the temperature at the ceiling is always higher than that on the floor because hot air is less dense than cold air. The difference in air temperature can be more than 15 degrees Fahrenheit. You can achieve cooling, without any prevailing breezes at all, by arranging vents in your house so the heat can escape in a fairly direct path.

Note that the openings are at different heights, which is key.

​To lay out your air-movement strategy, draw a rough floor plan of your house, marking all the windows, doors, skylights, vents, fans, and so on. Draw your attic, with all the vents and openings. Then, use what you know about prevailing winds to figure out what the natural ventilation scheme is for the house and attic.


Many different types of vents allow you to take advantage of the chimney effect.Typically, prevailing winds come from the southwest in the summer and the northwest in the winter. Some areas have very consistent prevailing winds, but other areas experience changes almost daily. Refine your understanding of the winds in your area by keeping a log.


On paper, experiment with different combinations of doors and windows and vents to determine how to achieve comfort without using fans. Then imagine using fans to forcibly move air.


Make sure that you follow some general ventilation rules:

• To increase the speed of the breezes, use smaller openings for the inlets and larger openings for the outlets.
• Make the air move over as long a path as possible. Windows a few feet apart don’t do much. Opening all the windows at the same time doesn’t do much, either.
• Hot air rises, so locate an attic vent at the highest part of your attic.
• Try to draw in air from cooler outside areas, but note that doing so may not be practical due to prevailing winds.
• Don’t open or close all windows at the same time; optimizing your breezes takes a strategy that ultimately boils down to trial and error.
• Determine a daily routine. What works best in the morning is rarely what works best in the afternoon or at night.