Green Building Primer

Ceiling Fans
Ceiling fans only affect the room in which they are installed. They work best when installed with their blades 7-9 feet above the floor and 10 - 12 inches below the ceiling. Larger blades move more air than smaller blades, but blade material has no effect on the amount of air moved. Larger blades provide more cooling in the summer and heat distribution in the winter at a lower velocity, which can be important in a space where a strong breeze would be unwelcome.

During the summer, fans create a wind chill effect, making a room more comfortable. In temperature climates, a combination of ceiling fans and natural ventilation may be enough to keep a space cool without air conditioning. In an air conditioned space, the use of ceiling fans can allow you to increase the set temperature by 4°F with no decrease in comfort.

During the winter, ceiling fans can help make a space feel warmer by redistributing warm air that has risen up to the ceiling back down to where a room's occupants are. For this purpose, a ceiling fan should be run at low velocity to avoid creating chilling drafts.



Whole House Fans
A whole house fan pulls air in through open windows, and exhausts it through the attic and roof. They're useful for cooling a building when outdoor temperatures are in a comfortable range. One of the most common uses of a whole house fan is to drawn in cool night air and exhaust indoor air that has heated up during the course of a day.

Resources:

• Fans by GreenBuilder.com
• Ceiling Fans and Other Circulating Fans by EERE.
• Whole House Ventilation by EERE gives guidelines for sizing and installing a whole house fan, as well as a general introduction to the topic.