Experts recommend at least on square foot of inlet vent and one square foot of outlet vent for each 150 square feet of attic floor area. However, this can be reduced by one-half if you install a vapor barrier beneath the attic insulation.

Vapor Barriers Basics

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Q: I want to install a whole house fan. However, I'm wondering if the fact that I have loose insulation in my attic presents a problem? Will the insulation blow around? Any installation tips for this project would also be appreciated!

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Attic Insulation and Ventilation

Insulation value is commonly referred to as resistance-value or R-value. R-value is the measure of a material's ability to resist heat flow. The higher the R-value, the more effective the insulation is in reducing heat flow. Insulation should be purchased on the basis of its R-value, not thickness or weight. One brand or type of insulation may be thicker or thinner than another. But if both have the same R-value, they will insulate equally.

Insulation

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Recommended R values
for the walls, ceilings and floors of your home for all areas of the USA and Canada.
posted November 28,1999.

R Values