Number of Powered Vents Needed?

Hey Guys-

To figure the number of roof vents needed use the following correct:

1 square foot for every 150 square foot of attic


1 square foot for every 300 square foot of attic with soffit vents.

But what if there’s a thermostatically controlled powered vent? How many square feet will a powered vent cover?

Pictures here are on a house that’s about 1000 square feet, soffit vents, and one powered vent…enough ventilation?


The code for ventilation would not change in the event of a “power vent” for during the three years of no utilities supplied to the house during its foreclosure period, the attic will still need venting.

Check your code references, again. I think you are missing the need for a vapor barrier. Remember, attic venting is ALL about removing moisture.

Thanks James, I didn’t think about it from an angle of the power being out. In terms of the vapor barrier, I guess I need further educated on that because I’m not following you there. Doesn’t the tar paper on the shingles serve as the vapor barrier?