Attic Ventilation Too Much Intake

As a certified licensed home inspector it is not correct to say too much ventilation is bad for an attic unless rain moisture is getting in.

Attic ventilation too much intake.

Roof ventilation keeps the air moving and stops mold from growing but too much ventilation can be just as bad as having none. Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge. I know the question will come up why am i using so much vented soffit. And when you put too many products on your roof that s improper ventilation.

Attic length x attic width 150 total vent space or net free area nfa. Is it possible to have too much attic ventilation. If a roofing contractor is going to be out of balance with the attic ventilation system it s better to have too much intake than too much exhaust because the excess intake converts to exhaust on the leeward side of the house. This gives me an intake of over 6139 sq inches.

In this post we cover the intake ventilation. If your attic floor has a vapor barrier you will need one square foot of nfa per every 300 square feet of attic floor area half of that will be intake half for exhaust. The ideal amount of attic ventilation is one square foot of vent space for every 150 square feet of attic area. Venting a homes attic is a very important best building practices will say 50 at the ridge and 50 at the soffits unobstructed.

I know intake must always exceed exhaust to avoid negative pressure possibilities but is this plan too far out of balance to the intake side. What happens is people put too many products on their roof. So how much intake ventilation do i need. This value is split evenly between intake and exhaust ventilation.

If there is no vapor barrier double it to one square foot of nfa for every 150 square feet of attic floor space half for intake half for exhaust. Do not use mechanical means electric attic fans. It s possible to have too much exhaust ventilation but you cannot have too much intake ventilation. All it takes to grow mold in your attic is stagnant humid air.

Tips for assessing your needs. If i put ridge vent on 100 of all ridges i end up with 2736 sq in of exhaust. If there is more intake ventilation than the attic s square footage requires it s not problematic because any excess intake converts to exhaust on the leeward side of the house. Intake area should always be equal to or more than exhaust area or intake air may be pulled from the interior of the building residence through openings in the ceiling e g can lights attic access doors.