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.
Attic ventilation too much intake.
I know the question will come up why am i using so much vented soffit.
What happens is people put too many products on their roof.
Venting a homes attic is a very important best building practices will say 50 at the ridge and 50 at the soffits unobstructed.
Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space.
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.
In this post we cover the intake ventilation.
If the attic ventilation system cannot be balanced 50 intake 50 exhaust it s better to have more intake than exhaust because it s been our experience most houses lack proper intake.
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.
Roof ventilation keeps the air moving and stops mold from growing but too much ventilation can be just as bad as having none.
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.
So how much intake ventilation do i need.
Is it possible to have too much attic ventilation.
2 focusing only on heat buildup.
The ideal amount of attic ventilation is one square foot of vent space for every 150 square feet of attic area.
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.
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.
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.
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.
It s possible to have too much exhaust ventilation but you cannot have too much intake ventilation.
Attic length x attic width 150 total vent space or net free area nfa.
All it takes to grow mold in your attic is stagnant humid air.
This gives me an intake of over 6139 sq inches.
