So I just had my roof done and wanted ridge vents. The roofer used VentSure® 4-Foot Strip Heat & Moisture Ridge Vents. I am trying however to check my math on my balance, and thing I have way to much exhaust venting.
The roofer used about 35 linear feet of ridge vents (the whole ridge). I have about 966 square feet of attic floor. And I have 40 soffit panels with a single strip of lanced holed venting, the area of the perforation is 24 by 5 inches roughly.
Now I know I have way more venting than I need (966/300 = 3.22 sq/ft), but I am worried about my balance.
By my calculations I have Free Net Area in the ridge of 700 sq inches (4.9 sq/ft). Using OC's 20 sq/in NFA per linear foot (20 x 35). Ridge Vent Stats
I could not find the exact NFA for my under eave soffit vents but I used the following logic to estimate. I have one strip of 24 " x 5" of lanced holes per soffit panel. So that is 120 sq inces of perforation area (or .83 sq ft). Looking at a similar product that is perforated all over I found it had a NFA of 5.87 sq in/sq ft. So I figured each of my soffit vents gave me a NFA of 4.5 sq inches (5.87 x .83). I have 40 soffit panels (with rafter channels so no blockage), so that should equate to 180 square inches of intake (1.25 sq/ft). So while I have enough total venting 6.15 sq ft... I have a ratio of 20% Intake to 80% exhaust.
Or are my calculations way off? How big of an issue is this?
I will say that because of the roof layout, one side of my house has 30 soffit vents and the other side has a length of 11 of them. The wind usually will hit the 30 soffit side first.