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2134 Views 6 Replies 3 Participants Last post by  Gary in WA
I am sure this topic has been beat to death. I live in a 2 story 2300 square foot house. Last summer I put on a new roof with Shinglevent II ridge vents.(approx 39 feet)

Our upstairs of our house is always hot in the summer. This spring I had a heat pump installed. Best purchase yet. This fall I plan on adding insulation. I currently only have R12, Code is R40. I installed rafter vents and made sure all soffits are open. The attic is approx 1200 square feet.

The soffits currently have 9 - 16"x2.5" vents cut out. 4 on the front of the house, 5 on the rear.The soffits are cedar tongue and groove.

Should I be adding intake vents or just leave it be? I have tried to figure out the math, but it seriously had me dreaming of numbers all I live in Vancouver British Columbia if that helps.
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To have a balanced system you will need 14-8x16 soffit vents. Your ridge vent has 18 sq. in. of net free area of ventilation per lineal ft. which is 702 of ventilation. Divide that by 56 which is the nfa of ventilation off an 8x16 aluminum soffit vent and you get about 12.5 I rounded up to make it even on both sides. Hope that helps.
You won't need that much, depends on the nfa of your vent, I would guess between 24-28 (14 each side) 2.5x16 vents.
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