I recently bought a 60-year-old house that hasn't seen much upkeep in over 20 years. We're preparing for the humid summer and I've noticed we have 7 soffit vents for our flat roof with about 1,630 square feet of attic space. From what I've read, the guideline says to have 1 square foot of vent per 150 square feet of roof. That means I should probably have around 12 vents. However, I'm wondering if there are diminishing returns with adding more vents? I have 3 walls at 28 feet and 1 wall at 24 feet—should I distribute more vents evenly around? Right now, I've got 2 vents on one 28' wall, 3 on the other 28' wall, none on the third 28' wall, and 2 on the 24' wall. I also have an extra 92 linear feet of soffit available. With a total perimeter of around 200 feet, is 12 vents spaced about 16.5 feet apart too far? Any insights would be really helpful as we also just redecked the roof and want to keep our energy bills down this summer!
2 Answers
It's great that you're getting ahead of the humidity issues! Soffits definitely play a crucial role in your home's ventilation, acting as the intake while your roof vents handle exhaust. The 1:150 rule you mentioned is a solid guideline, but don’t forget to balance your intake and exhaust—aim for a 50/50 ratio. Also, once you add the vents, make sure insulation isn’t blocking them off. If you're unsure, checking in with a local pro could give you more tailored advice!
Funny that you mention the roof area because a bit of math seems off. If you've got a 28x28 square dimension, that's only about 784 square feet for the attic. Unless your house has multiple floors or extensions, that might mean your current 7 vents are already adequate if you calculate based on the 1:150 rule. Just something to double-check when adding more vents!