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Community and Q&A

What is “plenty of soffit vents”?

Marsha Henry | Posted in GBA Pro Help on

I think I understand “Lstiburek’s Rules for Venting Roofs”. I need to contract for insulation and a new roof on a property (1950’s duplex) in the Pacific Northwest. The building has soffit vents – about 3 (approx 18” X 6”) per side, so 12 vents and NO other vents up top (has been like that for years and no moisture problems in the attic which does have insulation). Should I make the soffit vents continuous? Or, since it has been working well for all these years maybe just add a few more soffit vents and a ridge vent at the top (not to exceed in size the area of the soffit vents)? Would love some advice? I will be having all insulation removed, everything sealed, and new insulation installed.

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  1. GBA Editor
    Martin Holladay | | #1

    You'll get varying advice on this question. Here's my answer: if there are no signs of any moisture problems in your attic, you're probably fine.

    Most moisture enters the attic through air leaks in a home's ceiling. The best way to limit attic moisture problems is to plug air leaks in the ceiling. In previous decades, many experts falsely claimed that attic ventilation played an essential role in keeping attics dry. However, the research to back this up is lacking.

    In any case, it sounds like you don't have a problem.

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