DIY Home Improvement Forum banner

Too Much Soffit Venting?

8107 Views 2 Replies 3 Participants Last post by  Chemist1961
Hi all,

I live near Toronto Canada and want to add blown cellulose to the existing R40 blown fiberglass in the attic. The house has a hip roof with qty 6 8X8 inch roof vents. The square footage of the attic is approx 1500 sq ft.

The builder blocked 80% of the soffits with fiberglass where the top plate and roof meets before filling with blown fiberglass. The remaining 20% have plywood nailed into the rafters to create air intake chute.

Now comes my question -- should I unblock the all remaining soffits and add similar plywood wind baffle venting or the plastic vent chutes. In the summer it is extremely hot in the attic so more intake venting from the soffits should cool things considerably. On the other hand, there will be less insulation between the top of the walls and the roof. Can there be too much soffit venting.

1 - 1 of 3 Posts
Hi Art,
Ed is absolutely on the money. You will find info
There is a correct ratio between rooftop and soffit venting. Too tight a soffit opening cfreates a funnel effect. I had my roof redone last year and increasd the rooftop vents.
The upper level is noticeable cooler in summer now and I am upgrading insul to R50 as well. I am also adding venting in the plywood soffits by doubling the grille dimension and adding additional ones. You can also install a liner baffle attached to the underside of the roof which channels air above the insulation up toward the roof top while retaining the insulation above your wall's top plate.
FYI if you have a home energy audit done for about $300 before you add the insul you will likely get a provincial/federal rebate which covers most of if not all of your entire cost. Then apply for the new HRTC home reno credit and you'll be money ahead:thumbsup:
See less See more
1 - 1 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.