©2013 Green Building Advisor. From The Taunton Press, Inc., publisher of Fine Homebuilding Magazine.
I am going to be converting my vented attic to a sealed & insulated attic. We'll be applying spray foam to the underside of the roof deck between the 2x12 rafters, and at the gable ends. It's a simple gable roof, 8:12 pitch. It has a substantial overhang past the exterior wall, with angled fascia and angled soffit panels (i.e. the soffit panels are nailed directly to the underside of the rafter tails, at an 8:12 pitch)
There us currently a continuous 2" wide aluminum strip vent in the soffit. For some reason, even though the original house plans appear to have the strip vent near the edge of the roof adjacent to the fascia, it was actually installed about 20" away - measured diagonally along the soffit - from the edge of the exterior wall. Looks like it was to make life easier for the builder....they could just install uncut 4'x8' soffit panels along the outer edge of the overhang, put in the strip vents, and only have to cut the 20" panels between the strip vent and exterior wall.
One problem with spray foaming is that a portion of the roof is a cathedral ceiling. From the point where the roof rafters sit on the exterior wall, back to where the rafters meet the ceiling joists , it's about 5-6 feet of cathedralezed ceiling. Not only will it be difficult to apply foam this far in from the attic side, but the foam would flow into the soffit area, unless we install blocking in all of the rafter bays along the exterior wall. So, since we would have to remove those 20" strips of soffit panel to install blocking anyway, we've decided to spray the first 3' of the cathedral ceiling from the outside, and the other 3' from the attic side. This method also allows the contractor to get a good seal at the top plate of the exterior wall.
Okay, enough backround info. Here's the question...when I replace the 20" soffit panel strips, should I remove the soffit strip vent, or would it be okay to leave the vent where it is? It's obviously no longer needed for roof venting, but leaving it in place would allow me to re-use the existing soffit panel pieces. If I remove the soffit vents, I'll now have to cut (and prime, and paint) new 22" wide soffit panels. So what's the downside (if any) to leaving them in?
Climate Zone 4A