New siding for an old house in Portland Oregon
Built in 1914. Small 900 SF House with no sheathing. Siding is nailed to the studs and needs to be replaced. No insulation in the walls. If we sheath the house and install new siding with a rain screen, but don’t add insulation in the walls, will that sheathing and WRB (Hydro Gap) reduce the vapor permeability to the point where we have moisture issues in the walls? Getting conflicting advice that if we insulate in the stud bays, we also need to insulate on the exterior of the sheathing to avoid moisture issues. I’m fine with no insulation from an energy and comfort standpoint. We have mild winters and low energy costs and new windows have eliminated most draftiness.
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Replies
Roscoe,
The house will be fine from a moisture management perspective with the changes you are suggesting - with or without cavity insulation. Make sure to detail the new sheathing as an air-barrier.
Hydro gap is an improvement over regular WRBs, but doesn't give you most of the attributes that a rain-screen with furring does. That's the one option I would suggest considering.
If you are opening the walls to add sheathing, There is no downside - and plenty of benefits - to adding insulation to the stud bays.