Best way to improve airtightness when re-siding
I’m working on a renovation project where the client is re-siding their whole house in cedar shingles, as well as redoing the roof, adding some dormers, etc. The new roof is probably going to be a hybrid ccSPF+batt insulation type deal. The shingles will get a small rainscreen gap with either corrugated battens or a spacer mat.
I’m assuming the existing sheathing is plywood or OSB. 2×4 walls, probably with batt insulation. For now, let’s assume that they are not going to be adding any exterior rigid insulation.
The main opportunity to throw in a little energy efficiency upgrade to this primarily aesthetics-driven project seems to me to be to improve the airtightness of the wall assembly (and all the related details).
My main question is whether it makes more sense to specify that the existing sheathing be taped with a high quality tape like Siga Wigluv, establishing the sheathing as the primary air barrier, or if it is a better idea to use the new WRB as the primary air barrier.
I’m also curious as to if this seems like a cost-effective opportunity to improve the energy efficiency of the house, or if there are other good opportunities during residing that are worth looking into.
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Replies
Brendan,
Sealing air leaks is definitely a cost-effective measure. Of the two methods you suggest, the best would be to seal the sheathing seams with a high-quality tape.
Of course, you also need to seal other penetrations like hose bibs, electrical outlets, and air leaks between windows and window rough openings (if these areas are accessible).
If there are any suspected gaps in the insulation, locating and marking those gaps with an IR camera then spot-filling them with cellulose, drilling from the exterior prior to putting up WRB and siding would be worthwhile.