PVC trim provides the depth needed to accommodate an inch of insulation board.
PVC trim provides the depth needed to accommodate an inch of insulation board.

My clients’ 80-year-old Rhode Island home was suffering from chronic peeling paint, deteriorating shingles, and high energy bills. It was a prime candidate for new siding installed over a layer of rigid foam insulation. The standard 2x4 stud walls were already insulated with blown cellulose, but we estimated we could improve their thermal performance by almost 50 percent just by retrofitting an inch of R-5 XPS rigid foam to the exterior. The new foam also promised to significantly cut down on air infiltration — a big problem that we discovered during our initial blower-door testing — without overly complicating the installation of new red-cedar shingles.

Although the house could have used new high-performance replacement windows, too, the budget was already exhausted. Fortunately, the existing 6-over-1 double-hung windows and triple-track aluminum storms were in decent condition — but even with sizeable back band moldings, the casings and sills weren’t really deep enough to accommodate an inch...

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