Part 4: Air-Seal and Insulate a Nail Fin Window in a Wall with Exterior Rigid-Foam Insulation

Spray foam and high-quality sealant bridge all of the gaps between the framing, shims, and window for a durable and energy-efficient installation.

With window flashing done, the next step in any window installation is to air-seal and insulate. This work happens from the inside, and is the same regardless of water-resistive barrier (WRB). In this video, builder Jake Bruton walks through the theory of air-sealing and insulating, it’s importance to the overall function of a window installation and the comfort of the home, and the materials and methods needed to do the work well. Highlights include tips about how much foam to spray into the gap between window frame and rough opening, and how to tackle problematic details, like air-sealing around shims.

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[jbonegw]

Awesome series. Extremely valuable information.

[jwild]

Why use the sealant over the shim rathar than foam? I removed the trim on my windows, planning to use backer rod and foam, there is a shim but its super loose. Seems to not be doing anything, the house and windows are about 20 years old. Do i try to force the shim in deeper and see if it makes contact, or is it basicly useless now that the house has settled?

[goud]

So what, if any, downside is there to using foam vs. fiberglass? Foam seems superior aside from (maybe) being flamable.

[mestiza]

If the sill is sloped outward do you still need shims like he did here?