Bucks for Outsulation

One of the sticky details when installing exterior rigid-foam insulation is how to fasten flanged windows. Many window manufacturers frown on installing the window directly on top of the foam layer. A popular workaround is to install wood bucks between the framing and the window flange, but this creates a thermal bridge, which partially defeats the point of the foam. The best solution I’ve seen is the ThermalBuck. The high-density plastic-coated EPS-foam backer breaks the thermal bridge and won’t compress like typical foam insulation. The 8-ft. lengths can be integrated into rough openings, mitered at corners, and joined with Dap Dynaflex 800 sealant. Available in widths from 1 in. thick to 4 in. thick in increments that match common insulation thicknesses, they are sold with and without a drainage gap. The sill is sloped for drainage, and the interior flange is 1⁄2 in. thick. Price depends on thickness, but runs between $3.80 and $6 per ft.

—Patrick McCombe, senior editor

From Fine Homebuilding #285

Fine Homebuilding Recommended Products

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

Loctite Foamboard Adhesive

When foam board installations require an adhesive, it’s important to use compatible products like this adhesive from Loctite.

Buy at Amazon

Foam Gun

We like using a professional foam-dispensing gun as opposed to straw cans because it allows you to easily control bead size and reuse the can.

Buy at Amazon

Caulking Gun

It's important for any insulator to have a good caulking gun for air sealing or adhesives, and this one features a revolving frame that makes orienting the tip a breeze.

Buy at Amazon