Building Airtight Homes - Images 8-16

If a tub-shower unit is located against an exterior wall, fiberglass insulation and the poly air barrier need to be installed before the tub. All seams in the poly air barrier are taped with red contractor’s tape from 3M.

The Lessco box is a 6 1/2x7 1/2x2 7/8-inch airtight plastic box that’s installed at the same time as a regular electrical box.

After a wall is insulated, the poly air barrier is taped to the flange of the Lessco box, and the Lessco box is insulated with scraps of fiberglass or cellulose. Note that all plumbing penetrations in the wall are sealed with contractor’s tape.

Where a partition intersects an exterior wall, a strip of poly is installed on top of the 2x8 drywall nailer before the partition is built. Note that the wall poly is taped to the Tenoarm poly that protrudes from under the bottom plate.

In homes where the ceiling poly can’t be installed in a single sheet, it’s installed room by room. When building the top-floor partitions, the framers must install a strip of poly between the top plates and the ceiling joists. Later, the ceiling poly in each room will be taped to the perimeter flaps

A conventional recessed can fixture can be installed in a site-built foam box. The box, which is sized to provide 2 inches of free air on all sides of the fixture, is assembled with Tremco to seal the seams.

When planning for a light fixture above a tub, it sometimes makes sense to lower the ceiling to keep the electrical box from penetrating the poly ceiling barrier.

A polyethylene “bib” is added around the exterior of each window before it’s installed. Several extra pleats of poly are provided at the window corners, so that it can later be folded flat against the interior of the studs.

A strip of duct tape over the poly provides reinforcement for the staple heads.

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