Air-Sealing for Hot Climates

FWater vapor from humid outdoor air has condensed on the cold surface of the interior poly in this 10-year-old home, creating a zone of chronic dampness. Note the black patches of mold on the fiberglass batts.

The same approach was used for a demand water heater’s rough-in (above); the gas line is on the right in the photo and the hot and cold water lines are at left.

To exclude outdoor air as well as bulk water, this dryer-vent pipe was sealed to the housewrap with a flexible flashing panel and butyl tape.

The gap between the subfloor and wall sheathing in this home allowed unconditioned air to flow through a basement closet equipped with an outside door and into the living space above it.

Smaller gaps between the framing and sheathing at the eaves — and around pipe and wire penetrations in partitions — were sealed with black canned foam.

A proprietary spray rig is used to apply flexible latex foam to potential leak points between framing members,

between framing and panel edges,

and at wire penetrations.

Once the air-sealed framing is covered with staple-up netting, the cavities are filled with blown fiberglass, which the author finds more reliable than batts. According to the manufacturer, the latex sealant is designed for use with either material.

Potential leak points in the framing of this partition between a living space and garage were sealed with sprayable caulk before the foam sub sprayed the cavities and overhead roof deck. Ductwork will be installed in the conditioned space between the roof deck and ceiling, which should improve the performance of the home’s air conditioning and heating.

The 2x4 framing adjacent to the doorway has been sprayed with a thin layer of closed-cell foam, which will later be covered with a thicker layer of spray cellulose, already visible on the taller wall at right in the photo.

Note how the ceiling above the doorway has been insulated with open-cell foam. Cracks between the slab and bottom plates are sealed with flexible caulk.

To prevent interference with the drywall and trim, caulk at framing members is immediately tooled flat.

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