Steps to Attic Sealing:
- Seal all small cracks, gaps, and holes. Using an acrylic-latex or silicone caulk inserted into a caulk gun, seal all small cracks in the sheet rock ceiling, around plumbing pipes, and other small voids within the attic.
- Seal recessed lighting. A quarter inch of fire-rated, non-combustible caulk is applies to stop any small air leaks around recessed lighting.
- Seal around electrical boxes, piping, and wiring. A quarter inch of fire-rated, non-combustible caulk is applies to stop any small air leaks between the electrical box and the wall. The same procedure can be done around electrical piping entering or exiting the attic space.
- Seal the flue with aluminum flashing. Form a three-inch insulation dam to prevent insulation from contacting the flue pipe. Cut enough aluminum flashing to wrap around the flue plus 6 inches. Cut slots 1 inch deep and a few inches apart along the top, and bend the tabs in. Cut slots about 2 inches deep along the bottom and bend out the tabs. Wrap the dam around the flue and secure the bottom by stapling through the tabs. For round flues, cut half circles our of two pieces so they overlap about three inches in the middle. Press the flashing metal into a thick bead of high-temperature caulk and staple or nail it into place. Finish by sealing any remaining gaps around the structure with fire-rated, non-combustible caulk. Caution: Do NOT use spray foam for this step. Now put insulation back right up against the dam.
- Seal larger gaps with foam insulation. If the space around plumbing pipes is wider than three inches, foam insulation should be used. Fiberglass insulation may need to be stuffed into the space to serve as a backer for the expanding foam. Once the fiberglass insulation is in place, follow the material’s directions to foam the space around the pipe.
- Seal behind knee walls. Finished rooms built into attics often have open cavities in the floor framing under the sidewalls or knee walls. Even though insulation may be piled against or stuffed into these spaces, they can still leak air. As with attic bypasses, look for signs of dirty insulation to indicate air is moving through. If accessible, these cavities should be plugged in order to stop air from traveling under the floor of the finished space. If these areas are accessible, use a 24″ long batt of fiberglass insulation places in a plastic garbage bag. Fold the bag over and stuff it into open spaces under the wall (a piece of rigid foam board sealed with spray foam also works well for covering open joist cavities). Again, cover with insulation when you’re done. NOTE: be careful not to get expanding foam on your clothes or coveralls as the foam is very sticky and can be difficult to remove once set.