With insulation, the only time you can have too much of a good thing is when the ceiling or attic insulation blocks the roof’s ventilation. As shown in the illustration on p. 205, there must be a clear pathway for air to move from the eaves to the ridge.
In the house shown here, we nailed OSB baffles in place on the walls between the roof trusses to prevent the attic insulation (blown-in cellulose) from spilling into the eaves and covering soffit vents. When a house has a cathedral ceiling, there is no attic space to fill with insulation. Instead, fiberglass batts must be installed between the rafters. Be especially careful not to block the ventilation space between the rafters. Various cardboard and foam baffles are available to provide ventilation space and room for insulation according to the ceiling’s design. Staple the baffles between the rafters before installing the insulation (see the photo at right).
While you’re insulating the ceiling or attic, don’t forget the attic’s access cover or stairs. Rigid foam can be cut to insulate those openings. Using a compatible construction adhesive, glue several layers of foam on the top of the stairway or access hole cover.
If all we had to do were to fill the stud and joist bays, then insulating would be easy. Problems often arise because of all the pipes, wires, light
fixtures, and outlet boxes that are in walls and ceilings. For wires and pipes, cut a slice halfway through the batt and encase the pipe or wire in the insulation. It’s important not to compress the batts. In cold regions, make sure that you have insulation on the back of pipes (between the pipe and the exterior wall sheathing or siding) to keep them from freezing.
For electrical boxes, split the batt so that the insulation goes behind the box, as shown in the photos on p. 205. The front part of the batt can be neatly cut with a knife or scissors to fit around the box. Once the drywall is installed, you can use cover plates with foam or rubber gaskets over outlet and switch boxes to further reduce air passage.
Many recessed light fixtures generate so much heat that you have to leave a 3-in.
