The Insulation

INSTALLATION NOTES.

Fiberglass batts or blankets must be firmly attached to studs or joists to hold them in place. The installer needs to work the insulation around electric wires in the walls by separating some of the insulation along its length and sliding it behind the wire. In the same way, the insulation must be care­fully worked around wall receptacles. If the insulation is compressed, its insulation efficiency is greatly reduced.

When rigid plastic boards are used on interior surfaces, most building codes require that they be covered with a fire barrier, usually a '/2-inch layer of drywall. This is necessary because, in the event of fire, the plastic boards give off toxic gases when ignited.

THE VAPOR BARRIER.

Once the insulation is in place on the walls and ceilings, the vapor barrier comes next. Typically the barrier is a sheet of polyethylene film, asphalt-coated kraft paper, or aluminum foil. When a vapor barrier is installed in ren­ovated portions of the house and there is no barrier in unrenovated areas, you may want to discuss with your contractor painting at least the ceilings in those areas with a specially formulated paint to form a vapor barrier.

The vapor barrier serves two purposes that are especially important in colder climates. The vapor barrier, as its name suggests, prevents moisture in the air of the home from traveling outward through the walls and condensing when it meets colder air. Moisture in the walls could reduce the effectiveness of the insulation, but more important, it could also lead to decay of the wood structure. The other value of the vapor barrier is to prevent the infiltration of cold air from the outside through any chinks in the walls.