How to Install Fiberglass Insulation

Installing insulation reduces heating and cooling costs, as well providing a more comfortable living environment. Fiberglass insulation is quite easy to install, and can be done by only one person. If you are unsure what type of fiberglass insulation to use, help can be found at building supply stores or from your local building department.

Each type of fiberglass insulation has an "R-value" printed on it. An R-value measures how effective the insulation is: if an R-value is high, the insulation is thicker and more effective. Insulation with a low R-value is thinner and less effective. Different R-values are needed for insulation in walls, floors, and ceilings.

Vapor barriers are another variable in buying insulation. Vapor barriers — available in different forms — prevent the water vapor in indoor room-temperature air from leaving through the walls and condensing in the framing. Foil- and paper-faced insulation have vapor barriers, but many people choose to add polyethylene sheeting to faced or unfaced insulation as an effective vapor barrier.

Before installing fiberglass insulation, it is important to protect yourself. Long pants and a long sleeved shirt should be worn, along with gloves, a respirator or dust mask, and safety goggles. A utility knife and a staple gun are needed, as well as the fiberglass insulation, packing tape, and 6-mil polyethylene sheeting.

Unroll the fiberglass insulation or remove a batt from the package, and cut it to fit the space between the studs. Insulation should never be compressed to fit into a space, but cut to slightly longer and wider than the space available. Compressing insulation will make it less effective. When obstructions such or pipes or wires are within the framing, insulate around them. This can be done by peeling away half the thickness of the fiberglass insulation. The back half gets fitted behind the pipe or wires, and the front half can then be laid in front.

Insulation can be trimmed to fit around electrical boxes and other objects that are in the way. Gaps around windows and doors can be filled with scraps of fiberglass insulation or expanding spray-foam insulation. Follow manufacturer's directions carefully with spray-foam insulation.

After installing fiberglass insulation, install the vapor barrier. This is done by draping the polyethylene sheeting over the wall, with at least a foot (30 cm) of overlap. Staple the sheeting to the framing, using the utility knife to cut around windows and anything else in the way. You can seal the sheeting around electrical boxes with the packing tape. Sheeting hanging onto the floor or from the top of the wall can be cut when you are finished.