Why Insulate?
Uninsulated walls lose heat more quickly to the outdoors. This heat loss can cause
- Drafts across the floor,
- Discomfort from loss of body heat to cold wall surfaces,
- higher heating costs,
- Condensation on the interior surfaces and ideal conditions for mold growth, mildew and decay, and
- condensation within the wall cavity.
Insulating the wall increases its thermal effectiveness. The insulation:
- Reduces drafts caused by air leakage through the wall cavity;
- Keeps the interior surface warmer so occupants can lower the thermostat, but still be comfortable;
- Reduces movement of sound waves and dust so the house is quieter and cleaner; and
- Reduces potential for condensation and related problems.
Investing in wall insulation pays for itself with savings on the heating bill. Average payback is less than 5 to 10 years. Your actual period of payback will depend on factors such as lifestyle, home construction, and the cost of heating fuel.
Materials
There are several materials used to insulate the wall, with varying costs and effectiveness. Materials include cellulose, mineral fibers, and foam insulation. Some contractors also offer vapor barriers and vents as part of the installation.
Cellulose is made from shredded newsprint, treated with fire retardants. Monitoring by industry and government assures the homeowner the material has a standard R-value, is non-toxic, and will not burn or cause corrosion of pipes or wires. Cellulose is particularly effective in wall installations because of its ability to fill and pack even in tiny nooks and crannies within the cavity. Cellulose is also very effective in reducing air infiltration through wall cavities.
Mineral fibers such as fiberglass and rock wool are installed in some walls. Greater pressure is required to pack these materials into the cavity because they tend to catch on nails and hang up around tight places. In addition, larger drill holes are needed to install this type of material. Mineral fibers are most appropriate in homes or walls where moisture is a serious problem, because mineral fibers do eventually dry out. (Cellulose generally does not dry out once wet.)
Foam insulation has been used in the past, but is not as widely used today. Although it offers higher R-values than either cellulose or mineral fibers, problems have been experienced with blown in foam. This includes expansion of the foam during installation causing bowing of walls, and shrinkage of the foam over time, causing gaps in the insulation.
Installation could also include vapor barriers and vents. Almost all the moisture that creeps into the wall cavity arrives through holes and small cracks on the interior wall. Very little vapor passes through holes and small cracks on the interior wall. So a vapor barrier such as rated paints or visqueen is not necessary. Similarly, a vent plug on the exterior is not recommended.
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