Inside the walls of your home are a number of things that you may never see. Among them is a barrier of material called insulation. The basic purpose of insulation is to keep heat and cold from transferring between the inside and outside of the house. This has many benefits to you. It helps keep your home more comfortable by keeping warm air inside during the winter, and keeping cool air inside during the summer.
There’s also financial benefits as well. For example, by preventing warm or cold air from escaping, your furnace or heat pump will come on less often, thus reducing your energy bill costs. If that were not enough, there are also tax benefits for having appropriate insulation.
Insulation values are described by “R” values. R Values are a measure of thermal resistance. These values are generally set by building codes and not by the home builder. The higher the number, the denser the insulation and thus better it’s effectiveness. Currently, most building codes require Washington and Oregon state home builders to use R-38 or 39 in the ceiling, R-21 in the walls and R-30 in the floors. The reason it is higher in the ceiling is that heat rises and so a higher R value keeps the heat from escaping through the ceiling.
Over the insulation will be a thin layer of plastic called a vapor barrier. This keeps moisture that develops inside the house from getting into the insulation. Without this barrier, in winter months the warm moist air would transfer through the drywall causing the cavity to become cold enough for moisture to condense. The insulation would act as a sponge. The vapor barrier prevents this prevents this transference and helps keep the cavity dry.
Only the exterior walls are usually insulated. Interior walls have little if any effect on heat transference. However, some homeowners choose to insulate interior walls as an option for sound dampening. For example, if a bedroom wall is bordering a living area, the homeowner may choose to insulate that wall in order to muffle sound from a TV or stereo from so that people in the bedroom can sleep.