You need insulation in your home to provide resistance to heat flow. The more heat flow resistance your insulation provides, the lower your heating and cooling costs. Actual dollar savings will depend on present insulation levels and how much you add to them.
Heat flows naturally from a warmer to a cooler space. In the winter, this heat flow moves directly from all heated living spaces to adjacent unheated attics, garages, and basements, or to the outdoors; or indirectly through interior ceilings, walls, and floors — wherever there is a difference in temperature. During the cooling season, heat flows from outdoors to the house interior.
To maintain comfort, the heat lost in winter must be replaced by your heating system and the heat gained in summer must be removed by your air conditioner. Insulating ceilings, walls, and floors decreases this heat flow by providing an effective resistance to the flow of heat.
For good energy efficiency, your home should be properly insulated from the roof down to its foundation. This includes the following areas:
- Attic spaces
- Ducts in conditioned spaces
- Cathedral ceilings
- Exterior walls
- Floors above unheated garages
- Crawl spaces
- Slab-on-grade floors
Several areas are often neglected when a home is insulated. Some of the more common ones are:
- Walls separating living area from the attached garage
- Walls and ceiling of basement garages
- Sloping ceiling areas in upstairs rooms where the ceiling has been “clipped” to accommodate the roof rafters
- Narrow cracks around window and door framing
Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and density. In calculating the R-value of a multi-layered installation, the R-values of the individual layers are added. Installing more insulation in your home increases R-value and the resistance to heat flow. It is important to note that true results are directly related to completely filling all gaps and voids.
Properly insulating your home will decrease this heat flow by providing an effective resistance to the flow of heat.
More information can be found on the Web about whole-wall R-values.