Unless your home was specially constructed for energy efficiency, you can usually reduce your energy bills by adding more insulation. Many older homes have less insulation than homes built today, but adding insulation to a newer home may also pay for itself within a few years.
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, basements, and even to the outdoors. Heat flow can also move indirectly through interior ceilings, walls, and floors—wherever there is a difference in temperature. During the cooling season, heat flows from the outdoors to the interior of a house.
To maintain comfort, the heat lost in the winter must be replaced by your heating system and the heat gained in the summer must be removed by your cooling system. Properly insulating your home will decrease this heat flow by providing an effective resistance to the flow of heat.
To determine whether you should add insulation, you first need to find out how much insulation you already have in your home and where.
A qualified home energy auditor will include an insulation check as a routine part of a whole-house energy assessment. An energy assessment, also known as a home energy audit, will also help identify areas of your home that are in need of air sealing. (Before you insulate, you should make sure that your home is properly air sealed.)
When insulating your home, you can choose from many types of insulation. To choose the best type of insulation, you should first determine the following:
• Where you want or need to add insulation
• The recommended R-values for areas you want to insulate.
Understanding R-Value
The R-value is a measure of thermal resistance used in the building and construction industry. The higher the R-value, the greater the insulating effectiveness. Under uniform conditions it is the ratio of the temperature difference across an insulator and the heat flux (heat transfer per unit area). Heat transfer through an insulating layer is analogous to electrical resistance. R-value is the reciprocal of U-value. The U-value (or U-factor), more correctly called the overall heat transfer coefficient, describes how well a building element conducts heat.
The US Department of Energy has recommended R-values for given areas of the USA based on the general local energy costs for heating and cooling, as well as the climate of an area. There are four types of insulation: Rolls and batts, Loose-fill, Rigid foam, and Foam-in-place. Rolls and batts are typically flexible insulators that come in fibers, like fiberglass. Loose-fill insulation comes in loose fibers or pellets and should be blown into a space. Rigid foam is more expensive than fiber, but has a higher R-value. Foam-in-place can be blown into small areas to control air leaks, like those around windows. Increasing the thickness of an insulating layer increases the thermal resistance. For example, doubling the thickness of fibreglass batting will double its R-value,
The R-value is a measure of insulation's heat loss retardation under specified test conditions. The primary mode of heat transfer impeded by insulation is convection but unavoidably it also impedes heat loss by all three heat transfer modes: conduction, convection, and radiation. The primary means of heat loss across an uninsulated air-filled space is natural convection, which occurs because of changes in air density with temperature.
The amount of insulation or R-value you'll need depends on your climate, type of heating and cooling system, and the section of the house you plan to insulate.
Properly insulating your home will not only help reduce your heating and cooling costs but also make your home more comfortable.
