INSULATION AND AIR SEALING
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What Is It and How Does It Work?

There are some effective measures you can take to reduce energy consumption in your home that are visible on a daily basis, such as replacing your HVAC system or installing new windows. However, there are also some less-visible steps that are equally, if not more, critical to making your home as efficient as possible. Proper insulation and air sealing are two key examples. Insulating your walls and sealing gaps and cracks in your home's envelope will reduce unwanted heat transfer and infiltration, leading to lower heating and cooling costs and a more comfortable home.

Insulation provides resistance to heat flow in your home—preventing warm indoor air from leaving your home during the winter, and preventing hot outside air from entering your home during the summer. A well-insulated home will have lower heating and cooling bills. Because heat always flows from a warmer space into a cooler space, warm air flows into your house in the summer and flows out of your house in the winter. Insulation provides resistance to this heat flow all year round. The thermal resistance that insulation provides is measured by its R-value – the higher the R-value, the more effective the insulation will be, if properly installed.

A properly air sealed home is tightly constructed to prevent against infiltration. Infiltration is the unwanted leaking of air through cracks and gaps in your walls, windows, doors, and connections between walls and floors. Infiltration provides ventilation, which is needed in any home, but it is not ideal ventilation since it cannot be controlled. Air sealing is the process of protecting against uncontrolled infiltration. Preventing infiltration can reduce unwanted heat gains and losses and excess moisture buildup. There are some fairly simple, yet effective ways to provide better air sealing for your home. Caulking and weather-stripping around windows, door frames, and other potential gaps in your home’s envelope can be very inexpensive, yet can provide big savings on heating and cooling costs. Also, sealing fireplaces and attics can prevent unwanted heat gains and losses. Integrating a comprehensive ventilation system, either natural or mechanical, is a more involved way to take control of the air flow in and out of your home.

What Are the Options?

There are many different types of insulation. The type that you use will depend on the existing conditions of your home, cost of different materials in your area, and the relative effectiveness of different types of insulating materials. The different types of insulation that you should consider are:

Blanket insulation
Loose-fill insulation
Reflective insulation
Rigid insulation
Spray foam insulation

Air sealing your home can include a series of steps that prevent unwanted infiltration. Areas that typically are at risk for causing air leaks include window frames, door frames, joints between walls and ceilings, and around penetrations in walls and ceilings such as for lighting fixtures. The steps you can take to properly air seal your home include:

Caulking
Weather-stripping
Natural ventilation
Whole-House ventilation
Attic and fireplace seals


Where Can I Get More Information?

U.S. Department of Energy: Air Sealing
U.S. Department of Energy: Insulation