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Insulation Guide

Insulation Types

Adding insulation to your home is a simple task requiring no special tools or skills. Depending on the size of your home, it should take between one to two days to insulate.


Why Insulate?

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Insulation is one of the smartest investments you can make in your home because it provides year-round comfort and savings in many important ways:

Lower energy bills
Insulation keeps your home warmer in the winter, which lowers your heating costs. In the summer, insulation keeps your home cooler, which eases the load on your air conditioner.

Quieter, more comfortable living
Insulation can actually absorb sound, reducing the unwanted noise from appliances, audio equipment, conversation and other sources of sound that are transmitted through your walls and floors. Insulation also keeps your family more comfortable by making it easier for your furnace or air conditioner to maintain a constant temperature.

Healthy home, healthy environment
Reducing your family's overall formaldehyde exposure can make your home healthier and safer. Using formaldehyde-free fiberglass insulation can help you achieve that reduction and follow the California Air Resources Board's recommendations to use formaldehyde-free building materials, including insulation, so that it emits little or no formaldehyde. Fiberglass insulation helps prevent the growth of potentially hazardous mold and mildew that can result from trapped moisture in your walls, air ducts and ceilings.

Increase energy efficiency
Insulation is one of the most important factors in the comfort and energy efficiency of any building. By air sealing your home, adding insulation or replacing old windows with ENERGY STAR® qualified windows, you create a thermal envelope that encloses heated or cooled living spaces. This not only maintains comfort, it also saves energy and helps lower your energy bills.

To increase the energy efficiency of your home, you should insulate all exterior walls that separate conditioned spaces from unconditioned spaces, including areas like knee walls that open to attics or garages. Insulating attics closes the thermal envelope from above. To make a more "secure" envelope, make sure you fill all cracks or openings with insulation. To control heat leakage, apply caulk or foam sealants around openings like window and door frames and any openings where wires or pipes go through the envelope.

Control sound
Sound is a very persistent traveler; unless contained, it goes over, under, around and through obstacles. There are two basic pathways by which sound can travel from room to room: through the air and through solid building materials. The easiest way to make your home quieter is to use sound-control insulation in the interior walls. Even if you only insulate key rooms, you'll notice the difference.

From walls to floors to retrofit applications, fiberglass insulation provides the ultimate sound control. Fiberglass insulation products have been shown to significantly reduce interior noise levels, lowering the unwanted transmission of sound from one room to the next. Used in conjunction with the caulking of joints and resilient channels for drywall attachment, the transmitted sound of televisions, stereos and ventilation systems can be reduced by as much as 75% to 80%.

Control moisture
Everyday activities such as cooking, washing and bathing add moisture to the air in your home in the form of vapor. This vapor can become trapped inside walls, resulting in mold and mildew growth, which can damage your home and present a potential health concern.

Vapor retarders keep the moisture in the air in your house from condensing in the wall cavities. Whether your vapor retarder is a facing or a film, it must be placed on the warm-in-winter side of the wall. If you live in a cold climate, place the vapor retarder between the interior of your home and the insulation. If you live in a hot, humid climate, place the vapor retarder toward the outside of the wall cavity.

Check your local building codes for vapor retarder requirements.

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Where to Insulate

Checking your current attic insulation depth is a good first step. You need up to 19 inches (or R-49). If you don't have enough, it may be an indication that your home is underinsulated and may not be properly sealed. Adding insulation to underinsulated areas and sealing air leaks are the fastest, easiest ways to help you lower your energy bill.

Locating underinsulated areas

There are several key areas that are often uninsulated or underinsulated. Because they allow cold or unconditioned air to pass through, maintaining a comfortable temperature requires more energy, creating higher bills.

Check these areas for the opportunity to add insulation. It can lower your bills and keep the house quieter, too.

  • Attic: Slide a yardstick or tape measure into the existing insulation. If it is not up to 19 inches deep, add more to lower your bills.
  • Basement: Check rim joists and basement walls.
  • Crawlspaces: Check between floor joists if vented, and check perimeter walls if unvented. Ground should be covered with a 6 mil polyethylene sheet.
  • Exterior walls and floors: Turn off the electricity first, then check by removing an electrical outlet cover.
  • Garage: Check garage walls and ceilings that are adjacent to conditioned spaces in the house.
  • Knee walls: check behind kneewalls, which are walls between living spaces and the garage or attic.

Avoid the chimney effect

In cold weather, warm air is continually rising. Leaks into the attic allow the expensive, heated air to escape into the attic, while at the same time drawing in cold air to displace it from the basement or other exterior leaks. This continuous air movement makes the home feel drafty and raises energy bills. By sealing attic air leaks, you plug the escape route of rising air and effectively stop the chimney effect.

Check around your attic for these common sources of attic air leaks:

  • Between floor joists behind knee walls
  • Attic hatch
  • Wiring holes
  • Plumbing vents
  • Open soffit (the box that hides recessed lights and the finished space above cabinets)
  • Recessed lights
  • Furnace flue

The more you insulate, the more your energy savings can add up. Insulating attics, walls, ceilings and crawlspaces can have a dramatic effect on your energy savings and can create a more comfortable home year-round.

Insulating for optimal results

The thermal envelope establishes a boundary. Heated or cooled areas are entirely enclosed by the envelope. Unconditioned spaces such as the attic, crawlspaces and the garage are outside the thermal envelope. You should insulate all exterior walls that separate conditioned spaces from unconditioned spaces. Insulating attics closes the thermal envelope from above.

To further ensure the conditioned living spaces of the home are enclosed, all cracks or openings should be filled with insulation. To control heat leakage, apply caulk or foam sealants around openings like window and door frames and any openings where wires or pipes go through the envelope.

Insulation is also used in interior walls, ceilings and floors for sound control and sometimes to create a thermal envelope from room to room.