Chapter

Should I Insulate My Home?

Insulate your home when:

  • You have an older home and haven’t added insulation. Only 20% of homes built before 1980 are well-insulated.
  • You are uncomfortably cold in the winter or hot in the summer.  Adding insulation creates a more uniform temperature and increases comfort.
  • You build a new home or addition, or install new siding or roofing.
  • You pay high energy bills.
  • You are bothered by noise from outside.  Insulation muffles sound.

R-Value of Insulation

Check the insulation in your attic, ceilings, exterior and basement walls, floors and crawlspace to see if it meets the levels recommended for your area. Insulation is measured in R-values—the higher the R-value, the better your walls and roof will resist the transfer of heat. The DOE recommends ranges of R-values based on local heating and cooling costs and climate conditions in different areas of the country. The map and chart below show the DOE recommendations for your area. State and local code minimum insulation requirements may be less than the DOE recommendations, which are based on cost effectiveness.

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Four Types of Insulation

Although insulation can be made from a variety of materials, it usually comes in four types, and each type has different characteristics.

Rolls and batts or blankets are flexible products made from mineral fibers, such as fiberglass and rock wool. They’re available in widths suited to standard spacings of wall studs and attic and floor joists: 2×4 walls can hold R-13 or R-15 batts; 2×6 walls can use R-19 or R-21 products.

Loose-fill insulation is usually made of fiberglass, rock wool, or cellulose in the form of loose fibers or fiber pellets. It should be blown into spaces using special pneumatic equipment. The blown-in material conforms readily to building cavities and attics. Therefore, loose-fill insulation is well-suited to places where it’s difficult to install other types of insulation.

Rigid foam or foamboard insulation is typically more expensive than fiber insulation, but it’s very effective in buildings with space limitations and where higher R-values are needed. Foam insulation R-values range from R-4 to R-6.5 per inch of thickness, which is up to two times greater than most other insulating materials of the same thickness.

Foam-in-place insulation can be blown into walls. It reduces air leakage if it’s blown into cracks, such as around window and door frames.

Where to Insulate

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1. In unfinished attic spaces, insulate between and over floor
joists to seal off living spaces below.

2. In finished attic rooms with or without dormers:

  • 2A. insulate between studs of kneewalls;
  • 2B. insulate between studs and rafters of exterior walls and the roof;
  • 2C. insulate ceilings with cold space above; and
  • 2D. extend insulation into joist spaces to reduce air flow.

3. Insulate at exterior walls, such as:

  • 3A. walls between living spaces and unheated garages, shed roofs, and storage areas;
  • 3B. foundation walls above ground; and
  • 3C. foundation walls in heated basements.

4. Insulate above cold spaces, vented crawlspaces, and unheated garages. Also:

  • 4A. insulate any portion of the floor in a room that cantilevers beyond an exterior wall;
  • 4B. insulate slab floors built directly on the ground;
  • 4C. insulate foundation walls of unvented crawlspaces; and
  • 4D. extend insulation into joist spaces to reduce air flow.

Adding insulation in the areas shown above may be the best way to improve your home’s energy efficiency. Insulate either the attic floor or under the roof. Check with a contractor about crawlspace or basement insulation.

Insulation Tips

  • Consider factors such as your climate, building design and budget when selecting insulation R-values for your home.
  • Use higher-density insulation, such as rigid foamboard, on exterior walls, in cathedral ceilings, and on exterior walls.
  • Ventilation helps with moisture control and for reducing summer cooling bills. Attic vents can be installed along the entire ceiling cavity, from the soffit to the attic, to help ensure proper air flow to make a home more comfortable and energy-efficient. Do not ventilate your attic if you have insulation on the underside of the roof. Check with a qualified contractor.
  • Recessed light fixtures can be a major source of heat loss, but you need to be careful of how close you place insulation next to a fixture unless it’s marked “IC,” which means it’s designed for direct insulation contact. Check your local building codes for recommendations.

Long-Term Savings Tips

One of the most cost-effective ways to make your home more comfortable year-round is to add insulation to your attic.

Adding insulation to the attic is relatively easy. To find out if you have enough before adding more, measure the thickness of the insulation that’s currently installed. If it’s less than R-30 (11 inches of fiberglass or rock wool, or 8 inches of cellulose), you could probably benefit by adding more. Most U.S. homes should have between R-30 and R-60 insulation in the attic. Don’t forget the attic trap or access door.

If your attic has enough insulation and your home still feels drafty and cold in the winter or too warm in the summer, chances are you need to add insulation to the exterior walls, as well. This is a more expensive measure that usually requires a contractor, but it may be worth the cost if you live in a very hot or cold climate. If you replace the exterior siding on your home, you should consider adding insulation at the same time.

You may also need to add insulation to your crawlspace or basement. Check with a professional contractor.

  • Follow the product instructions as specified on the product packaging for guidelines on proper installation, and be sure to wear the proper protective gear when installing insulation.

Insulation for New Construction

For new homes in most climates, you will save money and energy if you install a combination of cavity insulation and insulative sheathing. Cavity insulation can be installed at levels up to R-15 in a 2×4-inch wall, and up to R-21 in a 2×6-inch wall. The insulative sheathing, used in addition to this cavity insulation, helps to reduce the energy that would otherwise be lost through the wood frame. For example, in Zone 5, you could use either a 2×4 wall with R-13 or a 2×6 wall with R-21. For either of those two walls, you should also use an inch of insulative sheathing that has an R-value of R-5 or R-6.

Today, new products are on the market that provide both insulation and structural support and should be considered for new home construction and additions. Structural insulated panels, known as SIPs, and masonry products, such as insulating concrete forms, or ICFs, are two of these newer products. Some home builders even use an old technique borrowed from the pioneers: building walls using straw bales. Radiant barriers (in hot climates), reflective insulation, and foundation insulation should all be considered for new home construction. Check with your contractor for more information about these options.