Insulation is made from a variety of materials, and it usually comes in four types: rolls and batts, loose-fill, rigid foam, and foam-in-place.

Rolls and batts-or blankets-are flexible products made from mineral fibers, such as fiberglass and rock wool. They are available in widths suited to standard spacing of wall studs and attic or floor joists: 2 in. x 4 in. walls can hold R-13 or R-15 batts; 2 in. x 6 in. 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 odd-sized building cavities and attics with wires, ducts, and pipes, making it well suited for places where it is difficult to effectively install other types of insulation.

Rigid foam insulation is typically more expensive than rolls and batts or loose- fill insulation, but it is very effective in exterior wall sheathing, interior sheathing for basement walls, and special applications such as attic hatches. Foam insulation R-values range from R-4 to R-6.5 per inch of thickness, which is up to 2 times greater than most other insulating materials of the same thickness.

Foam-in-place insulation can be blown into walls, on attic surfaces, or under floors to insulate and reduce air leakage. You can use the small pressurized cans of foam- in-place insulation to reduce air leakage in holes and cracks such as window and door frames, and electrical and plumbing penetrations.

There are two types of foam-in-place insulation: closed-cell and open-cell. Both are typically made with polyurethane. With closed-cell foam, the high-density cells are closed and filled with a gas that helps the foam expand to fill the spaces around it. Closed-cell foam is the most effective, with an insulation value of around R-6.2 per inch of thickness.

U.S. Department of Energy Recommended* Total R-Values for New Wood-Framed Houses

All of Alaska is in Zone 7 except for the following boroughs in Zone 8:

• Bethel
• Northwest Arctic
• Dellingham
• Southeast Fairbanks
• Fairbanks N. Star
• Wade Hampton
• Nome
• Yukon-Koyukuk
• North Slope

Zone 1 includes:

Hawaii, Guam, Puerto Rico and the Virgin Islands

These recommendations are cost-effective levels of insulation based on the best available information on local fuel and materials costs and weather conditions. Consequently, the levels may differ from current local building codes.

Open-cell foam cells are not as dense and are filled with air, which gives the insulation a spongy texture. Open-cell foam insulation value is around R-3.7 per inch of thickness.

The type of insulation you should choose depends on how you will use it and on your budget. While closed-cell foam has a greater R-value and provides stronger resistance against moisture and air leakage, the material is also much denser and is more expensive to install. Open- cell foam is lighter and less expensive but should not be used below ground level where it could absorb water. Consult a professional insulation installer to decide what type of insulation is best for you.