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James Dulley's
House Insulation Guide

Checking your home's insulating system is one of the fastest and most cost- efficient ways to use a whole-house approach to reduce energy waste and maximize your energy dollars. A good insulating system includes a combination of products and construction techniques that provide a home with thermal performance, protect it against air infiltration, and control moisture. You can increase the comfort of your home while reducing your heating and cooling needs by up to 30% by investing just a few hundred dollars in proper insulation and weatherization products.

Adequately-insulated homes save money for homeowner's every month. It helps us conserve vital energy resources for our children and for the future. Energy-efficient houses help the environment through lower rates of air pollution emissions from plant and on-site combustion of fuels for heating, air-conditioning and ventilation.

Where to Insulate

Adding insulation in the attic, to walls, floors, basements and crawl spaces may be the best way to improve your home's energy efficiency.

Insulation

First, check the insulation in your attic, ceilings, exterior and basement walls, floors, and crawl spaces 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 roofs will resist the transfer of heat. The U.S. Department of Energy (DOE) recommends ranges of R-values based on local heating and cooling costs and climate conditions in different areas of the nation. The map and chart show the DOE recommendations for your area. State and local codes in some parts of the country may require lower R-values than the DOE recommendations, which are based on cost- effectiveness.

Although insulation can be made from a variety of materials, it usually comes in four types – batts, rolls, loose-fill, and rigid foam boards. Each type is made to fit in a different part of your house. Batts are made to fit between the studs in your walls or between the joists of your ceilings or floors. Batts are usually made of fiber glass or rock wool. Fiber glass is manufactured from sand and recycled glass, and rock wool is made from basaltic rock and recycled material from steel mill wastes. Rolls or blankets are also usually made of fiber glass and can be laid over the floor in the attic. Loose-fill insulation, usually made of fiber glass, rock wool or cellulose, is blown into the attic or walls. Cellulose is made from recycled materials treated with fire-retardant chemicals.

Rigid foam boards are made of polyisocyanurate, extruded polystyrene (XPS or blueboard), expanded polystyrene (EPS or beadboard), or other materials. These boards are lightweight, provide structural support, and generally have an R-value of 4 to 7 per inch. Rigid board insulation is made to be used in confined spaces such as exterior walls, basements, foundation and stem walls, concrete slabs, and cathedral ceilings.

Should I Insulate my Home?

The answer is probably “yes” if you:

Have an older home and haven't added insulation: in a recent survey, only 20% of homes built before 1980 were well insulated;

Are uncomfortably cold in the winter or hot in the summer — adding insulation creates a more uniform temperature and increases comfort;

Build a new house or addition, or install new siding or roofing;

Pay excessive energy bills;

Are bothered by noise from the outdoors — insulation helps to muffle sound;

Are concerned about the effect of energy use on the environment.

Insulation Tips

Consider factors such as your climate, building design, and budget when selecting insulation R-value for your home.

Use higher density insulation, such as rigid foam boards, in cathedral ceilings and on exterior walls.

Ventilation plays a large role in providing moisture control and reducing summer cooling bills. Install attic vents to help make sure that there is one inch of ventilation space between the insulation and roof shingles. Attic vents can be installed along the entire ceiling cavity to help ensure proper airflow from the soffit to the attic, helping to make a home more comfortable and energy efficient.

Do not block vents with insulation, and keep insulation at least 3 inches away from recessed lighting fixtures or other heat-producing equipment unless it is marked “I.C.” — designed for direct insulation contact.

As specified on the product packaging, follow the product instructions on installation and wear the proper protective gear when installing insulation.

The easiest and most cost-effective way to insulate your home is to add insulation in the attic. To find out if you have enough attic insulation, measure the thickness of insulation. If there is less than R-19 (6 inches of fiber glass or rock wool or 5 inches of cellulose) you could probably benefit by adding more. Most U.S. homes should have between R-19 and R-49 insulation in the attic.

If your attic has ample 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.

(a) These recommendations are based on the assumption that no structural modifications are needed to accommodate the added insulation.

(b) For new construction, R-19 is recommended for exterior walls. Jamming an R-19 batt into a 3-1/2-inch cavity will not yield R-19 because compression reduces the R-value.

(c) Insulate crawl space walls only if the crawl space is dry all year, the floor above is not insulated, and all ventilation to the crawl space is blocked. A vapor barrier (e.g., 4- or 6-mil polyethylene film) should be installed on the ground to reduce moisture migration into the crawl space.

(d) Thermal response of existing space for cooling benefits does not suggest additional insulation.

New Construction

For new construction or home additions, R-19 insulation for exterior walls is recommended for most of the country. To meet this recommendation, most homes and additions constructed with 2 x 4 walls require a combination of wall cavity insulation, such as batts, and insulating sheathing, such as rigid foam boards. You may want to consider building with 2 x 6 framing instead of 2 x 4 framing to allow room for thicker wall cavity insulation — R-19 to R-21.

When shopping for insulation watch for the ENERGY STAR® label and the National Association of Home Builders (NAHB) certification.

Go to column 448 for more information about insulation.

          Ceiling         Basement
Zone Gas Heat
Pump
Fuel
Oil
Electric
Furnace
Attic Cathedral Wall
(A)
Floor Crawl
Space (B)
Slab
Edge
Interior Exterior
1 x x x   R-49 R-38 R-18 R-25 R-19 R-8 R-11 R-10
1       x R-49 R-60 R-28 R-25 R-19 R-8 R-19 R-15
2 x x x   R-49 R-38 R-18 R-25 R-19 R-8 R-11 R-10
2       x R-49 R-38 R-22 R-25 R-19 R-8 R-19 R-15
3 x x x x R-49 R-38 R-18 R-25 R-19 R-8 R-11 R-10
4 x x x   R-38 R-38 R-13 R-13 R-19 R-4 R-11 R-4
4       x R-49 R-38 R-18 R-25 R-19 R-8 R-11 R-10
5 x       R-38 R-30 R-13 R-11 R-13 R-4 R-11 R-4
5   x x   R-38 R-38 R-13 R-13 R-19 R-4 R-11 R-4
5       x R-49 R-38 R-18 R-25 R-19 R-8 R-11 R-10
6 x       R-22 R-22 R-11 R-11 R-11 (C) R-11 R-4
6   x x   R-38 R-30 R-13 R-11 R-13 R-4 R-11 R-4
6       x R-49 R-38 R-18 R-25 R-19 R-8 R-11 R-10
(A) R-18, R-22 and R-28 exterior wall systems can be achieved by either cavity insulation or cavity insulation with insulating sheathing. For 2 inch x 4 inch walls, use either 3-1/2-inch thick R-15 or 3-1/2-inch thick R-13 fiberglass insulation with insulating sheathing. For 2 inch x 6 inch walls, use either 5-1/2-inch thick R-21 or 6-1/4-thick R-19 fiberglass insulation.
(B) Insulate crawl space walls only if the crawl space is dry all year, the floor above is not insulated, and all ventilation to the crawl space is blocked. A vapor retarder (e.g., 4- or 6-mil polyethylene film) should be installed on the ground to reduce moisture migration into the crawl space.
(C) No slab edge insulation is recommended.
U.S. Department of Energy Recommended* Total R-Values
for New Construction Houses in Six Insulation Zones
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*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. In addition, the apparent fragmentation of the recommendations is an artifact of these data and should not be considred absolute minimum requirements.