Insulation - Insulation And Weatherization - 5/1/2004 - House Energy Efficiency Insulation

Insulation - Insulation And Weatherization

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.

Where to Insulate: Adding insulation in the areas shown in Figure 56 may be the best way to improve your home's energy efficiency.

Insulation: Should I insulate my home? 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. At the DOE web site you can find a more accurate and simpler method of determining your insulation needs by using the Interactive ZIP Code Insulation Program, which uses your zip code and some information about your house to tell you where to add insulation. The program was developed by the Energy Division of the Oak Ridge National Laboratory. 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 fiberglass or rockwool. Fiberglass is manufactured from sand and recycled glass, and rockwool is made from basaltic rock and recycled material from steel mill wastes. Rolls or blankets are also usually made of fiberglass and can be laid over the floor in attics. Loose-fill insulation, usually made of fiberglass, rockwool or cellulose, is blown into the attic or walls. Cellulose is usually made from recycled newsprint treated with fire-retardant chemicals.

Rigid foam boards are made of polyisocyanurate, extruded polystyrene (XPS), 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.

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-22 (7 inches of fiberglass or rockwool or 6 inches of cellulose) you could probably benefit by adding more. Most U.S. homes should have between R-22 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. You may also need to add insulation to your crawl space and basement areas. Either the walls or the floor above the crawl space should be insulated.

New Construction: For new construction or home additions, R-11 to R-28 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, or rigid foam boards. If you live in an area with an insulation recommendation that is greater than R-20, 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.

Weatherization: Warm air leaking into your home during the summer and out of your home during the winter can waste a substantial portion of your energy dollars. One of the quickest dollar-saving tasks you can do is caulk, seal, and weather-strip all seams, cracks, and openings to the outside. You can save 10% or more on your energy bill by reducing the air leaks in your home.

Sealing Air And Moisture Leaks

Air leaks between your home's interior and the outdoors can be a constant drain of energy and money. The air leakage in a typical U.S. home is equal to leaving a window wide open. To stop these air leaks, all doors and windows should be weather-stripped; all seams, cracks, and openings to the outside should be caulked or sealed. 

Moisture control is also an important aspect of maintaining an energy efficient home. If humid air leaks into cool spaces, moisture can condense on the cool surfaces and cause damage. In addition, moist insulation has a lower R-value than dry insulation, so moisture problems will lower your home's energy efficiency. 

One aspect of moisture control is to seal air leaks around electrical outlets, switches, and penetrations through the building envelope for plumbing, wiring, ventilating, heating and cooling, and attic access. For instance, a hot water pipe may pass from your unheated basement up into your kitchen. Hardware stores sell a variety of grouts and sealants to plug the gaps around pipes such as these, as well as gaskets to install behind electrical outlets and switches. 

Vapor barriers (also called vapor retarders) are another form of moisture control. Vapor barriers include polyethylene sheets, low-perm-rated paints, laminated asphalt-covered building paper, vinyl wall coverings, and foil-type wallpapers. Vapor barriers are now routinely installed in walls during construction projects such as home additions. For existing homes, paints or wallpapers may be the only appropriate options. 

Vapor barriers are included on batt or blanket insulation. Vapor barriers should always be placed on the "warm-in-winter" side of the insulation. Do not install a vapor barrier over existing insulation. 

Air infiltration barriers (also called air retarders) are complementary to vapor barriers. Ideally, air infiltration barriers are comprised of one or more air-impermeable components that are sealed at all joints and penetrations to form a continuous airtight membrane around the building. 

When located on the "warm-in-winter" side of insulation, air barriers can double as vapor barriers. Polyethylene sheets are one example of a vapor and air barrier. When located on the "cold-in-winter" side of insulation, as is often done in wood stud construction, the air barrier must be vapor-permeable. Typical vapor-permeable air barriers include polyolefin fabric wrap on sheathing, pressed cardboard, and pleated polystyrene with paper facings.