Everything You Need to Understand About Insulation Everything You Need to Understand About Insulation
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 percent by investing just a few hundred dollars in proper insulation and weatherization products.
Where to Insulate
Adding insulation in the areas shown here may be the best way to improve your home's energy efficiency.
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 chart below shows the DOE recommendations for eight areas. 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.
Do You Need More Insulation?
The answer is probably "yes" if you:
- Have an older home and haven't added insulation - in a recent survey, only 20 percent 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.
- 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.
U.S. Department of Energy Recommended Total R-Values for Existing Houses in Eight Insulation Zones
|Ceilings below ventilated attics||Floors over|
|Exterior walls (wood frame)||Crawl space walls|
|Gas, oil, or|
|Gas, oil, or|
|Gas, oil, or|
|Gas, oil, or|
- These recommendations are based on the assumption that no structural modifications are needed to accommodate the added insulation.
- 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.
- 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.
- Thermal response of existing space for cooling benefits does not suggest additional insulation.
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.
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 weatherstrip 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.
Sources of Air Leaks in Your Home
Areas that leak air into and out of your home cost you lots of money. Check the culprit areas listed here:
- Dropped Ceiling .
- Recessed ligh.
- Attic entrance
- Electric wires & box
- Plumbing utilities & penetration
- Water & furnace flues
- All ducts
- Door sashes & frames
- Chimney penetration
- Warm air register
- Window sashes & frames
- Baseboards, coves, interior trim
- Plumbing access panel
- Electrical outlets & switches
- Light fixtures
First, test your home for air tightness. On a windy day, hold a lit incense stick next to your windows, doors, electrical boxes, plumbing fixtures, electrical outlets, ceiling fixtures, attic hatches, and other locations where there is a possible air path to the outside. If the smoke stream travels horizontally, you have located an air leak that may need caulking, sealing, or weatherstripping.
- Caulk and weatherstrip doors and windows that leak air.
- Caulk and seal air leaks where plumbing, ducting, or electrical wiring penetrates through exterior walls, floors, ceilings, and soffits over cabinets.
- Install rubber gaskets behind outlet and switch plates on exterior walls.
- Look for dirty spots in your insulation, which often indicate holes where air leaks into and out of your house. You can seal the holes by stapling sheets of plastic over the holes and caulking the edges of the plastic.
- Install storm windows over single pane windows. Storm windows as much as double the R-value of single pane windows and they can help reduce drafts, water condensation, and frost formation. As a less costly and less permanent alternative, you can use a heavy duty, clear plastic sheet on a frame or tape clear plastic film to the inside of your window frames during the cold winter months. Remember, the plastic must be sealed tightly to the frame to help reduce infiltration.
- When the fireplace is not in use, keep the flue damper tightly closed. A chimney is designed specifically for smoke to escape, so until you close it, warm air escapes – 24 hours a day!
- For new construction, reduce exterior wall leaks by either installing house wrap, taping the joints of exterior sheathing, or comprehensively caulking and sealing the exterior walls.
How Does Air Escape?
Air infiltrates in and out of your home through every hole, nook, and cranny. About one third of this air infiltrates through openings in your ceilings, walls, and floors.