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Articles -> Energy Saving -> Pad your Pad
Pad Your Pad
Insulating your home
by Jason Miller
Starting Out: Your New Home
Let's take a look at the major players, starting with fiberglass. For ease of installation, nothing beats fiberglass batts, which are inexpensive and well suited for walls. But adequate performance isn't a sure bet. First, the batts must completely fill each stud cavity. Empty spaces allow air leakage, quickly reducing the effective R-value. The rated R-value of any insulation (displayed prominently on most insulation products) is arrived at by the manufacturer. This number may be higher than the effective R-value (what you actually get), depending on the quality of the installation. Think of it this way: when was the last time your car's mileage matched exactly the advertised mileage?
Proper installation is key. Fiberglass batts are permeable; that is, air and moisture move easily through them. An air barrier and a vapor barrier must be installed in order for fiberglass to be effective. In addition, you should be able to stand across the room and see no voids at the top or bottom of the batts, or around electrical boxes and pipes. Properly installed fiberglass insulation experiences minimal settling (one to two percent) and maintains its thermal performance for the life of the building.
Fiberglass is not the best material for insulating floors. The protection from air movement that fiberglass needs is tough to achieve. Plus, it's prone to voids and tends to sag over time.
For insulating attics and walls, however, blown-in fiberglass and cellulose are a good fit, literally. They fill odd-shaped spaces larger than two inches.
If you choose blown-in insulation, your greatest concerns should be full coverage and settling. Loose-fill fiberglass is blown into open attics at densities that are not high enough to block air movement, so it requires very careful air-barrier detailing. Loose-fill cellulose offers somewhat more resistance to air movement, but it still requires a good air barrier and vapor barrier in the ceiling.
Cellulose will usually settle about 20 percent by volume, unlike fiberglass. To be accurate, your builder or subcontractor should use the number of bags of insulation per 100 square feet, as listed on the bag label. Some manufacturers also give a figure for "initially installed depth." Blown-in cellulose "one-ups" blown-in fiberglass in that its R-value is unaffected when the temperature outside is 70-76 degrees colder than inside. In that environment, the R-value of fiberglass decreases by 35 to 50 percent.
Expanding foam solves many problems, including frozen pipes (install foam between the pipe and cold source) and cold floors (insulate them with foam; it glues itself to the floor and seals out the chill). In its installation stage, expanding foam releases steam, carbon dioxide and ammonia gas, but most off-gassing occurs in the first week after installation, and after 30 days there are no emissions. Rest assured, there is minimal risk to your installer and no risk to you.
Foam's major drawback, for many consumers, is its price tag. Installed, it runs about double the price of fiberglass. But remember, that figure doesn't take into consideration the cost of carefully installed housewrap, vapor barriers and careful air sealing that proper fiberglass batt installation requires. Foam does the work usually done by the insulation, the vapor barrier, the air barrier and the labor involved. Think "effectiveness," then make your decision. When all the pros and cons are considered, you'll realize that there are several areas of your home where foam is the only satisfactory alternative.
What if you've lived in your home for several years and suspect that more insulation is needed? The steps you take to achieve this end need to be logical and methodical.
Next, determine your current insulation level. Check in key locations such as basement walls, exterior walls and floors above cold spaces. In unfinished areas where structural elements are exposed, you can see the type of insulation and measure its thickness. Checking insulation in finished walls and other areas is more difficult. Your local home store or lumberyard should be able to guide you through the process.
Then evaluate the benefit of added insulation. What do you want out of this? More comfort? A quiet interior environment? More money to spend on the opera instead of the power company? Sit down and do the math. Which improvements can your budget support, and what are the returns in terms of savings? The hard numbers will help you to decide where you'll begin.
The weekend comes and it's time to get started. Are you up to the task? Insulating unfinished floors, ceilings and walls is fairly easy for the do-it-yourselfer. Installing insulation in the cavities of exterior walls is more difficult and usually performed by a contractor. You can, however, rent equipment for sidewall insulation, if you wish. Be sure you're clear on how the equipment works. Ask for any brochures or other literature that may be available.
Last, get smart about insulation. You've only read a small portion of the information that's available on the subject. Read and learn until you're comfortable enough to make a decision, and then act. Every moment you wait is another few cents wafting out of your home through those nooks and crannies you thought didn't matter.
Now you're on the path to a well-insulated home. And you're getting warmer.
Doing It Yourself?
Quick Tips for Independent Types
- Safety first! Whether installing or removing fiberglass, cellulose or expanding foam, wear protective clothing, goggles and a respirator. Disposable filters with two elastic bands provide a far better seal than masks with a single band. Rubberized half and full-face masks are best.
- Avoid the "fiberglass itch." When removing fiberglass, seal off the rest of your house with taped plastic sheeting. Send the kids to Grandma's house while you're working, and make sure the area is clean before they return. Renting a special vacuum cleaner equipped with a high-efficiency filter is a good idea, too.
- Don't forget to fluff. Fiberglass batts are compressed in the package and may not spring back to full thickness. Fluff it up to full thickness; wear your respirator while you do it.
- Because a perfect batt fit is difficult even for professional installers, consider using sprayed-in insulation (wet-spray cellulose, blown-in fiberglass blankets or sprayed-in foam) instead of batts in exterior walls.
Hand Warmers:
A Sampling of What's Out There
Fiberglass, traditional batt: The most common insulation, available everywhere. Doesn't settle or disintegrate with age. Fire-resistant. Not a vapor barrier. Doesn't seal well. Inexpensive. R-value per inch: 3.1 to 4.3*.
Fiberglass batt with MIRAFLEX® fiber: Features are similar to regular fiberglass, with these advantages: It's virtually itch-free, has none of the formaldehyde traditional batts use as a binder and can be compressed more in the package. R-value per inch: 2.9.
Cellulose: Made of mostly recycled shredded paper plus boric acid or other fire retardant. Sprayed dry, dampened with acrylic binder or wet into attics or walls. Unless densely packed, can settle if sprayed dry. Extremely dusty during installation. While the R-value of blown-in fiberglass has been shown to decrease by 35-50% when temperature outside is 70-76 degrees colder than inside, cellulose's R-value is unaffected. R-value per inch: 3.7 to 3.8.
Polyicynene foam: Not to be confused with polyurethane foam, this insulation is made of modified urethane, a plastic similar to that in mattress foams. Sprayed into walls and attics with water as the blowing agent. Stabilizes wobbly plaster. Seals gaps. Almost impermeable to moisture and air. Expensive, but actually less than the cost of fiberglass, based on effective R-value rather than rated R-value. R-value per inch: 3.6.
Polyurethane foam: A sprayed-in plastic for walls, attics and roofs. Blowing agent is an ozone-depleting hydrofluorocarbon. Almost impermeable to moisture and air movement. Seals gaps. Can't be used in existing walls unless drywall or plaster is removed. Expensive. R-value per inch: 6.7 to 7.3.
Expanded polystyrene foam board: Similar to disposable coffee cups. Made of petroleum byproduct; up to half can be recycled polystyrene. Blowing agent, pentane, doesn't deplete ozone. Good for narrow or hard-to-reach places, roofing or prefabricated wall panels. Impermeable to moisture. R-value per inch: 3.6 to 4.2.
*All R-values shown are rated R-values—not effective R-values. R-value is a measure of resistance to the flow of heat through a given thickness of a material, with higher numbers indicating better insulating properties. Source: This Old House, September/October 1996.
Get More Facts
Based in Alexandria, Virginia, the North American Insulation Manufacturers Association (NAIMA) participates in government affairs, medical research and residential building service committees. It offers a variety of fact sheets, brochures and other practical literature on product performance standards, safety concerns, installation guidelines and more.
For more information and to learn the name of a professional polyicynene insulation contractor near you, call Icynene Inc. at 1-800-946-7325.
Your state's Department of Public Service should have a variety of guides designed to help you save energy in your home. Call or write them, and request the necessary materials. It's a great first step to saving money—they're free!
Sources: This Old House, September/October 1996; Journal of Light Construction, October 1996; Ken Wiggers, American Environmental Services; Owens Corning; Minnesota Department of Public Service; Builder, November 1996; Home Energy, January/February 1996.
Photo/Graphic courtesy of Owens Corning
