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Want to save energy? Consider upgrading insulation.

Unheated areas underneath ground floors, such as crawl spaces and basements, are good places to add insulation. (Bill O'Leary/The Washington Post)

If your home is underinsulated or has a lot of air leaks, heat escapes during winter and your hard-earned money floats away, too. In summer, heat flows into cool spaces in your home, raising your cooling bill.

Because attics in most homes are easily accessed and unfinished, they’re ideal targets for improving insulation. How much you’ll pay to do this depends on how much you need to add — and whom you hire to do it.

In the Washington area, the U.S. Energy Department recommends attics be insulated at R-38 or better. Check what type of insulation you already have (loose fibers, granules, batts, etc.) and measure its thickness. To achieve an R-38 rating, loose fiberglass particles should be laid at a thickness of about 15 inches, rock wool particles at 13 to 14 inches, cellulose (looks like shredded newsprint) at 10 inches and batts (blankets that come in rolls) at 12 inches.

Checkbook’s undercover shoppers collected quotes from Washington-area contractors to add insulation to increase the rating of a sample unfinished attic from R-11 to R-38. Those prices ranged from $1,704 to $5,580. Since the work isn’t cheap, even if you hire an inexpensive outfit to do it, is it worth it?

There are several online tools that can help homeowners learn about the effects of various green improvements. One very useful calculator is the Lawrence Berkeley National Laboratory’s Home Energy Saver tool. Using it, we found that for a sample area home the energy savings from adding insulation will eventually pay off project costs. For one sample home, Checkbook found that improving attic insulation from R-11 to R-38 would generate utility savings of about $200 per year, which would recover $2,000 in installation costs in about 10 years.

Unheated areas underneath ground floors, such as crawl spaces and basements, are also good places to add insulation. Crawl spaces should be dry year-round (moisture causes insulation to deteriorate), and a vapor barrier should be placed on the floor of the crawl space.

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If your home was built in the 1970s or later, its exterior walls probably have adequate insulation. If your home is older, it might be worthwhile to install insulation or improve what has deteriorated. To do so, installers drill access holes between each pair of wall studs, blow in insulation and then patch and reseal the openings.

This is much more time-consuming, messy and costly than insulating an open unfinished attic or a crawl space. But if you’re doing a major renovation or replacing siding, it’s worth adding this task, if needed: For an average-size home in this area, adding R-11 of insulation to uninsulated exterior walls is likely to save $300 to $400 in energy costs per year.

Also assess how your home passively wastes energy by looking for areas in outside walls, windows and doors that allow conditioned indoor air to escape.

Most homes have holes, cracks and gaps that let cold air in and warm air out in the winter — and do the reverse in the summer. One little leak might not seem like much, but the cumulative effect of several can add up to the equivalent of leaving open a small window. Finding and plugging leaks costs very little money yet yields significant savings.

A good energy auditor can track down leaks for you. But you can sleuth out major ones on your own. Most leaks occur where different building materials meet — brick and wood siding, foundation and walls and between the chimney and siding. Other common problem areas are around windows and doors; mail slots; points of entry for electrical and gas lines, cable/internet wiring and phone lines; outdoor water faucets; spots where vents pass through walls; cracks or gaps in siding, stucco, masonry and all foundation materials; and around window air-conditioning units.

Use caulk to seal any cracks or gaps measuring less than ¼-inch wide and polyurethane foam sealant for larger ones.

To minimize leakage around doors and windows, install weatherstripping. Open-cell foams are inexpensive and relatively inefficient but easy to apply and suitable for low-traffic areas. Vinyl is more expensive and lasts longer. Metals last for years and provide a decorative element for older homes. Also add sweeps to the bottoms of all exterior doors to seal gaps there.

Prevent drafts around outlets and light switches located inside exterior walls by adding insulating receptacle gaskets, which cost less than $5 each.

If you have window air-conditioning units, remove them during the winter, or insulate them from the outside with an air-conditioning cover ($20 to $60). During summer, install units tightly within windows.

Combined, dealing with air leaks can save 5 to 20 percent of your heating and cooling costs.

Hiring an installer

In addition to adding insulation, contractors can help with identifying and sealing leaks.

At, you can find ratings and reviews submitted by local consumers for insulation companies they used. Fortunately, that feedback is for the most part positive. Until Sept. 1, Washington Post readers can access Checkbook’s ratings of insulation contractors free via

Get several price quotes. Ask prospective companies how they plan to do the work, what materials they plan to use, and why. Be wary of exaggerated claims of energy savings. Be sure to ask contractors for proof of workers’ compensation and liability coverage.

Get a contract that details the size of the area to be insulated, what type and how much insulation will be installed and the resulting R-value (required by the Federal Trade Commission). For blown-in loose-fill insulation, the contract should also state the depth in inches of insulation present before new insulation is added and the depth after the work is done.

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Before work begins, a rep should inspect the job site and check for any issues — for example, to make sure there is no exposed wiring in any area. (Insulation cannot be installed over old knob-and-tube-style wiring.)

Other matters to cover in a contract

In attic spaces, the contract should promise that the company will keep attic vents free of blockage. Typically, a company will use fiberglass batts to build a dam around spaces that should not be covered by insulation. In addition, be sure the company will insulate the attic’s access panel or pull-down stairway.

Check for any recessed lighting fixtures (like can lights) that are exposed in the attic. If they are marked “IC” (insulated contact), it means insulation can contact them. If they are not IC-rated, be sure the contractor promises to keep insulation a minimum of three inches away to avoid a fire hazard.

If ductwork, boiler pipes or hot-water-supply pipes run through the area to be insulated, the contract should require the contractor to insulate them with R-6 insulation.

If you will be insulating walls, the contract should specify where the company will create holes, how many and how the openings will be closed and repaired.

Unless your job requires more than one day’s work (most don’t), don’t agree to pay until all work has been completed.

Before paying, check that all cracks were sealed as agreed upon, that the amount of insulation added matches the proposal and that loose-fill insulation was applied evenly. Also, make sure the crew has cleaned up the area.

Kevin Brasler is executive editor and Mike Knezovich is contributing editor of Washington Consumers’ Checkbook magazine and, a nonprofit with a mission to help consumers get the best service and lowest prices. It is supported by consumers and takes no money from the service providers it evaluates. You can access Checkbook’s unbiased ratings of local insulation companies free until Sept. 1 at

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