Understanding and Improving Your Home’s Envelope

Why Sealing and Insulating Your Home Helps with Saving Energy Costs

The exterior of your home—the outer walls, ceiling, windows, and floor—is called the “envelope” or “shell.” As a knowledgeable homeowner or with the help of a skilled contractor, you can save up to 20 percent on heating and cooling costs (or up to 10 percent on your total annual energy bill) by sealing and insulating your home envelope. It will also make your home more comfortable and help your heating and cooling system run more efficiently.

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To improve your home’s envelope, you can make these changes yourself:

If your attic is accessible and you like home improvement projects, you can do-it-yourself with help. We have step-by-step instructions for sealing common air leaks and adding insulation to the attic to block heat loss in winter and heat gain in summer.

You can also hire a contractor who will use special diagnostic tools to pinpoint and seal the hidden air leaks in your home. A Home Energy Rater can help you find contractors that offer air sealing services in your area.

Finding Hidden Air Leaks that Suck Out Energy

Be sure to look for and seal air leaks before you install insulation because it performs best when air is not moving through or around it.

Many air leaks and drafts are easy to find because they are easy to feel—like those around windows and doors. But holes hidden in attics, basements, and crawlspaces are usually bigger problems. Sealing these leaks with caulk, spray foam, or weather stripping will have a great impact on improving your comfort and reducing utility bills.

common hidden air leaks in homes

Homeowners are often concerned about sealing their house too tightly; however, this is very unlikely in many older homes. A certain amount of fresh air is needed for good indoor air quality, and there are specifications that set the minimum amount of fresh air needed for a house. If you are concerned about how tight your home is, hire a contractor, such as a Home Energy Rater, who can use diagnostic tools to measure your home’s actual air leakage. If your home is too tight, a fresh air ventilation system may be recommended.

After any project where you reduce air leakage, have a heating and cooling technician check to make sure that your combustion appliances ( gas or oil fired furnace, hot water heater, and dryer) are venting properly.

Adding Insulation to Your Home

Insulation keeps your home warm in the winter and cool in the summer. There are several common types of insulation—fiberglass (in both batt and blown forms), cellulose, rigid foam board, and spray foam. Reflective insulation (or radiant barrier) is another insulating product that can help save energy in hot, sunny climates. When correctly installed with air sealing, each type of insulation can deliver comfort and lower energy bills during the hottest and coldest times of the year.

Insulation performance is measured by R-value—its ability to resist heat flow. Higher R-values mean more insulating power. Different R-values are recommended for walls, attics, basements, and crawlspaces, depending on your area of the country. Insulation works best when air is not moving through or around it, making it very important to seal air leaks before installing insulation to ensure that you get the best performance from the insulation.

To get the biggest savings, the easiest place to add insulation is usually in the attic. A quick way to see if you need more insulation is to look across your uncovered attic floor. If your insulation is level with or below the attic floor joists, you probably need to add more. The recommended insulation level for most attics is R-38 (or about 12 – 15 inches, depending on the insulation type). In the coldest climates, insulating up to R-49 is recommended.

ENERGY STAR® Qualified Windows

ENERGY STAR® Window diagramWindows are an important part of your home’s envelope. ENERGY STAR qualified windows feature advanced technologies such as invisible glass coatings, vacuum-sealed spaces filled with inert gas between the panes, improved framing materials, better weather stripping, and warm edge spacers, all of which reduce undesirable heat gain and loss.

  • Increase savings. With more efficient windows, you can save money and use less energy. Installing ENERGY STAR qualified windows can reduce energy bills by about 7 – 24 percent compared to non-qualified windows. Your estimated savings will vary depending on current heating and cooling costs in your region.
  • Improve comfort. ENERGY STAR qualified windows do more than just lower energy bills; they keep your home’s temperature consistently comfortable. During the winter, the interior glass of ENERGY STAR qualified windows stays warmer compared to typical windows, even when the temperature outside dips well below freezing. In the summer, most ENERGY STAR qualified windows reduce the heat gain into your home, without reducing the visible light.
  • Protect your valuables. Drapes, wood floors, a favorite photograph: all these things can fade or discolor after repeated exposure to direct sunlight. ENERGY STAR qualified windows have coatings that keep out the summer heat and act like sunscreen for your house, protecting your valuables from harmful, fading ultraviolet light without noticeably reducing visible light.

Look for the ENERGY STAR. The ENERGY STAR guidelines for windows are tailored to four climate zones. For example, windows in the North are optimized to reduce heat loss in the winter, while windows in the South are optimized to reduce heat gain during the summer. For optimal results, select ENERGY STAR qualified windows that are appropriate for your climate zone.

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