Insulate & Ventilate

Sealing Air Leaks

Improving your home’s insulation and sealing air leaks are the fastest and most cost-effective ways to reduce energy waste and make the most of your energy dollars. Be sure to seal air leaks before you insulate, because insulating materials won’t block leaks.

Air leaks can waste a lot of your energy dollars. One of the quickest energy and money saving tasks you can do is caulk, seal, and weather strip all seams, cracks, and openings to the outside.


Tips for Sealing Air Leaks:

ins-and-ventEnergy Loses(Test your home for air tightness. On a windy day, carefully hold a lit incense stick or a smoke pen next to your windows, doors, electrical boxes, plumbing fixtures, electrical outlets, ceiling fixtures, attic hatches, and other places where air may leak. If the smoke stream travels horizontally, you have located an air leak that may need caulking, sealing, or weather-stripping)

– Caulk and weather-strip doors and windows that leak air.

– Caulk and seal air leaks where plumbing, ducting, or electrical wiring comes through walls, floors, ceilings, and soffits over cabinets.

– Install foam gaskets behind outlet and switch plates on walls.

– Inspect dirty spots in your insulation for air leaks, and mold. Seal leaks with low-expansion spray foam made for this purpose and install house flashing if needed.

– Look for dirty spots on your ceiling paint and carpet, which may indicate air leaks at interior wall/ceiling joints and wall/floor joists, and caulk them.

– Cover single-pane windows with storm windows or replace them with more efficient double-pane low-emissivity windows. See the Windows section for more information.

– Use foam sealant on larger gaps around windows, baseboards, and other places where air may leak out.

– Cover your kitchen exhaust fan to stop air leaks when not in use.

– Check your dryer vent to be sure it is not blocked. This will save energy and may prevent a fire.

– Replace door bottoms and thresholds with ones that have pliable sealing gaskets.

– Keep the fireplace flue damper tightly closed when not in use.

– Seal air leaks around fireplace chimneys, furnaces, and gas-fired water heater vents with fire-resistant materials such as sheet metal or sheetrock and furnace cement caulk.

– Fireplace flues are made from metal, and over time repeated heating and cooling can cause the metal to warp or break, creating a channel for air loss. To seal your flue when not in use, consider an inflatable chimney balloon. Inflatable chimney balloons fit beneath your fireplace flue when not in use, are made from durable plastic, and can be removed easily and reused hundreds of times. If you forget to remove the balloon before making a fire, the balloon will automatically deflate within seconds of coming in contact with heat


Weather StrippingA worker installs insulation in window.

Weather stripping is a necessary but often forgotten part of a home’s energy envelope. Insulating the attic, floors, walls, and ceilings and installing new windows and doors are all pointless unless these items are complemented by sealing the home with weather stripping. Weather stripping is very inexpensive and easy to install.



Properly installed insulation in walls, floors, and attics keeps your home comfortable in any season. The first thing we recommend is to simply do your research. To find personalized recommendations, you can use the ZIP-Code Insulation Program to find the best insulation level for your new home. Alternatively, you can use the U.S. Department of Energy’s R-Value Recommendations Calculator to find out how much insulation is needed in your area.

R-Value is the thermal resistance measurement used for insulation, indicating its resistance to heat flow. Be sure to check the insulation levels in any home you are considering.

US Department of Energy ZIP Code Insulation Calculator: 

R Value Calculator per Zip Code:


Insulation TypesRetrofit old house with energy saving insulating

Insulation is made from a variety of materials, and it usually comes in four types: rolls and batts, loose-fill, rigid foam, and foam-in-place.

Rolls and batts—or blankets are flexible products made from mineral fibers, such as fiberglass and rock wool. They are available in widths suited to standard spacing of wall studs and attic or floor joists: 2 in. x 4 in. walls can hold R-13 or R-15 batts; 2 in. x 6 in. walls can use R-19 or R-21 products.

Loose-fill insulation is usually made of fiberglass, rock wool, or cellulose in the form of loose fibers or fiber pellets. It should be blown into spaces using special pneumatic equipment. The blown-in material conforms readily to odd-sized building cavities and attics with wires, ducts, and pipes, making it well suited for places where it is difficult to effectively install other types of insulation.

Rigid foam insulation is typically more expensive than rolls and batts or loose-fill insulation, but it is very effective in exterior wall sheathing, interior sheathing for basement walls, and special applications such as attic hatches. Foam insulation R-values range from R-4 to R-6.5 per inch of thickness, which is up to 2 times greater than most other insulating materials of the same thickness.

Foam-in-place insulation can be blown into walls, on attic surfaces, or under floors to insulate and reduce air leakage. You can use the small pressurized cans of foam-in-place insulation to reduce air leakage in holes and cracks such as window and door frames, and electrical and plumbing penetrations.

There are two types of foam-in-place insulation: closed-cell and open-cell. Both are typically made with polyurethane.

With Closed-cell foam, the high-density cells are closed and filled with a gas that helps the foam expand to fill the spaces around it. Closed-cell foam is the most effective, with an insulation value of around R-6.2 per inch of thickness.

Open-cell foam cells are not as dense and are filled with air, which gives the insulation a spongy texture. Open-cell foam insulation value is around R-3.7 per inch of thickness.

The type of insulation you should choose depends on how you will use it and on your budget. While closed-cell foam has a greater R-value and provides stronger resistance against moisture and air leakage, the material is also much denser and is more expensive to install. Open-cell foam is lighter and less expensive but should not be used below ground level where it could absorb water. Consult a professional insulation installer to decide what type of insulation is best for you.


Insulation Tips:

– One of the most cost-effective ways to make your home more comfortable year-round is to add insulation to your attic, including the attic trap or access door, which is relatively easy. To find out if you have enough attic insulation, measure the thickness of the insulation.

– Consider factors such as your climate, home design, and budget when selecting insulation for your    home.

– Use higher R-value insulation, such as spray foam, on exterior walls and in cathedral ceilings to get more insulation with less thickness.

– Install attic air barriers such as wind baffles along the entire attic cave to help ensure proper airflow from the soffit to the attic. Ventilation helps with moisture control and reducing summer cooling bills, but don’t ventilate your attic if you have insulation on the underside of the roof. Ask a qualified contractor for recommendations.

– Be careful how close you place insulation next to a recessed light fixture—unless it is insulation contact (IC) rated—to avoid a fire hazard. See the Lighting section for more information about recessed lights.

– Follow the manufacturer’s installation instructions, and wear the proper protective gear when installing insulation.


Insulate your home when:

You have an older home and haven’t added insulation. Homes built before 1950 use about 60% more energy per square foot than those built in 2000 or later.

You are uncomfortably cold in the winter or hot in the summer-adding insulation creates a more uniform temperature and increases comfort.

You build a new home or addition or install new siding or roofing.

You pay high energy bills.

You are bothered by noise from outside-insulation muffles sound.


Typical CostRebates

Project: Install Ceiling Insulation

Difficulty level: Intermediate

Typical cost: $.30 to .50/sq. ft. (based on 6-in. fiberglass batts)


Project: Install Floor Insulation (when space below floor is unheated)

Difficulty level: Intermediate

Typical cost: $.30 to .50/sq. ft. (based on 6-in. fiberglass batts)


Project: Blown-in Wall Insulation

Difficulty level: Advanced or professional

Typical cost: $1 to $2/sq. ft. of wall (includes material and labor)



Open window against a white wall and the cloudy sky and sunWhen scouting a new home, windows are important to keep in mind because they can account for 10%-25% of your heating and cooling bills. Daylight and views aside, ventilation and heat from the sun can make a significant impact on your home’s energy efficiency. If your windows are letting in too much hot air, your central air conditioner is going to work much harder to cool your home in the summer.

To reduce this issue, keep a look out for double-paned storm windows with low-e” coatings, which can reduce heat loss through windows by 25%-50%. Weather stripping is also important for sealing your home’s climate.

An important measurement to keep in mind is a window’s U-factor, which is an insulation measurement for windows. A U-factor is the rate at which a window, door, or skylight conducts non-solar heat flow. A low U-factor is better for insulation in colder climates.

If your home has single-pane windows, consider replacing them with double-pane windows with high-performance glass— low-E or spectrally selective coatings.

In Colder climates, select gas-filled windows with a Low-C coatings to reduce heat loss.

In Warmer climates, select windows with Spectrally Selective coatings to reduce heat gain.


Typical Cost

Project: Window Replacement

Difficulty level: Advanced

Typical cost: $200 to $800 per window (cost more with a professional installation)

Typical payback: 15 to 30 years


NEW Window Tips:

– Check to see what rebates or other incentives are available for window replacement. Click on our “Energy Rebates” Tab for more information!

– Choose high-performance windows that have at least two panes of glass and a low-e coating.

– Select windows with both low U-factors and low SHGCs to maximize energy savings in temperate climates with both cold and hot seasons.

– Choose a low U-factor for better insulation in colder climates; the U-factor is the rate at which a window, door, or skylight conducts non-solar heat flow.

–  Look for a low solar heat gain coefficient (SHGC)—this is a measure of solar radiation admitted through a window, door, or skylight. Low SHGCs reduce heat gain in warm climates.

– Look for the ENERGY STAR label when purchasing new windows for your home.


Window Rating Label

Virtually all new windows have performance ratings that consider a number of factors—there are more important choices than “plain” or “insulating” glass. The most important factor in cold climates is the U-factor. U-factor is a measure of heat flow, equal to the inverse of the R-value, and the lower the U-factor the better. In warm climates, aim for a low solar heat gain coefficient (SHGC). For mixed climates, a combination of both ensures the best performance.

worlds best

So you Decided Not to Replace your Windows… follow these Tips to Improve their Performance:


Outside Cold Air…Warm Air Savings

– Use a heavy-duty, clear plastic sheet on a frame or tape clear plastic film to the inside of your window frames to reduce drafts. High performance window film (like Vista Enerlogic) can significantly increase winter heat retention and decrease summer heat gain without the cost of window replacement.

– Install tight-fitting, insulating window shades on windows that feel drafty after weatherizing.

– Close your curtains and shades at night to protect against cold drafts: open them during the day to let in warming sunlight.

– Install exterior or interior storm windows, which can reduce heat through the windows by 25%-50%. They should have weather stripping at all movable joints; be made of strong, durable materials; and have interlocking or overlapping joints.

– Repair and weatherize your current storm windows, if necessary.


Outside Hot Air…Cool Air Savings

– Install white window shades, drapes, or blinds to reflect heat away from the house.

– Close curtains on south- and west-facing windows during the day.

– Install awnings on south- and west-facing windows.

– Apply sun-control or other reflective films on south-facing windows to reduce solar heat gain.

– Look for whole-unit U-factors and SHGCs, rather than center-of-glass (COG) U-factors and SHGCs. Whole-unit numbers more accurately reflect the energy performance of the entire product.

Air Ducts


Your air ducts are one of the most important systems in your home, and if the ducts arc poorly sealed or insulated they are likely contributing to higher energy bills.

Your home’s duct system is a branching network of tubes in the walls, floors, and ceilings; it carries the air from your home’s furnace and central air conditioner to each room. Ducts are made of sheet metal, fiberglass, or other materials.

Ducts that leak heated air into unheated spaces can add hundreds of dollars a year to your heating and cooling bills. Insulating ducts that arc in unconditioned spaces is usually very cost effective. If you are installing a new duct system, make sure it comes with insulation.

Sealing your ducts to prevent leaks is even more important if the ducts are located in an unconditioned area such as an attic or vented crawl space. If the supply ducts are leaking, heated or cooled air can be forced out of unsealed joints and lost. In addition, unconditioned air can be drawn into return ducts through unsealed joints.

Although minor duct repairs are easy to make, qualified professionals should seal and insulate ducts in unconditioned spaces to ensure the use of appropriate scaling materials.


Minor Duct Repair Tips:

– Check your ducts for air leaks. First, look for sections that should be joined but have separated and then look for obvious holes.

– If you use tape to seal your ducts, avoid cloth-backed, rubber adhesive duct tape—it tends to fail quickly. Instead, use mastic, butyl tape, foil tape, or other heat-approved tapes. Look for tape with the Underwriters Laboratories (UL) logo.

– Be sure a well-sealed vapor barrier exists on the outside of the insulation on cooling ducts to prevent moisture condensation.

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