Finding and Fixing Home Air Leaks

You've insulated and caulked, but your house still fills cold and drafty. It's time to search for the remaining home air leaks: Inspect bottom plates, electric outlets and switches, beam pockets and junctions, vanities and sinks.


A blower door is installed in one of a home's entries so that the building can be pressurized to find air leaks.


Content Tools

When the temperature dropped and heating costs jumped — two signs of fall — you decided to improve the thermal performance of your home. So to button up your house, you headed down to the hardware store to buy some of those do-it-yourself weatherization kits that you'd seen advertised so widely. You picked up storm windows, rolls of weather stripping and tubes of caulk to seal cracks around doors and windows.

Yet, although you then spent an entire weekend on your weatherization project, winter has shown you that your house is still fairly drafty. There must, you reason, be other places that are letting the north wind blow in.

Finding the Other Home Air Leaks

According to Carl Ellerbrook, an "energy doctor," 80 to 90 percent of the home air leaks (called infiltration) in most houses come from holes that people don't even know about. The average dwelling has 10 or so leakage areas, which may account for as much as 40 percent of the home's total heating and cooling requirements, and those window and door kits you installed only took care of two

of them. To really snuggle up for the winter, you've got to find the rest of the gaps in your dwelling's shell.

Ellerbrook's business — through his company, the Sunup Energy Group Ltd. of Old Snowmass, Colo. — is finding and sealing the other leaks. To do so, he performs energy audits using a sophisticated device called a blower door. This huge fan fits into an exterior doorway and pressurizes a building to increase the leakage rate. Then Carl uses a smoke pencil to trace drafts to their sources. With the blower door and smoke pencil, he can pinpoint even small leaks.

"Because every house is different," states Carl, "it's nice to use a blower door and smoke pencil to take the guesswork out of finding leaks." Still, after several years of experience with that equipment, Carl has learned where most of the typical problem areas are in the average home. So although a competent energy audit is the best way to find the thermal leaks in your home, checking out Carl's list of the 10 worst offenders will go a long way toward keeping you cozy when the snow flies.

"You'll find air infiltration anywhere there's penetration through the inside or outside shells of a building," says Ellerbrook. Make a complete walk-through inspection of your house, examining the following areas with particular care. Then seal each leak from the inside of the house. Weatherization materials will last much longer indoors, where they're protected from harsh weather, and moisture problems within the wall will be avoided.

Bottom Plates

"If you don't do anything else," says Carl, "seal all gaps between the subfloor and the bottom plate." In new construction, this can be done by caulking the bottom plates (the bottom, horizontal boards in walls) as they're installed. In existing buildings, however, you'll have to seal between the baseboards and the bottom plates.

A polyurethane foam sealant applied to the cracks will fill any gaps and stop infiltration. This material is particularly useful for leaks that are large (¼ to 2 inches wide), because it will expand to fill the cavity. When you use the material, however, be sure to pull carpet back and move furniture out of the way to avoid spills. It's also a good idea to practice a little before you attempt your first touchy sealing job.

Electric Outlets and Switches

Remove the cover plates from all switches and outlets and install foam gaskets. These should be readily available at hardware stores. To get a really tight seal, you can add plastic socket plugs to unused receptacles.

Outlet and switch covers can actually account for up to 20 percent of your home's air leaks, and the gaskets cost only about $1.35 for a package of six. This is one of the least expensive, easiest sealing jobs you can tackle.

Beam Pockets and Junctions of Dissimilar Materials

Since heat rises, you could be losing a lot of energy through cracks in the ceiling. Caulk thoroughly around the edges of beams and anywhere two different materials meet. Because the dissimilar materials shrink and expand at different rates, cracks are fairly common.

As long as the gaps aren't too large, caulk is the best sealant for visible parts of the ceiling. It can be smoothed to make the patch job barely discernible. Ellerbrook recommends Geocel's elastomeric copolymer caulk because it's extremely flexible, but adds that any siliconized acrylic latex caulk with a 15- to 25-year warranty will work acceptably. A quality caulk will cost about $6.00 per tube.

Vanities and Sinks

The holes that are drilled under kitchen and bathroom sinks for plumbing runs are often oversized to allow for a little error in layout. The offending gaps are then covered with flanges and, unfortunately, are seldom sealed. Lift the flanges on all pipes that pass through the walls or floor of your home, and seal them with foam.


Gaps between a door and its frame should be sealed with weather stripping, but the frame itself should be caulked to prevent leakage around the outside of the door jambs. To seal the bottoms of doors, use weather-stripping tape and vinyl door sweeps on all sills. If you have metal doors, it's a good idea to pick a product that uses magnetic weather stripping to provide a tight seal.

Con-Serv, Incorporated makes a garage door insulating cover that attaches to the inside and adds R-5. The vinyl-faced fiberglass also helps seal a leaky door. Expect to pay about $65 for one of these kits.

Window Air Leaks

There are a great many products available for sealing windows, but the most practical retrofit is to apply heavy plastic and seal it to the window frame with polyethylene tape. An equally easy, but slightly less effective, approach is to use caulking cord, for which you can expect to pay about $3.00 per roll.

You can also buy kits for sealing windows. The Bede system, for example, includes a plastic sheet that attaches to vinyl channels. When the material is heated with a hair dryer, it draws up "drum tight" for a crystal clear appearance. This treatment costs about 60 cents per square foot.

While you're working on your windows, you should also consider using insulated shades or shutters. Not only will these increase the R-value of the glazed area, but they'll help seal as well.

Air Conditioners and Attic Fans

Fans and air conditioners should be covered with plastic and sealed with tape or caulk when they're not in use. Con-Serv makes an indoor air-conditioner cover that seals, insulates and reflects heat. Another option is to remove the unit from the window for the winter and store it in a sheltered location.


Caulk around the fireplace mantel and sides, using foam backer rod to fill cracks that are too big for caulking alone. Stone fireplaces to which drywall abuts are particularly troublesome. Also, check the fireplace damper to see that it closes tightly and seals well. (Since you'll be using the fireplace during the winter, the only good remedy for a leaky damper is to replace it.)

Wiring Penetrations

Use a polyurethane sealant around all wires that penetrate the house walls. It will take a close inspection to find all of the holes that have been drilled for these items, but a thorough sealing job will cure a lot of small, nagging drafts.

Other Holes

You'll probably be surprised to see how badly the frames of exhaust vents, recessed lights, registers and trapdoors seal to the surrounding material. These ill-fitting devices can let a tremendous amount of air into your home. Remember, too, that vents — whether they be for bathroom exhaust fans, your clothes dryer or a range hood — should have a flap that seals automatically when the appliance isn't in use. In addition, if you have registers that are closed off, install a magnetic seal over them: Most operable registers leak at a rate of 30 to 40 percent of maximum capacity when closed. (Be aware, however, that furnaces with burners may overheat if too many registers are closed.)

These 10 steps will cut energy-wasting air leaks in your home down to a tolerable level, but the building will probably still allow enough air to pass through the shell to keep the indoor environment fresh. In general, only those buildings that were built to be tight will need an air-to-air heat exchanger.

Once you've stopped the wind from blowing straight through your house, you can attend to other areas of energy efficiency. Add insulation (if your dwelling doesn't already have an adequate thermal blanket), have your furnace tuned, replace its air filter, insulate your water heater's tank and delivery lines, install water-saving shower heads and faucets and consider using products such as insulating pads for your beds, destratification fans to pull warm air down from the ceiling or a clothes dryer heat exchanger. By sealing up tight and then nibbling away at the energy wasters and home air leaks in your household, you can save a small fortune every winter!

The Energy-Auditing Business

Making house calls as an energy doctor is a profession with obvious potential. Eighty percent of the housing that's available today will still be in use when the year 2000 rolls around, and at least half of those buildings are veritable energy sieves. It's hard enough now to pay the utility bills on an energy eater, and as fuel prices rise, owners of such dwellings are going to need help!  

Carl Ellerbrook says that it takes about $10,000 to get started in the energy-auditing and weatherization business...that's enough to cover equipment, materials and advertising. You'll need a blower door, a smoke pencil, a tape measure, a compass, plastic sheets and tape to perform the energy audit. Then a ladder, a caulking gun, a drill, a carpet kick tool and common hand tools will be needed to make the repairs.  

You’ll also have to keep a stock of weatherization supplies on hand. These include polyurethane foam, caulking, outlet seals and plugs, backer rod, vinyl door sweeps and storm window kits. An average house of 1,800 square feet could need as many as 50 tubes of caulk, 5 pounds of polyurethane foam and 100 outlet and switch gaskets. Be sure to keep paper towels, bags and a can of acetate on hand to clean up spills.  

It's best to work in pairs when weatherizing a house — some jobs just seem to demand at least three hands. Also, you can expect to put in 30 to 60 person-hours on each building, so doubling up gets you in and out of a customer's home more quickly.  

You should find it easy to get people excited about saving energy if you can convince them that they'll also be saving money. Use simple advertisements in newspapers, fliers and word of mouth to get your message out. Be sure to let people know that you can offer either a basic energy audit or complete service, including weatherization.  

Your audit should consist of measuring the air changes per hour of the house (this is done with the blower door), inspecting the building for problem areas and reporting to the homeowneron the procedures you recommend (include a prioritized list of steps to be taken and the savings possible with each). You should offer other basic energy conservation materials and services, such as insulation, water-saving faucets and water heater insulation.  

The actual amount you charge will vary greatly depending on the job. Ellerbrook's Sunup Energy Group Ltd. charges 35 to 50 cents per square foot of floor area for its services. A small weatherization business can grow rapidly within a few years. Ellerbrook started in 1982 and has already joined with architect Peter Dobrovolny to form a full-service residential energy business. Sunup now offers complete active and passive solar consulting, a passive solar design and construction service and retail sales of energy-conserving products, along with home energy audits and weatherization.  

With today's heightened energy consciousness, the time is ripe to market conservation.