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Air leaks and drafts in your home envelope are responsible for a host of problems including moisture damage, inflated utility bills, and pests. Assessing your home’s leaks and filling them with caulk, spray foam, or weather stripping is the first step towards lowering your bills and protecting your home against pest- or weather-related harm.
Insulation will cover the leaks but will not stop the air flow, and therefore should only be added after leaks and drafts have been sealed. When sealing and weatherizing, be sure to maintain adequate ventilation through a controlled system (as opposed to air leakage) to prevent the accumulation of harmful pollutants, moisture, and odors.
Product Types
How It Works
The first step to sealing and weatherizing your home is to determine where the air leakage is occurring. The most effective technique is to hire a technician to perform a blower door test to discover leaks by depressurizing your home. Homeowners can also find some air leaks themselves by looking at areas where different materials meet, such as foundation and walls, or chimneys and siding.
The most common sites for air leakage include the following:
- Doors to the outside: any door that opens to the outdoors can be a source of leakage. Use weatherstripping to minimize the air exchange around closed doors.
- Switch plates and light switch covers: The hole in the wall behind most switch plates and light switch covers is a surprisingly substantial source of leakage. Use fireproof electrical insulation or pre-fabricated liners to stop this air flow.
- Attic trap door: Heat loss is very common through the seams of the attic trap door. The type of sealing best suited for your home will depend upon the frequency with which you access the attic.
- Bathroom fans: Fans that are vented to the attic can serve as flues that carry heated or air-conditioned air up and out of your home. Better insulation will help the fan remove moisture without constantly leaking air.
- Air ducts: If your home is heated or cooled by a forced-air system, air ducts are responsible for transporting air to the different areas of the house. While some are difficult to access, others are exposed and should be sealed to reduce bills and improve functionality.
Air barriers are effective both in preventing air leakage and controlling moisture in your home. While the most common type of air barrier is the house wrap used during construction, other types of insulation also block the flow of air into and out of your home. The very materials used to build your home are air barriers—drywall and sheathing, for example. In terms of additional insulation, foam board and dense-packed cellulose are the most effective, while fiberglass is not. In fact, fiberglass acts as an indicator of leaks by collecting dust. Humidity is important to consider when selecting air barriers; vapor diffusion retarders may be helpful in warm, damp climates. A continuous air barrier is the most efficient protection against leakage. It involves sealing all holes and seams between any sheets with caulk, gaskets, and/or foam sealants.
Sealing can be achieved through a variety of strategies, including air barriers, airtight drywall, caulking, and weatherstripping.
Ventilating your home is essential for both safety and structural soundness. Natural ventilation, fans and ducts, and spot ventilation are all methods of ensuring that your home is adequately exchanging air with the outdoors.
Click to learn more about caulking and weatherstripping
Low Cost Savings Tips:
- Most leaks are actually a series of leaks; if the leak is plugged in the area that is easiest to reach, it often does not need to be plugged in other areas.
- Seal the largest leaks first and save the smaller, less visible leaks for later. Sealing exhibits diminishing returns as it continues.
- Sealing or caulking your home can be done in steps—there is no need to retrofit your entire home in a weekend.
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- If you added up all the cracks and leaks in the average home, the total area would be equal to a 14’’x14’’ opening to the outdoors.
- It is essential to stop air leaks before adding insulation—the effectiveness of the insulation will be dramatically reduced, as will the likelihood of its being damaged by moisture.
- Air leaks occur through more than just the noticeably drafty areas of your home—the largest sources are not always obvious!
- Caulking and weatherstripping are two simple and inexpensive solutions that usually pay for themselves in a year, according to experts.
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Home Envelope 
