Reducing the amount of air that leaks in and out of your home is a cost-effective way to cut heating and cooling costs, improve durability, increase comfort, and create a healthier indoor environment. Caulking and weatherstripping are two simple and effective air-sealing techniques that offer quick returns on investment, often one year or less. Caulk is generally used for cracks and openings between stationary house components such as around door and window frames, and weatherstripping is used to seal components that move, such as doors and operable windows.  

Air leakage occurs when outside air enters and conditioned air leaves your house uncontrollably through cracks and openings. Relying on air leakage for natural ventilation is not recommended. During cold or windy weather, too much air may enter the house. When it's warmer and less windy, not enough air may enter, which can result in poor indoor air quality. Air leakage also can contribute to moisture problems that affect occupants’ health and the structure’s durability. Sealing cracks and openings reduces drafts and cold spots, improving comfort.

The recommended strategy is to reduce air leakage as much as possible and to provide controlled ventilation as needed. Before air sealing, you should first:

• Detect air leaks
• Assess your ventilation needs for indoor air quality.

You can then apply air sealing techniques and materials, including caulk and weatherstripping. If you're planning an extensive remodel of your home that will include some construction, review some of the techniques used for air sealing in new home construction and consider a home energy assessment to identify all the opportunities to save energy and money in your home.

• Hire an energy assessor or other weatherization expert to test your home for air tightness.
• Caulk and weatherstrip 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 on any visual 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.
• Replace single-pane windows 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.
• Check your dryer vent to be sure it is not blocked. This will save energy and may prevent a fire.
• Replace exterior 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 into contact with heat. A reasonably capable do-it-yourselfer can create an inexpensive, reusable fireplace flue plug by filling a plastic trash bag with fiberglass batt scraps and jamming it into the flue. Attach a durable cord with a tag that hangs down into the fireplace to (1) remind you the flue is blocked and (2) provide an easy plug removal method.  If you want to save money on fireplaces, replace them with an EPA-certified insert, installed by a certified professional. 

Note that air sealing alone doesn’t eliminate the need for proper insulation to reduce heat flow through the building envelope.