Weatherize Your Home—Caulk and Weather Strip
Consumer Energy Information: EREC Fact Sheet

Warmed or air-conditioned air mixes with outside air through gaps in your home's thermal envelope—exterior walls, windows, doors, the roof, and floors. Such air leaks can waste large amounts of energy.

Most experts agree that caulking and weather stripping any gaps will pay for itself within one year in energy savings. Caulking and weather stripping will also alleviate drafts and help your home feel warmer when it's cold outside. However, these two weatherization techniques can't replace the need for proper insulation throughout your home.

Assessing air quality
Because caulk and weatherstripping limit indoor-outdoor air circulation, you should assess your indoor air quality before you apply them. Some homes contain dust, mould, carbon dioxide, and other indoor air contaminants. Sealing air leaks in these homes, without proper ventilation, can also seal in their indoor air pollutants. Therefore, any plan to tighten the thermal envelope of a home should be accompanied by a look at your home's ventilation needs.

This fact sheet does not cover indoor air quality assessment and ventilation.

Detecting air leaks
You may already know where some air leakage occurs in your home, such as an under-the-door draft that makes you want to put on socks. But you'll probably need to search to find the less obvious gaps.

Look at areas where different materials meet, like between brick and wood siding, between foundation and walls, and between the chimney and siding. Also inspect around the following for any cracks and gaps that could cause air leaks:

• Door and window frames
• Mail chutes
• Electrical and gas service entrances
• Cable TV and phone lines
• Outdoor water faucets
• Where dryer vents pass through walls
• Bricks, siding, stucco, and foundation
• Air conditioners
• Vents and fans.

Depressurize your home to help detect leaks. On a cool, very windy day, turn off the furnace. Shut all windows and doors. Turn on all fans that blow air outside, such as bathroom fans or stove vents. Then light an incense stick and pass it around the edges of common leak sites. Wherever the smoke is sucked out of or blown into the room, there's a draft. Or just turn on all your exhaust fans (don't need to turn off the furnace) and try one of these methods:

• At night, shine a flashlight over all potential gaps while a partner observes the house from outside. Large cracks will show up as rays of light. Not a good way to detect small cracks.
• Shut a door or window on a piece of paper. If you can pull it out without tearing, you're losing energy.

For a more thorough and accurate measurement of air leakage, you can hire a technician to conduct a blower door test in your home. Blower doors are variable-speed fans with a frame and shroud that allows them to fit inside a variety of door frames. Pressure gauges determine airflow through the fan, as well as fan-induced pressure. The leakier a house, the more airflow required to induce a pressure difference. When used as a diagnostic tool, a blower door can also reveal the location of many leaks.

Caulking

Selection
You can use a caulking compound to seal leaks in a variety of places throughout your home, including around windows and door frames. In addition to plugging air leaks, caulking can also prevent water damage inside and outside of the home when applied around faucets, ceiling fixtures, water pipes, drains, bathtubs and other plumbing fixtures.

You can use a caulking compound to seal leaks in a variety of places throughout your home, including around windows and door frames. In addition to plugging air leaks, caulking can also prevent water damage inside and outside of the home when applied around faucets, ceiling fixtures, water pipes, drains, bathtubs and other plumbing fixtures.

Caulk forms a flexible seal for cracks, gaps, or joints less than 1 quarter-inch wide. Most caulking compounds come in disposable cartridges that fit in half-barrel caulking guns (if possible, purchase one with an automatic release). Some pressurized cartridges do not require caulking guns. When deciding how much caulking to purchase, consider that you'll probably need a half-cartridge per window or door and four cartridges for the foundation sill. Caulking compounds can also be found in aerosol cans, squeeze tubes, and ropes for small jobs or special applications.

Water-based caulk can be cleaned with water, while solvent-based compounds require a solvent for cleanup. Caulking compounds also vary in strength, properties, and prices. (See Table 1. Common Caulking Compounds at the bottom of this article)

Application
Although not a high-tech operation, caulking can be tricky. Read and follow the instructions on the compound cartridge. And save yourself some trouble by remembering a few important tips:

• Clean all areas to be caulked for good adhesion. Remove any old caulk and paint, using a putty knife or a large screwdriver. Make sure the area is dry so you won't seal in moisture.
• Hold the gun at a consistent angle. Forty-five degrees is best for getting deep into the crack. You know you've got the right angle when the caulk is immediately forced into the crack as it comes out of the tube.
• Caulk in one straight continuous stream, if possible. Avoid stops and starts.
• Send caulk to the bottom of an opening to avoid bubbles.
• Make sure the caulk sticks to both sides of a crack or seam.
• Release the trigger before pulling the gun away to avoid applying too much caulking compound. A caulking gun with an automatic release makes this so much easier.
• If caulk oozes out of a crack, use a putty knife to push it back in.
• Don't skimp. If the caulk shrinks, reapply it to form a smooth bead that will seal the crack completely.

Weather Stripping

Selection
Weatherstripping can seal leaks around movable joints, such as windows or doors. You need to choose a type of weatherstripping that will withstand the friction, weather, temperature changes, and wear and tear associated with its location. For example, when applied to a door bottom or threshold, weatherstripping could drag on carpet or erode as a result of foot traffic. Weatherstripping in a window sash must accommodate the sliding of panes—up and down, sideways or out. The weatherstripping you choose should seal well when the door or window is closed while allowing it to open freely.

Choose a product for each specific location. Felt and open-cell foams tend to be inexpensive, susceptible to weather, visible, and inefficient at blocking airflow. However, the ease of applying these materials may make them valuable in low-traffic areas. Vinyl, slightly more expensive, holds up well and resists moisture. Metals (bronze, copper, stainless steel, and aluminum) last for years and are affordable. They can also provide a nice touch to older homes where vinyl might seem out of place. You can use more than one type of weatherstripping to seal an irregularly shaped space. Take durability into account when comparing costs.
(See Table 2. Common Weatherstripping at the bottom of this article)

To determine how much weatherstripping you will need, add the perimeters of all windows and doors to be weather stripped. Then add 5 to 10 percent to accommodate any waste. Also take into consideration that weatherstripping comes in varying depths and widths.

Application
Weather-stripping supplies and techniques range from simple to the technical. Consult the instructions on the weather-stripping package. Here are a few basic guidelines:

Weatherstripping should be applied to clean, dry surfaces in temperatures above 20° F (-7° C).

Measure the area to be weather stripped twice before you cut anything.

Apply weatherstripping snugly against both surfaces. The material should compress when the window or door is shut.