Caulk and Weatherstripping

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, mold, 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.

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.

Common Caulking Compounds
Caulking Compound	Recommended Uses	Clean-up	Shrinkage	Adhesion	Cost	Comments
Silicone: Household	Seals joints between bath and kitchen fixtures and tile. Forms adhesive for tiles and metal fixtures. Seals metal joints as in plumbing and gutters.	Dry cloth if immediate; mineral spirits or naphtha.	Little or none.	Good to excellent.	High	Flexible: cured silicone allows stretch of joints up to three times normal width or compression to one-half the width.
Silicone: Construction	Seals most dissimilar building materials such as wood and stone, metal flashing, and brick.	Dry cloth if immediate; mineral spirits or naphtha.	Little or none.	Good to excellent.	High	Permits joints to stretch or compress. Silicones will stick to painted surfaces, but paint will not adhere to most cured silicones.
Polyurethane, expandable spray foam	Expands when curing; good for larger cracks indoors or outdoors. Use in nonfriction areas, as rubber becomes dry and powdery over time.	Solvent such as lacquer thinner, if immediate.	None; expands quite a bit.	Good to excellent.	Moderate to high.	Spray-foam quickly expands to fit larger, irregular-shaped gaps. Flexible. Can be applied at variable temperatures. Must be painted for exterior use to protect from ultraviolet radiation. Manufacturing process produces greenhouse gases.
Water-based foam sealant	Around window and door frames in new construction; smaller cracks.	Water.	None; expands only 25%.	Good to excellent.	High.	Takes 24 hours to cure. Cures to soft consistency. Water-based foam production does not produce greenhouse gases. Will not over-expand to bend windows (new construction). Must be exposed to air to dry. Not useful for larger gaps, as curing becomes difficult.
Butyl rubber	Seals most dissimilar materials (glass, metal, plastic, wood, and concrete.) Seals around windows and flashing, bonds loose shingles.	Mineral spirits or naphtha.	From 5% to 30%.	Good.	Moderate to high.	Durable 10 or more years; resilient, not brittle; can be painted after one week curing; variable shrinkage; may require two applications; does not adhere well to painted surfaces. Toxic, follow label precautions.
Latex	Seals joints around tub and shower. Fills cracks in tile, plaster, glass, and plastic; fills nail holes.	Water.	From 5% to 10%.	Good to excellent.	Moderate.	Easy to use. Seams can be trimmed or smoothed with moist finger or tool. Water resistant when dry. Can be sanded and painted. Less elastic than above materials. Varied durability, 2 to 10 years; will not adhere to metal; little flexibility once cured; needs to be painted when used on exteriors.
Oil or resin-based	Seals exterior seams and joints on building materials.	Mineral spirits or naphtha.	From 10% to 20%.	Good.	Low.	Readily available. Least expensive of the four types. Rope and tube form available. Oils dry out and cause material to harden and fall out. Low durability, 1-4 years; poor adhesion to porous surfaces like masonry; should be painted; can be toxic (check label). Limited temperature range.

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.

Common Weatherstripping
Weatherstripping	Best Uses	Cost	Advantages	Disadvantages
Tension seal: Self-stick plastic (vinyl) folded along length in a V-shape or a springy bronze strip (also copper, aluminum, and stainless steel) shaped to bridge a gap. The shape of the material creates a seal by pressing against the sides of a crack to block drafts.	Inside the track of a double-hung or sliding window, top and sides of door.	Moderate; varies with material used.	Durable. Invisible when in place. Very effective. Vinyl is fairly easy to install. Look of bronze works well for older homes.	Surfaces must be flat and smooth for vinyl. Can be difficult to install, as corners must be snug. Bronze must be nailed in place (every three inches or so) so as not to bend or wrinkle. Can increase resistance in opening/closing doors or windows. Self-adhesive vinyl available. Some manufacturers include extra strip for door striker plate.
Felt: Plain or reinforced with a flexible metal strip; sold in rolls. Must be stapled, glued, or tacked into place. Seals best if staples are parallel to length of the strip.	Around a door or window (reinforced felt); fitted into a door jamb so the door presses against it.	Low	Easy to install, inexpensive.	Low durability; least effective preventing airflow. Do not use where exposed to moisture or where there is friction or abrasion. All-wool felt more durable and more expensive. Very visible.
Reinforced foam: Closed-cell foam attached to wood or metal strips.	Door or window stops; bottom or top of window sash; bottom of door.	Moderately low	Closed-cell foam an effective sealer; scored well in wind tests. Rigid.	Can be difficult to install; must be sawed, nailed, and painted. Very visible. Manufacturing process produces greenhouse gas emissions.
Tape: Nonporous, closed-cell foam, open-cell foam, or EDPM (Ethylene Propylene Diene Monomer) rubber.	Top and bottom of window sash; door frames; attic hatches and nonoperable windows. Good for blocking corners and irregular cracks.	Low.	Extremely easy to install. Works well when compressed. Inexpensive. Can be reinforced with staples.	Durability varies with material used, but not especially high for all; use where little wear is expected; visible.
Rolled or reinforced vinyl: Pliable or rigid strip gasket (attached to wood or metal strips.)	Door or window stops; top or bottom of window sash; bottom of a door (rigid strip only).	Low to moderate.	Easy installation. Low to moderate cost. Self-adhesive on pliable vinyl may not adhere to metal; some types of rigid strip gaskets provide slot holes to adjust height, increasing durability. Comes in varying colors to help with visibility.	Visible.
Door sweep: Aluminum or stainless steel with brush of plastic, vinyl, sponge, or felt.	Bottom of interior side of in-swinging door; bottom of exterior side of exterior-swinging door.	Moderate to high.	Relatively easy to install; many types are adjustable for uneven threshold. Automatically retracting seeps also available, which reduce drag on carpet and increase durability.	Visible. Can drag on carpet. Automatic sweeps are more expensive and can require a small pause once door is unlatched before retracting.
Magnetic: Works similarly to refrigerator gaskets.	Top and sides of doors, double-hung and sliding window channels.	High	Very effective air sealer.
Tubular rubber and vinyl: Vinyl or sponge rubber tubes with a flange along length to staple or tack into place. Door or window presses against them to form a seal.	Around a door.	Moderate to high.	Effective air barrier.	Self-stick versions challenging to install.
Reinforced silicone: Tubular gasket attached to a metal strip that resembles reinforced tubular vinyl	On a doorjamb or a window stop.	Moderate to high.	Seals well.	Installation can be tricky. Hacksaw required to cut metal; butting corners pose a challenge.
Door shoe: Aluminum face attachment with vinyl C-shaped insert to protect under the door.	To seal space beneath door.	Moderate to high.	On the exterior, product sheds rain. Durable. Can be used with uneven opening. Some door shoes have replaceable vinyl inserts.	Fairly expensive; installation moderately difficult. Door bottom planning possibly required.
Bulb threshold: Vinyl and aluminum	Door thresholds	Moderate to high.	Combination threshold and weatherstrip; available in different heights.	Wears from foot traffic; relatively expensive.
"Frost-brake" threshold: Aluminum or other metal on exterior, wood on interior, with door-bottom seam and vinyl threshold replacement.	To seal beneath a door.	Moderate to high.	The use of different materials means less cold transfer. Effective.	Moderately difficult to install, involves threshold replacement.
Fin seal: Pile weatherstrip with plastic Mylar fin centered in pile.	For aluminum sliding windows and sliding glass doors.	Moderate to high.	Very durable.	Can be difficult to install.
Interlocking metal channels: Enables sash to engage one another when closed	Around door perimeters.	High.	Exceptional weather seal.	Very difficult to install as alignment is critical. To be installed by a professional only.

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.
  

Credit: U.S. Deptartment of Energy