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How to caulk window air leaks

A man caulks a window using a caulking

A man caulks a window using a caulking gun. Credit: iStock

Air leaks in homes account for a sizable amount of energy loss. Many are found where window frames meet interior and exterior wall surfaces and window trim. Here's how to solve the problem.


Inspect inside and outside your home. Look for cracks where the window frame touches anything that's not a window. For example, the window may contact stone, brick, wood or vinyl siding and plaster or drywall. The cracks may be the thickness of a piece of paper or the width of a pencil. Inside your home, look where any wood trim around the window contacts the window frame or the wall surface.


Buy several tubes of siliconized acrylic caulk. Consider caulk that dries clear, so you don't have paint. Avoid pure silicone caulk, which is very hard to expertly install silicone caulk. You want caulk that is water-washable and easy to clean up.


Purchase a high-quality caulk gun and a good grout sponge. High-quality caulk guns usually cost about $20 and sport a higher thrust ratio of about 18:1 -- this means you have to squeeze the handle more times to get the caulk to flow from the tube. Although this may seem like more work, yYou get far greater control than the inexpensive caulk guns. Grout sponges have nice rounded edges, not sharp corners.


Only caulk the exterior cracks at your home if the air temperature is above 40 degrees and will stay there for at least 12 hours. Read the label of the caulk to see if the instructions say differently. You want the caulk to cure before it freezes.


Trim the tip of the caulk tube, slowly taking off just small amounts of the plastic. You want the hole at the tip of the tube to be no wider than 1 / 8 inch. Wide holes let too much caulk flow, creating a huge mess. You can always trim more off the tube tip. Start with a small hole to see how it works.


Using soapy water, wipe the area on each side of the crack to be caulked. Dry it immediately with an old towel. You don't want the area around the crack to be dirty so dirt gets into the fresh caulk as you smooth it. Clean around all cracks before you start to caulk.


Apply the caulk to just 2 linear feet of the crack. Glide the nozzle over the crack at a speed that allows just a small amount of excess caulk to rise above the actual crack. Do not apply too much caulk.


Glide your finger across the crack so the caulk is pushed into the crack. If large amounts of excess caulk build up on your finger, lift your finger from the crack and deposit the excess caulk onto the crack that's yet to be caulked. Finish tooling the caulk with your finger until all the caulk has been smoothed.


Dip the grout sponge in warm, clean water. Squeeze out any excess water. No water should be dripping from the sponge. Slide the sponge with moderate pressure over the crack, making sure you don't gouge out fresh caulk from the crack. You're trying to use the sponge to clean off any caulk from the edges of the crack where your finger smeared it. Rinse the sponge frequently and make repeated passes until all smeared caulk is removed from either side of the crack.


Change sponge water frequently so the window, trim and wall surfaces do not get fouled with caulk.

EXTRA TIP If you've not caulked before, practice first. Locate other cracks around your home in out-of-the-way areas or start with the windows you see least. It won't take much practice to get professional results.

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