How to Caulk Window Air Leaks

Air Leaks in homes account for a sizable amount of energy loss. Many air leaks are found around the edges of windows where the window frame meets the interior and exterior wall surfaces and window trim. Here’s how to solve the problem.

Degree of Difficulty:

Step One: Do a quick inspection of the inside and outside of your home. Look for cracks where the window frame touches up against anything that’s not a window. For example, your window may contact brick, stone, wood or vinyl siding and plaster or drywall. The cracks may be as small as the thickness of a piece of paper or as wide as the diameter of a pencil. On the inside of your home look at both sides of where any wood trim around the window contacts the window frame or the wall surface.

Step Two: Purchase several tubes of siliconized acrylic caulk. Consider using caulk that dries clear so you don’t have to do any painting. Avoid using pure silicone caulk. It is very hard to expertly install silicone caulk. You want caulk that is water washable and easy to clean up.

Step Three: Purchase a high-quality caulk gun and a good grout sponge. High-quality caulk guns usually are priced around $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, you get far greater control than the inexpensive caulk guns. Grout sponges have nice rounded edges, not sharp corners.

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

Step Five: 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 one-eighth inch. Wide holes allow too much caulk to flow creating a huge mess. You can always trim more off the tube tip. Start with a small hole to see how it works.

Step Six: Wipe the crack to be caulked with soapy water to clean the area on each side of the crack. 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. Do all the cleaning around all cracks before you start to caulk.

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

Step Eight: Using your finger, glide it 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 this 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.

Step Nine: Dip the grout sponge in warm clean and clear 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 over the crack until all smeared caulk is removed from either side of the crack.

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

Summary: If you’ve not caulked before, I urge you to 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.

This column was shared in the November 12, 2013 AsktheBuilder Newsletter.

Column: HT001