How to Caulk Old Windows for the Winter

Applying a bead of caulk

Old windows can be costly in extreme temperatures. When the weather turns cold and the wind kicks up, old windows are notorious for letting the heat escape from a house. Proper caulking can help keep the heat inside and the cold outside. Keep in mind that some older windows require glazing rather than caulk. If you are uncertain which to choose, there are many resources available to help you make that determination (see Resources).

Things You'll Need

• Utility knife
• Silicone caulk (match paint color)
• Putty knife
• Turpentine or naphtha
• Caulking gun

Instructions

1. Place the blade of the utility knife between the window and the old caulking. Pull the utility knife along from one corner of the window to the other. Cut slowly to get the best results. When cutting next to a wooden window, keep the blade of the knife as perpendicular to the window as possible to avoid damaging the wood.

2. Repeat step 1 until the old caulk is removed. If removing silicone caulk, you may need to use turpentine or naphtha to help remove it. Apply it with a soft cloth. Use a window scraper to remove bits and pieces of the solvents that get left behind on the glass.

3. Cut the cap on the tube of caulk at a 45-degree angle and place the tube in a caulking gun. If the tube of caulk has an inner seal, puncture it with a long nail or a similar sharp object.

4. Place the tip of the tube in a corner where the glass meets the wood. Pull the caulk along the seam until the seam is sealed. At the end of a run, stop squeezing the trigger and ease the tip away from the window. Repeat this for all of the window's seams.

5. Use the putty knife to smooth the edges of the caulking. Another option for smoothing a caulk line is to dip your index finger in water and then slide it over the caulk.

Tips & Warnings

• Do not use caulk to replace glazing as the seal will be compromised. Do not leave the utility knife or caulking unattended in the presence of children.

Resources

• Caulk Buying Guide
• Repairing Windows with Glazing