How to Stop The Draft in Your Basement

Drafty basements can waste a lot of energy. But its not just obvious things like windows that can be the source of drafts. The sill plate is the the wooden plate that runs all around the top of your foundation and it can let in more cold drafty air than an open window. Heres how I fixed my drafty sill plate, you can easily do the same.

Difficulty: Easy

Instructions

Things You'll Need:

• Caulk
• Screwdriver
• Backer Rod
• Fiberglas Insulation

1. 
   The sill plate goes across the foundation but underneath the joists

   Find the sill plate in your basement. The sill plate is underneath the joists but sits on top of the foundation. There may also be a layer of plastic between the sill plate and the foundation. Thats there to stop the sill plate from getting damp.

2. Put your hand near the sill plate on a really cold day. Test locations all around your basement to see if there is a noticeable draft. Sometimes its obvious, if you see light coming through the sill plate from outside, you definitely have a problem. Even a tiny gap between the concrete and the sill plate can leak a lot of cold air along the whole perimeter of your basement.

3. 
   Fill this open cavity between the joists with fiberglass insulation

   Trim the sill plastic back if it overhangs. Dont remove it though, it protects your sill plate from dampness. Above the sill plate, push fiberglas insulation into any open cavities. Where the joists are perpendicular to the sill plate, its easy to cut small rectangles of fiberglas and push the into the space between joists.

4. 
   Push the fiberglass into the cavity with your fingers or a stick

   Where the joists run parallel to the sill plate, its a little harder to push the fiberglas into the cavities. You might need a wooden stick to help push it in. Try not to compress the fiberglas. Seal up all the open cavities.

5. 
   Caulking the joint between the sill plate and the foundation

   Once all the fiberglas insulation is in place, start caulking the joint between the concrete foundation and the sill plate. This is a great way to learn how to caulk since its most likely your work will be covered up anyway. By the time you have caulked along 1 whole wall you will be getting good at caulking and will do a great job on the remaining walls.

6. Sometimes the gap between the sill plate and the foundation will be larger than the bead of caulk. If that happens fill the cavity with foam rubber "backer rod" and then caulk top and bottom of the foam rod. Backer rod can be purchased from many home improvement centers in various diameters.

7. Smooth or "tool" the caulk with your finger as you go. This will force it into the cavity and make a nice tight seal that looks more attractive. Keep wiping your finger off with a damp cloth

Tips & Warnings

• Dont forget to caulk around window openings
• Make sure your windows seal properly

Resources

• More information about sealing drafts