Feb 12 , 2019
Stop the drafts with outlet insulation
Many homeowners install plain foam gaskets between electrical cover plates and the switches/receptacles. However, those gaskets don’t always seal well. Infrared thermograph images of those outlets will show cold air still entering (which means warm air escaping) the house.
We’ll show you more effective methods that permanently seal those leaks. Sealing is easy to do and you can complete the entire house in about four hours. The materials cost less than $25, one of the best investments you’ll ever make! All you need is a caulk gun, caulk and aerosol foam. Here’s how to do it.
Buy the materials
Gaps around ceiling boxes must be sealed with an ‘intumescent’ fireblocking caulk or foam. Ordinary spray foam burns too quickly, opening the gap and creating a chimney effect that feeds the fire. Intumescent caulk or foam, on the other hand, swells when heated so it prevents that airflow. Regular caulk or foam can be used on wall-mounted boxes.
If the electrical boxes aren’t mounted flush with the drywall, adding a box extender will make them easier to seal. They’re available at most home centers for single, round and multiple-gang boxes.
Fill ceiling box gaps with fire-blocking foam
Invert the spray foam can and shove the tube up into the gap. Gently squeeze the trigger and slowly pump foam into the gap. Let it cure for about two hours. Then cut off the excess and reinstall the light fixture. Intumescent foam works best to seal large gaps (larger than 1/8 in.) around ceiling boxes. But the foam drips out as it expands and is difficult to remove after it cures. So turn off the power and double-check with a voltage sniffer. Then remove the light fixture, spread a drop cloth to protect the floor below, and inject the foam (Photo 1). Intumescent fire caulk doesn’t drip like foam, so you don’t have to remove the light fixture or cover the floor.