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If you discover a large cold air leak where the caulking is missing around a window or door, along the siding or around your foundation, you don’t have to wait until spring to x it. But you will need to use special application techniques to do the job right. 

First, make sure that temporary measures won’t work until warmer weather arrives. Stu foam weather stripping or a piece of foam backer rod into the offending crack. However, don’t use duct tape or any other adhesive-backed materials; they likely won’t stick – and if they do, you’ll have a big, gooey mess to clean up before you can properly caulk the crack in a few months. In addition, don’t use berglass insulation, because it’s not a good air barrier. 

Most caulks work best when applied above 40 degrees; use below that temperature can diminish the adhesion, curing and long-term performance of the caulk. So, buy a special low-temperature caulk or one that contains silicone or rubber in its formulation. Then follow these tips for the best chance of success – even in below-zero temperatures. 

  • Choose a day when the weather forecast calls for no precipitation, the mildest temperature of the week and the smallest di erence between daytime and overnight temperatures. Wait until the warmest part of the day to caulk. 
  • Make sure all surfaces of the area to be caulked are clean and dry. A nearly invisible coating of ice may cover the area, so lightly wipe the area with acetone or methyl ethyl ketone or carefully blow on the area with a hair dryer plugged into an outdoor circuit protected by a ground fault circuit interrupter. (Do not mix these two drying techniques!) Then gently wire brush the area to promote adhesion. 
  • Warm the caulk inside your house to room temperature – a least 60 degrees – for a day before application. 
  • Be generous with your bead to allow for maximum expansion and contraction of the joint.

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