Air sealing can be anything from a quick, five-minute fix to a more involved weekend project. Your goal is to find the biggest leaks in your home’s envelope (that’s the roof, walls, windows, doors, and foundation that separate indoors from out) and patch them up.  

Like any DIY home improvement project, the danger of scope creep—when a simple project snowballs into something far bigger (and more expensive!) than you planned—is very real. These steps should keep your overeager spouse from ripping out the bathroom wall!  

Step 1: Find The Leaks 

Your eyes and hands are a great place to begin: 

• Look for visible gaps or cracks under doors or around windows where light shines through. 

• Feel for cold spots or drafts along walls, near baseboards, anywhere where cords or pipes enter your home from the outside, and around window and door frames. 

  
  

Searching for leaks around the whole house may sound like an entire weekend project in itself, so we recommend focusing your search on the top and bottom floors.  Air escapes from your attic and basement at a much higher rate than the middle of your home—fixes here will give you the biggest bang for your buck. 

Sometimes the leaks are obvious; sometimes they’re sneakier. A thermal camera can come in handy your search doesn’t turn up anything obvious. There are models in the $200-350 range that plug right into your phone—both Android and iPhone have options. 

What these cameras do best is highlight temperature differences (or “delta”), showing where warm and cool spots meet. The exact temperature of your walls or floors isn’t as important as spotting the pattern. This works best in winter and summer, when the temperature difference between the air in your home and the outside air are highest.  

Example: In this thermal image, blue vertical stripes showed where wooden wall studs touched the outside wall, creating a “thermal bridge” for heat to escape. A blue horizontal stripe along the floor showed a long-forgotten gap between the wall and floor.  

The images might reveal more areas that need sealing or insulation but, again, beware of scope creep! Decide what you want to get done before diving headfirst into this DIY project.

Step 2: Make the Fix 

One of the most common DIY tools for sealing small gaps and cracks is expanding polyurethane foam—available at any hardware store in a variety of brands and types. 

Our volunteers recommend large-format spray foam cans used with a reusable gun. They’re more cost-effective, especially if you’ll be doing multiple small projects over time. Also, it’s pretty messy! Acetone (nail polish remover) cleans up as long as you you get to it before it cures. 

Two quick disclaimers: 1) foam fills small gaps and cracks—don’t try to DIY insulate your whole attic using cans of foam! 2) foam is a fossil fuel product. Its carbon footprint is larger than natural insulations like wool. For small jobs sealing jobs its alright, but most larger insulation projects can be done with friendlier “bio-insulation" like wood, cotton, hemp and even straw bales.   

Beyond foam, weather stripping is a popular and simple way to plug leaks around doors and windows. You’ll start to see hardware stores start place their weather stripping right beside the checkout aisle in the fall. 

If your walls or floors are very cold to the touch in the winter, then foam won’t cut it. You will need an insulation update to fix that. Final warning: beware of the home improvement snowball!  

Step 3: Check Your Work 

Once the sealing is done, go back and re-check the area the same way you first diagnosed it—looking, feeling, or using your thermal camera. Comparing “before” and “after” will tell you if you’ve solved the problem or if there’s more work to do. 

The Long Game 

Air sealing isn’t always about one big fix. Small improvements, layered over time, can add up to a surprising boost in home comfort and heating efficiency. 

So don’t be discouraged if there’s no single “aha!” moment—every gap you seal is one more step toward a warmer home. We’ve even heard about someone who brings a tube of caulk to housewarming parties and goes around sealing leaks...talk about a housewarming gift!