A front door on a white home with a lot of windows. In a home like this, air-sealing your doors and windows will go a long way.
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Seal up that house

Why Air-Sealing is The Best DIY You Can Do

Steve Hansen
November 5, 2023

Have you ever looked at your heating and cooling bill and thought, “This is nuts!”? You’re not alone. Home heating uses more energy—29%—than any other system in the home, according to the U.S. Department of Energy. So, if you’ve wondered what you can do to shrink that figure, let’s talk about air sealing.

Air sealing is job #1 on your energy-efficiency mission. The main point is to have control of the conditioned air within your home, the air you’ve heated, cooled, or dehumidified. If air is leaking into and out of your home, you don’t have control, and “expensive” air that you’ve paid to condition is leaking out.

Where Are the Leaks?

The best way to address your home’s air-sealing problems is with an energy assessment, which is covered as a tax credit of up to $150 under the Inflation Reduction Act. With your assessment, a professional home energy auditor will perform testing on various parts of your home, including thermal imaging testing that shows the warmer and cooler areas in walls, indicating a lack of insulation. This is incredibly useful later when you get busy upgrading your insulation.

Your assessment should also include a blower-door test. This test involves installing a special blower, which is a powerful fan mounted into a door-sized frame, into one of the exterior doors. The rest of the doors and windows are closed during the test. The fan pulls the air out of the house, depressurizing it and pulling in outside air through the gaps and cracks scattered around the house. The assessor can then use a tool called a smoke pencil to locate drafts while the test is occurring.

A technician conducting a blower door test

After your test is complete, you’ll get a detailed report specific to your home. From there, you can get busy air sealing, knowing you are truly solving the problem. That link from the Department of Energy has 19 “trouble spots,” but here are some of the most common spots for air leakage:

  • Loose-fitting doors and windows
  • Gaps around door and window frames
  • Electrical outlets in exterior walls
  • Kitchen and bath fans
  • Plumbing, dryer, and furnace vents
  • Gaps where electrical service enters the house
  • Gaps where plumbing lines enter the house.

Where to Start Sealing

Now that you know where the leaks are, you can get to work. But what product is right for the job? You use caulk to fill gaps up to about ¼-inch wide in a stationary surface or material. For a wider gap, you can use expanding spray foam. You’ll find this labeled as “gap and crack filler,” which expands minimally, and the standard form, which seems to expand 10x or so. The standard stuff can bend a door frame out of alignment as it cures and wreck all your work, so I almost never use that. Be advised that spray foam will degrade from UV radiation, so if you use it outside, you must paint it. That said, I always plan to smooth caulk or foam while it’s wet and then paint it later anyway so it looks tidy. Foam is ugly-looking stuff. Here’s a whole lot more information about caulk and the whole process.

If you have one stationary surface and one moveable surface, as you do with doors and windows, you use weatherstripping. I’m counting 14 listings here. Whew! But getting the appropriate product makes a huge difference in actually getting a good air seal, and you’ll see descriptions such as “beneath a door” and “around a door,” so you’ll know you’re on the right track. Door sweeps are one example of a simple and effective product that installs quickly and is appropriate whether you own your home or are renting. You can find them in screw-on and adhesive models.

For a lot of homes, getting the door and window drafts sealed is more than half the battle. After that, take a look at any gaps around the door and window frames and caulk those if necessary.

Next up, I would look at adding plastic film to drafty windows. Just in case you’re not familiar with this product, it’s pretty simple, but you do have to follow the instructions. First, apply the double-sided tape to the window frame, then apply the plastic film as evenly as you can to the tape. Then heat shrink the film with a hair dryer. This product works well to seal out drafts from older windows!  

What’s Next?

If you have your assessment report, you may have a long list of gaps to fill. If not, I would look at the following items in any order.

Electrical outlets/switches in exterior walls: Most of these are a bit drafty, but all you have to do is pull off the faceplates and install these foam gaskets. You’ll need to do this for both outlets and switches, by the way.

Seal the Attic Hatch: Most attic hatches are sketchy, as it’s just tough to get a good seal there. Some are just a panel, and some have stairs that pull down. Either way, you can look at sealing it off with a product like this, or go the DIY route if you have some skills.

Seal the Basement Windows and Doors: If you have a basement, oftentimes the windows and doors have been treated as an afterthought, so are ripe for improvements. Weatherstripping and caulking, as you did on the main floor, will be helpful.

Seal plumbing, dryer, fan, and furnace vents: Using either caulk or minimally expanding foam, go fill those gaps! It’s best to start outside unless the gaps are at the second story, and you don’t want to work up high. In that case, work inside and do your best.

Seal gaps where electrical service and plumbing lines enter the house: Caulk or foam, again, as necessary. You’ll want to keep checking on these gaps yearly, as expansion and contraction tend to keep opening up gaps over time.

That’s A Good Start!

As you tackle the most egregious leaks, you should see a difference in your utility bills very soon. You might also see a change in indoor air quality as your home becomes “tighter,” so an air purification system may be a wise move, especially if you have a gas range and/or gas furnace. Heat recovery ventilators and energy recovery ventilators might also be appropriate, depending on your circumstances.

Here’s to lower energy bills!

Editor’s note: If you make a purchase through our affiliate partner links, we may receive a commission. This does not impact the recommendations we make.

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