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How to find air leaks—A troubleshooting guide.

Every home has air leaks that make it less comfortable. Learn how to find them (and what to do to get rid of them).

Every home has air leaks that make it less comfortable. Learn how to find them (and what to do to get rid of them).

If you’re looking to cut energy waste in your home, data shows that—by far—one of the best ways to do that is to find and fix air leaks.

“Air leaks?” you say. “What about my old HVAC system?”

Don’t get us wrong: Having an efficient HVAC system and sufficient insulation is important. But, according to EnergyStar, air leakage is responsible for up to 40% of the energy loss in American homes (1). 

This means that almost half of the energy you use to heat and cool your home disappears through the holes in your house’s structure. Yikes.

So finding the leaks in your home—and then fixing them—can go a long way toward improving your home’s efficiency and comfort.

So how do you find air leaks in your house?

Looking for air leaks is usually a job best left to a professional—and we’ll tell you why—but we’ve put together a comprehensive list of easy, at-home techniques you can use to see where air is escaping your home.

(Then, of course, we’ll explain how to fix them for good.)

Here’s what we’ll be covering:

Ready to find where air is escaping your house? Let’s get started.

air sealing

What do you mean when you say “air leaks”?

A quick definition: Air leaks are gaps or openings that allow air to enter and exit your home.

They can be found in any number of places, including:

  • Around doors and windows
  • In the attic
  • Around electrical outlets
  • Around the structure’s foundation
  • The rim joists
  • Near plumbing fixtures

Just about every house in the U.S. has these leaks, and, frankly, that’s understandable.

It’s natural for homes to settle, shift, and develop gaps as years go by. (You can thank the second law of entropy for that. Nothing lasts forever!)

But leaving these gaps untreated is like leaving your front door open all the time.

In the winter, the heat you’re paying for will escape through your house’s air leaks, and cold air will come in instead. No good, and certainly not comfortable. 

In the summer, the opposite happens, and you’ll be swamped in a stuffy room with hot, muggy, unpleasant air from the outside while the cool, conditioned air you pay for slips out of your house.

In both cases, and in all seasons, having a house full of air leaks means your HVAC system will have to work overtime to maintain the temperature you want, which wastes energy and drives up your utility bills.

And the worst part, of course, is that air leaks can make your house super uncomfortable.

Don’t worry. There’s a fix—and it’s called air sealing. But first, we have to find the air leaks!

You can save an average of 15% on heating and cooling costs when you seal and insulate (2). Pair that with heat pump HVAC, and homeowners can cut energy use up to 50%.

How to check for air leaks—easy air leak tests you can perform right now 

Checking for air leaks sounds intimidating, but it really isn’t. We’ll walk you through the process. You’re about to be your own DIY draft detector.

Use your eyes

The first step in finding air leaks is to… look for them. Take a walk through your home and look for any cracks or gaps—however small. It’s likely you’ll find air leaks around:

  • Doors
  • Windows 
  • Baseboards
  • Electrical outlets
  • Plumbing fixtures
  • Attic hatches

Also, if you can do so conveniently, check around the foundation (where your house meets the ground).  Normal settling can cause gaps between cement blocks and bricks, and these gaps can allow air in.

Scope out the attic, too, if you’re able. Lighting fixtures, ductwork, electrical wiring, and bathroom fans all are a good place to start looking for open gaps and seams.

Another visual anomaly to look for is chipped or missing caulk.

Caulk is the sealant that’s used to fill cracks and gaps in a home’s structure, so if you see any cracks or gaps that are filled with what looks like putty, that’s caulk. If it’s cracked, chipped, or missing entirely, that’s an indication that air might be getting through.

Check for air leaks caused by cracked or missing caulk around fixtures and electrical

Lighting fixtures, ductwork, electrical wiring, and bathroom fans all are a good place to start looking for open gaps and seams.

Basically, you’re looking for cracks, places where structural materials don’t quite seem to meet, and anything that doesn’t look right. 

As previous generations used to say: If something doesn’t look right, it probably isn’t.

Word to the wise: Just because you don’t see any gaps doesn’t mean there aren’t any—not all air leaks will be visible to the naked eye. Sometimes they can be hidden behind walls, ceilings, and floors.

Use your hands

The second step in finding air leaks is to use your hands to feel for incoming air.

Start by turning off any fans, humidifiers, and other sources of moving air in your home. You should also close any exterior doors and windows. 

Then walk through your house and gently hold your hand around the edges of doors and windows, light switches, electrical outlets, and plumbing fixtures.

If you feel a draft or a current of air coming in, hey… you’ve found an air leak. (Congratulations?)

Two quick tips here:

  1. First, this trick really works better in the wintertime, because it’s easier to feel cool air coming in than warm air.
  2. The second tip is to dampen your hand before you perform the test—it’ll make you that much more sensitive to incoming air and may help you to detect leaks you might otherwise have missed.

(Need more troubleshooting advice? Read Why is my house so cold?)

Use a dollar bill to check for air leaks

Here it is! One of the most useful things you can still buy with $1.

It’s a super simple test, too: Essentially, you want to go to each window and door in your house, close that window or door on the dollar bill, and then see if you can pull your money back out again.

If your window or door is greedy and won’t give you your cash back easily, that’s a good sign. It’s probably closing tightly enough to keep outside air out. 

But if the dollar bill slips right back out, then the window is not closing tightly enough and might be letting air in. (Learn how to fix drafty windows here.)

By the way, you can technically do this test with any appropriately-sized piece of paper. Maybe your most recent utility bill, if you need to take out some aggression?

Use tissue paper to check for air leaks

Tissue paper is also a great way to check for air leaks.

Just grab a length of toilet paper and move it—slowly and methodically—around the perimeter of your window and door frames. 

Watch for it to waver. When it does, you’ve found another air leak.

Note that, for this to work, you’ll definitely need to turn off any fans or other sources of moving air in your house.

One of the best things about this test is that it makes it easy to see which leaks are letting in the most air. A light waver means a small leak. A big waver? Well, you’ve clearly got bigger problems.

Another bonus of the tissue paper test? It makes for a hilarious scene for any other household members to walk in on.

One of the best things about DIY air leak tests, like this one, is that it makes it easy to see which leaks are letting in the most air.

Use incense or a candle to check for air leaks

Another very visual way to check for air leaks is to do a DIY home pressurization test using a candle or incense—both of which are extremely sensitive to airflow.

Here’s how to do this simple DIY air leak test:

  1. First, pick a day that’s cool (preferably cold!) and windy. 
  2. Then make sure that your house is completely shut up. Close your windows and doors. Close your fireplace flues and any other access points to the outside. Don’t forget your pet doors!
  3. Next, turn off any appliances that use combustion fuel (think: gas-burning water heaters and furnaces).
  4. Finally, turn on all the exhaust fans in your home, such as the ones in your kitchen and bathroom as well as your stove top vents.
  5. Done all that? You’re ready. Light the candle or get the incense smoking, and then hold the flame or smoke near doors, windows, and any other potential places where air might be leaking in or out. (We probably don’t need to tell you this, but if you do use a candle, be careful. We’re not responsible for accidents.)

If the flame wavers or the smoke is blown away from the stick, that’s an indication that there’s unwanted air movement.

If you’re uncomfortable with waving a live flame around your windows—or you don’t want your whole house to smell like patchouli incense—a variation on this trick is to use a smoke pen (sometimes also called a smoke pencil) instead of a candle or incense. 

Smoke pencils cost about $50, but they produce a safe, non-toxic smoke and last up to three hours. You can even refill them if your neighbors are jealous of your newfound air leak knowledge.

Use an air leak detector

If you’re serious about finding the leaks in your home, using an air leak detector is one of the most accurate at-home tests. There are two main types: 

  • Thermal leak detectors 
  • Ultrasonic leak detectors

Thermal leak detectors work by detecting temperature differences in the air.

Ultrasonic leak detectors work by detecting sound waves that are produced by air leaks.

Both types of air leak detectors are available at most hardware stores, and they typically cost between $20 and $50 (here’s a highly-rated one that costs about $40). 

Air leak detectors are a relatively inexpensive tool, and you may even be able to find one in a home tool lending library.

To use an air leak detector, simply turn it on and move it around the perimeter of your home, around doors and windows, etcetera—you know the drill by now.

The air leak detector will beep or make some other obvious sound when it detects an air leak. Pretty straightforward.

Mentioning air leak detectors is a bit of a cheat on our part, since you probably don’t have one of those laying around at home. 

But they’re a relatively inexpensive tool, and you may even be able to find one in a home tool lending library. (Don’t know your local tool lending library? Find one by Googling “tool library [YOUR TOWN]” or by visiting LocalTools.org.)

Now that we’ve covered the best DIY ways for you to check for air leaks, let’s talk about how the professionals do it.

(Because—let’s face it—you’re eventually going to want a professional to do this.)

blower door test for air leaks

What is a blower door test?

A blower door test is the most comprehensive and reliable way to find every single air leak that’s wasting energy in your home.

This test is conducted by a professional who will use a specialized machine to pressurize or depressurize your home. By doing this, they can identify exactly where air is leaking in or out of your home—so they can fix it with air sealing.

The big question here, of course, is why would you get a blower door test if you can test for air leaks yourself? 

The truth is, while you can do some great DIY air leak tests on your own, no home test is going to catch 100% of the air leaks in your home.

And if you don’t know where all the holes and gaps are, you’ll never be able to comprehensively fix the problem and make your house comfortable.

Ultimately, the blower door test is the best way to get an accurate assessment of your home’s airtightness. It’s worth investing in if you’re ready to fix your house’s problems at the source.

By the way, if your home qualifies to work with Sealed, you can get all of these professional diagnostic tests done—and the problems fixed—for no (or very little) upfront cost.

The ultimate fix for air leaks? Air sealing.

The goal of air sealing is to find and then seal all of the nooks, gaps, and open seams in your house. 

That way, the air you pay to heat and condition will actually stay in your house—and you’ll stay comfortable 365 days a year. (Novel concept!)

Air sealing can be done in a number of ways, depending on the type of air leak and where it’s located. 

The most common type of air sealant is caulk, which is used to fill small gaps and openings. Other types of sealants include:

  • Weatherstripping
  • Spray foam (which expands into crevices and is great for filling hard-to-reach areas)
  • Gaskets

Experts also install special fire-rated covers for lighting and plumbing fixtures to stop air leaks at the source.

Is air sealing a do-it-yourself job? It could be—but only if you’re a sucker for punishment. 

We highly recommend working with a professional.

It may sound like we’re biased, but the fact is that there are literally hundreds of places air can escape in your home, and the professionals know exactly where to look and what type of supplies are needed to seal each kind of leak. 

They are also expertly trained in air sealing correctly to allow the appropriate amount of healthy airflow in your home. 

(Quick fact: Air sealing or insulating the wrong way can cause moisture problems that can lead to structure and indoor air quality issues. It’s crucial to get air sealing right. That way, you’ll reduce your energy waste and drafts for good.)

There are literally hundreds of places air can escape in your house. Professionals know exactly where to look and what type of supplies are needed to seal each kind of leak.

Ultimately, it takes building science knowhow and a lot of gumption and determination to go into every dusty, dirty, spidery space and seal up problems.

You’ll get the best results when you hire an experienced professional. (See if you qualify for expert air sealing with Sealed here.)

And speaking of that…

Say goodbye to air leaks—permanently

It’s intimidating to realize you have an air leak problem—especially if you’ve got a lot of other things to manage (who doesn’t) and double-especially if you’re the person who manages the household budget (we get it).

Remember: Air leaks are a huge waste of the energy you purchase to heat and cool your home. Which means air leaks are big money-wasters, but they also make your home feel really uncomfortable.

So here’s the deal: If your home qualifies for Sealed, our experts will take charge of the situation, put together a custom home upgrade plan that will make your house feel amazing (even if it’s an old and drafty house that’s hard to heat). 

We oversee the entire project, too. We’ll hire experienced and vetted professionals in your area. We negotiate the cost. We stay accountable to the results and make sure the work is done right.

And you simply get to enjoy your home.

Plus every home upgrade package with Sealed is tailored to your situation, so you’ll get what you need (and nothing you don’t). 

Need new HVAC, new insulation, or air sealing? We’ll figure it out and let you know. You make the final call.

What’s more—yes, there is more!—you can make your house feel incredible for very little upfront cost (maybe even zero upfront cost).


How to find air leaks: Frequently asked questions

What are the basic air sealing techniques?

The most commonly used air sealing technique is caulking, which is used to fill small gaps and openings. Other types of air sealing techniques include: 

  • Weatherstripping
  • Spray foam
  • Gaskets
  • Specially-designed and fire rated covers for fixtures 

(Learn more about air sealing here.)

What is an air leak detector? Where can I find one?

An air leak detector is a small, handheld device that uses sensors to detect air leaks. There are two kinds of air detectors: ultrasonic and thermal. Ultrasonic air leak detectors detect the high-frequency sound that can be heard when air is escaping from a hole or crack. Thermal air leak detectors work by detecting temperature differences between the inside and outside of a home.

You can find air leak detectors at most hardware stores.

What is a thermal leak detector? Do they work?

A thermal air leak detector is a handheld device that uses sensors to detect temperature differences. When used correctly, they work well to detect air leaks in your home, but they’re definitely not a substitute for getting a professional blower door test.

What are some signs that I have air leaks in my home?

Here are a few indicators you have air leaks in your house:

  • You feel drafts near doors or windows
  • Your energy bills are higher than normal (or are higher than your neighbors)
  • You use more energy than houses that are newer or larger than yours
  • You see cracks or gaps in your home’s exterior 
  • You experience uneven temperatures between rooms
  • You have a lot of dust in your home

It’s highly likely you have air leak issues in your home, as most houses in the U.S. do!

How to check for air leaks around windows

One way to check for air leaks around windows is to shut all the windows and doors and then hold a burning incense stick near the window. If the smoke wavers, you have an air leak. You can also hold some tissue paper around the window—if the tissue moves, you’ve got unwanted airflow. That’s the short version! Be sure to read our full list of tips here.

Need a quick fix for drafty windows? Discover if plastic over windows can help insulate your windows (spoiler: it doesn’t)—or read Do thermal curtains work? to learn the truth about thermal curtains.

How to locate drafts in the house

Go into the drafty room, shut all the doors and windows, and move your hand—slowly—around the perimeter of all doors and windows, as well as any other potential access points to outside air. Feel any air coming in? There’s your leak (one of them, anyway). Tap here for more tricks to find air leaks.

Keep in mind that DIY tests will only uncover the most obvious leaks—you’ll need a professional to do a blower-door test if you want a full analysis of the issue.

Ready to fix air leaks for good? (And cut your energy waste that shows up on your monthly utility bills?) Discover how you could get air sealing, insulation, and even HVAC upgrades at no upfront cost with Sealed. Take our quick quiz to see if you qualify.




July 22, 2022