Air Sealing: Benefits, Concerns, & How-To Find the Leaks

Air can easily leak in and out of a home through cracks, joints between different materials, where holes have been drilled to allow pipes and wire to enter the structure, and many other openings. Some of the popular areas for air leakage is around doors, windows, attic access panels, recessed ceiling lights, electrical outlets, switch plates, and plumbing penetrations in the kitchen or bathrooms. As part of your regular maintenance schedule, you should be checking your home for signs of potential problem areas. This leakage can not only increase your heating and cooling costs, but also reduce indoor comfort and allow moisture into the structure causing major issues.


Air-Sealing one’s home is one of the most inexpensive strategies you can employ to help you save money on your utilities and feel more comfortable as soon as it is completed. In most cases, the money spent will easily be recouped within the first year. This is one reason why it is #1 on DOE’s priority list for weatherizing homes. Your energy savings will vary based on how much air leakage you have. In some cases, with a well built home you may not realize hardly any savings, while some have saved over 20% on their bills.  Not only does air-sealing one’s house help lower your utilities and make one more comfortable, it can help improve the air quality inside the home, help prevent moisture problems and prolong your HVAC system.


Many people worry that if you seal a house too tightly, it can affect the indoor air quality by trapping all the inside air inside. While this is a concern, if you live in an older home, it would be nearly impossible for you as a homeowner to get it that tight by simply following these tips. On should also remember that there is a reason that vents are installed in bathrooms and kitchens and should be used appropriately. The American Lung Association does recommend that one seal up all air leaks in a house and use an ERV or HRV system to provide fresh filtered air. We commonly use these systems in all our new construction projects and in certain remodeling projects.

Another item that may concern many is if you have a gas water heater, fireplace, or furnace located in your home. If it is not pulling in replacement air from outside for combustion (sealed units) & you turn on a bathroom or kitchen vent – you could possibly create a back draft where the smoke and fumes are pulled back into the house. If you have any doubts, please call in a specialist to evaluate this issue. Even if you do not think this will be an issue, a CO detector should still be installed in case there are ever any problems, like a leaky exhaust vent.

Checking for air leaks:

Before one starts sealing leaks, it actually helps if you know where they are. One of the most effective ways to detect air leakage is to have a qualified Energy or Weatherization Auditor perform a “blower door” test; or a more comprehensive style inspection involving duct testing, infrared scans, &/or modeling. In some areas of the country, your local electric company may actually offer either of those services above for free or at a discounted rate. However, with a little knowledge one can easily perform their own evaluation and start saving money now, instead of waiting around for an audit.

During the winter months, when it is windy out is when most people realize they have an issue. Many of the larger leaks are discovered because they feel a draft coming in from around a window, a door, etc… During the year, some are some leaks are easily spotted by an excessive amount of dirt surrounding an outlet, a light, on the wall by the window trim, etc…

A popular test used to check the seals on your refrigerator and freezer will work for checking around your doors and windows. Simply take a piece of paper and close the door or window on it; if you can pull the paper out easily, (i.e. without tearing it or tugging on it) you have a leak that is wasting energy. Using this method, you should check around the entire opening. Another popular one for doors is the flashlight test. At night have someone go outside & shine the light at the doorway, if you see light inside you have a leak that needs to be corrected.

Many energy auditors will setup a blower door and depressurize the house to help find the air leaks. Once the house is depressurized, they walk around and use a smoke pencil to pinpoint the leaks. You can actually do the almost the same thing with items already in your own house. Instead of a smoke pencil, you can use an incense stick or a slightly damp hand. Instead of a specialized blower door to depressurize your house, close all the exterior windows & doors, turn off your HVAC system and turn on all your exhaust fans in the kitchen and bathrooms. This should depressurize your house enough to allow you to start pin pointing the leaks. All you need to do is now is walk around the house with a lit incense stick, passing it close to areas where there are likely to be leaks. When smoke is either sucked away from or blown into the room, you have found a leak. If you are using your hand that is slightly damp, you should be able to feel the air movement.

Air Sealing & Insulation Series:

Other Related & Upcoming Articles


  • Mike Hines (@eXapath)

    A very helpful post, thanks.

    Ironically, I just had my home weatherized including a blower door test yesterday. Found lots of opportunity for sealing and noticed an immediate improvement in comfort once the three-hour weatherization session was complete. I’m curious to see how it impacts my energy bills in the coming months.

    I live in CT and our local utility subsidizes the weatherization process. Out of pocket expense was $ 75.00 and the service included blower door test to identify air infiltration, crack sealing with caulk, gap sealing with foam, CFL replacement bulbs, outlet sealing, and installation of low flow water valves. Also included a comprehensive list of things I can pursue as a homeowner to make further improvements in the years to come.

    Best $ 75.00 I’ve spent in years!

    Thanks for the posting.

  • Anonymous

    Good advice there, Sean. I like to say that you can never make a house too tight – but that doesn’t mean you won’t have problems in a tight house. If you’ve got a leaky house with atmospheric combustion appliances, you shouldn’t seal it up until you can ensure that those appliances will get enough air for combustion.

    On carbon monoxide, the only device I recommend is the one made by George Kerr and his company, CO Experts. You can buy it from his website and read all about why the UL approved models for sale at your local home improvement stores won’t save you. Here’s the link:

    On the topic of do-it-yourself testing for air leakage, a while back I ran across a website that tells you how to make your own blower door. I haven’t tried it yet, but it seems like it should work. Here’s the link:

    Finally, although many homes do have air leakage at the doors and windows, there’s a lot more of it through the ceiling or floor (unless the house is on a slab). The attic of older houses almost always has open chases and lots of other places to reduce the leakage in a hurry. Going down under the house, find your way to the bathroom and look for the ‘six-pack hole’ under the bathtub. You’ll also find open chases and other leaks down there.

    • SLS Construction

      First thanks for the comments Allison, and that is a very good point on combustion appliances & the “six-pack” hole which in many cases I find to be the size of either a 12-pack or full case. I guess I do need to get the ball rolling again on this series so I can take care of that information.

      As for the CO detector – I as a builder can’t recomend that product due to it not “meeting” the safety standards as required by the codes – sure it might exceed them, but unless it meets the approval standards I would be liable

      Interesting idea on the blower door, however I think I will stick with my Retrotec. For an average Homeowner, it would probably be cheaper for them to pay for the audit but one never knows.

      • Anonymous

        You certainly can recommend a better CO monitor, Sean. You still have to install the UL approved one if required, but then you tell the client that because their safety is important to you, you’re also going to install one that will really keep them safe.

        Yes, you’re absolutely right about it being cheaper & easier to pay an audit, but since you mentioned DIY air-sealing and air-leak detection, I thought I’d throw that in there. It’s definitely not for the technically challenged homeowner, though.

        • SLS Construction

          LOL – not for the technically challenged – I like that one, but I know a few people in my area that would positively be drooling over that if I sent them the link…

          As for the CO detector, I guess I might have to order one from them one day & see what it’s like – it would take quite a bit though to truly sell me on recommending one though (ok I am sometimes overly cautious – I admit it)

          Thanks again for the comments Allison, I do appreciate them

  • Neo

    Turn on your dryer it sucks more air then probably all exhaust fans combined. Its also probably the biggest air leaker when on but few people acknowledge that and nobody seems to have a solution