Straight Talk Articles

Sealing Air Leaks, Step by Step
August, 2020

Dear Pat and Brad: 

I love my older home, but it’s drafty and uncomfortable in the winter.  What can I do to make it less drafty that won’t cost me an arm and a leg? – Cris


Dear Cris: Your problem is not unusual. In a typical home about half of the air leaks to the outside every hour.  Your home may leak even more.  The leakiness of homes varies, however.  Some newer homes are already quite airtight and shouldn’t be sealed tighter.


The good news, especially if you don’t want to spend a lot of money right now, or if you’re hesitant to invite contractors into your home, is that a person who’s a little handy can seal a lot of leaks with a little time and effort, without spending a lot of money. 


Here are three steps to get you started.  There’s much more to learn than we can cover here, so if you’re serious about this you should go online and do more research (1).



The first step is a thorough visual search of the inside and the exterior of the house.  Look for gaps and holes in the exterior walls, the floor and the ceiling. These will often occur where different building materials meet, such as the top of cement foundation walls or around windows and doors.    Another common source of air leakage is where pipe or wiring penetrates a wall, floor or ceiling.  Ductwork located in unheated crawl spaces or attics can be a major leaker.


Exterior doors and openable windows deserve your attention. Open each door or window and put a dollar bill between the door or window sash and the frame. If you can pull the bill out easily when the door or window is closed again, the seal is not tight. If a window sometimes rattles when it’s closed or when it’s windy, it probably leaks.


The best way to find all the leaks is to hire an energy auditor to do a blower door test.  The blower door is a large fan that is mounted in a doorway to depressurize the house.  The auditor can then find the leaks and may even be able to recommend ways to seal them up. 


It’s possible to do your own whole-house pressure test. The Department of Energy has some detailed instructions at  You’ll have to turn completely off anything in your home that combusts fuel, such as a gas or oil furnace, or a gas water heater.   Close doors and windows.  Then, turn on everything that moves air to the outside, such as bathroom and kitchen exhaust fans and the clothes dryer.  As air is pulled from the inside of the house, outside air will be sucked through cracks and gaps.  You can make these leaks visible by lighting a stick of incense and holding it near suspected leak areas. Anywhere smoke is pulled toward the inside indicates an air leak.



There’s a complete list of materials on the website mentioned above. Here’s a starting list, with some rough cost estimates:


CAULK: you’ll need to get a caulk gun ($4+) and caulk ($4-$10). We suggest indoor/outdoor waterproof silicone or latex caulk that is water-soluble until it cures and paintable when dry.


EXPANDING SPRAY FOAM: ($4.00-6.00 for a can). This is a very effective leak plugger, but it’s a messy job. 


WEATHER STRIPPING: (Price varies with type and length). There’s a large variety of weatherstripping made of vinyl, metal and felt or open-cell foam to fit all kinds of situations.


PRE-CUT FOAM SOCKET SEALERS: ($3 for a pack of 24)


CHIMNEY PLUG BALLOON: ($50-$90)(2). You may need this if your chimney flu doesn’t seal well. Buy a square or round one to match the shape of your chimney’s flu(3).


ADHESIVE PLASTIC WINDOW INSULATION SHEETS: ($2-$14, depending on size). You may need these later in the year, for windows that can’t be sealed and don’t have storm windows.



If you are unfamiliar with how to apply any of these materials, we recommend watching online tutorial videos(4) and/or asking a local pro for advice.


This process may be fair bit of work, but it can lead to fewer drafts and a lower energy bill!

This column was co-written by Pat Keegan and Brad Thiessen of Collaborative Efficiency. For more information on sealing leaks, go to the August 2020 More Information Page.



(2) search for “chimney plug balloon”




Chimneys are a common source of air leaks. Source: EE Image Database.