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Sealing Air Leaks at Home for Year-Round Savings

by vscontent on November 3, 2015

Before you think about replacing your HVAC system, conduct a thorough inspection of your home’s insulation and air leaks. Even if you need a new heating and cooling unit due to old age and disrepair, improving insulation and finding and sealing the holes in its shell may allow you to lessen the need for a larger unit.

how to seal air leaks in ducts and at home

Air Sealing Benefits

When Pacific Air Systems technicians arrive to inspect your home for a new HVAC unit, they will measure your home and calculate the proper size equipment. If you have a sealed home with good insulation, we may recommend a smaller unit, which could say you time and money.

In addition to saving on a new HVAC unit, sealing air leaks in your ducts and around your home can save you around 30% off your heating and cooling bill, amounting to hundreds of dollars savings every year!

Sealing and insulating can also help:
  • reduce outside noise
  • keep critters out
  • reduce the amount of dust and pollen
  • improve humidification levels
  • reduce the risk of ice dams

Warning: if you do make major changes to your home’s insulation, make sure you consult with a professional HVAC contractor to determine if your have the right amount of ventilation for your combustion gases. This is often required by cities and utilities. There is a danger of compromising your indoor air quality and safety by having a home that is too tight.

Finding Air Leaks

Before you grab the caulk gun, you’ll want to find your air leaks first. Here is a map of the common air leaks found in home:

finding and sealing air leaks

Here are the first places you should check for air leaks:

Checking for Air Leaks

It’s best to check for air leaks on a windy day when air is pushing up against your home. Start your inspection by going around your home and conducting a visual inspection. Use post-it notes or something else to mark the locations where you suspect an air leak.

To test for air leaks, you can try a couple of different methods and find the best one for you:

  • Use your hand with a little water on it to “feel” the air leaks. If you feel cold air on your hand, you have an air leak.
  • Use a thin piece of toilet paper and observe how the paper moves when you hold it up to air leak prone areas.
  • Light an incense stick and watch the smoke. If the smoke begins to swirl and behave erratically, you have an air leak.

Sealing Air Leaks


Use one or more of the methods above to detect air leaks in your ductwork. If you think your ducts are leaking a large amount of air, it may be a good idea to seal all the cracks and seams that you can access.

Although you may think duct tape would be a good product to use on ducts, it’s not! Instead, use mastic sealant or aluminum foil tape to seal your ductwork. Make sure you wear old clothing if you use mastic sealant. And remember to clean and prep the surface before applying any tape or mastic.

Click here for more information on ductwork problems and how to fix them, including duct sealing tips.

Air Sealing with Caulk:

After going around the inside of your home checking for air leaks and outside of the perimeter of your home looking for cracks and gaps, you’re ready to apply the caulk.

If the crack you are trying to seal is larger than 1/4 inch, use expandable foam spray instead!

expandable foam insulating sealant


How to Caulk Doors and Windows

Materials: weatherproof caulk (click here for a caulk buying guide), a caulk gun (caulk tubes are for smaller projects), box cutter, old clothing, soap and water, and a cloth.

1.   Chip away old caulk and clean the surface with a damp, soapy cloth. Make sure the surface is completely dry before moving on to step 2.

2.   Carefully cut the tip off of your caulk tube near the end and poke a hole in the tip using a wire hanger or nail. Place the tube in the caulk gun and use the trigger handle to apply pressure.

3.   To achieve a finished look to your caulking job, watch this video:

4.   Fill all the cracks and gaps that you can find around your doors and windows. Use a damp finger or the Caulk Easy Spray used in the video above to smooth out your stream of caulk.

Watch this video for more tips on sealing air leaks in windows and doors:

Weatherstripping Doors and Windows

You may also use weatherstripping, a long rubber strip with adhesive, to seal air leak in your doors and windows. Similar steps apply:

1.   Clean and prep the surface.

2.   Double-check your measurements before cutting.

3.   Test  your job for air leaks using an incense stick or the dollar bill test: if you close your door or window on a dollar bill, you shouldn’t be able to remove it without opening the closed door/window.

Professional Aeroseal Duct Sealing

Fortunately or unfortunately, the majority of your home’s ductwork is inaccessible, hidden behind walls and ceilings. You may be able to seal a lot of air leaks, but you won’t get them all without a professional solution.

This is where Aeroseal Duct Sealing comes in. Aeroseal is a noninvasive, nontoxic technology that seals ductwork from the inside. The sealant comes with a 10 year warranty and can seal the whole duct system in under an hour.

Watch this This Old House video to learn how Aeroseal works:


To keep you home safe and your energy bills low, check out our other blog articles:

For professional duct sealing solutions in the Tacoma/Lakewood area, call Pacific Air Systems at 253.292.3995 for 24/7 service!

Since 1984, we’ve been proudly serving our communities in Federal Way, Graham, Spanaway, University Place, Steilacoom, Sumner, Lakewood, Puyallup, Tacoma and Gig Harbor.

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