How to find air leaks in the house

Sealing the air leaks in your house can go a long way towards making your home more comfortable and cheaper to heat and cool. Detecting the source of cold air leaks in your house could go a long ways to saving money on your utility bills.

Looking for Air Leaks in the House

First, look for dirty spots on your carpets, ceilings and insulation. When air leaks into your home, it often carries dust and dirt with it, leaving telltale marks behind.

Check for air leaks around doors and windows by closing them onto a piece of paper. You shouldn’t be able to pull the paper out without it ripping. If you can, you’ve got a leak to seal.

You can find large leaks at night by shining a flashlight over areas you suspect might be leaking air. Have someone look at your house form the outside. If they see the light, there’s a crack. You won’t find small air leaks this way, though.

Smoking out the Leaks

A better way find a lot of the cracks and gaps that let air leak in or out of your home is by using a smoke pencil. Air likes to travel from warm to cool, so choosing a cool day is best when checking for air leaks – you can see where the smoke tries to exit your house. A windy day is ideal for finding air leaks. Shutting the furnace off and setting your exhaust fans to blow air out of the house helps, too.

You’ll know when you find an air leak by watching the smoke. Bring it close to where you think there might be a crack leaking air. Instead of curling upwards the smoke will flatten out and flow toward the gap.

Take your smoke pencil around to all the areas in your home that might have leaks. Most air leaks occur where two different parts of your building meet. The joins between your foundation and the walls, in your attic where the top sill meets the roof, next to the chimney, where two different types of siding meet, and anywhere you have an added-on room or porch are all prone to air leakage.

Some other places you might find air leaks in your home:

  • Around door and window frames
  • Under doors
  • Around light fixtures – especially ones on the top floor or on outside walls
  • Attic entrances
  • Old coal chutes
  • Electrical switches and outlets
  • Around plumbing pipes
  • Flues and vents
  • Anywhere you have a pipe or wire coming in, like cable or electric wires or gas services
  • Air conditioners and fans
  • Mail slots and chutes
  • Through cracks in brickwork or in a rubble foundation

Be sure to check all your ductwork, too. Even if your basement is tight, air leaking from ducts keeps your furnace from running efficiently.

Bring in the Pros

Even if you think you’ve found all the air leaks your house could possibly have, it could still be worth your while to bring in a consultant to do an energy audit in your home. A blower door test and inspection with an infrared camera could reveal hidden air leakage that you never knew was there – but which could be costing you every time your furnace or air conditioner kicks on.

Whether you choose to do it yourself or get help from the pros, finding the cracks and gaps that let air leak from your home is the first step to saving hundreds of dollars a year on your energy bills – and increasing the comfort level of your home.

Next step? Fill the gaps with caulking and weatherstripping!

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