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Save energy by tightening your home envelope

How to find air leaks in your house (And seal them)

Air leaks in your home can cause serious problems. Not only can they allow cold air to sneak into your home during the winter, but they can also cost you money. The more air that escapes your home, the more heating and cooling you’ll need to keep your home at a comfortable temperature, which can get expensive. In this article, you’ll find all you need to know to find and seal air leaks in your home.

What is a building envelope?

A building envelope, also known as a thermal envelope, is defined as the materials of a house or commercial building that separate the exterior from the interior. Your home’s envelope is basically the barrier that keeps you from experiencing the extremes of the outside environment and keeps the inside of our your home comfortable, dry and energy-efficient. A home’s structural envelope typically includes windows, doors, walls, ceiling and foundation. Air leaks through these areas are significant sources of heating and cooling losses in a home. Stopping air leaks is one of the best ways to conserve energy, save money and increase comfort.

1. Conduct a blower door test

You may already know where some air leakage occurs in your home, such as a drafty door but you’ll need to find the less obvious gaps to properly seal your home. For an accurate measurement, hire a qualified technician to conduct an energy assessment, which includes a blower door test that can help detect smaller, less noticeable air leaks.

What is a blower door test?

A blower door test measures the airtightness of a home by pulling air out using a special fan called a blower door, which lowers the air pressure inside. When the inside air pressure is lowered, the higher outside air pressure flows into the home through unsealed cracks and openings, showing where your home is in need of weatherization.

Blower door test cost

On average, a home energy audit, which includes a blower door test, could cost you as little as $100 or as much as $1,500. According to Home Advisor, on average, most people spend $419 for a blower door test. This could fluctuate depending on the service provider you choose and where you live. Contact your local electric cooperative prior to hiring someone to conduct a blower door test, as they may offer free or reduced-cost audit options. 

2. Inspect areas where different materials meet 

As mentioned above, the best way to find air leaks in your home is to have a professional energy audit conducted. However, if you are unable to do so, there are additional things you can do to find some leaks.

First, look at areas where different materials meet, such as between brick and wood siding, between foundation and walls, and between the chimney and siding. Also, inspect the following areas for any cracks and gaps that could cause air leaks: 

  • Door and window frames
  • Electrical and gas service entrances
  • Cable TV and phone lines
  • Outdoor water faucets
  • Dryer vents
  • Foundations
  • Air conditioners
  • Vents
  • Fans

3. Perform a smoke test to find leaks

Using a professional energy auditor is the best way to find leaks in your home. But if you are unable to have an audit, try performing a smoke test to find some of the leaks on your own. This test can also be used to test how well your home is ventilated after sealing the air leaks in your home.  

  • Turn off your furnace on a cool, very windy day.
  • Shut all windows and doors.
  • Turn on all exhaust fans, such as bathroom fans or stove vents.
  • Light an incense stick and pass it around the edges of common leak sites. Wherever the smoke is sucked out of or blown into the room, there is a draft.

4. Other DIY ways to find air leaks

In addition to the methods we’ve already described, here are a couple more creative ways you can find air leaks that might be costing you money.

  • Shine a flashlight at night over all potential gaps while a partner observes the house from outside. Large cracks will show up as rays of light, but small cracks will not.
  • Shut a door or window on a piece of paper and try pulling it out. If it doesn’t tear, you are losing energy.
  • Purchase an infrared laser thermometer to help find drafts. This is an inexpensive way to determine where you may need to tighten your home, especially around door and window frames. Simply compare the temperature of your home to the exterior window and door frames of your home and compare to the temperature of your home. If the frame is sealed properly the temperature of the frame should be the same as the room in which it resides. However, if you notice a change in temperature it’s likely that you have a leak in your frame.

How to seal air leaks in your home

Once you find where your home is leaking air, you must seal up those leaks to reap the benefits. Here’s how you can seal the air leaks in your home to help you conserve energy and save money.

  • Caulk and weather-strip doors and windows that leak air.
  • Caulk and seal air leaks where plumbing, ducting or electrical wiring penetrates through walls, floors, ceilings and soffits over cabinets.
  • Install foam gaskets behind outlets and switch plates on walls.
  • Look for dirty spots in your insulation, which often indicate holes where air leaks into and out of your house. You can seal the holes with low-expansion spray foam made for this purpose.
  • Look for dirty spots on your ceiling paint and carpet, which may indicate air leaks at interior wall/ceiling joints and wall/floor joists. These joints can be caulked.
  • Install storm windows over single-pane windows.
  • Use foam sealant for larger gaps around windows, baseboards and other places where warm air may be leaking out.

How to apply caulk like a pro

Applying a consistent bead of caulk, whether it’s silicone or some other kind, can take some practice to achieve. By following the steps listed below, you can properly caulk and seal those pesky air leaks throughout your home. 

  1. Insert the tube into the caulking gun.
  2. Cut the tip at a 45-degree angle at the desired thickness
  3. Use the wire or a nail to break the seal at the base of the spout.
  4. Squeeze the trigger of your caulking gun, while moving the tip steadily along the joint to be filled.
  5. Smooth the bead with your finger, making sure both edges are covered.

The importance of proper home ventilation

When creating an energy-efficient, airtight home through air sealing techniques, it’s very important to consider ventilation. Unless properly ventilated, an airtight home can seal in indoor air pollutants. Ventilation also helps control moisture, another important consideration for a healthy, energy-efficient home.

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