Even small air leaks in your attic can result in a big energy loss when it comes to heating and air conditioning. Find out what you need to know about how to air seal an attic. You will definitely see the savings add up if you take the time to complete this weekend project.

Benefits of sealing attic leaks
Learning how to air seal an attic will not only save you money on your utility bills, but can help control the humidity in your house which will definitely make summer in Savannah more bearable. You may also notice that your house seems quieter due to added insulation, and since air brings with it pollen and dust, you should also notice your indoor air quality improve. Less dust means less dusting and that’s always a bonus.

Common places for air leaks
Kneewalls, wiring holes, furnace flues and plumbing vents all have the potential for allowing air to escape into to the attic. Dropped ceilings, recessed light fixtures and the soffits that house them, air ducts, and the slanted ceilings over your staircases are also common sources of air leaks.

Before you begin your project, you will need to make a rough sketch of your floor plan that you can take into the attic with you. This will serve as a map to help orient you once you get into the attic, and a place to note air leaks as you detect them.

How to find leaks
You could have an energy evaluation completed by a qualified energy assessor. They will do a blower door test and use an infrared scanner to determine where problem areas are in your house. At the end of the evaluation, you will receive a detailed report from the assessor that will include places that may be leaking air into the attic.

You can also do a low-cost version of the blower door test yourself. By running a box fan on high in an open window and closing all the other doors and windows, you create pressure in the house. You can now climb into the attic and feel for leaks. To find small air leaks, look for tell-tale signs like insulation blowing around or dirty insulation (a sign that unfiltered air is making it’s way into the attic). Make sure to note all of these spots on your sketch before you descend to collect your supplies.

Be prepared
After determining where the leaks are, you will either need to seal them or add more insulation. You can get all the supplies you need at a local hardware store. Remember that attic heat can be intense, so take the necessary precautions. Stay safe. This probably isn’t a job you want to tackle in mid-July.


  • caulk: acrylic and high temperature silicone
  • caulk gun
  • fiberglass insulation
  • large garbage bags
  • foil insulation
  • aluminum flashing
  • expanding foam insulation
  • weatherstripping

Tools and safety supplies

  • safety goggles
  • kneepads
  • dust mask
  • disposable coveralls, gloves and hat
  • flashlight or clamp light
  • utility knife
  • staple gun

The basics of how to air seal an attic
Once you have your supplies, you need a game plan. When planning how to air seal an attic, work from big to small in order to make the most of your time.

  • Soffits, drop ceilings, and open joist spaces. Begin by filling the garbage bags with 16-inch strips of insulation, and use these to stuff any open joist spaces and soffits. For dropped ceilings: pull back existing fiberglass insulation, insert reflective foil insulation, seal with caulk and return the existing insulation to its place.
  • Furnace flues. Use aluminum flashing and high temperature caulk seal up the cavity around the flue and to build a required 2-inch barrier around it before replacing the fiberglass insulation.
  • Small air leaks. Pull back existing insulation, seal with caulk or expanding foam, and return insulation.
  • Attic hatch. Attach fiberglass to the back of the attic hatch door and line the stops with weather stripping on your way down.

There may be many reasons that this isn’t a job you want to take on by yourself. If the insulation shows evidence of moisture, you have limited ventilation in your attic, or you have an excessive amount of recessed lighting, you may want to call in the professionals. The experts at Byrd Heating and Air Conditioning are ready to help. We have been providing excellent service to the residents of Savannah and the surrounding communities for more than 20 years.

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