Air Leak Sealing

Did You Know…

  • That According to the Canadian National Research Council, Air Leakage is Responsible for 30-50% of a Typical Homes Energy Loss?!

What is Air Leakage?

Home Air Leakage Diagram

  • Air Leakage is when the heated or cooled air inside your home escapes to the outside, and outside air infiltrates into your home.
  • This diagram from the US Department of Energy shows how air leakage occurs.   The process of heated air escaping the top of your home as colder, outside air is sucked in around your foundation is called Stack Effect, and stack effect is what drives air leakage. 
  • When you feel a cold draft in your home, you are fact feeling air leakage!


What is Air Leak Sealing?  Why is it Critical?

  • On a cold day, would you think twice before shutting an open window?  Of course not! The concept of air leak sealing your home is no different
  • Air leak sealing is the ‘sealing up’ of cracks, holes, and seams that exist in your home’s ‘air barrier.’ Your air barrier is what keeps the air conditioned by your furnace and air conditioner from escaping your home!
  • Air leak sealing measures are vital. Effectively air sealing your home could improve its heating and cooling efficiency by 10-20% alone (and that is before adding additional insulation)!

First Time Hearing About Air Leaks?

Click here to see what the Department of Energy’s Oakridge National Laboratory has to say about air leakage in homes and the importance of sealing air leaks.

Why Does my Home Become so Dry During the Winter?

  • Air leakage in your home negatively affects your comfort in several ways.  First you feel it in the form of drafts and cold spots on cold days.
  • Secondly extreme dryness in your home during winter is often caused from air leakage.  Cold outside air is often very dry because cold air cannot hold as much moisture as warm air.  When cold, low relative-humidity air infiltrates your home through leaks, it mixes with the warm, higher relative-humidity air inside and effectively dries it out.  This continual process makes many homes unpleasantly dry during the winter!

Why Can’t I See These Air Leakage Sources?

Dirty fiberglass around leaky recessed light indicates air leakage. Next shot shows light air sealed using airtight box.

Dirty fiberglass around leaky recessed light indicates air leakage. Next shot shows light air sealed using airtight box.

  • Air leakage sources are typically hidden beneath insulation or in places that are difficult to reach in your attic.
  • Air leaks proliferate in attics and basements, wasting massive amounts of energy.  They come in many forms: electric wires, plumbing pipes, recessed lights, attic ladders, basement rim joists, etc.
  • Most attics possess hidden air leakage sources that when combined would equal a medium sized window left open!

What About Air Leakage Issues in Basements?

Air sealing rim joists

Air sealing rim joists

  • Basements contain important air leakage sources. Outside air infiltrates where the sill plate sits on the foundation wall and around the rim joists.
  • During winter, cold air seeps into the home through this area as warm air escapes from the top of the home.
  • Typically rim joists and sill plates are sealed with spray foam.

 But the other guy said air sealing was a waste of time?!

  • If another insulator tells you that air sealing is a waste of time, what he’s really saying is that he is either completely ignorant of modern building science principles or that his crew is too unreliable or lazy to do the actual work.
  • Simply put, the forces behind stack effect will cause your home’s conditioned air to leak directly through blown or rolled insulation. Before re-insulating, air leaks MUST be sealed.
  • Don‘t just take our word for it. Find out what the Department of Energy has to say about the benefits of air sealing.

Why On Hot Summer Days is my Upstairs Much Hotter Than Downstairs?

Infrared image of ceiling in summer shows gaps in attic insulation

Infrared image of ceiling in summer shows gaps in attic insulation

  • On hot summer days, your attic can heat up to nearly 140 degrees.  If your attic is insufficiently insulated, you will start to feel this heat coming into the upper floor of your home by late morning / early afternoon.
  • If your attic was insulated with rolled fiberglass batts, it is likely there are substantial gaps around framing, wires, plumbing pipes, etc.  This will cause ‘hot spots’ on the ceiling, as shown on the second infrared image.
  • By having Insulwise properly air seal and re-insulate your attic with blown cellulose insulation to the recommended R-49, your home will become much cooler on hot days.  You will also see your A/C bills drop substantially!
  • Another reason for this is an under-insulated attic, but the two go hand in hand.