Air Sealing

Heat moves in 3 ways:

Convection, Conduction, Radiation. The most common form of heat-loss from a home is through air leakage which is a form of Convection. The ideal home’s thermal boundary is designed to minimize the moment of heat. By being properly air sealed, well insulated, and having energy efficient windows and doors.

Air is constantly moving through your home, being influenced by temperature and pressure. Warm air rises and moves toward colder temperatures. As indoor air escapes your home it is replaced by old outside air. So air sealing your home is the most cost effective way to reduce energy/heat loss.

You burn fuel and spend money in order to heat your home. As you heat your home you are also heating the air in your home, this warm air then escapes through cracks and spaces in sheetrock, outlets, windows and framing. As the heated air leaves your home it naturally draws cold outside air into your homes structure. When cold outside air is drown into your home it drops the ambient temperature and then requires the heating system to now burn more fuel to reheat the house. Once the amount of air leakage is reduced, then the infiltration of cold air is also automatically reduced. This slowing down of air leakage makes a home feel less drafty and saves money and energy since the air that contains heat is no longer leaving your home. Since warm air rises the most common area of leakage is the attic. This is a high pressure point and pushes the air out. The basement being the low pressure point of your home and allows outside air to enter.

Prior to doing any insulting in an attic the attic flat needs to be properly air sealed. Air will still be able to escape into the attic if it is only insulated.

Using a foam gun, spot air sealing in an attic consists of sealing all of the top plates, wire and pipe penetrations, access hatch and duct registers. Fire caulk can be used around recessed lights, chimneys and bathroom exhaust fans.

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Chimney chase and surrounding top plates air sealed. Flashing and fire caulk used around chimney.

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Sealed top plate and wire penetration in attic


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IR image of heat leaking through unsealed attic top plate

Once the attic is properly air sealed it is also beneficial to air seal the basement as well. The sill plate of the house, where is sits on the foundation, is a weak spot and tends to allow outside air into the basement. Even though by air sealing the attic the amount of air entering into the basement will be reduced, your home has many points of air leakage and air infiltration and by air sealing the high and low pressure points of your home , this will stabilize the overall air movement in your home.

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Basement sill band air sealed with gun foam

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Basement sill band insulated and air sealed with closed cell spray foam








The best way of measuring the results of air sealing is to perform a blower door test before and after the air sealing. This will show how many CFM’s (cubit feet per minute) of air leakage was reduced. The blower door is also a helpful tool in finding points of air leakage by creating a high pressure in the home and exaggerating leaks. An IR camera can be used in conjunction with the blower door to locate area where the cold air in entering the thermal boundary of your home.

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IR image showing cold air leaking over door threshold into house while blower door is running.

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IR image of air leakage around window.

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Blower Door set up

Cozy Home Performance has years of experience in performing air sealing in attics and basements as well as using diagnostic tools such as a blower door and IR camera to locate weak areas in the thermal boundary.





If you are experiencing higher than normal energy bills or if you home always feels drafty and cold, give Cozy Home Performance a call or fill out an Intake Form, and we will be happy to visit your home and perform a home energy assessment to determine how the thermal boundary of your home can be improved and reduce your energy consumption.

Testimonials from Cozy Home Customers

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Cozy Home Performance is hands down the best energy diagnostic and insulation company in the Valley. Mark and his crew enter and exit your work stream seamlessly, on time and on budget. The key is the knowledge, experience and personal responsibility each employee brings to his work. Mark not only has design experience, he also has the creative spark that leads to innovative solutions to unique problems. With all forms of insulation under one roof, careful diagnostics and appropriate choice of material, one always get the most out of every insulation dollar from Cozy Home Performance!!
John Ferriter, in construction in the Valley for 45 years
I’m happy that the incentive was more than anticipated (As a Home Performance Contractor with Mass Save Cozy Home secured $2,760 in project incentive funds.). I enjoyed working with you and your crew. Everyone was pleasant to deal with. They were professional and courteous and when I had questions, the answers were in a non-technical response so I could understand. Each day they left the area clean.
D.N., Easthampton, MA
Someone from the utility company was here today to inspect the work resulting from their incentive. They were very positive both about the quality of the recommendation, and the quality of the work. I am pleased too. I’m almost looking forward to next winter to see the difference.
Phil, Northampton, MA
The house definitely feels different – hard to explain the feeling, maybe more solid? Anyway, we have checked out all the work areas that we could and are really impressed. We can already feel the difference in some rooms – even with the warmer weather! Thanks to all the guys who were at the house. They were all very polite and pleasant and seem to have done an awesome job!
K.C., Goshen, MA