by Kert Heinecke

Green building in its current manifestation is primarily hype. The market, quick to jump on the bandwagon, has focused primarily on tangible products that may draw envy from neighbors, but do little to actually preserve precious resources and reduce your energy bills. The real decision to go ‘green’ should start with the decision to minimize the home energy footprint. Growing consensus among building scientists suggest that the first major step to improving a homes energy efficiency is home air sealing, and it is feasible for all existing homes. When you add the current tax credits and utility company rebates to the equation, the opportunity to take this first step towards the energy smart home is nearly impossible to ignore.

So why Air Seal?

Starting back with the energy crisis of the 1970’s and continuing into the 80’s, there was a push in the building industry to make homes more energy efficient by increasing the R-value of the building envelope. The thinking at the time was that if we add more insulation, and thereby increase its R-value (a measure of a materials resistance to heat flow) we could slow down the heat loss that is conducted through the building envelope. While this thinking was right on and took us a step in the right direction, it failed to consider the complete heat transfer picture. More recent studies have now concluded that houses will continue to under perform thermally unless air leakage has been addressed.

A tight building envelope, one that has been properly air sealed, can provide numerous benefits to its owners and the environment. Energy conservation quickly rushed onto everyone’s radar last year as the cost of fuel skyrocketed.

As we see the cost of energy continue to rise, conserving energy and reducing our energy bills will continue to be at the forefront of the public consciousness. In several recent projects, we have seen energy bills reduced by as much as 30% through the implementation of strategic air sealing.

In New England, where cold winters and chilly evenings are a given, we can all appreciate the value of occupant comfort as we are forced to put on sweaters or sit under blankets to combat a winter chill. Leaky window sashes and doors that lack weather stripping are obvious sources of drafts. On the other hand, the less apparent sources, the smaller gaps and cracks that exist in all structures seem to small to be concerned with. When added together, all of these smaller gaps can equal the size of a typical window sash or larger being left wide open in the middle of winter. While sweaters and blankets have become iconic symbols of winter coziness, no one would choose to wear a sweater instead of closing the window.

Perhaps one of the strongest arguments for air sealing is building durability. The greatest contribution we can make towards green building and resource conservation is to construct buildings to last for generations. When it comes to building durability in cold climates like ours, Air sealing is used not to stop infiltration, but ex-filtration of air. In the winter, warm interior air is laden with moisture from occupant respiration, cooking, and bathing. When this moisture filled air moves through the building envelope, it eventually comes into contact with a cold surface that is below the dew point temperature. When this occurs, the moisture condenses and builds up leaving large quantities of water in the building structure. This water can lead to rot, decay, and mold growth that undermine the buildings integrity.

The other impact on building durability from air leakage is ice damming. Icicles are a standard prop in the stage set of New England winter, but they are also evidence of a problem that can lead to numerous areas of damage including plaster and structural damage from leaks inside the house as well as damage to siding, gutters, and shingles outside the house. Ice damming is typically caused by the stack effect. As warm air rises within the conditioned interior, it escapes through the numerous small leaks in the ceiling. Over time, this escaping heat can greatly increase the temperature of the roof surface melting the snow which then refreezes as it reaches the cold eaves line forming the ice dam. The only way to effective way to battle all of these issues is through strategic air sealing.

Air Sealing Basics

The premise of air sealing is really quite simple, but execution is the key. Air sealing is the systematic location and sealing, or stopping, of the major leaks in a homes building envelope.

The process typically starts with a thermal envelope performance audit consisting of blower door testing, and a visual inspection of the building envelope using an infrared camera. The blower door is an indispensable tool. The blower door is a large fan that is installed in the main entry door and depressurizes the house. It is used to run a series of tests that result in a calculated volume of air leakage under normal conditions. With this data, it is possible to determine how much money and energy is being lost to air leakage. Conversely, it makes predicting savings from air sealing a snap and provides an important piece of data necessary for cost benefit analysis of the actual work ahead.

The blower door is also used during the visual inspection. Again, by depressurizing the building, it is possible to exaggerate the effects of air leakage. With even a modest temperature difference between indoors and outdoors, the leaks become immediately apparent when viewed with an infrared camera. The camera uses infrared technology to read the surface temperatures of the building envelope from the interior, and represents them graphically with an operator determined color coding scheme (e.g. Blue is cold, red is hot). With these two tools, an inventory of problem areas can be developed in about 1-2 hours time, and the remediation plan can be targeted to realize the greatest reduction in energy consumption and the largest improvement in building performance and durability.

This article has been provided by, Feinmann Inc., a Boston company known for its thoughtful and beautiful design, a well-articulated process, superb craftsmanship, responsive service, and the best value for the cost. With a little inspiration and a lot of follow-through, the Feinmann team has transformed hundreds of homes in the Boston area from good to great. Photographs courtesy of Feinmann Inc. For more information visit www.Feinmann.com.

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