Weatherization Guide

Weatherization Guide

Overview

Reducing the amount of air that moves in and out of a building will provide two benefits. The first is that it will reduce heating and cooling costs, and the second is that it will improve indoor comfort. Usually, the best way to identify areas to be addressed is by starting with an in-home energy assessment (also known as an "energy audit"). These are done by professionals, which are sometimes available at no or low cost from local utility companies, resulting in a series of specific recommendations and next steps to cost effectively reduce energy use. The most comprehensive type of assessment will include a blower door test, using a high speed exhaust fan temporarily placed in a door opening to depressurize a building, allowing areas of leakage to be pinpointed and sealed. But, there is also a lot that a do-it-yourselfer can do independently.

To know where to start, identify the thermal envelope of the building, which is the barrier between the intended conditioned space (the occupied parts of the building that is heated or cooled), and the unconditioned space (the unoccupied parts of the building that are not heated or cooled). When finding and sealing air leaks, the priority should be to seal between the conditioned spaces and unconditioned spaces, such as around exterior walls, which is more important than sealing gaps on interior walls between two conditioned spaces.

A second key concept to take into account is the "stack effect". During cold winter days heated indoor air will rise, with conditioned air being pushed out through leaks near the top of a building, while unconditioned air from outdoors will be drawn into the building from leaks in the basement or crawlspace.  Conversely, on summer days, hot outside air will be drawn into an attic, with cooler indoor air exiting from leaks lower in the structure.  Thus, sealing between the top floor and the attic, and between the bottom floor and the crawl space or basement, will deliver the greatest benefit. 

Leaks Up High

Because many weatherization measures can be done by homeowners and renters, and because the products used are often relatively inexpensive, the payback on do-it-yourself air sealing is often seen in less than a year, which means the savings over the course of a year will exceed the cost of the measures installed. When also planning to add insulation, undertake weatherization and air sealing work first, because penetrations are far easier to access before insulation is in place.

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Efforts to reduce air leaks that contribute to high heating costs should begin in the attic, identifying penetrations between the conditioned space and the unconditioned space. Air leaks are most likely to be found...

• around ducts that pass through the attic
• chimney penetrations from the living space through the attic
• penetrations for plumbing vent pipes
• openings around the perimeter of an attic hatch or door
• electrical junction and light fixture boxes
• bathroom and wholes house fans
• near the top of exterior wall framing

When inspecting for air leaks, especially if any insulation is to be disturbed, it is prudent to wear protective clothing, gloves, and a dust mask or HEPA respirator.

Leaks Down Low

The next most important area of focus would be eliminating infiltration/exfiltration from the unconditioned space under a house or building to/from the conditioned area. These air leaks are likely to be found around...

• ducts that pass through the crawl space or basement
• plumbing and furnace vent exhaust pipes
• areas around water pipes leading to exterior faucets
• the sill plate where the foundation and framing meet
• openings around the perimeter of a basement door

As with work in an attic, in crawl spaces and unfinished basements, is always a good idea to wear protective clothing, gloves, and a dust mask or HEPA respirator.

Leaks On the Sides

Finally, reducing leaks around the perimeter of a building have the potential to reduce drafts, especially on windy days, improving comfort. A variety of temporary measures (especially good for renters), as well as permanent measures that can deliver savings for years, are readily available. Dirty areas on perimeter walls and ceilings often point to where air infiltration may be occurring.  The obvious areas to weatherize include....

• exterior doors and door frames
• window sashes and frames
• penetrations for service entrances (cable TV, electric, natural gas)
• exhaust vent flashing
• around window and through-wall air conditioners
• electric wall outlets

Measure List

Following are some of the easiest do-it-yourself measures available. Some of these may be available through this Web Site, as well as through local hardware and big box stores. 

* Actual prices will vary

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Other Considerations

Common sense practices can also make a big difference, such as closing keeping windows and door closed when the heating or air conditioning systems are running, closing fireplace and wood stove flues when the fireplace or stove is not in use, and turning off kitchen and bathroom exhaust fans once they are no longer needed. These can all help to reduce uncontrolled air infiltration and exfiltration.

While a blower door test undertaken by home performance professionals will most accurately find sources of uncontrolled infiltration, a non-professional can search for leaks by first closing all windows and doors and turning on kitchen and bathroom exhaust fans simultaneously, and then pass a damp hand (or a lit incense stick) near likely locations. Doing this on cold days is best.

With comprehensive air sealing complete, especially when done by a professional, buildings may require some amount of controlled ventilation to preserve indoor air quality and remove excess moisture. Products such as ENERGY STAR® certified heat and energy recovery ventilators can accomplish this while transferring the temperature of the conditioned air being exhausted to the incoming fresh air from outside. In general, ERVs and HRVs should exhaust air from kitchens and bathrooms, while introducing fresh air into bedrooms and living spaces. Some ENERGY STAR® certified bathroom exhaust fans also have a low cubic foot per minute (cfm) speed to support continuous exhaust without the need for additional ventilation ductwork.

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Additional Resources

• U.S. Department of Energy Energy Saver Site: energy.gov
• U.S. Environmental Protecton Agency "Seal and Insulate with ENERGY STAR Site":  energystar.gov
• U.S. Environmental Protection Agency ENERGY STAR Upgrade Site: Six Energy Efficiency Improvements

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Disclaimer: The content presented on this page was prepared by the individual(s) listed below, and does not necessarily refect the views of the company or companies utilizing this site.

Contributor: Philip Scarbro

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