Air Leaks


Air leaks:


Reducing air leakage is one of the lowest cost steps to save energy from heating and
cooling. It is also one of the simplest and should be done before other steps. If
your home is so leaky that you are trying to heat and cool the outside, it doesn’t matter
how insulated your walls and roof are or how efficient your furnace and air conditioning
is. Air sealing is also one of the top priorities for home comfort.


Some things to consider about air sealing:


  • Air sealing only helps when you are actively heating or cooling the inside of the house. When the weather is nice, or when you are cooling with fans instead of air conditioning, you want to be able to open windows and let air flow through the house. Sealing cracks, but make sure you can maintain air flow when you need it.
  • In poorly ventilated homes, extensive air sealing can create indoor air quality or moisture issues, which could require additional exhaust fans or humidifiers or dehumidifiers (all of which use energy). You are probably not able to over-seal your home with do-it-yourself air sealing unless you have experience and special equipment. However if you are hiring contractors to help air seal your home, you should make sure they are performing high-quality work that does not create additional ventilation problems.




Seal cracks in exterior walls and cracks around baseboards, windows, doors, and other
easy to access gaps. If it is cold outside, you can often feel cold air coming in through
these gaps, especially on lower floors – a blower door test as part of a home energy audit
can also help you find cracks you may have missed. You can seal cracks permanently
using tube caulk and a caulk gun, or use rope caulk, a removable air-sealing putty, to fill
cracks around windows that you want to remove in the future.


Leaky windows are a key location where up to 35% of a home’s warm air can escape in
the winter. Eliminating air leaks from windows is a primary way to save on home
energy consumption. This goal can be achieved equally well by a thorough sealing of
window cracks or much more expensive window replacements. Replacing windows
has an added benefit in terms of aesthetics and ability to operate the windows and has a
slight impact on building insulation. Replacing windows is very expensive and has very
little energy saving advantage over sealing leaks with rope caulk and weatherstripping at
around 1% of the cost of replacing windows.


If you are replacing the caulking around windows the first step is to remove the remaining caulk first for a clean layer. Weather stripping can involve a self-stick foam,
rolled up rubber, or plastic V-flex that are easy to purchase and can be applied to virtually any window. Leaky doors can have similar problems, and can be sealed with rubber, foam, or metal door-jamb seals.


These materials are all low-cost (probably under $100 for your whole home) and can be
installed with minimal home improvement expertise.

Some ways you can do this:

  1. Find and buy these materials at a local hardware store and install them yourself,
  2. If you don’t know what you need or how to install it, you can get the products you need from Cooperative Energy Futures, an Our Power coalition partner and a local energy cooperative, at retail rates and/or receive training in how to use them in your home with a $10 home workshop.
  3. Some other energy efficiency programs will provide some air sealing materials for free (Community Action for low-income households) or do some installation themselves at reduced cost (Community Energy Services for homeowners), but in general they do not teach you how to do these things yourself.




Sealing joints in duct work with a special foil or mastic will increase efficiency in
delivering heated or cooled air where needed. According to the Department of Energy,
a building could be losing 20% of heating and cooling efficiency just from duct leaks.


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