How to Insulate Windows

Benefits of Insulating Windows

As we mentioned, windows can be a costly feature of a home, accounting for substantial heat loss in cold weather and heat gain in warm weather. Single-pane windows, found in nearly 50 percent of American homes, are the most extreme in terms of energy-inefficiency [source: Money Matters 101]. Improving the energy infrastructure of your home will reduce home heating and cooling costs and help reduce fossil fuel consumption, slowing down the carbon emissions that are disrupting the global climate.

Heat loss through windows takes place in four distinct ways:

  • Air leaks directly in and out from gaps along the edges (infiltration).
  • Heat passes through the window glass (conduction).
  • Heat energy flows from a warm object toward any cooler object nearby until equilibrium is achieved (radiation). This can cause up to 65 percent of the heat loss from your home.
  • Because heat rises and cool air sinks because of their different relative densities, the cold air at the interior surface of an icy windowpane flows toward the floor, sucking more air behind it toward the window (convection). This movement eventually causes the overall room temperature to drop. This is why it's so important to cut off the flow of air in the vicinity of the window [source: Brighthub].

Effective window insulation prevents heat loss and also helps regulate the surface temperature of the interior glass. Without significant heat loss through leakage or convective airflow, insulated windows ensure an even temperature throughout the interior of the home, increasing energy efficiency. They also make it possible for heated homes to maintain a higher humidity level, and thus better air quality, with a reduced risk of condensation on the windows.

Are you convinced that any effort to insulate your windows is worthwhile and saves money and energy? If you need more convincing, check out the links below.

Related HowStuffWorks Articles


  • 00orange00. "Insulating Your Windows." (Accessed 02/21/2009)
  • AllSands. "How to Insulate Windows." (Accessed 02/20/2009)
  • Build It Solar. "Bubble Wrap Window Insulation." (Accessed 02/20/2009)
  • Hughes, Eric. "How 2 insulate windows." (Accessed 02/20/2009)
  • Money Matters 101. "Money-Saving Tips: Windows." (Accessed 02/20/2009)
  • Mother Earth News. "The Homemade Thermal Shade." Mother Earth News, November-December 1983. (Accessed 02/21/2009)
  • Pandolfi, Keith. "Drape Away Drafts." This Old House magazine. (Accessed 02/21/2009),,20253692,00.html
  • Serious Windows. "Fiberglass Windows Deliver the Highest Levels of Comfort and Energy Efficiency." (Accessed 02/20/2009)
  • Shurcliff, William. Thermal Shutters and Shades (Brick House Publishing, 1980), p.2. (Accessed 02/21/2009)
  • Silva, Tom. "How to Insulate a Window with Sash Weights." This Old House television (Accessed 02/20/2009),,20051453,00.html