Home Energy

Storm Windows

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Even windows that are caulked and weatherstripped lose a great deal of heat through the glass. By installing storm windows, you can reduce this heat loss and cut air leaks around the window frames.

One of the best insulators is trapped air. A storm window installed inside or outside traps air between it and the existing window. Air space of ¾ to 4 inches is recommended. If they have a good seal, storm windows also reduce moisture formation on the window. This moisture, or condensation, can freeze resulting in frost and ice on the window.

Storm Window Options

There are three basic types of “add-on” storm windows:

  1. Plastic film storm windows – the low cost plastic type that you can make yourself or purchase as a kit and place inside or outside the existing window
  2. Glass or plastic sheets – medium-priced removable glass or rigid plastic windows (rigid plastic storm windows should be mounted inside the home)
  3. Combination storm windows – more expensive, but permanent (usually with an insect screen) and are mounted outside the existing window

All three are equally effective, but the higher-priced windows are more attractive and more convenient. They also give you the option of opening your windows to allow for natural ventilation.

Selection and Do–It–Yourself Installation Tips

Plastic Film Storm Windows*

Rigid Plastic Sheets*

* Although plastic films and rigid outdoor sheets can be applied to the window, they are easier to install on the inside. That’s especially true for apartment dwellers and those with multi-story homes. There’s no wind damage when they are installed indoors. Interior mounted storm windows also cut infiltration heat loss when mounted on the outside frame of an interior window.

Combination Storm Windows

Air Sealing Storm Windows

The effectiveness of a storm window depends on the airtightness of the primary existing window sash and frame. To assure an energy-saving installation and to control window moisture, you should caulk and weatherstrip the primary window sash and frame. To create an effective air space, the storm window should also be weatherstripped.