Weatherizing Your Old Single Pane Windows

By | December 7, 2017

Photo by Toa Heftiba

Many homeowners in older homes experience energy loss with old single pane windows, and outright window replacement can be costly and out of reach for some homeowners. Fortunately, there are many ways to improve the performance of existing windows at a far lower cost than replacement. Weatherizing windows focuses on stopping cold drafts and improving insulation.

Window Locks

First, ensure that all windows have functional and properly adjusted locks. Two locks per window is ideal. When windows are locked, the sashes (i.e., the moveable frames of the windows) pull together and form a tight seal that helps to block airflow. Locking your windows also helps ensure that the sashes are sealed properly and limits movement during strong winds.

Caulking Around Window Trim

Next, look around each window frame. If you see gaps or worn caulking, remove it and recaulk. Before caulking, make sure that the humidity is low and the temperature is above 45o F so that the caulking can set. If caulking around window frames outside, be sure to use a weather resistant caulking.


Check and replace worn weatherstripping around windows. Weatherstripping comes in different materials (e.g., foam, felt, vinyl, metal) and durability varies between them. Consider how effective it is at blocking drafts and how it looks on the window if it is visible. Be sure to follow instructions and clean and prepare the surface before applying.

If missing or worn, install a foam gasket where the top and bottom sash make contact with the head (the top of the window frame) and sill (the bottom of the window frame) respectively. Additionally, be sure a V-seal weatherstrip is installed where the sashes make contact with each other in the middle of the window. Again, if installation is required, make sure to follow instructions and clean and prepare the window surface so that the adhesive will work effectively.

Window Insulation Kits

Window insulation kits utilize a plastic sheet that is taped to the inside of the window frame then heated with a hair dryer to shrink the plastic to a tight fit. The plastic sheet seals the entire window and helps to stop cold air drafts. This type of treatment is best used for windows that you plan on keeping closed throughout the winter.

Window Treatments

Window treatments can also be used to provide insulation. Make sure that window treatments cover the entire length of the window.

  • Cellular or honeycomb shades create an insulating barrier to the window that prevents the transfer of heat. These types of shades come in various colors, lengths, and thicknesses.
  • Drapes and shades with thermal liners can also prevent the transfer of heat.
  • Plantation shutters, although more costly than drapes or shades, can provide an added layer of insulation.

Storm Windows

Interior or exterior storm windows can be mounted over existing windows and can reduce the infiltration of cold air and can prevent up to 50% of heat lost. Storm windows also provide the additional benefit of soundproofing and can reduce maintenance by sheltering the window from weather.

This article was first published in the Daily Progress.