Benefits

Improved energy efficiency is the main reason for storm windows. Windows are big holes in the wall. Glass is not a good insulator. Windows are not energy efficient. They can only be made less inefficient. But it's our fault: we like light! Living in a cold, dark cave is energy efficient!

Warm air gets out and cold air enters in two ways.

• Air leaks around the window is the principal problem.
• Glass conducts heat and cold in and out.

Storm windows help with both problems.

• First, a tightly sealed storm window is another barrier against air infiltrating.
• Second, storm windows are a second layer of glass in the window opening. But, the important thing is that a tight storm window and a well-weatherized window sash create a dead air space between them. This dead air space is insulating and inhibits heat conduction.

Low-e glass is available on new storm windows. Low-e glass reflects heat back into the house in the winter and back outside in the summer.  MORE ON LOW-E GLASS

Many historic houses already have storm windows, but they need an occasional tune up. For example, aluminum storm window panels come with weatherstrips. Over time they may wear out. The strips are easily replaced to improve the air seal. Original wood storms also may need to have weatherstripping refreshed. 

Storm windows add a second layer of window security. A thief has to deal with the storm as well as the main window. Anything that adds complications adds time, and increases the chance of being seen, reported, and caught: more risk for the bad guys is a deterrent. 

Storm windows also protect the historic window sash, glass, and paint from the deteriorating effects of weather. This is rather obvious, but often is overlooked. 

• Storm window protection can add several years to the maintenance schedule for repair or repainting.
• A deteriorated historic window can be "mothballed" by putting a storm window over it until there is an opportunity to repair or restore the window.