The number one source of heat loss in most homes are windows. While experts say replacing your primary windows with more energy efficient ones is the best way to reduce that heat loss, they also agree that it can be an expensive one.
Fortunately, there is a budget friendly alternative — Internal Storm Windows aka Internal Window Insulation Inserts. The Department of Energy  has endorsed Internal Window Insulation inserts.

…the DOE recommends that homeowners should consider replacing their primary windows before adding exterior storm windows. But the DOE’s top budget alternative is to install interior storm windows.

 

Overcoming past challenges
Storm windows were popular in the 1970s, but most were exterior-fitting. While they saved energy, there were some challenges in using them, too: they were difficult to install, especially on a home’s upper floors; they weren’t always attractive; didn’t allow much sunlight to pass through; and there were frequent problems with condensation building up between the storm window and the primary window.

Interior storm windows, however, don’t come with many of these issues. Because they attach to the inside of the window frame, upper-floor installation is much easier. In addition, interior storm windows don’t affect a home’s exterior appearance, and most designs strive to be unobtrusive and to allow for maximum light to pass through. And with correct installation, the moisture issues are far less prevalent.

Climate Seal is the oldest and one of the country’s leading producers of these internal storm windows. According to Matt Petit from Climate Seal, installing these internal storm windows can reduce energy loss by 30%-50% – resulting in a significant cost savings.

Here’s how they work:
When you install the Climate Seal insert over an existing window, an insulated dead-air space is created, keeping heat in during the winter and out during the summer. Climate Seal’s magnetic seal is virtually airtight. The bellows design expands and contracts as temperatures change, preventing the insert from popping-off. Therefore, the seal is maintained and annoying drafts are eliminated. The bellows adjust for installation of contoured moldings.