Original and old windows are the most threatened element in preservation today, despite the fact that they are character-defining features of both the exterior and interior of a historic building. The replacement window industry aggressively markets to owners who don't know what to do with their rattling windows. Replacing an old window with a factory-made model destroys the rich variety of window details that makes each old house unique. Fortunately, there exist sensitive, cost-effective solutions for the owner to consider before plunking down hundreds of dollars to buy a modern replacement. Here are the two most effective:

Weatherstripping. Cold air blows in around the sash because they have to be loose enough to operate. Over time the surfaces wear, enlarging the space. The solution is to insert weatherstripping between the sash and the frame and where the sash meet. Weatherstripping can be simple self-stick vinyl tape, or it can be a more expensive but longer-lasting copper or zinc strip. If your window has a pulley at the top of the frame, that is another source of cold air. Cover this with a self-stick pulley cover, available at many home improvement stores.

Storm windows. A single pane of glass provides no resistance to the transfer of heat. Although new windows with triple glazing can claim reductions of up to five times the heat loss, installing storm windows is more cost effective and has the advantage of preserving the original window. There are many models to choose from, including double-hung wood units and custom-painted aluminum units matching your color scheme. Storm windows also can be installed from the inside, although they must be sealed to prevent moisture condensation on original sash that can lead to mildew and rot.

- Michael Lynch, Vice President for Properties & Preservation