If you are among the many homeowners who have older windows that are drafty in winter and lead to high fuel bills, indoor storm windows could be a solution for you. Indoor storms are relatively inexpensive, lightweight, easy to install and remove, and can be ordered for home delivery from several vendors on the web.
Indoor storms are relatively simple in construction. Built from a thin frame, typically aluminum, with a tightly stretched thick 
clear acrylic film sheet sandwiched between the frame components, they are custom made to the measurements of your window. The storm windows have a gasket or expandable foam seal around the edges to achieve a tight compression fit while allowing for easy installation and removal. They are amazingly strong, and the acrylic film will not easily stretch or tear. These convenient storm windows give you another layer of protection against the elements, creating an extra layer of insulation– like going from single pane to double pane windows. The clear acrylic film allows for good visibility without condensation on the inside, and provides added soundproofing from the outdoors. The only drawback is that you have to remove and store them once the weather warms up because you cannot open the windows with the inserts in place.
One vendor offering these indoor storm windows is windowinserts.com, with their EnergySavr™ window insert. (Tip: look for online coupons or discounts if ordering.) Cost with shipping is dependent on window size but usually runs around $100 for most double hung windows. This is about 20% of the cost of a replacement window and less than adding an exterior storm window. In addition, there is no outdoor work involved, no painting, and no removal or replacement of window molding. Some companies even offer several frame colors, such as white, brown, and tan.
These storm windows do not qualify for any MassSave rebates, but they are effective and will help save money and energy over the long run.
Craig Forman is a board member of Green Newton and the lead organizer of Heat Smart Newton.