If your old windows leak, fog and sweat puddles of condensation, you might replace them. But at $200 or more a unit and as much again for installation, high-quality, high-efficiency windows can break a home improvement budget.
Another option: spend a lot less to improve the windows you already have.
The best improvement is a modern, double-glazed, low-E window. But you can significantly reduce heating and cooling bills with interior or exterior storms. They reduce temperature transfer through the glass and air movement through porous frames.
Overall, old, single-glazed windows are only about one-third as energy-efficient as modern, low-E units. And when it's cold and windy outside, an old window loses energy about 10 times faster than an equal area of insulated wall. In many homes, heat transfer through and around older windows accounts for more than 25 percent of home heating and cooling bills, according to the Department of Energy.
Stopping air leaks is generally the biggest energy benefit. But an extra layer of glazing (even thin plastic sheeting) also reduces heat loss by insulating the glass, the sash that holds it, and most of the casing with a layer of trapped air.
Dead air has an R-value of about 0.9 per inch. (R-value is the standard measure of insulating materials: the higher the number, the greater the thermal value.) Dead air doesn't compare well to insulation such as fiberglass batts at about R-3.5 per inch. But you can see through it, which is handy on a window.
Savings vary according to climate and window condition, but the DOE estimates that installing exterior or interior storms can reduce heat loss through windows by 25 to 50 percent. As a bonus, storms also significantly reduce the flow of street noise.
Storm window materials
Storms range from inexpensive plastic sheets or films designed to last one heating season, to triple-track glass units with low-E coatings that should last as long as windows. Glass offers better visibility and longer life than plastic. But glass is heavier and more fragile. Plastic panels are stronger and lighter, but they scratch more easily.
Most traditional storms that you put on and take off the house every year have wooden frames. But you can also use aluminum and vinyl. Wood offers more insulation value than metal or plastic, but requires periodic refinishing to keep the frame from deteriorating in the weather.
If you like the look of wood-framed storms, one option is to scrape them thoroughly once, and protect the wood with penetrating stain instead of paint. Stain is easier to renew as it fades over the years, and an extra coat now and then will seep in instead of building up on the edges and keeping the storm from fitting.
Aluminum readily conducts heat, which sometimes can make the frame sweat as much as the glass. But aluminum requires no maintenance, as long as you don't make the mistake of painting it.
Vinyl frames also don't need scraping and painting. But they should be made with UV stabilizers to keep sunlight from eroding the material. Vinyl can eventually become brittle and crack in cold weather as it expands on a sunny day and shrinks at night. Also, dark colors tend to fade on units left on the house year round.
Exterior storm windows are not quite as effective as interior storms because they must have weep holes near the bottom to drain condensation. That creates some air movement. Without holes (or with holes that are plugged), the windowsill and main window sash can eventually rot from built-up moisture.
Inside storms have several convenient features. You install and remove them without straddling bushes or climbing ladders to reach second-story windows. They don't deteriorate in the weather. And they don't disfigure the facades of architecturally detailed houses.
For rigid plastic, you need an unobtrusive, demountable installation with narrow frames that match the window trim color.
For cost-effective heat-shrink plastic you don't need a frame. It is chemically treated to shrink when heated, which removes all the wrinkles and makes the optically clear film unnoticeable.
The plastic is widely available in window and door kits that include double-faced mounting tape. You stick the tape to the inside of the window frame and the plastic to the tape, then use a hair dryer to heat the film. The plastic gradually tightens, which removes the wrinkles and leaves a clear film stretched over an insulating layer of dead air.Copyright © 2015, The Baltimore Sun