"They make a difference. They make a big difference!" Margaret Erdman was referring to the shutters she had made for the windows of her ranch house. The Scituate, Mass., schoolteacher hadn't any figures to back her statement, just "an obvious awareness of the increased comfort in the home" with the shutters in place each evening.
Mrs. Erdmann chose 1-inch rigid styrofoam, "the type you can buy at any hardware store," for her shutters and has only since discovered that 2-inch thick styrofoam board is available.
Fred Kennedy of Duxbury, Mass., selected pliable 4-inch thick urethane foam, used in the upholstery industry for making mattresses, cushions, and the like, to insulate one large bedroom window. He found it "blocked out the cold in a most effective manner." Mr. Kennedy cut the urethane to shape and Mrs. Kennedy covered it with appropriate material. When in place, this unusual "shutter" gives the appearance of a wall hanging. It fits snugly enough so that "we just push it into place and there it says," the Kennedys say.
In recent years home-energy experts have been pointing up the heat-collecting value of a clear-glass window facing the sun. But at the same time, all the benefits will fly literally out of a window each night if it is left uncovered. That is so because glass conducts heat back into the outdoor cold once the sun has gone down, almost as efficiently as it lets in radiant heat during the day. But, as there are more hours or no sun during the cold months of the year, an unprotected window ends up losing far more heat than it gains. in any event, heat is far too valuable a commodity to waste whatever its source -- the sun, the coal mine, or the oil well. In some homes, particularly those with moderate to good wall insulation, heat lost through and around windows and doors may be responsible for as much as 50 percent of the heating bill.
As energy costs rise, the importance of insulating shutters is being increasingly recognized. An interesting booklet, "The Fuel Savers," put out by Total Environmental Action Inc. of Harrisville, N.H., states the value of rigid shutters this way: "If used every night, an insulating shutter of about 10 square feet (an average window size) made of 2-inch styrofoam will save you up to 7 1/2 gallons worth of oil heat every winter." If your home has 10 such windows, that's the equivalent of some 75 gallons of precious oil a heating season.
Any curtain or shade pulled across a window at night helps cut down on heat loss but nowhere near as effectively as a shutter. The idea of an insulating shutter is to stop warm room air from circulating across cold window panes, losing heat in the process. So the more snugly a shutter fits, the more effective it is. Heat transfer through the shutter by conduction is effectively prevented by the choice of materials (metal conducts heat rapidly, wood does so far more slowly) and the inclusion of dead-air spaces in the design. The reason styrofoam, fiberglass wool, and similar materials are so effective is that they contain millions of tiny dead-air spaces, all of which slow down the loss of heat by conduction. For the same reason, sawdust is a better insulator than an equal thickness of solidwood.
Some of the most effective shutters can be made using solid foam plastics, as did the Erdman and Kennedy households. Covering these shutters with a fire-resistant material (many plastics give off toxic fumes if set afire) is an obvious advantage. Others can be made by sandwiching any one of a variety of loose or soft insulations between two pieces of plywood. It is advisable, too, to include a vapor barrier next to the inside face of the shutter. This prevents moist air, which might slowly penetrate the shutter, from condensing on the cold glass, freezing, only to melt and form pools on the windowsill when the sun shines in.Ultimately, unless wiped away every morning, this collection of moisture can induce rotting of the wooden sills.
A disadvantage of a shutter is that it has to be stored somewhere during the day. For this reason some people prefer insulated curtains or shades. These might be marginally less effective, but they are still impressive savers of energy. Total Environmental Action suggests annual savings of up to 5 gallons of oil per window, depending on the quality of the curtain.
The thicker the fabric and the tighter the weave, the less air will pass through a curtain. Similarly, a multilayered fabric is better than a single thickness curtain. Some very effective curtains have been made by tacking bubble cap (a flexible sheet of plastic bubbles used primarily as a packing material) between two layers of material. Its disadvantage is that it is bulky and cannot be drawn as neatly as thinner materials.
It is important to fasten the sides of insulated curtains to the outside edge of the window frame. This will prevent air from circulating behind the curtain. Velcro fastening tape will form an effective seal. Be sure, too, that the curtain is weighted at the bottom so that it can be tucked securely into the sill. Blocking any gap at the top of the curtain is somewhat less important unless the curtain is being used to exclude outside heat during the summer.
While do-it-yourself projects have obvious economic advantages for the homeowner, an increasing variety of commercial fixtures are being made available. One, the quilted window shade, cuts heat loss through a window by as much as 79 percent. A rigid shutter with a prove track record is Cornestones' Sunsaver.