By now, just about everyone knows how much energy windows can waste in the winter. Even the best double-glaze units will lose heat about eight times faster than an insulated wall. Fortunately, as the price of energy goes up, more and more solutions to that problem are being developed.

Some of the best ones come in the form of window shades -- not ordinary shades, which save only about 15 percent of your energy, but the new breed of specially made thermal shades, some of which can make your windows just about as energy-conserving as a well-insulated wall. Let's look at the three types I've seen so far.

INSULATING SHADE. The first true thermal shade, this still has the best performance. Independent tests show that it can deliver an R-vale of as much as 17 in conjunction with a double-glazed window -- better resistance to heat loss than the typical stud wall insulated with mineral wool. Early models were built on a standard wooden shade roller, and somewhat clumsy to operate. Now a new model has a bead-chain and sprocket arrangement that makes opening and closing much simpler. This five-layer shade goes for about $3 a square foot, but the installed price will be somewhat higher since the shade requires a special frame to achieve a good seal around the window. For more information write Insulating Shade Co., Inc. Box 282, Branford, Connecticut 06405.

CURTIN WALL. Here's another multilayer shade with impressive R-values (between nine and 12). This one is fully automatic, raising and lowering itself electrically according to commands from a thermostat that has a reversing switch so you can set it to gain and retain heat during the winter, and exclude solar heat in the summer. Curtin Wall is intended for use on large expanses of glass, such as picture windows and sliding glass doors. Price is about $4.25 per square foot. For more information, write Thermal Technology Corp., Box 130, Snowmass, Colorado 81645.

WINDOW QUILT. This multilayer shade includes fiberfill insulation to achieve an R-value of around five. That's not as high as the other two, but it's more attractive. Price is about $3 a square foot. The manufacturer is Appropriate Technology Corp., Box 975, Brattleboro, Vermont 05301.

NOTE: All these shades require effective air seals around their edges, which calls for special frames. Installation is more than a simple matter of hanging the shades. All three shades qualify as energy-saving devices eligible for income-tax credits. This lets you take 15 percent of the installed cost of the shades off your federal income-tax bill.