This article was prepared by John Rothchild and Daniel Yergin, the authors of ''Stop Burning Your Money: The Intelligent Homeowner's Guide to Household Energy Savings'' (Random House), and was written by Mr. Rothchild. Mr. Rothchild has been a co nsultant to the Federal Department of Energy. Dr. Yergin is a lecture r at Harvard University's Energy and Environmental Policy Center. IN many apartments and houses, adding interior thermal protection to windows may be easier, less expensive and ultimately more profitable than installing outside storm windows. Working from the inside may be the best solution for loft dwellers whose heat is escaping through skylights or extra-large windows. Indoor storms may also help homeowners who have put up exterior storm windows but still find that their fuel bills are high. Some of these internal window modifications may also be useful for renters who do not choose to invest in expensive improvements to their landlords' building and who suffer the discomfort of cold rooms.

Storm windows represent only a partial correction. They stop about half the heat that would otherwise escape through a single-pane window. The heat that continues to escape takes a lot of money with it. It is not uncommon for the windows of an apartment or a house to lose more heat than all the walls combined, even if the windows are double-paned or covered with storms. A variety of products have become available in the last few years to trap the heat before it ever gets to the window. These include shades, shutters and reflective films. Some of these perform as well as or better than exterior storms. They may be more convenient to install and they have an important additional advantage: They can be opened to let in sunlight. Windows, after all, are not always losing heat. When the sun is shining on them directly, most windows, double-paned or those with exterior storms, are heat gainers. At various times of the day they are the channel through which additional warmth enters the room.

That is heat you want to retain during the night. Day or night, the big energy losers are north-facing windows. They should be given priority attention, since a north-facing apartment can be much colder than a similar south-facing apartment in the same building.Hungry Girl Weight Loss Success Stories Most of the shades and screens mentioned below can be operated so that the windows let in the daytime heat, and then can be covered, reducing the outflow when the thermal tide turns in the other direction. Window Cleaning Price UtahInsulated Curtains and Window QuiltsHow Does Cd Lens Cleaner Work A tight-fitting curtain can give almost the same energy performance as a storm window, raising the R-value (resistance to heat loss) of the existing window from R-1 to R-2.

If the curtains are heavy, quilted or made with an insulating material, so much the better. For generations, residents of Appalachia have been putting quilts over their windows during cold winters. The most important thing is the proper seal against the window casing. It is the dead airspace between the curtain or quilt and the window that does most of the insulating. There are many ways to get such a seal. Adhesive strips around the perimeter of the window casing and the curtain can do the job. Or you can install the curtains on tracks, similar to those used on sailboat masts. Of course, the curtains have to be opened and closed at the right time to have value as energy savers. If you leave home in the dark and come back in the dark, leave the curtains on the southern windows open and those on the northern windows closed. Ideally, position your curtains in response to the sun's path across your building. Indoor Plastic Storm Windows Even a simple piece of plastic, either rigid or film that is put over a window from inside, has the same fuel-saving potential as a storm window installed outside.

Both the inside plastic and the outside storm window are doing the same thing: creating a dead airspace that acts as an insulator. Inside plastic coverings are an inexpensive alternative for people who do not want to block off their view with shutters and yet do not want to install standard exterior storms. There is one possible problem to be aware of with indoor window treatments - moisture. Any time one surface is warm and another is cold there is a potential for condensation. There need be no concern with curtains that are opened and closed every day. But care must be taken with insulated panels that are installed and not removed for the rest of the winter. You should check periodically to make sure that water has not collected between the panel and the window, where it could damage the wood of the window casing. The best way to counteract the moisture is to seal the panel or the indoor storm window so carefully that moist air has no chance of leaking around it. These resemble the standard white shades still found in old hotels, except that the shade part is constructe d of a thermal material.

Some units even have a choice of ma terials to absorb or reflect heat, so the shades can be used in wi nter and in summer. Depending on what materials are used, the R-v alues of these shades can be very high. Manufacturers claim a range from R-4 (twice as good as single-paned windows with a storm or a double-paned window) to R-14 (equal to a well-insulated wall). The shades usually slide upand down inside on a track, which is installe d inside the window casing to make an airtight seal. Custom roll-down thermal shades can be expensive, but in some cases, such as a sliding glass door on a north wall, the energy saving is considerable. Insulating Panels or Shutters Covering a window at night with an insulating panel can be one of the cheapest ways to turn windows into thermal assets, especially if you do it yourself. The panels can be made from rigid insulation, sandwiched between outer layers of wood or decorative materials. Properly installed, these panels can give a window the approximate Rvalue of an uninsulated wall.