Come autumn, both home makeover TV shows and redecorating aficionados themselves take their work inside, sprucing up the house for the long winter months by adding richer color and texture. But you don't necessarily need to focus on interiors to find ways to add extra warmth to your decorating scheme. New fashions in window treatments can make your house look and feel cozier even when you gaze out the window at the bleak weather outside.

In the past two years, interior shutters have become the hottest window fashion on the market. Among window treatment commercial centers surveyed recently by Drapers & Window Coverings magazine, interior shutters are generating more than 81 percent of their total window treatment sales.

Part of the appeal of interior shutters is practical. Unlike blinds—which sag eventually, are difficult to clean, and feature unsightly cords that can be dangerous to small children—and drapes, which fade and need washing, interior shutters are low-maintenance and durable. They also provide effective insulation, which helps save on heating costs, along with the ability to regulate and block light unequalled by any other type of window covering: you have the option of eliminating sunlight completely and providing full privacy, or allowing partial sunlight and privacy, at the flick of a louver handle.

Interior shutters can be costly—up to $200 or more per window—but are a good investment, adding to a home's overall resale value. Plus, they never need replacement.

And interior shutters look just as well as they operate; in fact, designers are currently touting them as "the ultimate window covering," and for several good reasons. Installing interior shutters immediately transforms an ordinary window of any size, shape, and style into an ever-changing source of light and dark, a space in which mood and ambiance can easily be controlled. With their clean lines and simple, sleek good looks, interior shutters work well in both traditional and contemporary decors. Installed painted or varnished, they can complement, contrast, or highlight a room's architectural details and wall color. Interior shutters work well in any room, and can be dressed up in more formal rooms with a fabric valance or drapery. Best of all, say designers, interior shutters can be admired from both inside and outside—installing them throughout the front of your house makes for decidedly strong curb appeal.

Interior shutters come in traditional (smaller, thinner louvers) and plantation (larger, thicker louvers). Choose full- or café size, and an outside mount for design detail, or inside mount to eliminate light leaks. Interior shutters come in varnished, painted, or unfinished wood; extruded vinyl; or Polywood, an engineered wood substitute made from solid resin with a baked-on paint finish. For do-it-yourself types, interior shutters are quickly and easily installed (although many home furnishing centers offer low-cost installation services), and the tools required are minimal. While a table saw makes cutting easy, you can actually accomplish all the necessary cutting with hand tools. Beyond that, all you need to do is drill holes and install screws.

If you haven't got the wherewithal for interior shutters, or you simply can't imagine a window without colorful fabric surrounding it, you can still add warmth to both your room and its décor by layering window coverings. Window layering of three or even four coverings offers extra insulation and the option of varying privacy and light in the room. It can jazz up a room, whether your overall décor is contemporary and minimal or old world and sumptuous—and it keeps the warm air inside and the cold air out.

There's only one rule for window layering: Start light in both color and texture, building in color and texture as you move outward. For the bottom layer, try the newest rage—matchstick blinds, available unfinished or painted. Next, install a single or double curved metal curtain rod. The second layer should be a pair of sheer gauze panels chosen to contrast with or complement the blind. Add a third layer of silk on the outer rim of the double curtain rod, and top with brocade or velvet drapes on a decorative pole complete with finials and tie-backs. Pull open each layer of curtaining just enough to reveal the one beneath, and voila! Goodbye cold, hello coziness!