There are so many ways to make a house energy efficient, and the most important choices happen at construction. But many of us must be content with drafty older houses or cheaply constructed newer houses, and may feel at a loss for elegant solutions to our expensive and wasteful climate control problems. If, for warmth, you’ve ever been known to tack heavy plastic to the windows or huddle around a halogen bulb, take heart. A few deliberate décor choices can help you create interior spaces that are energy efficient and beautiful.
In a well-designed house, warm air stays inside in winter and outside in summer. It’s a simple principle. The goal is to be the master of this energy flow so you can enjoy natural light and breezes when you want them and snuggle up tight inside a hibernating den when you’d rather keep nature’s forces at bay. Think of your walls and floors as big, semipermeable surfaces and your windows as gaping holes. The decorative materials you choose should intelligently support or offset their existing insulating and heat-resistant qualities.
On average, 25 percent of warm or cool air in the home is lost through the windows. It’s important to have efficient windows (see “Window Shopping,” page 74), but the window treatments you select can significantly improve their performance.
Sunlight streaming through a window brings heat into the room. To keep the sun out, reflective light-colored blinds are one option. If you prefer dark colors to match your decorating scheme, look for products backed with light colors or a thin layer of aluminum that will reflect some of the sun’s rays. Blackout shades or drapery liners are also effective options for reducing solar heat gain. You may encounter window treatment products rated with a summer shading coefficient, which measures their effectiveness in preventing solar heat from entering the house. Low numbers are best (a window treatment that reduces heat gain by 75 percent has a shading coefficient of .25; one that reduces by 90 percent has a coefficient of .10).
Cooler climates and seasons present the opposite challenge. Cellular (honeycomb) shades are a versatile method of retaining heat. The air pockets in their layered-fabric construction trap interior air and prevent it from escaping through windows. Sold in many colors, fabrics, degrees of opacity, and thicknesses, cellular shades add 2.0 to 4.8 R-value to windows.
Solar shades are more translucent than cellular shades. Chicago interior designer Laura Barnett finds these unobtrusive, woven mesh fabric screens the most effective energy-saving solution for high-rise condominiums with large windows. “They don’t obscure the view, they come in several neutral colors that won’t fight with your walls, window trim, and any additional treatments such as draperies,” she says.
To block out visible sunlight as well, insulating shades are the best bet. They consist of three to five quilted layers of materials that insulate, act as a radiant barrier, and prevent condensation. To be effective, insulating shades must be sealed against the window frame with magnetic or grooved tracks when closed. These shades provide R-values up to 4.9.
Blinds and shutters are an acceptable choice if they are wood, but avoid metal blinds—they readily conduct heat into the house in summer and help it escape in winter. Metal blinds also lose heat convectively at their edges and between the slats.
If you prefer the look of fabric drapes, backing them with durable cotton felt or suede will improve their performance measurably. Barnett points out that “a felt drapery liner also drapes and hangs better than some of the stiffer blackout options.” If you install drapes without the addition of a liner or insulating shade, hang them with a closed-top cornice, choose a tight weave, and make sure there’s plenty of center overlap that touches the sill or floor. If the top or bottom is open, closing the drapes will actually make the room colder by creating a wind tunnel where warm air is cooled against the window and then passed through the bottom into the room.
Floor covering and wall covering
The biggest problem with floors and walls is conductive heat loss and gain, but there are several smart decorative touches that can minimize this effect. Wool carpet with a thick pad is an effective insulator that prevents heat loss in the winter and gain in the summer. Area rugs over bare floors provide seasonal flexibility. They can be replaced with cool grass mats and rugs in hot weather or removed altogether. Also consider cork and linoleum tiles, which are natural insulators.
Take advantage of any passive heating and cooling opportunities your home design affords. If you have large southern or southeastern windows, consider using tile, stained or patterned concrete, or brick flooring directly in front of those windows as thermal mass. It will absorb the sun’s heat during the day and release it in the evenings. Light-colored paint on the ceiling and walls will reflect light down to the thermal mass.
Drafty exterior walls will benefit from additional covering. Cork tiles or paper-backed wallpaper and fabric, fiber, and paper wall coverings are earth-friendly materials that provide better insulation than paint. Look for foil-backed wallpapers that reflect heat back into the room and prevent it from conducting through the walls. And have fun with functional art textiles—tapestries and quilts placed on exterior walls will beautify and insulate the space.
It may seem silly to consider the energy efficient properties of furniture, but furnishings should be chosen with the same care given the walls and floor. Shiny, polished colors and surfaces will reflect heat back to the walls or floors where it can be stored efficiently. And overstuffed, high-backed furniture is an age-old trick for shelter from drafts. Skirted furniture is also a good idea for drafty rooms.
If you’re willing to update the look of a room with a few seasonal tricks, your decor won’t work at cross-purposes with natural climate changes. For example, seasonal slipcovers can make furniture appropriate for summer or winter. Use cotton fabrics in light colors for summer and dark textured fabrics for winter insulation. Remove tablecloths and stick to smooth, cool surfaces in warm weather.
Furniture arrangement can be seasonal as well. Move furniture close to heat sources in winter and away from direct sunlight in summer. Space furniture farther apart in summer to promote ventilation. Light, openstyle furniture such as wicker should always serve the warmest rooms because this type of material doesn’t retain heat.
If you are working with passive heating and cooling, make sure your furniture doesn’t block the sun’s rays from reaching the thermal mass. The general rule is to leave at least 70 percent of a mass wall or floor uncovered. Allow air to circulate by maintaining air spaces under furniture. Likewise, don’t cover vents or block heat from radiators. Make sure there’s room for warm air to circulate.
Large pieces of furniture such as bookshelves, armoires, and entertainment centers can double as insulation for outside, non-mass walls. Or place heavy, dark pieces near a window where they will act as thermal mass, absorbing and releasing the sun’s heat.
Include a few functional accessories that improve energy flow. Folding screens can block drafts and shield windows on cold, windy, or overcast days. Ceiling fans save up to 40 percent on summer energy bills and up to 10 percent in winter. Set fans at reverse on low speed in winter—this action pushes trapped heat near the ceiling down to where you can feel it.