Windows are a major source of heat transfer in a building. Energy-efficient window treatments are environmentally friendly by reducing use of fuels for heating and cooling; they save money as well. Window coverings retard the transfer of heat, block ultraviolet (UV) radiation and reduce air infiltration by providing an insulated barrier in front of window glass. Insulated window treatments keep heat in during winter and cool air in during summer. Some materials like wood, bamboo and natural fabrics not only insulate, but are bio-degradable and recyclable.
Cellular or honeycomb shades block UV light and filter sunlight. The space between cells creates an insulating barrier by trapping air. Honeycomb shades are made as single or double-celled; double cells have more airspace and better insulation. Honeycomb shades come in a great variety of opacities, colors and pleat sizes. Transparent cellular shades transmit light but block UV light. Blackout cellular shades have an additional layer of material that prevents light from penetrating through the shade. Sidetracks enhance energy-efficiency by hugging the window frame which keeps drafts from infiltrating around the shade.
Curtains dress up a window and achieve a high insulating value. Using multiple layers allows the most flexibility for regulating light and controlling heat exchange. Sheers at the window can be used on sunny days to allow light into the room; they have little insulating effect. A middle tier of blackout or insulating curtains can be closed at night or on very cold days to keep heat in. Blackout curtains come in a variety of materials, colours and fabrics that have excellent insulating properties. Several manufacturers market foam-backed curtains that have both light-reducing and insulating properties.
Interior draperies made of tightly woven fabrics like jacquards or napped fabrics like flannel impede heat transfer through window glass, block UV light and reduce drafts. Heavy silks, velvets and wools can be used in a variety of styles for decorative effect while enhancing energy-efficiency. Adding lining and interlining to decorative curtains enhances the insulating properties. For maximum insulating value, curtain rods should be hung approximately 30 cm (12 inches) above the window frame and approximately 15 cm (6 inches) on either side to prevent airflow around the frame.
Blinds are another way to dress up a window and create an energy-efficient barrier. Both horizontally and vertically slatted units are available in metals like aluminum, an assortment of fabrics and many types of wood. Fabric vertical blinds look elegant on a bay or French door with their simple lines and soft look. They can be paired with curtains or swags, which enhance both visual appeal and energy efficiency.
Wood is a good insulating material and gives a warm, snug feeling to a room. Routless, or no-hole, wooden slats increase energy efficiency by stopping air and light from penetrating through cord holes. Slat widths vary from approximately 2.5 cm (1 inch) to 6.5 cm (2.5 inches), and can be matched to the decor of a room. Blinds can be used with curtains to give interest to windows, allow modulation of light and maximize the insulation value.
Liberty-Belle Howard is a UK blogger with a keen interest in green issues. She’s currently writing on behalf of Hillary’s Blinds.