Optimum home energy efficiency is largely a matter of managing heat. Windows are a major source of unwanted heat gain and heat loss in most homes. On a summer day, solar heat energy passing through windows raises indoor temperatures, boosting monthly HVAC costs. On a winter night, conversely, heat readily radiates outward through window glass, your furnace cycles on more often to compensate, and heating bills rise.
Window treatments are one way to inhibit this process and improve energy efficiency. Here are three options for closing the window to heat gain and loss.
Drapes and Curtains
Fabric helps absorb and repel heat, particularly if it’s the right color. Light or medium-colored drapes and curtains with plastic backing are effective to reduce summer solar heat gain through a window by about one-third. Heavy curtains drawn at night in winter can cut heat loss through the glass by 10%. Effectiveness of drapes and curtains is enhanced by choosing full-length varieties that extend all the way to the floor. Using velcro tabs to attach the outer edge of the drape to the wall also helps increase effectiveness in heat control.
Shutters and Blinds
Operable exterior shutters and indoor blinds are made of solid materials that physically block solar energy. Blinds may also be coated with a reflective layer facing outward that rejects sunlight. While these options substantially shade rooms, reducing heat gain in summer and lower cooling costs, they are less effective at reducing winter heat loss. On cold nights, heat energy radiates through slots between the slats of shutters and blinds and escapes.
Transparent polyester film that adheres to glass, window film can cut heat gain in summer by over 50% while still allowing 80% of visible light to enter. Newer products known as “low emissivity” film also somewhat reduce heat loss through windows in winter. Effectiveness of window films can be compared by two standards—Solar Heat Gain Coefficient (SHGC) and Visible Transmittance (VT)—typically included in product specs.
Ask the energy efficiency pros at Aggressive Mechanical Contractors for more about the benefits of window treatments.
Our goal is to help educate our customers in Monmouth County, New Jersey and surrounding areas about energy and home comfort issues (specific to HVAC systems).