Just as layered clothing keeps you warm in winter, layered curtains on windows help keep the cold air out. Increasing the type of layers of curtains and the quality of the fabric in those layers can increase the r-value of curtains up to r-8. R-value is the measure of resistance to heat loss of a single particular material or combination of materials; the lower the number the greater the heat loss. Zero is no insulation and 12 corresponds to walls with 4-inch insulation. Curtains must be fit snuggly to the window for maximum effectiveness.
Position of Curtains
The most effective insulation starts with correct positioning of the curtains on the window. Cover as much extra space beside, above and below the windows as possible. The finished drapes should extent at least 12 to 14 inches past the window on each side and above the window and puddle on the floor 6 inches. At each side the curtains must return to the wall.
Layers of Curtains
Curtains start with an r-value of 1. A good quality drapery lining will provide an additional 1; using blackout or thermal lining will increase the r-value by about 3; adding a flannel interlining will increase the r-value another 3 or 4 for a total of about 8.
Additions to Curtains
Blackout lining is a base fabric with three thin layers of acrylic applied that adds thickness and does not allow any light to pass through. Thermal linings are a base fabric with a layer of acrylic foam applied that inhibits light passage but is designed specifically to prevent heat loss. Curtains constructed of these fabrics and that attach to existing curtains with pins, loops, or Velcro are available in home decor DIY stores and through catalog shopping. More than one layer can be added; if bulk becomes a problem, consider installing an additional curtain rod just below the existing one.
The Effect of a Valance
A valance mounted just above the curtain rod will also increase the effectiveness of the curtains. Valances should have the same layers as the curtains, be board mounted to prevent cold air from escaping up and be at least 12 to 14 inches in length.
- "Energy Conserving Window Treatments"
- "Shades of Comfort";The Warm Company;2000
- Photo Credit Jupiterimages/Photos.com/Getty Images
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