When selecting an energy efficient window treatment, primary importance should be given to its R Value (resistance to heat/air conditioning) loss of transfer.
The following table gives general ratings for different window covering materials. The higher the R Value, the better the resistance to heat and air conditioning loss.
Window Treatments
1 layer glass at R Value = .89
2 layers of glass at
R Value= .81
Aluminum blinds
1.20
3.01
Pleated shades (varies by fabric)
1.20 to 1.30
3.01 to 3.11
Vertical blinds (varies by material - freehanging fabrics will insulate less than solid vinyls or fabrics with vinyl groovers)
1.0 to 3.0
2.81 to 4.81
Cellular shades (varies by fabric and number of cells- dual or triple celled shades will insulate more than single celled shades)
