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Testing Programs

Thermal Insulating Value of Cellular Shades with and without Side Seals

Abstract 

The thermal insulating characteristics of two types of cellular shades, light-filtering and light-blocking, were measured under cold-weather conditions.  These thermal resistance values, or R-values, were measured both with and without the side seals.  These cellular shades were manufactured under the trade name Comfortex Symphony® ConforTrack™ Plus, and were double-cell shades, with 9.5 mm (3/8”) cells arranged to form a double layer.  The measured R-values were dramatically improved with the side seals, but in all cases were significantly lower than the advertised values.  The light-blocking shades had significantly higher R-values than the light-filtering shades.  The measured R-values decreased with decreasing outdoor temperatures. 

To avoid specifying the units throughout the report, R_SI will be used to specify R-values in SI units of m² ˚C/W, and R_US will be used for United States units of ft² ˚F hr/Btu.  At an outdoor temperature of -7˚C (20˚F), the R-value for the light-filtering shades without side seals was R_SI = 0.10 (R_US = 0.57), while the addition of the side seals more than doubled the R-value to R_SI = 0.21 (R_US = 1.2).  For the light-blocking shades without side seals, the R-value at an outdoor temperature of -7˚C (20˚F) was R_SI = 0.13 (R_US = 0.74), while adding the side seals more than doubled this value to R_SI = 0.35 (R_US = 2.0).  These values are significant relative to typical R-values for windows, so the addition of this type of shade can significantly reduce heat losses through windows.  Current building codes in colder parts of the United States require minimum window R-values (without shades) of R_SI = 0.50 (R_US = 2.9), so adding light-blocking shades with side seals can increase the effective combined minimum R-values by 70%.    

A previous report showed higher R-values for insulating shades than those reported here, but errors in the analysis used in that report are documented in this report. 

The complete report is available at:   Report on Thermal Resistance Values for Cellular Shades with and without Side Seals