Greenhouse Covering Insulation Comparison Greenhouse Covering R-Value U-Value 6mm Twin-Wall Polycarbonate 1.54 0.65 4mm Twin-Wall Polycarbonate 1.43 0.70 Single Pane Glass, 3mm 0.95 1.05 Poly Film, 6mm 0.83 1.20 Click to see full answer. Furthermore, is polycarbonate a good insulator?Polycarbonate is mainly used for electronic applications that capitalize on its collective safety features. Being a good electrical insulator and having heat-resistant and flame-retardant properties, it is used in various products associated with electrical and telecommunications hardware.Likewise, what is the U value of polycarbonate? Energy Efficient Glazing Roof Glazing Thickness U Value Polycarbonate 16mm 2.4w m/2k Polycarbonate 25mm 1.6w m/2k Polycarbonate 35mm 1.5w m/2k Clear Tripleshield Glass 24mm 1.2w m/2k Then, what is the R value of 6 mil plastic? When selecting a 6 mil greenhouse plastic, you need to make sure it is not a product out of China. . Typically a single layer of polyethylene film has an R value of approximately 0.85. A double poly cover consisting of two layers of poly has an approximate R value of 1.25.What is a good R value for Windows?“As a comparison, Energy Star–rated windows typically hold an R-value of 3. By increasing the R-value from 3 to 5, average heat loss through the window is reduced by 30 percent to 40 percent.” Designed for new construction and replacement projects, the windows can achieve a U-factor as low as 0.15.