Code Description U-Value R-Value Solar Heat Gain Visible Light Transmittance
Clear Dual Dual pane, clear glass, no coatings 0.480 2.084 0.760 81%
Clear Tri Triple pane, clear glass, no coatings 0.310 3.226 0.685 74%
LOW-E HS1-C180 Dual pane, one Low-E coating, Argon 0.260 3.846 0.685 79%
LOW-E HS2-C180 Triple pane, one Low-E coating, Argon 0.184 5.433 0.615 73%
LOW-E HS3-C180 Triple pane, two Low-E coatings, Argon 0.133 7.521 0.560 70%
SUNSTOP HS4-C270 Dual pane, one SunStop coating, Argon 0.248 4.033 0.367 70%
SUNSTOP HS5-C270 Triple pane, one SunStop coating, Argon 0.186 5.377 0.338 63
SUNSTOP HS6-C270 Triple pane, two SunStop coating, Argon 0.124 8.065 0.310 54

Values are in METRIC. All performance for C.O.G. (centre of glass) ratings are based on Vision v4.0 simulations. All C.O.G U- and R-values are based on ASHREA Winter Conditions. Framing, cladding, frame type and other items will affect the overall thermal values of a complete window.

U Value: the total heat transfer out of a window (Btu/hr-sq ft-F or W/sq m- C). The lower the number the better the glass. 

R-Value: the amount of heat retained by the window. The higher the number the better the glass.

Solar Heat Gain Coefficient: the amount of solar radiation which enters the house through radiation. This is expressed as a dimensionless number between 0 and 1. It represents the heat gain through 3mm clear glass.

Visible Light Transmittance: measures how much of the visible light is entering the building through the glass. 1.0 would mean all of the light was getting through and 0 would mean none of it was getting through. Our atmosphere naturally filters out 5% of the visible light. Clear glass with no coatings lets in approx. 90% of visible light.