Legend

Windows

Energy Efficiency Ratings

U = U-value (W/m² – K) – The lower the number, the more energy efficient the product.

SHGC = Solar Heat Gain Coefficient – The higher the number, the higher the solar gain.

ER = Energy Rating (W/m² or dimensionless) – The higher the number, the more energy efficient the product.

The ER (Energy Rating) format was changed to all positive numbers (dimensionless) in October, 2004 by CSA (Canadian Standards Association) to address consumer confusion over negative numbers. The older format had a mixture of negative and positive numbers (W/m²). In our listings, all ER numbers that appear in the older format are shown in bold coloured type. An approximate conversion to the new format can be made by adding 33 to these numbers.