Energy Rating (ER) of Window -- CSA

An ER rating for windows and sliding doors is derived from: Solar heat gain, Heat loss through frames, center and edge of glass; Air leakage heat loss

The combined effect of all three is measured in number of watts per square metre and is either positive or negative. A positive number represents a net heat gain and helps in reducing the home's heating costs. A negative number indicates that the product loses more energy through heat loss and air infiltration than it gains in solar energy absorbed from the sun i.e. the home's heating system has to work harder in colder weather.

ER numbers range widely depending on the type of window and design options. For example, fixed windows score better ER ratings than operating windows.

Operating windows and sliding doors typically have a negative ER number, ranging from -30 (indicating weaker energy performance) to -5. Fixed windows can be designed to have positive numbers ranging from -20 to +10.

A typical ER rating for insulated steel doors with wood frames is -22.

CSA-Canadian Standards Association

"a not-for-profit, non-statutory, voluntary membership association engaged in standards development and certification activities... 2000 standards covering the life sciences, environment, electrical and electronic products, communications systems, building construction, energy, transportation/distribution, materials technology, and quality business management. "