Energy efficiency

ER RATING FOR SLIDING WINDOWS AND DOORS

These openings are characterized by large panels (80 to 95%), an opaque surface (5 to 20%) and discontinuity between two sliding panels or a sliding panel and an inactive panel.

The winter energy rating (ER) of these units is measured by taking into account the solar input (S), losses by conduction (-C) and by infiltration (-I). The resulting equation for calculating the "ER" is:

ER=S-C-I

For these components, when solar gains exceed the total of conduction and infiltration losses, we can determine the net positive heat input. In this case, the opening acts as a passive solar panel, resulting in reductions of annual heating costs for an entire building. The more positive the ER value is, the higher the energy savings originating by this passive solar panel will be.

In cases where the losses by conduction and infiltration exceed the solar input, there will be an increase in energy consumption. The more negative the ER results are, the higher the energy costs will be in relation to this type of opening.

EXISTING METHODS TO MEASURE THE ENERGY PERFORMANCE OF SLIDING DOORS AND GLASS WINDOWS, ACCORDING TO THE CAN/CSA A440.2.

In the early nineties, a standard rating to measure the energy efficiency of sliding glass doors and windows was established. The CAN/CSA A440.2 Standard (Energy rating system for sliding glass windows and doors, Ref. no 16) was created to find a method to test the thermal efficiency of windows either by using computer simulation or laboratory testing. Many hypotheses had been put forward as to ways to obtain a comparative ER energy performance rating which would be internationally effective for products that are specified by the Standard. Furthermore, the Standard enabled the informed user to acquire specific RES energy performance ratings for products with known dimensions, geographic location and orientation.

APPLICATION AREAS OF THE CAN/CSA A440.2 STANDARD

The CAN/CSA A440.2 Standard applies to fixed and opening windows that meet the CAN/CSA A440 norm and to sliding doors that meet the CAN/CGSB 82.1 norm, which are meant to be vertically installed on walls of residential constructions. This Standard specifies a testing method for the energy rating (ER) of windows that are submitted to residential heating. The equation used to measure thermal efficiency incorporates solar heat gains; heat loss through frames, spacers and glass; and air leakage. The energy efficiency measure takes into account the vertical installation in a typical residence, an average climate zone representative of Canada, and the average sun radiance condition for the four cardinal directions. The energy efficiency measure provides a tool for the comparison of different products of fenestration concerning their influence on the residential heating system and its annual energy consumption.

PRODUCTS EXCLUDED FROM THE CAN/CSA A440.2 NORM

Products such as entrance doors and garage doors have been excluded from the development of the CAN/CSA A440.2, but this was uniquely to simplify and carry out its completion rapidly. Actually, the norm specifies that computer simulation procedures can be applied to measure the efficiency of these products concerning solar gains, and losses by conduction.