Most Efficient criteria for windows

Natural Resources Canada (NRCan) recognition criteria for residential windows sold in Canada


ENERGY STAR Most efficient 2019

Windows that meet Version 4 of the ENERGY STAR technical specification for residential windows, doors and skylights sold in Canada.

A window is defined as an assembled unit consisting of a frame/sash component holding one or more pieces of glazing functioning to admit light and/or air into an enclosure and designed for a vertical installation in an external wall of a residential building. This definition also includes all transoms greater than 700 mm (27 in.) in height.


  1. Window must be manufactured by an ENERGY STAR Canada Participant.
  2. Window must be sold in Canada, registered with NRCan as ENERGY STAR certified and posted on the Canada/NRCan website.
  3. Window must meet the labelling section of the Guidelines for the labelling and promotion of ENERGY STAR certified fenestration products (amended June 2015).
  4. Window must meet the following specific criteria:
    1. An Energy Rating (ER) of 36 (unitless) or higher,
    2. A U-factor of 1.14 W/m2·K (0.20 Btu/h·ft.2·°F) or lower and have an ER of 26 (unitless) or higher.


The 2019 Most Efficient designation will be effective from January 1st to December 31st, 2019. Most Efficient models will be available on the energy efficiency ratings search engine for ENERGY STAR certified windows. 

The Most Efficient symbol will be provided to eligible manufacturers and their dealers upon request. The 2019 Most Efficient designation may be used in association with window products recognized during this period for as long as the model remains on the market. The 2019 Most Efficient symbol must not be applied directly to the window as a label.

The ENERGY STAR name and symbol are trademarks registered in Canada by the United States Environmental Protection Agency and are administered and promoted by Natural Resources Canada.