Therm, Window Performance & the PHPP

In 2019 the British Columbian Provincial government in Canada commissioned a reference procedure for using Therm to determine window performance values. (American window manufacturers, hint, hint – you can reference this procedure too.) Produced by RDH Building Science and Peel Passive House Consulting, the preface states in part:

“Canadian window manufacturers are now aware that federal and provincial governments intend to use a combination of incentives and regulations to dramatically improve the energy performance of windows to less than 1.0 W/(m²-K) by 2030. These actions flow from the December 2016 Pan-Canadian Framework on Clean Growth and Climate Change 1 , Canada’s plan to meet greenhouse gas emissions targets, grow the economy, and build resilience to a changing climate.

Manufacturers looking to develop products with U-factors of less than 1.0 W/(m²-K) may wish to consider the market opportunity presented by the growing Canadian market demand for affordable Passive House windows.

The methodology presented in this document was developed jointly by RDH Building Science Inc. and Peel Passive House Consulting Ltd. It was created specifically to clarify the differences between North American and Passive House window thermal energy performance standards, and to provide a way for North American window manufacturers and energy simulation practitioners to accurately determine the energy performance parameters required to qualify them for use in Passive House buildings designed to the International Passive House Standard (IPHS). It shows how the industry-standard and publicly available LBL THERM software, together with a Microsoft Excel worksheet, can be used to accomplish this in a manner recognized by the Passive House Institute.

This methodology enables window manufacturers to report the performance of their existing products in Passive House terms, and to design next-generation windows for the growing Canadian and North American Passive House building market.