TA-23-C060 – Pathways to Achieve Thermal and Energy Performance of Residential Windows to meet 2030 NZE Target

In Canada, the Pan-Canadian Framework (PCF) on Clean Growth and Climate Change outlines strategies to achieve net-zero energy housing and buildings while reducing carbon footprints in the building sector. Residential windows have been identified as a crucial area of focus in achieving energy efficiency and reducing GHG emissions. Collaborating with the residential window industry, aspirational thermal and energy performance goals for windows have been established. However, the current thermal performance requirement for windows has remained stagnant at a u-factor of 1.6 W/m2K (0.28 Btu/ft2.F.hr) for several years. To address this, the window industry and regulatory researchers are working together to improve the thermal and optical performance of windows while minimizing disruptions to manufacturing processes for easy adoption. In achieving net-zero energy homes, it is crucial to reduce heat loss to lower heating loads, while also optimizing solar gains to prevent overheating, especially in colder northern climates. Evaluations of various housing archetypes have shown that a u-factor of 0.82 W/m2K (0.14 Btu/ft2F.hr) and mid-range solar heat gain coefficient (0.25 to 0.45) can facilitate net-zero energy targets in most northern climate zones. Fenestration component analysis has identified several options, including low-e glazing, inert-gas fills, and framing materials. However, it is important to note that at least triple-glazed windows are necessary. Insights from analyzing US and Canada's window databases have provided valuable information on tripleglazed windows. This paper elaborates on the results of thermal and solar-optical analyses of various combinations of glazing, placement, and emissivity of different surfaces (surface 2, 3, 4, or 5), inert-gas cavities, and frame materials. Additionally, window operator type (such as fixed, casement, sliders) is also considered to achieve lower u-factors and optimal solar heat gain coefficients.