• RDH Building Science

With the growing interest in the Passive House standard for energy efficient buildings, European fenestration products are being used more frequently in North American jurisdictions. This has created challenges for building designers and product manufacturers as the differences between North American, European ISO and Passive House thermal performance rating systems for windows have led to misunderstandings about the appropriate criteria for energy efficient product selection. The same window will have different U‐value and solar heat gain ratings under each of these systems, and there is no straightforward way to compare North American and European product performance. This study was undertaken to better understand the ISO and Passive House fenestration energy rating systems by comparing them with the NFRC/CSA rating system used in North America. In addition to identifying the conceptual differences between them, this study uses computer simulation methods to illustrate how these differences can result in significantly different product ratings.

Prepared by RDH for BC Housing.

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