Retrofit alert: know when fire-rated components are called for

16 October 2020 by Jason Quinn

Fire rating of the building/windows is not something we usually need to worry about in new, detached single-family homes, as the clearance to the property boundaries is sufficient.

But during retrofits—especially ones that involve a change of use—fire regulations can have a big impact. It’s best to avoid the need for fire-rated windows as they are big money and poor performers from a thermal perspective. My guess is four times the cost of a decent triple-glazed window, for a fixed double-glazed, fire-rated window with quite poor energy performance.

In a high-performance building, the solution is often to install a single-glazed, fire-rated window AND a thermal window (either double- or triple-glazed). Splitting the functions just makes it easier.

You can sometimes avoid the requirement for a fire-rated window by opting instead for a skylight slightly further from the boundary. That would be another valid reason to ignore my general advice to avoid skylights.

BRANZ has a nice summary of the boundary requirements for Building Code Acceptable Solution C/AS1.

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