H1 and your windows: what the 6th edition changed

H1/AS1 6th edition was published on 27 November 2025 and removed the Schedule Method, which is where the familiar minimum window R-values came from. The previous edition may still be used until 26 November 2026. H1 applies to work that needs a building consent, so a consent-exempt retrofit in an existing house is not held to a window R-value by it.

What actually changed

H1 is the energy efficiency clause of the Building Code, and H1/AS1 is one of the acceptable solutions that shows how to comply. The 6th edition, published 27 November 2025, removed the Schedule Method: the simple lookup table that let a designer satisfy H1 by picking components with at least a given R-value, including windows. Designers now use the other compliance methods in the document.

Why installer blogs still quote a window R-value

Under the 5th edition with amendment 1, the Schedule Method set minimum window R-values of R0.46 in climate zones 1–4 and R0.50 in zones 5–6 (BRANZ's H1 FAQs). Those two numbers were easy to quote, so they spread across the industry. They are still legitimate for work using the 5th edition until 26 November 2026, but they are not what the current edition says, and after that date they will simply be out of date.

Does H1 apply to a retrofit?

Usually not directly. H1 bites on building work that needs a consent. Window work in an existing dwelling of up to two storeys is commonly exempt under Schedule 1 Exemption 8, so no consent means no H1 assessment for it. Exempt work must still comply with the Building Code generally — the exemption is from the consent process, not from the rules.

Where it does apply to you

• A new build, or a new dwelling within an existing one, is consented work and H1 applies in full.
• An alteration that needs consent — moving or enlarging an opening, structural work around a window — brings H1 into scope for that work.
• A window that has failed its 15-year durability requirement takes the work outside Exemption 8, so the consent, and H1 with it, comes back.

What to ask for instead of an R-value

For a retrofit, the useful specification is the unit itself: the glass type, whether it is low-E, the cavity width and what fills it, and the spacer. EECA notes that low-E glass can improve performance by up to 30% and argon fill by 5–20%, and that gaps of 12–16mm perform best. Ask for those in writing on the quote, and ask for the manufacturer's warranty on the sealed unit.

What we do about it

We do not quote a compliance R-value for retrofit work, because the current acceptable solution no longer publishes one for the Schedule Method and most retrofits are not consented anyway. Our quotes state the unit specification instead. If your job does need a consent, that is flagged at the measure, before you commit.