OT_131: BRANZ Bulletin 670 (2022) — Specifying Windows and Doors under H1 (5th ed Energy Efficiency): by-zone…

OT_131: BRANZ Bulletin 670 (2022) — Specifying Windows and Doors under H1 (5th ed Energy Efficiency): by-zone…

Source

https://www.branz.co.nz/pubs/bulletins/bu670/ — original source (opens in a new tab; the file is not redistributed)

BRANZ Bulletin 670 (2022) — Specifying Windows and Doors under H1

The windows/doors companion to the H1 5th-edition thermal-envelope bulletins already in the corpus ( OT_043 overview + schedule, OT_044 calculation method, OT_057 the guide). Carries the full six-climate-zone window/door R-value schedule the model's ④c building_standard = standard baseline rests on — windows/doors are the weakest element of the envelope (R0.37→R0.50 vs roof R6.6, wall R2.0) — plus Table 2: measured construction R-values for generic double- and triple-glazed window systems by frame type (aluminium 23% frame → uPVC 34% / timber 41%) and glazing/gas/spacer combination, each with its SHGC. The commonly-installed basic double-glazed aluminium IGU (R0.26) no longer complies anywhere. Envelope specification only — no cost or currency data. Read verbatim (pdftotext -layout) → data_quality: verified.

Summary

BRANZ Bulletin 670 (Issue 670, updated Oct 2022 — a minor-update reissue of the identically-named/numbered April 2022 original) is the window- and door-specific practical guide to the H1 5th edition of the New Zealand Building Code’s Energy Efficiency clause, mandatory for new building work from 3 November 2022. It sets out the schedule-method minimum construction R-values for vertical windows and doors across the new six climate zones (Table 1, with a staged transition to 1 May/2 November 2023 and a housing / not-housing split), explains how each physical element of a window drives its thermal performance (framing material, thermal breaks, warm-edge spacers, low-E coatings, IGU gas fill), and reproduces BRANZ-calculated construction R-values for generic window systems together with their solar heat gain coefficient (Table 2). It also covers skylights (Table 3), the WEERS window-rating scheme, and installation. For Neobiome Intelligence it completes the window/door element of the current NZ code thermal envelope — the building_standard = standard reference (heat_demand_multiplier 1.00) against which the model’s high-performance and Passive House multipliers (CR_017) are measured — extending the single R0.46 window figure summarised in OT_043 and the Zone-3 point value in OT_057 to the full by-zone schedule and, via Table 2, to per-frame/per-glazing achievable R-values.

Key claims

- claim: "On 29 November 2021 MBIE announced changes to the minimum thermal performance requirements for compliance with NZ Building Code clause H1 Energy efficiency. The 5th edition of Acceptable Solution H1/AS1 and Verification Method H1/VM1 incorporates higher minimum construction R-values for roofs, floors and windows and minor increases for some walls. The three climate zones in NZS 4218:2009 are replaced by six climate zones, and the 5th edition now applies only to all housing and buildings up to 300 m². From 3 November 2022 the 4th edition H1 documents can no longer be used for building consent applications, and only the new methodologies (Appendix E) for establishing the thermal resistance of windows, doors and skylights can be used."
  source_location: "§1.0.1, §1.0.3, §1.0.5, §1.0.6, §1.0.10 (pp.1–2)"
- claim: "The change is significant: the minimum thermal performance for windows in the new zones 5 and 6 (part of the old zone 3) jumps from R0.26 to R0.50 (R-value units m²K/W). Most window and glazing systems installed in the past do not achieve this new value and therefore cannot be used in new building work when using the schedule method."
  source_location: "§1.0.4 (p.1)"
- claim: "Schedule-method minimum construction R-values for vertical windows and doors (Table 1), by climate zone across the transition (3 Nov 2022 / 1 May 2023 / 2 Nov 2023): zones 1 and 2 — R0.37 / R0.37 / R0.46; zones 3 and 4 — R0.37 (housing) or R0.46 (not housing) / R0.46 / R0.46; zones 5 and 6 — R0.37 (housing) or R0.50 (not housing) / R0.50 / R0.50. Two-step transition: climate zones 1–2 (upper North Island) go R0.37 (3 Nov 2022) → R0.46 (2 Nov 2023); housing in zones 3–6 goes R0.37 (3 Nov 2022) → R0.46 (zones 3 and 4) or R0.50 (zones 5 and 6) from 1 May 2023."
  source_location: "§1.0.7, §1.0.8, §1.0.9 + Table 1 (pp.1–2)"
- claim: "The construction R-value is the total thermal resistance of all the various physical elements that make up a window system. The requirements for working it out are given in Appendix E of H1/AS1 and H1/VM1 (the thermal performance tables for windows in NZS 4218:2009 no longer apply); Table E.1.1.1 in Appendix E of H1/AS1 is for housing only. The construction options tabulated are: framing material (aluminium, thermally broken aluminium, uPVC, timber); glazing (double or triple pane — single glazing is not an option); spacer (aluminium or thermally improved); gas fill (dry air, argon or krypton); glass (low-E with four performance levels, or clear); U-values (W/m²K, centre-of-glazing only, the inverse of R-values); and R-values (m²K/W) for complete windows accounting for both glazing and frames."
  source_location: "§2.0.1, §2.0.2 (pp.1–2)"
- claim: "Framing material ranks by thermal performance: timber and uPVC window frames offer the best performance (relatively poor conductors of heat), followed by thermally broken aluminium frames; aluminium itself gives relatively poor thermal performance because of its high thermal conductivity. A thermal break in an aluminium frame is typically a very-low-conductivity reinforced plastic (polyamide) joining the inner and outer parts; its performance relies on installation ensuring the internal aluminium half-shell is not exposed to outside air. Spacers separating the glass panes can be aluminium or, preferably, a much-lower-conductivity 'warm edge' / thermally improved spacer that reduces heat loss."
  source_location: "§3.1.1, §3.2.1–3.2.2, §3.3.1 (pp.2–3)"
- claim: "Low-E (low-emissivity) glass has a microscopically thin transparent metal coating that reflects long-wave infrared radiation and heat back. Table E.1.1.1 refers to Low E1, Low E2, Low E3 and Low E4 (numbers indicating thermal performance levels from basic to very high). The technology has improved considerably: newer products in some cases give 10 times the thermal performance of older low-E glazing, and double glazing with the newest low-E coatings can perform about as well as some entry-level triple glazing without the additional weight and size."
  source_location: "§3.4.1–3.4.3 (p.4)"
- claim: "IGU gas fill options in H1/AS1 and H1/VM1 are air, argon and krypton. Argon (about 1% of Earth's atmosphere) is a better insulator than air, reducing window heat loss by 3–9% compared with an air-filled IGU. Krypton is an even better insulator than argon but is only 1 part per million of the atmosphere, is more expensive, and IGUs with krypton filling had not been commercially produced in Aotearoa New Zealand to date (2022). A wider gap between panes (12 or 16 mm rather than 8 mm) usually increases R-value for air, though gas fills work better with smaller gaps."
  source_location: "§3.5.1–3.5.2, §3.6.1 (p.4)"
- claim: "Construction R-values (m²K/W) for generic vertical window systems (Table 2), by frame type and average frame % — Aluminium 23%, Thermally broken 27%, uPVC 34%, Timber(56 mm) 41% — with SHGC. Double glazing: '4 Clear / 16 / 4 Clear', air, aluminium spacer, SHGC 0.77 → R 0.26 / 0.32 / 0.40 / 0.44; Low-E¹/Clear, argon, aluminium spacer, SHGC 0.56 → 0.30 / 0.39 / 0.50 / 0.56; Low-E²/Clear, argon, improved, SHGC 0.55 → 0.33 / 0.42 / 0.56 / 0.63; Low-E³/Clear, argon, improved, SHGC 0.57 → 0.35 / 0.46 / 0.63 / 0.71; Low-E⁴/Clear, argon, improved, SHGC 0.54 → 0.37 / 0.50 / 0.69 / 0.77; Low-E⁴/Clear, krypton, improved, SHGC 0.37 → 0.40 / 0.54 / 0.76 / 0.85. Triple glazing (aluminium 'not available'): Clear/Clear/Clear, air, improved, SHGC 0.69 → 0.38 / 0.50 / 0.56; Low-E²/Clear/Clear, argon, improved, SHGC 0.50 → 0.48 / 0.66 / 0.74; Low-E³/Clear/Clear, argon, improved, SHGC 0.52 → 0.52 / 0.73 / 0.81; Low-E³/Low-E³/Clear, argon, improved, SHGC 0.47 → 0.59 / 0.86 / 0.95; Low-E⁴/Low-E⁴/Clear, argon, improved, SHGC 0.43 → 0.62 / 0.91 / 1.01. Values were calculated by BRANZ (area-weighted averages from two houselots, WEERS modelling with modifications, from a 2021 aluminium window specification by a large group builder); the notes warn uPVC results may be less representative than aluminium because of product variation."
  source_location: "Table 2 + Notes 1–3, §5.0.5 (p.5)"
- claim: "Most window and glazing systems that previously complied with H1 will not comply with the 5th edition — for example, a basic double-glazed aluminium-framed IGU (clear glass, aluminium spacers and air fill) with its accepted R-value around R0.26, very commonly installed in new houses in recent years, will no longer comply for new building work anywhere in the country under the schedule method. Thermal performance (Rwindow) should be determined before other requirements such as visible light transmission, UV, SHGC, security, privacy, noise control and ease of cleaning."
  source_location: "§5.0.2, §5.0.3 (p.5)"
- claim: "The 5th edition update made no change to the solar heat gain coefficient (SHGC) requirements — SHGC measures how well a window blocks heat from the sun, and excessive radiative heat flow can lead to houses overheating (a growing problem in NZ, to be considered in a future H1 revision). Until this is addressed, architects and designers should ensure the windows they specify do not contribute to a house overheating in summer. Compliance is not the only driver of thermal performance: window size and location (more/larger north-facing windows for passive solar; fewer/smaller south-facing to cut heat loss; west-facing designed to limit late-afternoon overheating), opening area for summer ventilation, shade devices (eaves, roller blinds), and installation all matter."
  source_location: "§1.0.2, §1.0.12, §5.0.6 (pp.1, 5)"
- claim: "Skylights (Table 3): minimum construction R-values, by climate zone (3 Nov 2022 / 1 May 2023): zones 1–2 — R0.37 (housing) or R0.46 (not housing) / R0.46; zones 3–4 — R0.37 (housing) or R0.54 (not housing) / R0.54; zones 5–6 — R0.37 (housing) or R0.62 (not housing) / R0.62. In new zones 5 and 6 the minimum has increased from R0.31 to R0.62. The schedule-method skylight-area limit is unchanged — no more than 1.5 m² or 1.5% of the total roof area (whichever is greater). Skylights should be used sparingly: over a year they almost always lose more energy than they gain, and in summer they contribute to overheating."
  source_location: "§7.0.1, §7.0.3, §7.0.5 + Table 3 (p.6)"
- claim: "BRANZ and the Window and Glass Association New Zealand developed the Window Energy Efficiency Rating System (WEERS), which combines the thermal performance of the frame and glazing together with window size to calculate the specific thermal performance for any window; some suppliers provide a WEERS certificate recording the R-value of each window and the R-value for the houselot. WEERS implements ISO 10077-2:2018 (thermal transmittance of windows/doors — numerical method for frames) and its calculation is consistent with the H1/VM1 window construction calculation methodology. How windows are installed also affects performance: to maintain continuity of the thermal envelope a window should ideally be installed in line with the centre of the insulating layer (rebated or recessed), not surface-mounted with the cladding — though weathertightness implications must be understood before changing window positioning."
  source_location: "§4.0.1, §6.0.1–6.0.2 (pp.4–5)"

Neobiome Intelligence relevance

• ④c building_standard baseline — the window/door element, and the envelope’s weakest link. This bulletin completes the window/door row of the current NZ code thermal envelope (the standard building_standard, heat_demand_multiplier 1.00 CR_017) with the full six-zone schedule: windows/doors R0.37 (transitional, all zones from 3 Nov 2022) rising to R0.46 (zones 1–4) / R0.50 (zones 5–6). This extends OT_043 (which carried the single figure R0.46 for zones 1–2) and OT_057 (which gave only the Nelson/Tasman Zone-3 point value R0.46) to every zone, with the transition dates and the housing / not-housing split made explicit. Critically it confirms that windows/doors are by far the weakest element of the envelope — R0.37–0.50 against roof R6.6 and wall R2.0 — so glazing area and glazing spec are the dominant fabric-heat-loss lever for any Neobiome community build.
• Table 2 is the real design fork — frame + glazing choice spans R0.26 to R1.01. BRANZ-calculated construction R-values show the same code minimum is reached very differently by frame: the commonly-installed basic double-glazed aluminium IGU is only R0.26 (air fill, aluminium spacer — now non-compliant anywhere), whereas a low-E argon double-glazed unit reaches R0.37 aluminium / R0.50 thermally-broken / R0.69 uPVC / R0.77 timber, and a triple low-E timber unit reaches R1.01. Frame material carries most of the spread (average frame area rises aluminium 23% → thermally-broken 27% → uPVC 34% → timber 41%), so for NI a window is a design-dependent value bounded by these rows, not a fixed R-number: choosing thermally-broken/uPVC/timber frames + low-E + argon is the concrete route from bare compliance toward the high-performance (CR_017 ×0.50) tier on the glazing line. uPVC results carry a representativeness caveat (product variation in NZ).
• SHGC is carried but unregulated — the overheating flag NI must not lose. H1 5th edition regulates only conductive/frame heat loss, not solar heat gain; SHGC values are supplied in Table 2 (0.37–0.77) but there is no SHGC requirement, and BRANZ explicitly warns overheating is “a growing problem in NZ.” For a passive-solar Neobiome design this is the tension to model: high-SHGC clear glazing aids winter passive-solar gain (cf. LIT_018’s thermal-mass + overhang system) but risks summer overheating, managed by window size/orientation and shade devices (eaves on north, blinds on west) rather than by the R-value alone. Note the inverse relationship visible in Table 2 — the highest-R low-E/krypton unit has the lowest SHGC (0.37), so maximising winter conductive performance can suppress useful solar gain.
• Above-baseline path and skylight penalty. The window R-value can be traded within the H1 calculation method (OT_044) against better opaque elements, and WEERS (ISO 10077-2:2018, consistent with H1/VM1) is the supplier-side rating that lets a specifier verify a houselot R-value. Skylights are a quantified net-loss element — R0.31→R0.62 in zones 5–6, “almost always lose more energy than they gain,” capped at 1.5 m² or 1.5% of roof area — so NI should treat skylights as an overheating/heat-loss liability to minimise, not a daylighting free lunch.
• Scope note — no cost data. The bulletin is an envelope specification source; it carries no CapEx, glazing-cost or currency figures. Window/glazing cost stays with the above-code cost sources (CR_017 / OT_085); this page firms the requirement and the achievable-R-by-spec, not the price.

Research targets

Documents to retrieve

• (candidate, low priority) BRANZ Bulletin 658 Timber windows (cross-referenced in §8) — the timber-frame companion; timber frames give the highest window R-values in Table 2 (up to R1.01) and are a low-embodied-carbon choice, so it could firm the timber-glazing line for a Neobiome build. Marginal to the SSI/heat-multiplier calc (Table 2 already supplies the timber R-values).

Research gaps

• SHGC / solar-heat-gain and summer-overheating modelling for NZ passive-solar community design is surfaced but not resolved here — H1 regulates conductive loss only, and the winter-passive-gain vs summer-overheating trade-off (glazing SHGC × orientation × shade device) has no quantitative NZ model in the corpus. Partially adjacent to the passive-design evidence on LIT_018 and D04’s overheating notes; a design-side gap rather than a heat-multiplier input.
• The NZ-specific heat-demand delta (kWh/hh/yr) from glazing above the H1 baseline is already carried as the OT_043 gap and partly covered by CR_015 / CR_017’s multipliers — not re-opened here.

Notes

• Primary BRANZ technical bulletin, read verbatim via pdftotext -layout — every figure (R-values, transition dates, frame percentages, SHGC values, argon 3–9%, low-E 10×, skylight R0.31→R0.62, Table 2 full grid) traces to the raw → data_quality: verified. Issue 670, updated Oct 2022: a minor-update reissue of the identically-named and -numbered April 2022 original (stated on the back page). 7 pp. ISSN 2537-7310 (Online).
• Siblings in corpus: OT_043 (Bulletin 676 — H1 compliance overview + element R-value schedule), OT_044 (Bulletin 678 — H1 calculation method), OT_057 (House Insulation Guide 6th ed — the by-zone R-value tables). This page carries the window/door- and skylight-specific detail those three summarise. The companion bulletins for the other elements are 672 (floors) and 677 (roofs).
• No cost/currency content — envelope specification only. BRANZ documents are classified ot_ (cf. OT_006/OT_043/OT_044/OT_057).

Connections

Links to

Sources (7): CR_015 · CR_017 · LIT_018 · OT_043 · OT_044 · OT_057 · OT_085

Referenced by

Sources (3): OT_132 · OT_134 · OT_159

EDT domains (1): D04: Sustainable Habitat & Building Technology