OT_132: BRANZ Bulletin 672 (2022) — Specifying Floors under H1 (5th ed Energy Efficiency): Slab-on-Ground & Suspended…

OT_132: BRANZ Bulletin 672 (2022) — Specifying Floors under H1 (5th ed Energy Efficiency): Slab-on-Ground & Suspended…

Source

https://www.branz.co.nz/pubs/bulletins/bu672/ — original source (opens in a new tab; the file is not redistributed)

BRANZ Bulletin 672 (2022) — Specifying Floors under H1

The floors 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 floor R-value schedule the model's ④c building_standard = standard baseline rests on: slab-on-ground (unheated) R1.5 (zones 1–4) / R1.6 (zone 5) / R1.7 (zone 6); suspended, "other", and all heated floors R2.5 (zones 1–3) / R2.8 (zone 4) / R3.0 (zones 5–6). Envelope specification only — no cost or currency data. Confirmatory of OT_057 — at the pilot Zone 3 it carries the same H1 floor minimums OT_057 already records (slab-on-ground R1.5, suspended R2.5), corroborating the existing baseline rather than introducing new numbers. Read verbatim (pdftotext -layout) → data_quality: verified. ⚠ The raw filename (Bulletin672_reissue_SR_12_10.pdf) loosely says "roofs"; the actual content is FLOORS (the roofs bulletin is 677).

Summary

BRANZ Bulletin 672 (Issue 672, updated Oct 2022 — a minor-update reissue of the identically-named/numbered June 2022 original) is the floor-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 (housing from 1 May 2023). The 5th edition separates the minimum thermal performance of slab-on-ground floors from other floors (predominantly timber-framed suspended floors) and changes how a floor’s construction R-value is calculated, moving to six climate zones from the previous three. The bulletin sets out the schedule-method minimum floor R-values (Table 1), the definition of construction R-value, the slab-on-ground calculation via the new Appendix F look-up tables (area-to-perimeter ratio, edge/underslab insulation types, raft foundations for the first time), the suspended-floor route via NZS 4214:2006, and the calculation- and modelling-method compliance paths. For Neobiome Intelligence it firms the floor 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 — corroborating the Zone-3 point values in OT_057 (slab R1.5, suspended R2.5) rather than introducing new baseline numbers, and refining the floor range summarised in OT_043.

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, has six climate zones (replacing the previous three), and now applies only to all housing and small buildings up to 300 m². The new compliance requirements separate the minimum thermal performance of slab-on-ground floors from other floors and change the way the thermal resistance and construction R-value of slab floors are calculated."
  source_location: "§1.0.1, §1.0.3, §1.0.4, §1.0.8 (pp.1–2)"
- claim: "The previous H1/AS1 and H1/VM1 4th edition amendment 4 can still be used until 2 November 2022; from 3 November 2022 the 5th edition amendment 1 must be used. However, where building consent applications for housing are submitted before 1 May 2023, roof, wall and floor construction R-values can be equivalent to the previous (4th edition) requirements, and up until that date concrete slab-on-ground floors in housing are still deemed to achieve a construction R-value of R1.3."
  source_location: "§1.0.2 (p.1)"
- claim: "Schedule-method minimum construction R-values for floors (Table 1), applying from 3 November 2022 for buildings up to 300 m² excluding housing and from 1 May 2023 for housing: non-slab floors R2.5 in climate zones 1–3, R2.8 in zone 4 and R3.0 in zones 5 and 6; all heated floors the same as non-slab floors above; slab-on-ground floors (unheated) R1.5 in climate zones 1–4, R1.6 in zone 5 and R1.7 in zone 6. At the pilot Zone 3 these are the same floor minimums recorded in OT_057 (slab-on-ground R1.5, suspended R2.5) — this bulletin corroborates OT_057 and sets them in the full six-zone table."
  source_location: "§1.0.6 + Table 1 (pp.1–2)"
- claim: "The construction R-value is the total thermal resistance of all the physical elements that make up a floor (including the insulating effect of the ground under slab-on-ground floors) but ignores the effects of floor coverings such as carpets. Where part of a concrete floor is in contact with the ground and part suspended, the part in ground contact must be treated as a slab-on-ground floor and the other part treated as an 'other floor' type."
  source_location: "§2.0.1–2.0.2 (p.2)"
- claim: "Using the calculation method in H1/AS1, the floor insulation level can differ from the schedule figures provided the building as a whole performs at least as well as the reference building; for non-heated floors the construction R-value must be at least 50% of the schedule-method construction R-value for non-heated floors. The calculation method cannot be used to reduce the performance of floors with embedded heating systems — in these cases the schedule-method minimum construction R-values apply."
  source_location: "§2.0.4 (p.2)"
- claim: "Appendix F in H1/AS1 gives look-up tables of construction R-values for selected generic concrete slab-on-ground floors according to their area-to-perimeter ratio; the generic slab types include raft foundation slabs for the first time, and the calculations were carried out by BRANZ. The tables cover floor types (slab or concrete raft foundation floors), floor insulation types (no insulation; R1.0 vertical edge insulation; R1.2 or R2.4 full-cover underslab insulation; a 1.2 m wide strip of R1.2 or R2.4 underslab insulation along the slab perimeter; or a combination of edge and underslab), and external wall types (slabs under masonry veneer walls have a step-down and are treated separately). The normal polystyrene pods in a concrete raft foundation floor are not considered insulation under H1; raft foundation floors with pods but no additional insulation are regarded as uninsulated."
  source_location: "§1.0.7, §3.0.1–3.0.2 (pp.1–2)"
- claim: "To use the tables you need the slab area-to-perimeter ratio (the slab area inside the interior wall surfaces divided by the perimeter measured along those surfaces, excluding porches and attached garages) and the effective thickness of the external wall. The greater the area-to-perimeter ratio, the higher the slab-on-ground R-value; larger slabs and square or rectangular slabs have higher ratios and therefore higher R-values than smaller or irregularly shaped slabs of similar insulation. The minimum ratio shown in the tables is 1.6 — houses with a ratio below this (such as house (b) in Figure 1, ratio 1.24) cannot use the tables and need another approach (the modelling method in H1/VM1, the Appendix F calculation in H1/VM1, or an Alternative Solution). Figure 1 examples: (a) 256 m²/64 m gives a ratio of 4; (b) 47 m²/38 m gives a ratio of 1.24."
  source_location: "§3.0.3–3.0.7 + Figure 1 (p.3)"
- claim: "Some Appendix F tables cover slab construction with R1.0 vertical edge insulation, addressing significant heat transfer through the slab's vertical edge. Construction R-values are only given in Appendix F for edge insulation of R1.0 — BRANZ research (Study Report SR352) found very limited benefit in installing edge insulation of a higher R-value than this. Slab edge insulation is typically XPS (extruded) polystyrene, must be protected against impact damage, UV exposure and water absorption, and is installed on all exterior exposed vertical faces of the slab from the top edge down to the bottom of the footing."
  source_location: "§3.1.1–3.1.3 (pp.3–4)"
- claim: "Some previous methods of calculating slab-on-ground floor R-values can no longer be used for H1 5th edition, including NZS 4214:2006 and the 5th or earlier editions of the BRANZ House insulation guide, because the nominal soil conductivity and internal surface heat transfer coefficient have changed; the 6th edition of the House insulation guide (published digitally in 2022) takes account of this. Acceptable methods for determining the R-values of floors other than slab-on-ground floors are contained in NZS 4214:2006, and the construction R-value of other types of floors is verified using NZS 4214:2006."
  source_location: "§3.0.9, §4.0.2, §5.0.5 (pp.3–4)"
- claim: "For floors other than slab floors (likely predominantly timber-framed suspended floors) the minimum construction R-values are R2.5 in climate zones 1–3, R2.8 in zone 4 and R3.0 in zones 5–6, with by far the largest part of the thermal performance coming from the insulation material. NZ underfloor insulation includes polystyrene panels inserted between the floor joists and glass wool (fibreglass), wool or polyester sheets fitted between the joists; because 5th-edition insulation is likely thicker than 4th-edition, subfloor framing timbers should be checked for sufficient size. A ground vapour barrier under suspended timber floors is recommended — usually a 0.25 mm (250 micron) polythene sheet lapped 150 mm at the joints (NZS 4246:2016 gives detailed instructions)."
  source_location: "§4.0.1, §4.0.3–4.0.5 (p.4)"
- claim: "To allow flexible future use it is prudent to insulate the floor of any unconditioned space that may later be converted to habitable space. Concrete New Zealand suggests one way to achieve the elevated slab R-values required for heated floors is applying thermal insulation and a floating unreinforced concrete screed on top of the slab (enclosing the underfloor heating system, common overseas in countries such as Germany), with attention to detailing at the screed-to-wall junction to avoid thermal bridging; another suggested approach is thickening the underfloor insulation."
  source_location: "§6.0.1–6.0.2 (p.4)"

Neobiome Intelligence relevance

• ④c building_standard baseline — the floor-element detail, CONFIRMATORY of OT_057. This bulletin firms the floor row of the current NZ code thermal envelope (the standard building_standard, heat_demand_multiplier 1.00 CR_017) with the six-zone schedule: slab-on-ground (unheated) R1.5 (zones 1–4) / R1.6 (zone 5) / R1.7 (zone 6); suspended, “other”, and all heated floors R2.5 (zones 1–3) / R2.8 (zone 4) / R3.0 (zones 5–6). It confirms — does not change — the H1 floor baseline: at the pilot Zone 3 it carries exactly OT_057’s slab R1.5 / suspended R2.5, corroborating the existing figure rather than adding a new one — the other-zone values are the same bulletin’s fuller context table (and it refines OT_043, which carried floors only as the range “R2.5–R3.0”).
• Slab-on-ground vs suspended is a real build-spec fork. A concrete slab-on-ground floor needs only R1.5–R1.7 versus R2.5–R3.0 for a suspended timber floor, because the ground under the slab counts toward the construction R-value. For a Neobiome community build this favours slab-on-ground (also the thermal-mass path for passive-solar designs, cf. LIT_018) on the floor-insulation line, while a suspended floor carries a materially higher insulation requirement. A floor part-on-ground/part-suspended is split and each part meets its own rule.
• Above-baseline path is bounded. Via the H1 calculation method (OT_044) a non-heated floor may drop to 50% of the schedule R-value if traded off by better walls/roof, but floors with embedded heating cannot be reduced below the schedule minimum — a hard floor on the high-performance / Passive House trade-off space where underfloor heating is used.
• Slab R-value is geometry-dependent — not a single constant. The achieved slab-on-ground R-value rises with the area-to-perimeter ratio (larger, squarer slabs perform better; tabulated minimum ratio 1.6, below which the look-up tables cannot be used), and edge-insulation benefit caps at R1.0 (BRANZ SR352). NI should therefore treat “slab floor” as a design-dependent value bounded by the schedule minimums, not a fixed R-number.
• Scope note — no cost data. The bulletin is an envelope specification source; it carries no CapEx, insulation-cost or currency figures. Floor-insulation cost stays with the above-code cost sources (CR_017 / OT_085); this page firms the requirement, not the price.

Research targets

Documents to retrieve

• (candidate, low priority) The full H1/AS1 Appendix F slab-on-ground R-value look-up tables (construction R-value by area-to-perimeter ratio × insulation type × external-wall type, incl. raft foundations), referenced but not reproduced in this bulletin — would let NI compute a slab R-value for a given community footprint rather than relying on the schedule minimum. Marginal to the SSI/heat-multiplier calc (which uses the standard/high-performance/Passive House multipliers, not per-slab R-values), so deprioritised.

Research gaps

• The NZ-specific heat-demand delta (kWh/hh/yr) from building floors 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

• CONFIRMATORY of OT_057 — no new numbers added to the baseline. At the pilot Zone 3 the bulletin carries OT_057’s existing floor minimums (slab-on-ground R1.5, suspended R2.5). The other-zone values (R1.6/R1.7 slab, R2.8/R3.0 suspended) are the same bulletin’s fuller context table, not a new corpus figure for the model (which runs on the Zone-3 baseline + CR_017 multipliers).
• Primary BRANZ technical bulletin, read verbatim via pdftotext -layout — every figure (R-values, transition dates, area-to-perimeter ratios, insulation R-levels, vapour-barrier gauge) traces to the raw → data_quality: verified. Issue 672, updated Oct 2022: a minor-update reissue of the identically-named and -numbered June 2022 original (stated on the back page).
• Filename misnomer flagged: the raw is Bulletin672_reissue_SR_12_10.pdf, which loosely references “roofs” — the content is unambiguously FLOORS (the BRANZ roofs bulletin is 677; the windows/doors bulletin is 670). Recorded so the mis-labelled raw name does not cause a later mis-file.
• 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, corroborated here), OT_131 (Bulletin 670 — windows/doors). This page carries the floor-specific detail those summarise.
• No cost/currency content — envelope specification only. BRANZ documents are classified ot_ (cf. OT_006/OT_043/OT_044).

Connections

Links to

Sources (8): CR_015 · CR_017 · LIT_018 · OT_043 · OT_044 · OT_057 · OT_085 · OT_131

Referenced by

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

Sources (1): OT_134