H1/AS1 Energy Efficiency

What H1 asks of a building's thermal envelope, what the consent drawings have to show for it, and where its documents part.

H1/AS1Sixth Edition27 Nov 2025
NZS 4214:2006
NZS 4246:2016
E3/AS1Second Edition Amendment 75 Nov 2020
Building Product SpecificationsFirst Edition Amendment 12 Apr 2026

ToolConstruction R-value. Work out a roof, wall or floor from its layers, and the house against the reference building.Open →

What H1/AS1 asks

The requirements this building is held to, each with the paragraph it comes from.

What has to be shown The proposed building's temperature-specific heat loss is no more than the reference building's, for the climate zone and window area. That comparison is the calculation method.
H1/AS1 2.1.2.1, H1/AS1 2.1.2.6, H1/AS1 Equation 2.1, H1/AS1 Table 2.1.2.7
How each construction R-value is found Walls, roofs and floors other than slab-on-ground by NZS 4214, as 2.1.3.2 modifies it. Windows, doors and skylights by Appendix D. Slab-on-ground floors by Appendix E.
H1/AS1 2.1.3.1 a), H1/AS1 2.1.3.1 b), H1/AS1 2.1.3.1 c), H1/AS1 2.1.3.2
Minimum construction R-values Under the calculation method every roof in the proposed building is no less than R2.6, every wall no less than R1.0, and every floor other than slab-on-ground no less than R1.3, whatever the whole-building comparison makes up elsewhere.
H1/AS1 2.1.2.11 a), H1/AS1 2.1.2.11 b), H1/AS1 2.1.2.11 c)
E3/AS1 minimum R-values E3/AS1 sets minimum R-values of its own, whatever the calculation method allows: R1.5 for a framed wall with cavities, and R1.5 for a roof or ceiling of any construction.
E3/AS1 1.1.1 a), E3/AS1 1.1.1 d)
Insulation R-values Each insulation material's R-value is determined by the methods in Building Product Specifications 4.5.1 for its type of insulation, which call up AS/NZS 4859.1.
H1/AS1 2.1.3.3, BPS 4.5.1
Wall glazing area The calculation method applies only where the wall glazing area is no more than 40% of the gross wall area.
H1/AS1 2.1.2.5

H1 requirements to show in the drawings and documents

The construction R-valuesH1/AS1 2.1.3.1, H1/AS1 2.1.3.2
One for every roof, wall, floor and slab, and for the windows, doors, skylights and garage doors.
The heat loss against the reference buildingH1/AS1 2.1.2.6, H1/AS1 Equation 2.1, H1/AS1 Table 2.1.2.7
The calculation method: each element's area and construction R-value, the proposed building's heat loss, and the reference building's for the same areas in the same climate zone.
What each construction R-value rests onH1/AS1 2.1.3.1 a), NZS 4214, H1/AS1 2.1.3.3
For each roof, wall and floor: the cladding or roofing, any cavity, the framing and its spacing, the insulation with its thickness and declared R-value, and the lining; for a suspended floor, its sub-floor space.
The slabH1/AS1 E.1.2.1, H1/AS1 E.1.2.2
Its form, its edge and underslab insulation, the wall over its edge, and its area and perimeter.
The site and its climate zoneH1/AS1 C.1.1.2, H1/AS1 Table C.1.1.2
The address, and the climate zone the territorial authority puts it in.
Where the opening R-values came fromH1/AS1 D.1.1.1, H1/AS1 D.2.1.1, H1/AS1 2.1.2.13
For the windows, doors, skylights and garage doors: the supplier's figures, the generic values of Table D.1.1.1, or the default of 2.1.2.13 where none is known.
The products' compliance documentsH1/AS1 2.1.3.3, BPS 4.5.1
The manufacturer's documents for each product relied on, and for the insulation the basis of its declared R-value, such as a BRANZ Appraisal or a CodeMark certificate.

Reading H1/AS1

Why the documents say what they say, and how this page reads them where they leave a choice. Nothing here prints.

Which method, and what H1/AS1 changes in itH1/AS1 2.1.3.1 a), H1/AS1 2.1.3.2, NZS 4214 5.7: H1/AS1 2.1.3.1 a) sends walls, roofs and floors other than slab-on-ground to NZS 4214: surface resistances, the isothermal planes equations across the framing, and a ventilated cavity de-rated. 2.1.3.2 replaces the standard's definition of the bridged portion. Adjacent bridged layers are one portion; a portion takes in an insulation or air layer next to it; a homogeneous layer between two bridged layers is split half to each; and a pliable membrane or underlay is treated as absent. The page works the standard's arithmetic with that definition in place.
One route where there were twoH1/AS1 2.1.2, H1/AS1 Sixth Edition, main changes in this version: The sixth edition removed the schedule method, so the calculation method is the only route H1/AS1 itself gives for the thermal envelope; its other option, in 2.1.1.1, is H1/VM1's modelling method. A construction R-value counts through the building's heat loss, compared with the reference building's, and the minimums of 2.1.2.11, with those of 2.1.2.12 for heated elements, are the only per-element limits left. The fifth edition can still be used for consent applications submitted before 27 November 2026.
The cavity's temperature differenceNZS 4214 5.3.1.3, NZS 4214 Appendix F2, NZS 4214 Table E3: NZS 4214 Table E3 gives an air space's R-value at three temperature differences and leaves the choice to AS/NZS 4859.1 (5.3.1.3). The page reads 6 K, the difference the standard's worked example F2 assumes, and shows beside each air space what the other two would give.
The 38%, and a steel frameH1/AS1 2.1.3.1 a) i), H1/AS1 Appendix B, wall framing fraction, NZS 4214 5.7.3: 2.1.3.1 a) i) takes a framed wall at no less than 38% framing unless a lower fraction is shown to suit the building. The sixth edition set it to reflect typical walls with every member counted: lintels, sills, trimming studs and the studs at corners and junctions as well as studs, dwangs and plates. A light steel frame at the same spacing is nearer 13% by geometry, and steel conducts far better than timber, so the assumption costs a steel wall much more than a timber one. The way out is the paragraph's own: take the actual fraction off the framing drawings, tick A lower framing fraction on the framing layer and enter it. Without that take-off, 38% applies.
Why a wall's R-value differs between editionsH1/AS1 2.1.3.1 a) i), H1/AS1 Table 2.1.2.7, H1/AS1 Fifth Edition Amendment 1, 2.1.4.3 b) and Table 2.1.3.4A: The sixth edition changed the framed wall method and the reference building's wall together. The fifth edition counted studs, dwangs and plates and let lintels, sills, trimming studs and corner studs be left out (2.1.4.3 b)). The sixth assumes at least 38% framing, and lowered the reference building's wall from R2.0 to R1.6 as a consequence (Table 2.1.3.4A against Table 2.1.2.7). For timber the two very nearly cancel. The wall's own figure does not carry across: the same wall has a different R-value under each edition, so an R-value from an older drawing, a supplier's literature or a specification written before 27 November 2025 has to be worked out again, not compared. Both editions can be used until 26 November 2026.
What the window table kept, and what it droppedH1/AS1 Table D.1.1.1 note (1), H1/AS1 D.1.1.1 b), H1/AS1 Fifth Edition Amendment 1, Table E.1.1.1: Appendix D's table was revised in the sixth edition. Every row carried over from the fifth edition's Appendix E keeps its R-values. Double-glazed rows were added at a Ug of 2.9, 1.2 and 1.0; the top triple-glazed row moved from a Ug of 1.89 to 2.1, at lower R-values; and the double-glazed row at 0.90 is gone. Note (1) reads a unit the table does not list at the nearest Ug above it, so a double-glazed unit at 0.9 now reads at the 1.0 row and is worth less than it was, and the 2.9 row gives a value to units the old table did not reach. Above the top of the table the page gives no value: D.1.1.1 b), calculation to H1/VM1 Appendix D, is the route for a unit the table does not reach.
Claddings NZS 4214 has no row forH1/AS1 2.1.3.3, BPS 4.5.1, NZS 4214 Table E1: NZS 4214 Table E1 gives values for the claddings of its time: weatherboards, sheet, plywood, brick, concrete masonry, metal roofing and renderings. It has no row for autoclaved aerated concrete, a uPVC weatherboard, an aluminium composite panel, natural stone, a terracotta rainscreen or an insulated metal panel. Table E1(d)'s conductivity for PVC does not fit a uPVC weatherboard: it is a hollow extrusion, and its value depends on the air in its cells. So each is listed by name and takes the manufacturer's figure, as NZS 4214 5.1.1 allows. Enter the figure for the panel or board alone, from its current datasheet, not a system total: the cavity, framing and lining are layers of their own here. Behind a ventilated cavity the figure is de-rated with everything outside it (5.3.2), so a rainscreen barely moves the total. An insulated panel is the opposite, most of the wall, and is taken as insulation. An aluminium weatherboard needs no figure: Table E1(c) gives metal roofing no insulation value, and the page reads metal wall cladding the same way.
Cold roofs and warm roofsNZ Metal Roof and Wall Cladding Code of Practice 10.12, NZS 4214 5.3.2, NZS 4214 Table E3, NZBC E2, NZBC E3: The roofing trade sorts roofs by where the insulation is, as the metal roofing Code of Practice does in 10.12. A cold roof has it below the structure: at the ceiling or between the rafters, joists or chords, usually under a ventilated space (the roof space, or the space among the purlins or battens), or under a concrete deck with no ventilated space at all. Truss, Rafter and Membrane are cold roofs. A warm roof has it on the structural deck, directly under the roofing, with no ventilated space between: the Warm Roof type, and an insulated panel used as the roofing. The difference matters to the R-value because everything outside a ventilated space is de-rated (NZS 4214 5.3.2): in a cold roof the roofing counts for almost nothing, in a warm roof it counts in full. Warm roofs are also chosen to keep condensation out of the structure, which a construction R-value does not measure: that is a question for E2 and E3, and this page does not assess it.
Where the underlay goesRoofing manufacturers' installation literature, NZS 4214 Appendix F, notes to the worked examples, NZS 4214 Table E3 note (1), H1/AS1 2.1.3.2 iii): Where the roof underlay lies follows the roofing. Under longrun metal it lies on the purlins, directly under the sheet. Under concrete, clay or pressed-metal tiles it lies over the rafters or top chords, and the tile battens are fixed down through it. NZS 4214 treats an underlay as the edge of an air space and works each air space on its own (Table E3 note (1)), so under tiles the space among the battens and the roof space below the underlay are two ventilated spaces, not one. H1/AS1 2.1.3.2 iii), which treats a pliable underlay as absent, is about where a bridged portion ends, not about air spaces.
What lies over the roofingNZS 4214 Table E1, NZS 4214 5.2, H1/AS1 2.1.3.3: A roof is counted from its roofing in: nothing laid over the waterproofing has a value the sum can rely on. A roof garden's growing medium and drainage layer have no row in NZS 4214's tables, a growing medium's value changes with how wet it is, and the Appraisals for warm roofs and roof gardens give an R-value for the insulation board only. An inverted roof lays its insulation over the membrane, under pavers or stones, and rain runs beneath the boards; NZS 4214 has no correction for that. So both are drawn and not counted, which keeps the figure on the low side. Exposed rafters under a ceiling laid on top of them are left out for another reason: they are in the room, inside the inner surface.
The gap under a membrane roof's plywoodE2/AS1 8.5.1.4, NZS 4214 5.3.2, NZS 4214 5.7.2, NZS 4214 Table E3: E2/AS1 8.5.1.4 asks for the closed-in spaces under membrane roofs and decks to be ventilated so that moisture does not collect under the membrane, with a gap of at least 20 mm between the underside of the substrate and any insulation. The Membrane roof type draws that gap as the tops of the joists standing in a ventilated space. The sum reads it from Table E3 at its depth as a ventilated air space and de-rates everything outside it, the plywood and the membrane (NZS 4214 5.3.2). NZS 4214 5.7.2 does not allow Equations 5 and 6 for a member bridging a ventilated gap and leaves that case to test; the page leaves the joist tops out and counts only the part of each joist in the insulation, which gives the lower figure.
What this page does, of the ways the standard allowsNZS 4214 5.1.1, NZS 4214 Appendix E1.1, NZS 4214 6.3, H1/AS1 2.1.3.3, Building Act 2004 s 19(1): NZS 4214 5.1.1 lets a material's value come from a laboratory, an in-situ probe, the manufacturer or, except for insulation, the Appendix E tables, and an assembly's from calculation (5.3 to 5.7), in-situ measurement, a hot box test to ASTM C1363, the manufacturer or computer modelling. This page takes the calculation, because it can be checked line by line without a laboratory. A tested or modelled assembly, or a supplier's tested system value, is also allowed and is not what this page does. E1.1 says generic table data is not reliable enough for compliance, and that the manufacturer's information is to be sought where a material contributes much of the insulation. So the tables are used here only for what a cladding, board or lining adds, and every insulation value is the reader's, from Building Product Specifications 4.5.1 (2.1.3.3). An acceptable solution is itself only one of the routes Building Act section 19(1) lists as establishing compliance.

Windows, doors and skylights

ScopeH1/AS1 D.1.1.1 b), H1/AS1 D.1.1.2, H1/AS1 D.2.1.1: A house's windows may be read from Table D.1.1.1 or, by D.1.1.1 b), calculated to H1/VM1 Appendix D; opaque doors (D.1.1.2) and skylights (D.2.1.1) are always calculated. A supplier's construction R-value is that calculation. The tool takes it as given and does not check it.

Across the Code

Readings that belong to more than one clause, written once and shown on the page of each clause they touch.

Where a roof becomes a wallH1/AS1 Definitions, roof; E2/AS1 Definitions, roof and external wall; E2/AS1 1.1.1.1 c); C/AS1 and C/AS2 Definitions, external wall: H1/AS1 and E2/AS1 define a roof the same way: a surface at 60° or less to the horizontal. C/AS1 and C/AS2 come at the same line from the other side, defining an external wall as any exterior face within 30° of vertical, and say that this includes a roof. Both definitions take in 60° itself, so a face pitched at exactly 60° is a roof for energy efficiency and weathertightness and an external wall for fire. Steeper than 60°, it is not a roof to H1/AS1, and C treats it as an external wall. E2/AS1 goes further than a definition: its scope is limited to buildings whose external walls are vertical and whose roofs are 60° or less (1.1.1.1 c)), so a building with any face between 60° and vertical, a mansard for one, is outside E2/AS1 altogether, and its weathertightness has to be shown some other way, such as an alternative solution.

Also in H1/AS1, for the designer to confirm

Further requirements of H1/AS1, beyond those under What H1/AS1 asks. They do not print.

Wall framing fractionH1/AS1 2.1.3.1 a) i): A framed wall's construction R-value assumes a wall framing fraction of no less than 38% unless a lower one is demonstrated for the building.
InstallationH1/AS1 2.1.1.4: Insulation is installed so that it achieves its intended thermal performance without compromising the durability or safety of the insulation or the building elements, or the health and safety of the people who install it and live with it. NZS 4246 sections 5, 6, 7 and 10 are acceptable methods for bulk insulation in light timber and steel-framed residential buildings.
Slab perimeter insulationH1/AS1 2.1.1.4 comment, NZS 4246 10.3: H1/AS1 recommends protecting slab perimeter insulation against water absorption, UV and impact damage, and not encapsulating it as NZS 4246 10.3 step 2 would, because encapsulation can trap moisture.
R-values not knownH1/AS1 2.1.2.13: An element whose construction R-value is not known is taken at R0.18 if it is opaque and at R0.15 if it is a window or the glazing in a door.
Heated ceilings, walls and floorsH1/AS1 2.1.2.12, H1/AS1 Table 2.1.2.12: A heated ceiling, wall or floor in the thermal envelope is no less than Table 2.1.2.12's construction R-value for the climate zone, whatever the comparison says, except where it is only in rooms that contain a shower, bath or toilet.
Foil insulationH1/AS1 1.1.2.1, H1/AS1 Appendix B, H1/VM1 1.1.2.1: Neither H1/AS1 nor H1/VM1 applies to a building with foil insulation, material that includes a thin layer of heat-reflecting metallic foil.
AirflowH1/AS1 2.2.1.1: Windows, doors, vents and other building elements that allow significant movement of air are constructed so that they can be fixed in the closed position.
Hot waterH1/AS1 3.1.1.1: Hot water systems for sanitary fixtures and sanitary appliances with a storage water heater of up to 700 litres comply with NZS 4305.

Terminology

The terms H1/AS1 defines that this page uses, in the page's words, each with where the document defines it.

Construction R-valueAppendix B: The total thermal resistance of a typical area of a building element, air to air, surface resistances included, in m²·K/W.
Thermal envelopeAppendix B: The roof, wall, window, skylight, door and floor construction between conditioned space and unconditioned space, the ground or the outdoors.
Conditioned spaceAppendix B: The part of a building inside the thermal envelope that may be heated or cooled, directly or indirectly. A garage, conservatory or atrium expected to be heated or cooled is part of it.
Wall framing fractionAppendix B, 2.1.3.1 a) i): The percentage of the net wall area taken up by framing in the same plane as the insulation, every member counted; a wall with more than one framing layer may have a different fraction for each.
Foil insulationAppendix B, 1.1.2.1: Material that includes a thin layer of heat-reflecting metallic foil, usually aluminium. A building with it is outside H1/AS1 and H1/VM1 alike.
Heated ceiling, wall or floorAppendix B, 2.1.2.12: A ceiling, wall or floor with pipes, electrical cables or similar means of raising its temperature within the element or its finishes: underfloor or undertile heating, most commonly.
Slab-on-ground floorAppendix B: A concrete slab or concrete raft foundation in contact with the ground over its whole area.
Gross wall areaAppendix B: The net wall area (on overall internal dimensions), the wall glazing area and the opaque door area, added together.
Wall glazing areaAppendix B: The total area of windows, and of doors that include glazing, in walls of the thermal envelope: glazing, frames, opening tolerances, decorative glazing and louvres included; opaque panels, opaque doors and skylights not.
SkylightAppendix B: The translucent or transparent parts of the roof, frames and glazing included.
RoofAppendix B: A roof and the ceiling under it, where the building's outside surface is at 60° or less to the horizontal and its upper surface is open to the outside. A steeper face is an external wall.
Reference building2.1.2.1, Table 2.1.2.7: The building the proposed one is compared with under the calculation method: the same net roof, skylight, floor and gross wall areas, the gross wall area taken as 70% wall and 30% glazing, each element at the R-value Table 2.1.2.7 gives for the climate zone.
Bridged portion2.1.3.2, NZS 4214 5.7.1: The layers of a construction crossed by framing and worked together by the isothermal planes equations: the framing layer with any insulation or air layer touching it, as H1/AS1 2.1.3.2 defines it in place of NZS 4214's own.

Where the rest is

What this page reads, and what it points at rather than reads.