If you are building a new home, or doing major building work, clause H1 of the New Zealand Building Code is behind many of the insulation numbers on your plans. This is a plain-English overview of what it is and what changed recently. It is not a design guide, and your designer or builder is the person who works out what your plans need.
What H1 is
H1 is the energy efficiency clause of the Building Code. It sets how well the outer shell of a building, called the thermal envelope, needs to hold heat. The envelope is the roof, walls, floor, windows and doors.
The Ministry of Business, Innovation and Employment (MBIE) publishes an Acceptable Solution, H1/AS1, which is one way to show that a building meets the clause. You can read the current edition on the building.govt.nz H1/AS1 sixth edition.
Six climate zones
H1 divides New Zealand into six climate zones. Requirements are set by zone, and the zone is decided by the territorial authority (council district) your building is in.
The official list in that document puts the areas we work in across more than one zone:
- Climate zone 1: Western Bay of Plenty District, Tauranga City, Whakatāne District and Thames-Coromandel District
- Climate zone 2: Hauraki District and Gisborne District
- Climate zone 4: Rotorua District and Taupō District
If you are not sure which zone you are in, the table in Appendix C of the document is the one to check. It takes precedence over the map.
What changed in the latest edition
The sixth edition of H1/AS1 took effect on 27 November 2025. The main change for most people is that the schedule method has been removed. That was the simple option where each part of the building had a set minimum R-value.
What remains is:
- The calculation method, which looks at the whole envelope. Roof, walls, floor and windows are combined in a heat loss calculation, so a stronger result in one element can balance a weaker one in another.
- The modelling method, which follows Verification Method H1/VM1.
The fifth edition can still be used for a while. MBIE says it can show a building meets the code until 26 November 2026, and can be used for building consent applications submitted before 27 November 2026. The fifth edition is also where the earlier tightening took place, with transition dates of 1 May 2023 and 2 November 2023.
This is the kind of detail your designer, architect or builder keeps track of. If your plans were prepared before late November 2025, ask which edition they were drawn to.
Insulation is one part of the picture
Under the calculation method, insulation sits alongside window performance, wall framing and the size of the building. A well-insulated ceiling does not make up for everything else, and the reverse is true too.
MBIE also notes in H1/AS1 that for housing, meeting the internal moisture requirement elsewhere in the Building Code (E3) may need more insulation than H1 alone. That is a good reason to talk through ceiling, wall and floor insulation together, rather than just accepting the minimum for each.
Where Coastline fits
We install new build insulation at framing stage: ceiling, wall and underfloor. Your designer or builder decides what the plans call for, and the council sorts out the consent process. We install the insulation specified for your build. We do not design to the code or sign off that a building meets it.
Getting the insulation conversation started early helps. Before framing begins, it is worth asking your designer or builder:
- Which climate zone is the building in, and which H1 edition were the plans drawn to?
- What R-values are specified for the ceiling, walls and floor?
- Is there any part of the roof or floor where access will be tight?
- When will the framing be ready for insulation, so the install can be booked in?
We work across the Bay of Plenty, Coromandel and Hauraki, Gisborne and the East Coast, and Rotorua and Taupō. You can see the areas we cover if you are not sure we reach your site.
Not building new?
H1 applies to new building work. If you are looking at an existing home or a rental, a different set of rules applies. We cover that in what you need to know about current insulation standards, and the R-value basics are in understanding R-values in New Zealand insulation.
Planning a new build?
Send us your plans and we will talk you through the insulation for ceiling, walls and underfloor. Get a free, no-obligation quote and we aim to call you back within 48 hours. You can also call us on 027 482 0333.