29 August 2022

H1 101 – everything you need to know

Another day, another update to the Building Code. Understanding the changes to the H1 building code (and the changes to the changes) can be complex. Here we look at the details and specifications to make sure you’re up to speed and compliant when considering your next building project.

In November 2021, the Ministry of Business, Innovation and Employment (MBIE) announced changes to the Building Code with the aim of making new homes and buildings more energy efficient. The documents outline compliance pathways to meet minimum insulation requirements for new housing set out in clause H1 Energy Efficiency of the New Zealand Building Code. The changes to the insulation requirements represent the first step towards MBIE’s Building for Climate Change programme. This initiative will deliver warmer, drier, and healthier homes that cost significantly less to heat and will also generate carbon savings through energy efficiency.

What type of buildings does the update cover?

The scope of H1/AS1 has been reduced to cover only housing, and buildings other than housing less than 300 m2. Requirements applicable to buildings other than housing over 300 m2 have been combined into the new Acceptable Solution H1/AS2.

Climate zone changes

MBIE has expanded the number of climate zones used in the insulation requirements from three to six. This will allow the insulation requirements to better reflect the different temperatures experienced in each zone. These follow territorial authority (local government) boundaries.

H1/AS1 residential updates

Those involved in the design and construction of new builds will need to take into consideration the following:

  • Thicker roof assemblies.
  • Window frames will be required to be thermally broken as a minimum, and in colder climates will have to use high-quality low-e glass.
  • Slab on-grade is no longer just ‘deemed to comply’. It will require slab edge and possibly underslab insulation.
  • Slabs will also require an insulation ‘thermal break’ between garages and attached habitable spaces.

What does this mean for floors?

Slab on grade (concrete)

  • North Island, north and west coast South Island: R1.5*
  • East coast South Island: R1.6
  • Lower South Island: R1.7

*The R-value is the building industry term for thermal resistance. R-value can be given for a material or for an assembly of materials (e.g. a wall or a window). R-values are additive for layers of materials. The higher the R-value the better the performance.

Suspended floors (timber joist)

  • Climate 1 – 3: R2.5
  • Climate 4: R2.8
  • Climate 5 – 6: R3.0

What does it mean for walls?

  • R2.0 through all climate zones.
  • Not too dissimilar to current practice.
  • Care over timber content:
    • Consider stud savers.
    • Window positioning to align studs.
    • Design out dwangs (a horizontal bracing piece used between wall studs or floor joists to give rigidity to the wall or floor frames of a building).
  • Use of ply sheathing externally adds thermal resistance, as well as bracing.
  • The more timber in the wall, the higher the insulation batt R-value needs to be.

What does it mean for roofs?

  • R6.6 through all climate zones.
  • Truss heels raised to accommodate extra thickness.
  • Use of warm roofs/sandwich panels may become more prevalent.
  • Thickness dependent on product – as with walls, higher performing products can provide more thermal resistance for the same – or less – thickness.
  • Remember the 25mm ventilation gap.

What does it mean for windows?

Window minimum compliance in climates 1 – 4:

  • Thermally broken aluminium frame.
  • Improved Low-E, argon-filled double-glazing.

Window minimum compliance in climates 5 – 6:

  • Thermally broken aluminium frame.
  • High-performance Low-E, argon-filled double-glazing,

            or

  • uPVC frame.
  • Entry level Low-E, argon-filled double-glazing.

No longer complies – anywhere

  • Non-thermally broken aluminium frame.
  • Basic double-glazing (air-filled, no Low-E coating).

Window requirements, however, are undergoing an interim step-change as follows:

  • R0.37 windows permitted as a ‘phase-in’ for six months in the Central plateau, lower North Island and all of the South Island, and for one year in the rest of the country.

What will the updates achieve?

These changes are intended to significantly reduce (up to 40%) the amount of energy required to heat and cool homes.

How will compliance be demonstrated?

There are three pathways under H1 to demonstrate compliance – schedule, calculation, and modelling. The scheduling method will require the highest levels of insulation and does not provide an understanding of how a building will perform. The modelling method must be used for buildings with a glazing-to-wall ratio of over 40% but can be used for any building. Modelling allows for an optimised design, with a good understanding of actual building performance and its impact on users, and offsets building envelope heat loss with heat solar and internal heat gains.

When will the updates take effect?

Following public consultation, MBIE is extending the time to comply with new wall, floor, and roof insulation requirements for housing by a further six months. This change to the transition period has been made in recognition of pressure on the residential construction sector.

From 1 May 2023 new building work in homes must meet the new wall, floor, and roof insulation performance requirements. Window and door insulation requirements will see a staged implementation process beginning 3 November this year.

Construction in the upper North Island (climate zones 1-2) will keep to the previous timeline, with windows and doors requiring an interim minimum R value of 0.37 by 3 November 2022, and further requiring a minimum R value of 0.46 by 2 November 2023.

Construction in the rest of the country (climate zones 3-6) will now also have an interim increase. These zones will be required to reach a minimum R value of 0.37 for all windows and doors by 3 November 2022 and increase this to R0.46 (zones 3-4) and R0.50 (zones 5-6) six months later, on 1 May 2023.

By 2 November 2023, windows in new housing will be required to meet the increased performance levels for all parts of the country.

The amended Fifth Editions of Acceptable Solution H1/AS1 and Verification Method H1/VM1 are due to be published soon. To keep up to date, visit the MBIE website, or speak to one of our experts at hello@context.nz.