The H1 Clause of the Building Code regulates the energy efficiency of our built environment – covering wall, floor and roof insulation as well as the thermal performance of windows and doors.
Improvements to the requirements under H1 were published by MBIE in November 2021, and more recently, the transition periods for housing were updated.
This hub includes introductory information below, and soon, resources developed specifically for designers and architects, builders, and building officials.
The hub will be updated regularly. If you’d like to be alerted to updates, send Brett Francis an email.
Use our helpful calculator to understand what the thermal performance requirements are for windows and doors in housing. Just select your Territorial Authority and the date your consent will be submitted.
For windows and doors in housing, implementation phasing-in begins on 3 November 2022, with a further transition phase beginning 1 May 2023, and all requirements in effect as of 2 November 2023. These dates apply to when a building consent application is submitted.
For other buildings (such as communal residential and non-residential, commercial, industrial and so on) improved requirements come into effect on 3 November 2022. There are no phases or transition periods.
Of course, higher spec solutions can be used earlier and will result in a more thermally efficient building.
The window and glass industry has been closely engaged in this process and businesses have been preparing for these changes for some time. New Zealand’s glass industry has the glass supply in hand and will be ready to meet the new requirements as they come on stream. Window manufacturers and fabricators are also hard at work and on track to meet the coming demand.
Curtain walling is outside the scope of H1/AS1and H1/AS2, however either H1/VM1, H1/VM2 or an alternative solution can be used to demonstrate compliance.
There is a two part response to this question.
i) The individual residences forming part of a retirement village are housing and therefore must comply with H1/AS1.
ii) The other buildings in a retirement village are classified as communal residential, in Clause A1 of the Code, and are therefore not housing and will use H1/AS2 and H1/VM2 to demonstrate compliance.
Yes, The modelling method in H1/VM1 and H1/VM2 consider solar gains in the energy balance equation as in previous Editions of H1. However, the Schedule and Calculation Methods in H1/AS1 do not directly consider solar gains, except in the limitation of glazed areas.
In theory the answer is yes, but there are some difficulties. Windows using colonial bar will need to be modelled to understand the impact of the bars on the glazing, as they will reduce the performance of the IGU. There are also some manufacturing difficulties when used with Low E glass which will dictate their use.
Yes, there is nothing stopping their use. However their use will require the calculation of the overall window and door element performance and the combinations adjusted to compensate for the poorer performing components.
MBIE is currently working with industry experts and building researchers to develop window details for E2/AS1 that enable improved thermal performance. This will be included in a future Building Code update consultation.
Clause H1 of the Building Code sets minimum construction R values for windows and doors, but the Consented R value for any particular project may vary from these. It is the window supplier’s responsibility to demonstrate the product they’ve supplied to a specific site, meets or exceeds the R values nominated within the Consent. The ‘Statement of Thermal Performance’ was developed as a simple, one page document, provided with each houselot of windows, declaring the construction R values for windows and doors as supplied, and how the value has been determined.
It is the window supplier’s responsibility to provide the ‘Statement of Thermal Performance’ to their contracted party, usually the builder or homeowner, and it Is their responsibility to ensure the document is passed to the Council. At inspection, if the building inspector requires further information, then supporting documentation can be supplied on request.
Clause H1 of the Building Code sets minimum construction R values for windows and doors but is aimed at new construction where all the elements of the building envelope are considered. So how does Clause H1 apply to the retro glazing of windows and doors in an existing building?
Section 112 of the Building Act makes allowances for additions and alterations to existing buildings and how the Building Code applies to this type of work. To help explain this, the Association has developed a short Guide to Retro Glazing, for housing only, which can be downloaded from the members area of this site, but the important message is “In most cases a Building Consent will not be required for the retro glazing of existing windows, nor will they need to satisfy the requirements of Clause H1.”.
You should also understand the requirements of the Healthy Home standards for rental properties. The key facts are available here (pdf)
It is important you discuss the needs of your retro glazing project with your glass supplier so that can provide you with a range of options to suit the needs of your project, balanced with your budget.
Clause H1 of the Building Code sets minimum construction R values for windows and doors but is aimed at new construction where all the elements of the building envelope are considered. So how does Clause H1 apply to the replacement of windows and doors in an existing building?
Whilst replacement windows are typically new windows being installed into existing openings, the Building Act makes allowances for additions and alterations to existing buildings in Section 112. To help explain this, the Association has developed a short Guide to Replacement Windows, for housing only, which can be downloaded from the members area of this site, but the important message is “In most cases a Building Consent will not be required for ‘like for like’ replacement windows, nor will they need to satisfy the full requirements of Clause H1.”.
You should also understand the requirements of the Healthy Home standards for rental properties. The key facts are available here (pdf).
It is important you discuss the needs of your replacement window project with your window supplier so that can provide you with a range of options to suit the needs of your project, balanced with your budget.
There are seven building types defined in the Building Code, in Clause A1. You can view these here.
Different requirements for the thermal performance of windows and doors in H1 apply across three categories:
Note, that where areas of a building or site classify differently (i.e. a small office area, connected to a large warehouse, or a retirement village with both detached dwellings and a communal residential building), each area or building is treated separately.
For housing, initially, aluminium frames will require more thermally efficient glass (double glazing with a high quality Low E pane and an argon gas fill between) to meet the minimum requirements in the first transition period (3 November 2022 to 30 April 2023). From 1 May 2023 however, thermally broken aluminium frames will be required to meet minimum requirements. Many of the uPVC and Timber frame combinations with double glazed Low E IGUs will continue to meet or exceed the standards.
The Quick Reference Guides linked above provide a good overview of how the changes impact glass and framing choices.
No. There is no change in building or installation methods in this edition. However, you can choose to recess windows for better thermal performance. There can be some additional thermal performance gains in recessing windows and doors closer to the buildings primary insulation line, however details for this must also consider the weathertightness of the installation and how compliance with Clause E2 is demonstrated
R-values indicate the thermal resistance through a material, so describes how well insulation material resists heat flow. With R-values, the higher the value, the better the insulation and the better the thermal performance.
U-values indicate the thermal conductivity of a material and generally range between 0.1 (small heat loss) and 1.0 (high heat loss). A U-value is the inverse of an R-value, so if heat transfer through a material is minimal, its U-value will be low and its R-value will be high, making it a high-performing insulator.
Both values are used as ratings of energy efficiency. A U-value is often used to describe the performance of IGU’s (insulated glass units) while an R-value is used to describe the overall performance of the window frame and glazing combination.