The Building Performance team discusses proposed changes to make homes and buildings more energy efficient.
On 21 April 2021, Building Performance held a webinar to discuss the proposed changes to make homes and buildings warmer, drier and heathier with less impact on the environment.
For those who attended the webinar, there were some questions which we didn't get to on the day. We have been through the comments and questions and provided information below.
Remember, the consultation closes on Friday, 28 May 2021, so there is still time to get your submission in.
Background reports on H1 Energy Efficiency
Several participants in the webinar asked for further details on the analysis of insulation requirements to expand upon the information provided in the consultation document.
View the 2021 Building Code update consultation document - mbie.govt.nz
To provide further background on the proposals for consultation, we have provided copies of reports commissioned by MBIE on this topic. These reports were produced by BRANZ and Beca and provided information on the thermal modelling and cost benefit analysis for determining the R-values in the consultation document.
These reports provided a solid foundation for us to consider the implications for the design of new buildings in New Zealand. However, for more information on the regulatory context and other factors to consider for these proposals, we encourage you to review the discussion in the consultation document.
Building Code regulations
The annual Building Code update provides a predictable timeline for consultation and publishing new material to support compliance with the Building Code. This can include all parts of the Building Code system including the Building Code regulations (the 41 Building Code Clauses), acceptable solutions, verification methods and guidance information.
This year, there are no changes proposed to the Building Code regulations. However, a review of the current performance clauses for H1 Energy Efficiency, G5 Interior Environment and G6 Airborne and impact sound is currently in progress.
View the Building Code regulations - legislation.govt.nz
The changes we are proposing to climate zones will better reflect specific weather in different parts of New Zealand and will no longer be "one size fits all" for large parts of the country. Our aim in making these changes is to make sure homes and commercial buildings are more suited to the climate where they are being built.
The proposed six climate zones are based on thermal modelling of buildings using NIWA climate data files for 18 different climate stations. These climate stations were previously selected by NIWA to represent the different climates experienced around New Zealand. The proposed climate zone boundaries also take into consideration territorial authority (local government) boundaries to make it easier to follow and understand what requirements apply to the different parts of the country.
There will always be exceptions to the site specific conditions of a building so the modelling methodology in the H1 Energy Efficiency verification methods H1/VM1 and H1/VM2 are proposed to allow for adjustments for local conditions and project specific concerns.
The proposed R-values in the consultation document are construction R-values for roofs, walls, floor and windows. This is detailed in the draft acceptable solution and verification methods in the appendix of the consultation document. For example, H1/AS1 Subsection 2.1.4 describes the method for determining the thermal resistance of building elements and can be found on page 69 of the consultation document.
Insulation values from other countries are shown in the consultation document as a tool to illustrate that current New Zealand requirements are behind international standards with similar climates to New Zealand. Some people have commented on the values used to compare for England, Wales and Ireland. If you’re interested in seeing the source material it is available below.
Requirements for England [PDF KB] - gov.uk
Requirements for Wales [PDF KB] - gov.wales
Latest requirements for Ireland - gov.ie
For England and Wales, the values we've shown in the consultation document are the absolute minimum requirements for those countries. We chose to use these values to provide more of a fair comparison, and to be sure we are not overstating their performance.
Ireland now has higher performance standards than the values we show in the consultation document because our source document has been superseded by an updated version with Ireland’s requirements now going further.
High thermal mass walls
Allowances for higher thermal mass walls is proposed to be removed the Acceptable Solution H1/AS1. This is discussed in the consultation document in Section 1.4.6 "Other changes within H1/AS1 and H1/VM1". Verification Method H1/VM1 provides a better and fairer way to determine how much insulation is required for these types of buildings. Designers of buildings with high mass walls would still have the option of using the simpler compliance methods of H1/AS1 but without any special treatment of buildings with high mass walls.
The extent to which high mass walls can help reduce the amount of heating and cooling energy required to maintain comfortable indoor temperatures depends on a number of factors. For example, the density and thickness of the materials that the walls are made from, the size of these walls, whether the insulation is placed on the interior or exterior side of the walls and the extent to which the interior surfaces of the high mass walls are exposed to direct sunlight. Thus, the energy efficiency benefits of homes and buildings with high mass walls are best assessed through computer thermal modelling.
Airtightness, infiltration and thermal bridging
MBIE is monitoring other aspects that impact energy efficiency and a building's internal environment, and will work to resolve any issues in future Building Code updates such as airtightness and thermal bridging.
Residential building types
Energy savings and investment figures which are provided for Proposal 1: Energy efficiency for housing and small buildings are based on a detached single-storey house as this is predicted to remain the most popular building type in New Zealand.
Multi-unit dwellings such as apartments are included in Proposal 1 in the Building Code consultation document. The way multi-unit dwellings are used by their occupants is similar to other residential building types and different to large non-residential buildings such as office buildings. Therefore multi-unit dwellings are proposed to be covered by the same energy efficiency requirements as all housing. MBIE is aware that the thermal characteristics of apartments is different to low-rise detached homes. The Building for Climate Change programme proposes to introduce a more holistic framework for different building shapes and typologies.
Interactions with the Building for Climate Change (BfCC) programme
The Building for Climate Change (BfCC) programme is looking at system-level changes that need to be made to reduce carbon emissions while improving resilience of buildings in New Zealand. Last year, MBIE consulted on proposals to transform the operational efficiency of buildings, and to reduce the embodied carbon of buildings as part of the Building for Climate Change programme. These changes are proposed to be implemented in a series of well-signalled steps as New Zealand's building and construction sector moves towards net carbon zero.
The changes proposed to the level of insulation in buildings as part of this year's Building Code update represent a first step in the Building for Climate Change programme of work which will continue to transform housing and construction in New Zealand. The Building for Climate Change programme's Transforming Operational Efficiency proposed that new measures to reduce operational emissions, fossil fuel combustion, electricity use, thermal performance, services efficiency and water use. These are likely to be implemented in a series of steps. A direct comparison between the proposals in the Building Code consultation document versus the proposed caps of the Building for Climate Change programme's Transforming Operational Efficiency framework is not possible due to the significant differences in scope between the two.
Implementation of the Building for Climate Change programme's Transforming Operational Efficiency and Whole-of-life embodied carbon reduction frameworks will follow the changes proposed as part of this year's Building Code update at a later stage.
Summary of submissions from the 2020 BfCC consultation - mbie.govt.nz.