Providing independent information and links to guidelines and tools to help design and construct sustainable buildings.
Building Rating Schemes/Tools
This section contains information on Aotearoa New Zealand’s building rating tools.
Homestar™ is a New Zealand home rating and advisory tool that examines a broad range of home performance and resource consumption-related issues and is applicable to both new and existing homes.
The tool helps people assess the intrinsic value of their homes using a robust framework adapted from similar tools throughout the world, based around key indicators of warmth, health and resource performance.
A star system is used to indicate the overall performance of the house and ranges from 0–10. A 10-star rated home is an exemplar house across all areas of energy, comfort, health, water, waste, operation, proximity to amenities and material management.
Under an updated version of Homestar relaunched in 2021, homes have to prove they have lower levels of carbon compared to an average new home. The updated tool covers both the embodied carbon in the materials used to construct the building and the operational carbon from building use, for example in heating, hot water and lighting systems.
The rating tool has three interactive levels – for homeowners, building professionals and certified Homestar™ assessors.
BRANZ scientists carried out a desktop analysis of 10 Building Code-compliant houses and terraced homes to estimate the additional cost needed to achieve a higher level of Homestar. The designs analysed were selected from actual new buildings at Hobsonville Point.
The research (detailed in Study Report SR391) found that a 6-Homestar dwelling costs approximately 3% more to construct than a typical Building Code-compliant dwelling, and a 7-Homestar dwelling an extra 4%. These additional costs can be reduced when there are a number of similar homes in development.
In return for this increased capital cost, the benefits are lower running costs in the house, higher market value and improved occupant health and comfort.
The public housing agency Kāinga Ora has committed to the 6 Homestar standard for all its new homes.
HomeFit assesses the health, comfort, energy efficiency and safety of homes that have been lived in for some time. (Owners/designers of new homes should use the Homestar tool.)
An assessor goes through a property, looking at insulation, ventilation, heating and energy efficiency. The assessor considers the property’s performance in terms of providing a healthy warm and dry environment. If it meets certain requirements it gets a HomeFit stamp. Homes with a higher level of performance can get a HomeFit Plus rating. People selling or renting out a property can use the rating in their marketing material and advertising.
As well as the assessment service, there is an online check that people can use as a basic guide to a house and how improvements can be made.
The service was developed by the New Zealand Green Building Council with industry input.
HomeFit has been updated for the Healthy Homes Standards. A certificate issued after assessment by a trained assessor under HomeFit v2 can be used to show that the home complies with the Standards.
There are a number of overseas energy-related tools which have some application in New Zealand, such as the Canadian-based online software programme RETScreen.
RETScreen can be used to evaluate the energy production and savings, life-cycle costs, emission reductions, financial viability and risk for various types of energy efficient and renewable energy technologies (RETs). The software is free to download and the website includes data and case studies. Energy studies include technologies such as wind energy, solar hot water, solar space heating, biomass heating, passive solar heating, ground source heat pumps, photovoltaics and wind energy. Climate data for various locations in New Zealand is available.
Energy performance certificates in other countries
House performance rating systems, typically measuring energy or heating efficiency, are mandatory in some countries.
In the European Union, for example, Energy Performance Certificates (EPCs) must be obtained when a property is built, sold or rented. An EPC gives a property an energy efficiency rating from A (most efficient) to G (least efficient) and is valid for 10 years. It contains information about a property’s energy use and typical energy costs and recommendations about how to reduce energy use and save money. The rating must be included in advertisements.
EPC schemes are slightly different between countries. In the United Kingdom, homeowners can be fined if they do not get an EPC when they need one, and EPCs are publicly available and can be searched online by address.
In the USA, the Home Energy Score (developed by the federal Department of Energy) covers new and existing homes. It is not mandatory at national level but is a legal requirement in some jurisdictions.
BRANZ has a project underway studying the details of how EPC schemes operate in other countries. The research will provide the groundwork for the potential introduction of EPCs to New Zealand.
Another study, published in 2021, found that: “New Zealand should explicitly choose a design for our energy certification that rewards the behaviours and designs that support energy and resource efficiency.”
Updated: 18 August 2022