“Our buildings should continually strive to give back more than they take: more energy, cleaner water, richer soil and more habitat than they use or displace.”
BBE value
Each health claim below carries an evidence label, from Tier 1 (established) to Tier 4 (not supported by blinded trials), so you can see how strong the research is behind it. Traditional knowledge is shown separately.
Plan buildings efficiently, with multi-use spaces, for a smaller physical footprint
A smaller, well-planned house uses less material, needs less energy to heat and is quicker to clean. Good planning reduces circulation space, and fewer, multi-use rooms keep a feeling of spaciousness.
House size is the biggest single driver of a home's carbon footprint. In BRANZ studies of ten houses, almost 82% of the footprint could be attributed to floor area, while the average New Zealand house grew from 113 m² to 205 m² over 70 years (BRANZ, Design to Cut Carbon). Tier 1
2
Reuse and improve existing buildings, keep productive land for food, and build only on land suited to habitation
Improving existing buildings keeps the materials, energy and heritage already invested in them, rather than spreading new buildings across open landscape.
About 15% of New Zealand's land is highly productive, and national policy aims to keep it available for food and fibre (National Policy Statement for Highly Productive Land 2022, as amended).
Where land is degraded, a building project can help restore it, by replanting gullies, stream banks and eroding slopes. BBE value
Steep, erosion-prone land is better kept in permanent vegetation. The 2023 inquiry after Cyclone Gabrielle found that a mismatch between land use and land type worsened damage from sediment and woody debris (Ministerial Inquiry into Land Use in Tairāwhiti and Wairoa, 2023). Tier 1
3
Design the site and landscape to grow food and support natural habitat, balancing both
Growing food on your property makes for greater resilience in times of adversity, and fresher food every day.
Permaculture offers a design approach for more productive, lower-input land use, though its outcomes are still lightly researched (Ferguson and Lovell, 2014). Tier 3 Areas set aside as permanent habitat support native species and local water and air quality.
Aim to leave the site with more living soil, more planting and more habitat than before building began. BBE value
Lawns store some carbon in their soil, but keeping them costs energy. In one Californian study, emissions from mowing, fertiliser and other upkeep matched or exceeded the carbon the lawns stored (Townsend-Small and Czimczik, Geophysical Research Letters, 2010). Tier 2 BBE favours smaller lawns, clippings left in place, electric or hand mowers and little or no fertiliser, with trees, meadow and food planting in place of the rest. BBE value
What we grow and eat matters far more than how far food travels: transport makes up only about 6% of food-related emissions (Poore and Nemecek, Science, 2018). Tier 1
4
Choose building materials that are durable or biodegradable, reusable or recyclable, and from renewable or abundant sources
Timber from certified, well-managed forests (FSC or PEFC) is renewable, and subsoil for earth building is abundant in many places, though topsoil is finite. Much energy and labour goes into making materials and buildings, so durable and reusable materials make the most of that investment.
Timber and other plant-based materials hold carbon the plants absorbed as they grew, keeping it out of the atmosphere for the life of the building. Tier 1 Favouring these materials lets a building store carbon, not only emit it. BBE value
Materials from limited sources need to be reused or recycled, or demand will outstrip supply and drive more invasive extraction.
5
Choose building materials with lower environmental impact across their whole life: production, transport, installation, use, demolition and disposal
Life cycle assessment (LCA) and Environmental Product Declarations (EPDs) compare materials across every stage, from extraction to reuse or decay. BRANZ offers free NZ tools for this, including CO2NSTRUCT and LCAQuick.
Some materials have a benign working life but high impacts in production or transport. Others become a problem at demolition, creating toxic or non-biodegradable landfill.
6
Design to reduce construction waste and packaging, and plan for reuse and recycling
Dimensioning a building to suit standard sheet and unit sizes saves labour and offcuts. Ask suppliers about take-back schemes and reduced packaging.
Designing for disassembly means materials can be recovered when the building is altered or removed. In some off-site construction, only 2 to 3% of materials end up in landfill.
A typical new New Zealand house generates about 4 tonnes of waste, and construction and demolition waste makes up a third to a half of all waste to landfills and cleanfills (BRANZ Bulletin 671, 2022). Tier 1
7
Reduce energy demand first, then supply the rest from renewable, on-site or nearby sources, aiming for zero net imported energy and beyond
A well-insulated, airtight building built to Passivhaus-level performance needs very little heating, so a small renewable system can cover what remains.
On-site or nearby generation, such as solar, gives more autonomy and resilience in emergencies without sacrificing comfort.
Beyond zero, the aim is a building that generates more renewable energy over a year than it uses, sharing the surplus with its neighbours and the grid. BBE value
Burning fossil fuels is the main cause of global warming (IPCC Sixth Assessment Report, 2023). Tier 1
8
Plan developments to reduce reliance on cars, and use renewable energy for longer-haul transport
Neighbourhoods that mix homes, shops, entertainment and workplaces make walking and cycling practical. Car-sharing schemes can supply a car when one is needed.
Longer journeys and freight need an efficient network powered by renewable energy.
Transport fuels from fossil sources contribute to global warming (IPCC, 2023). Tier 1
9
Use water efficiently, and manage stormwater and wastewater on site where suitable, to reduce reliance on imported water
Our reticulated system treats all household water to drinking standard, yet around one litre in five is then flushed down the toilet (BRANZ, Level). [Tier 1] Using rainwater for toilet flushing, laundry and garden is the logical alternative. In an earthquake-prone country, a home with its own stored water wins. [BBE value]
Drinking water must meet the Water Services (Drinking Water Standards for New Zealand) Regulations 2022, and on-site wastewater systems need design to AS/NZS 1547:2012 and often regional council consent.
Many public networks are under strain: operators reported 11,535 wastewater overflows in 2024/25, around 31 a day (Taumata Arowai, 2025). Tier 1 Upgrading New Zealand's three waters networks is estimated to need $120 to $185 billion over 30 years (Department of Internal Affairs, 2021).
10
Restore and improve water quality before returning it to the natural environment
The aim is to return water to the land and streams cleaner than it arrived. BBE value
Natural streams clean and cool themselves: riffles and meanders aerate the water, and streamside planting shades it and filters runoff. Tier 1 Using lower-toxicity cleaners and body care products reduces what goes down the drain.
Straightening streams into channels speeds up the flow and can move flooding further downstream. Tier 1 Domestic and industrial pollutants can build up in wildlife through the food chain. Tier 1
Traditional and experiential knowledgeFollowing Viktor Schauberger, some hold that water's spiralling movement gives it vitality and self-cleansing power. These ideas are valued by many but are not supported by controlled studies to date.
How to Read the Evidence Labels
Each claim carries a label showing how strong the evidence is. This lets you weigh each recommendation for yourself.
Tier 1
Established. Backed by consistent research and accepted by health agencies such as the WHO.
Tier 2
Contested signals. Some studies show a link, others do not, and scientists still disagree. We apply a precautionary approach: reduce exposure where it is easy and affordable to do so.
Tier 3
Plausible, still being studied. A reasonable explanation exists, but there have been few good-quality studies so far.
Tier 4
Not yet confirmed in trials. Many people report real effects, and their experience matters. So far, controlled trials have not confirmed the cause that is claimed. Research continues, and BBE will update this guidance as new evidence emerges.
BBE value
A principle drawn from BBE’s research and decades of practice, held by BBE as central to more comfortable, caring design.
Traditional and experiential knowledgeTraditional and experiential knowledge, such as earth energies or Feng Shui, is shown separately. These practices are valued by many but are not supported by controlled studies to date, so they are not given an evidence tier.
References
BRANZ. Design to Cut Carbon: The Time Is Now. branz.co.nz.
BRANZ (2022). Bulletin 671: Reducing Construction and Demolition Waste.
Department of Internal Affairs (2021). Three Waters Reform: water industry commission reports.
Ferguson R.S. and Lovell S.T. (2014). Permaculture for agroecology: design, movement, practice, and worldview. A review. Agronomy for Sustainable Development, 34, 251-274.
Ministerial Inquiry into Land Use in Tairāwhiti and Wairoa (2023). Outrage to Optimism.
Ministry for the Environment and Ministry for Primary Industries. National Policy Statement for Highly Productive Land 2022 (amended 2025, in force 15 January 2026).
Poore J. and Nemecek T. (2018). Reducing food's environmental impacts through producers and consumers. Science, 360(6392), 987-992.
Standards Australia and Standards New Zealand. AS/NZS 1547:2012 On-site Domestic Wastewater Management.
