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.
Design buildings to keep technical electromagnetic fields low, especially in sleeping areas, and to avoid materials that build up static charge
People evolved within the Earth's natural electric and magnetic environment. Modern wiring, appliances and wireless devices add fields that did not exist before electrification, at levels far above natural ones.
High magnetic fields from wiring, switchboards and appliances are possibly carcinogenic (IARC Group 2B, 2002), based on a contested link with childhood leukaemia at 3 to 4 mG and above (Ahlbom 2000; newer studies show a weaker link, Amoon 2022). Tier 2
As a precaution, BBE recommends under 1 mG in sleeping areas, as low as reasonably achievable. This is a precautionary target, not a proven harm threshold. Synthetic surfaces can build up static charge, which is uncomfortable and attracts dust.
Traditional and experiential knowledgeSome traditions hold that earth energies, water veins and fault lines affect sleep and health. These practices are valued by many but are not supported by controlled studies to date.
2
Choose building materials with low toxicity, low radioactivity and low emissions of harmful chemicals
Inert materials, natural or synthetic, add little to indoor air pollution.
Many synthetic materials, finishes and adhesives release volatile organic compounds (VOCs) and formaldehyde, which can irritate airways (WHO Guidelines for Indoor Air Quality: Selected Pollutants, 2010). Tier 1
Some natural materials also need care: some granites emit radon, the second leading cause of lung cancer after smoking (WHO Handbook on Indoor Radon, 2009) Tier 1, and resinous timbers and natural fibres can trigger allergies in sensitive people.
3
Choose building materials that buffer humidity and allow vapour diffusion, to help moderate the indoor climate
Hygroscopic, vapour-open materials such as clay plaster and timber absorb and release moisture, which can help keep humidity in a stable range and reduce condensation, damp and mould (Cascione et al., University of Bath, 2019). Tier 1
The effect in a real house also depends on ventilation and the whole wall build-up. Some materials, such as clay, may also absorb certain pollutants. Tier 3
Damp and mould are linked to respiratory symptoms and asthma (WHO Guidelines for Indoor Air Quality: Dampness and Mould, 2009). Tier 1 Mould can also damage the structure.
4
Reduce the build-up and circulation of harmful vapours, particles, radon, bacteria, viruses and fungi indoors
A warm, dry building with adequate ventilation and low-emission materials and furnishings makes for a healthier indoor environment.
Pollutants build up from emitting materials, poor ventilation, excess moisture, or poorly maintained ventilation and air-conditioning systems. Dust mites thrive in damp, dusty conditions and are a major asthma trigger. Tier 1
5
Heat and ventilate the building with efficient, occupant-adjustable systems, favouring radiant heat and fresh air
Radiant heat warms people and surfaces rather than the air, which many people find more comfortable. Fresh air dilutes indoor pollutants and CO2.
With good design, natural ventilation works in many NZ climates. In cold, noisy or polluted locations, well-designed balanced ventilation with heat recovery (MVHR) and filtration can deliver cleaner air at lower energy cost.
Poorly maintained mechanical systems can harbour microbes, so filters and ducts need regular cleaning. Stuffy, poorly ventilated rooms are associated with drowsiness and reduced concentration. CO2 is a useful marker of stale air, though whether CO2 itself is the cause is still debated (Snow et al., Building and Environment, 2019). Tier 2
6
Keep indoor temperatures within a comfortable range, with some gentle variation between rooms and through the day
The WHO recommends a minimum indoor temperature of 18 °C in cold seasons (WHO Housing and Health Guidelines, 2018). Tier 1
The Passivhaus comfort range of 20 to 25 °C is the ideal target, with bedrooms at the cooler end. Aim for no more than 2 °C difference between floor and ceiling. Many people enjoy small differences between rooms and gentle daily variation, which can make a building feel more connected to the seasons. Tier 3
Long periods below 18 °C raise the risk of respiratory and cardiovascular illness, especially for older people and children (WHO, 2018). Tier 1 Overheating disrupts sleep and stresses vulnerable people.
7
Insulate against or isolate from unwanted noise and vibration
Pleasant sounds can be soothing or stimulating. Unwanted noise is not.
Long-term environmental noise is linked to sleep disturbance, annoyance and cardiovascular effects (WHO Environmental Noise Guidelines for the European Region, 2018). Tier 1
8
Light a building with daylight, or bright daylight-like artificial light, during the day, and warmer, dimmer light in the evening
Bright light during the day supports alertness and a regular sleep-wake cycle. This matters most for people who spend all day indoors. Warmer, dimmer light in the evening supports natural sleepiness.
Low daylight exposure is linked to seasonal affective disorder, and bright light therapy is a first-line treatment for it (Pjrek et al., Psychotherapy and Psychosomatics, 2020). Tier 1
Ordinary room light before bed suppresses melatonin, and blue-rich light does so most strongly (Gooley et al., Journal of Clinical Endocrinology and Metabolism, 2011). Tier 1
9
Provide a view of nature from main living and working spaces, and easy access to the natural environment
Views of nature and time outdoors support recovery from stress and mental fatigue (Ulrich, Science, 1984; Kaplan, Journal of Environmental Psychology, 1995). Tier 2
Access to fresh air, daylight and greenery supports wellbeing. Indoor environments with poor air and no connection to nature add to everyday stress.
10
Design for ergonomics, accessibility and safety
Ergonomics considers a person's comfort when using furniture or equipment, or moving around. Dimensions should suit the full range of people using the building, including children, older people and people with disabilities, following universal design principles (NZS 4121:2001, currently under review).
Poor ergonomic design causes accidents, and discomfort from long-term use and repetitive actions. Poor daily posture can lead to persistent and painful muscle and joint problems. A workstation set up to suit the user, such as the correct desk height and a chair suited to full-day use, together with regular changes of position, reduces the risk (WorkSafe NZ, 2024). Tier 2
Ergonomics is usually associated with furniture, yet the building sets many of the same dimensions: kitchen bench and basin heights, stair risers and treads, handrails, door handles, switch and socket heights, window sills and storage reach. Getting these right at design stage costs little and is hard to fix later.
Buildings also need to guard against falls, slips, trips, fire, burns, electrocution, cuts, vehicle impact and drowning.
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
Ahlbom A. et al. (2000). A pooled analysis of magnetic fields and childhood leukaemia. British Journal of Cancer, 83(5), 692-698.
Amoon A.T. et al. (2022). Pooled analysis of recent studies of magnetic fields and childhood leukemia. Environmental Research, 204.
Cascione V. et al. (2019). The response of clay plaster to temperature and RH sinusoidal variations. MATEC Web of Conferences, 282, 02005.
Gooley J.J. et al. (2011). Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. Journal of Clinical Endocrinology and Metabolism, 96(3).
IARC (2002). Non-ionizing radiation, Part 1: Static and extremely low-frequency electric and magnetic fields. IARC Monographs Volume 80.
Kaplan S. (1995). The restorative benefits of nature: Toward an integrative framework. Journal of Environmental Psychology, 15(3), 169-182.
Pjrek E. et al. (2020). The efficacy of light therapy in the treatment of seasonal affective disorder: A meta-analysis of randomized controlled trials. Psychotherapy and Psychosomatics, 89(1), 17-24.
Snow S. et al. (2019). Exploring the physiological, neurophysiological and cognitive performance effects of elevated carbon dioxide concentrations indoors. Building and Environment, 156, 243-252.
Standards New Zealand. NZS 4121:2001 Design for Access and Mobility: Buildings and Associated Facilities.
Ulrich R.S. (1984). View through a window may influence recovery from surgery. Science, 224(4647), 420-421.
WHO (2009). WHO Guidelines for Indoor Air Quality: Dampness and Mould.
WHO (2009). WHO Handbook on Indoor Radon: A Public Health Perspective.
WHO (2010). WHO Guidelines for Indoor Air Quality: Selected Pollutants.
WHO (2018). WHO Housing and Health Guidelines.
WHO Regional Office for Europe (2018). Environmental Noise Guidelines for the European Region.
WorkSafe NZ (2024). Setting up a healthy workstation when working from home.
Ready to Learn More?
Explore our courses on healthier, more ecological building and design.
