Science
Your environment is part of your physiology. What the research shows, how strong it is, and what can be done.
Core 7
Light
Circadian lighting · daylight exposure · evening environments
Air
Ventilation · filtration · humidity · pollutants
Thermal environment
Temperature · sleep · seasonal comfort
Water
Supply quality · fittings · testing · filtration
Acoustics
Background noise · night-time noise · sound between rooms
Materials
Finishes · furnishings · emissions · dust
Sleep environment
Darkness · quiet · overnight air and temperature
Beyond the core
Ageing in place & longevity
Falls · lighting for older eyes · temperature · adaptable homes
Biophilic design
Views · daylight · plants · natural materials
Sustainability
Energy · insulation · electrification · durable materials
How we grade evidence
Not all evidence carries the same weight. At the top are systematic reviews and meta-analyses, which pool the results of many studies, followed by randomised controlled trials in people, ideally placebo-controlled or with a sham comparison. Below those sit observational studies, which can show that two things go together but not that one causes the other, then laboratory and modelling studies, and finally case reports, expert opinion and lived experience. For many questions about buildings the top tiers don’t exist yet: you can’t easily blind someone to a window, and few trials run for years inside real homes. When case studies and lived experience are all there is, we still use them, but we tell you that is what the advice rests on and grade it accordingly.
Well supported
Consistent findings across good-quality studies, or a clear guideline or standards basis. We recommend these with confidence.
Reasonable
Plausible, low-risk and supported by some evidence, but not yet proven in the setting in question. We explain the trade-off and let you decide.
Not supported
Popular claims the evidence does not back. We say so, so you can spend your money elsewhere.
Our evidence standards
We cite peer-reviewed research, systematic reviews and guidelines from health and building authorities, and link to every source. Much of the research on indoor environments comes from offices, laboratories, schools and hospitals rather than homes. When we apply it elsewhere, we say so.
We review each page at least once a year and update it when significant new evidence appears. These pages are general information, not medical advice.