Time indoors
What the research found
U.S. respondents reported an average 87% of a day in enclosed buildings.
Important limitation
Klepeis et al. · 2001Not global, not a lifetime figure, and not all time at home.
Research
Evidence behind a healthier home.
We check health and building claims against original sources, explain the findings and their limits, and update our guidance when the evidence changes.
How we review evidence
Useful guidance begins with context.
Use original sources. We favour primary research, public-health agencies and technical standards over promotional summaries.
Explain the limits. Geography, population, method and outcome stay attached to the finding.
Label the evidence. Research, expert interpretation, lived experience and editorial judgement are labelled as different things.
Review the record. Material changes are dated and explained rather than quietly overwritten.
Evidence library
Findings, with their limits intact.
Eleven source summaries. Library updated 06 September 2026. Editorial summaries, not independent expert review.
Household air pollution
What the research found
Polluting fuels used in inefficient stoves remain a major global exposure.
Important limitation
World Health Organization · 2025The burden is concentrated in particular fuel, income and rural contexts.
Light at night
What the research found
Controlled studies link evening room light with altered melatonin timing.
Important limitation
Gooley et al. · 2011The study measured a biological response. It does not show that a lighting product treats poor sleep.
Light pattern
What the research found
Expert consensus supports brighter days, dimmer evenings and dark nights.
Important limitation
Brown et al. · 2022Recommendations have age, schedule and measurement boundaries.
Dampness and mould
What the research found
Persistent dampness and mould are associated with respiratory symptoms and asthma risk.
Important limitation
WHO guidelines · 2009Evidence is heterogeneous; no universal safe indoor spore count exists.
Home food environment
What the research found
What families provide, model and make accessible can support healthier eating.
Important limitation
Wyse et al. · 2012Kitchen design alone has not been established as the cause.
Views of nature
What the research found
Window views of nature may support psychological wellbeing.
Important limitation
Soga & Gaston · 2025Studies are highly varied; pooled physical-health effects were near zero.
Potted plants
What the research found
Passive houseplants show weak practical VOC-removal performance in typical rooms.
Important limitation
Cummings & Waring · 2020This does not dismiss aesthetic or psychological benefits.
Materials and reuse
What the research found
EPA guidance prioritises waste prevention, building preservation and design for adaptation.
Important limitation
U.S. EPA · Agency guidanceRetaining or reusing an item still requires checking its condition and suitability.
Energy and ventilation
What the research found
Reducing unwanted air leakage can reduce heating and cooling demand.
Important limitation
U.S. Department of Energy · 2021Air sealing must be considered alongside planned ventilation, moisture control and combustion safety.
Perceived restoration
What the research found
In two experiments, nature scenes felt more restorative than urban scenes.
Important limitation
Johnson et al. · 2022The viewed image did not improve measured sustained attention. A pleasant feeling is not evidence of a cognitive or clinical benefit.
Simple slogans rarely survive a closer look.
“We spend 90% of our lives indoors.”
A widely repeated simplification. The often-cited U.S. activity study reported 87% of one day in enclosed buildings, not a universal lifetime figure.
“Houseplants purify indoor air.”
Plants can bring pleasure and contact with nature, but passive pots remove too little VOC pollution to replace source control or ventilation in a typical room.
“Natural materials are non-toxic.”
Natural describes origin, not exposure. A useful specification also considers finishes, adhesives, emissions, moisture behaviour, cleaning and maintenance.
“This light will fix your sleep.”
Light timing matters, but a product claim is not a clinical outcome. Bright days, gentler evenings and dark nights are the more defensible starting pattern.