Did Passivhaus filter out this summer's wildfire smoke?
This summer's wildfires destroyed homes and damaged nature across the UK. The smoke they produced travelled much further: people living over 20 miles from the fires were affected. Smoke pollution is known to aggravate breathing and heart conditions, and those affected were advised to keep their windows closed, even through the heat, to limit exposure to the worst of the pollution.
What we want to know
It raises two questions for the Passivhaus Trust:
- What was actually in that smoke?
- Did the airtightness and filtered mechanical ventilation built into Passivhaus homes give occupants better protection than a typical home?
Where the answer might be
The answer may be sitting in a bin! The intake filters on MVHR systems catch what would otherwise have been drawn into the building, which means a spent filter from a home in a smoke-affected area is, in effect, a record of what that home's occupants were protected from. Study enough of them, and a clearer picture starts to form of what was in the air this summer, and how well Passivhaus performed against it.
The Passivhaus Trust is looking to team up with researchers to find out more, but to do this research, we need your dirty filters! If you own, manage, or have links to a Passivhaus project in South Wales, the West Midlands, the Scottish Highlands, East Anglia, or another smoke-affected area, we'd be glad if you could hold on to the spent filter at your next scheduled change, rather than disposing of it.
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I've been glad of our MVHR- plus-airtightness combo this past couple of weeks, not just for their heat-excluding and cool-conserving properties, but also because together they are keeping out a little at least of the smoke pollution drifting over here from the Wales wildfires. The smell still gets in to an extent, but I think the filters are excluding a proportion of the soot. And when the smell is at its worst, we can shut the ventilation right down for a few hours.
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What we need from you
- Keep the spent filter when it comes out at its next change.
- Note the date it was fitted and the date it was removed.
- Note the postcode of the property (just the first part if you'd rather keep it general).
- Put the filter, with those details, into the box or packaging the replacement filter came in.
- Get in touch using the button below, or email research@passivhaustrust.org.uk with the subject line "Dirty filters", and we'll confirm next steps for getting it to us.
This is early-stage, practical research built from real buildings. If it confirms what the building physics suggests, it will give the Trust further evidence for one of Passivhaus's benefits: resilience to a climate emergency impact that's likely to become more familiar in UK summers. If you're not in a position to contribute a filter but know someone who might be, please pass this on.
Join further discussions about scaling affordable comfort & resilience at the UK Passivhaus Conference this November, in London and online.
Further Information
PHT good practice guide: MVHR Maintenance, 2024
World Health Organisation: Wildfire smoke: a frequently underestimated health risk - 31 July 2026
UK Health Security Agency: Why severe wildfires are becoming more frequent in the UK and how to cope with the health risks - 14 July 2026
Previous PHT story: Healthy Homes guidance points to Passivhaus - 12th August 2026
Previous PHT story: Why building performance has never mattered more: the UK Passivhaus Conference - 17 July 2026
17th August 2026
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