Skip to content

Why we need airtight buildings: Outdoor air quality is getting worse

What's the best approach for dealing with this?

A recent post, If you're going to live a one tonne lifestyle, it's easier in a Passivhaus, was inspired by a discussion about air quality: Should we be sealing ourselves up in airtight buildings? It used to be that one would open the windows to get fresh air. Doctors demanded it when I was a baby, but things have changed. Air quality was getting better for decades after industry cleaned up its act or moved to China, coal furnaces were converted to gas and people stopped smoking. But it has been getting worse again thanks to climate change, as there are more fires, and more heat which promotes smog formation. There are also more cars and SUVs putting out more particulates.

Kate de Selencourt tried to explain the issue with her post Can airtight buildings protect your health? She writes:

London skyLloyd Alter/ Philishave building and orange sky/CC BY 2.0

British cities – and London in particular – break the law on levels of air pollution on a near-constant basis. And people are increasingly aware of what a serious risk this poses to health. Respiratory illness, heart disease, dementia – and even reduced thinking ability and increased crime rates – have all been linked to air pollution.

But the key question is: are we safer inside our buildings? Much depends on the building. A study of schools in London found that Nitrogen Dioxide (NO2) levels in modern, airtight schools were half of the levels outside, whereas in old Victorian era schools, NO2 levels were only 10 to 30 percent lower.

Tienanmen squareLloyd Alter/ morning in Tienanmen Square/CC BY 2.0

Similar results were found in Chinese schools:

Looking specifically at the larger particles, PM2.5 and PM10, the researchers found that buildings with better air tightness showed relatively greater reductions in particulate matter indoors. Reductions of around 30-50% compared to outdoors were seen in the more airtight buildings, compared with only a 10-15% reduction in the leakiest.

A Dutch school study confirmed that properly maintained mechanical ventilation systems with regularly replaced filters could make a big difference. But to work, you have to control the source of the air, so the building has to be airtight. As the saying goes:

Build tight and ventilate right

What started our debate was Rosalind Readhead's complaint that we are following the wrong approach. We should note that de Selencourt is writing this article for SIGA, which manufactures the tapes and sealants used to make a building airtight. Now that I understand that sticking plaster is not a SIGA adhesive material but a Band-Aid, I want to say that Rosalind is absolutely right. Kate de Selencourt agrees with Rosalind too, and said so in her conclusion:

Air pollution harms and kills people, especially the young and those already infirm. The first priority must of course be to reduce and remove the problem at source by social and political change.

Small changes in the immediate environment may help a little. Schools can lobby local authorities to re-route busy traffic, and exhort parents not to drive up close or wait with idling engines. Planting trees and shrubs around homes, schools and other buildings can also filter out some pollution.

It's time for bigger changes. Some wealthy schools in London are crowd-funding living walls while they drive their kids to school in Land Rovers; forget exhorting parents not to drive, just ban the cars.

But it is always good to have a backup: “as building users generally have little or no immediate control over outdoor air quality, it is important to offer as many layers of protection as possible, for the many hours people spend inside.” Roll out that SIGA tape.