Does the airtightness of a Passivhaus really last, or does it decay?
Are design and construction skills in the UK really able to deliver enduring standards of airtightness?
Do airtightness technologies last, or do they decay?
The Racecourse estate was completed in 2011. A lot has happened since then. Materials have dried and had the opportunity to shrink. Components, like windows and doors, have been used and had the chance to develop signs of wear and tear. Satellite TV has been installed, involving putting cables through the building envelope.
So do Passivhauses progressively become more and more leaky, or does the airtigntness endure over time?
To answer these questions we recently teamed up with Mark Siddall from LEAP Architects and Prof David Johnston from Leeds Beckett University. Together we undertook air tightness tests on bungalows within the Racecourse Estate. We combined these results with studies undertaken by Leeds Beckett University.
The result? We created the largest, and most comprehensive, longitudinal study of airtightness in UK Passivhaus homes. The resulting paper, Longevity of airtightness in Passivhauses was peer-reviewed and presented at the International Passive House Conference 2016 in Darmstadt, Germany.
The airtightness test is one of the very few physical tests to be carried out on completion of a dwelling, as opposed to an inspection. This is surprising in the context of the many sample tests that are regularly carried out as part of any quality assurance process on manufactured goods. The most expensive product that most of us will ever buy will only have had one actual test on completion. And like an MOT on a car, it only tells you the condition at the time of the test.
So how long does airtightness last? How much airtightness is lost as the house dries out, there is some movement, and construction products cure and degrade over time?
We can advise on airtightness strategies that will work and last.