On Monday the timber frame contractors of our Welsh Passivhaus prototype social housing managed a fantastic first air test result of 0.29 air changes per hour under 50 pascals air pressure! This is one of the best air test results carried out by a UK contractor so far; more than twice as good as the minimum standard required for a Passivhaus, 34 times better than UK Building Regulations, and right up there with the best current German construction standards.

It’s a really great show of what can be achieved by the UK construction industry where there is a keen and motivated and diligent contractor teamed with diligent architects providing a carefully thought out and thoroughly explained airtightness rationale.

It’s wrong for architects to make generalizations that the UK construction industry is unable to achieve European standards of construction quality. It’s up to architects to learn from the best European techniques and support contractors with design strategies and drawing techniques that assist contractors rather than hinder them in their efforts. For example, the line of airtightness must be made abundantly clear in the contract documentation and designers must define the stages at which testing is undertaken, ensuring that the line of airtightness is fully visible at the first air test.

We find contractors are pleased to see details such as window-wall junctions presented at four stages of the construction process in order to help them understand what they need to do to achieve the finished detail. Our job architect’s 3 days on site to explain the drawings and the airtightness regime necessary at the crucial point of fitting windows was also very important for the final airtightness result in the Welsh prototype.

Well done Holbrook Timber Frame Ltd!