One of the unknowns throughout the building work was how air-tight we could make Ridgeway. We were told it was more difficult with a conversion and we would be doing well if we got a 3 (m3/hr/m2 air loss at a pressure of 50 Pa).
I don’t understand the formula but the lower the number the better. English building regs for new houses is 10, while extensions and renovations do not have to be measured. At the start of the project I told Karl, the builder, that we were aiming at 1. His reaction was: “That would look good on the CV.”
The approach was to nag every tradesman who cam through the door, follow the architect’s instructions and use vast quantities of tape, expanding foam and mastic on every join and anything that looked like a hole.
The first test came out at 2.45 which comfortably meets both German and Swedish building regs. As we don’t need a further test to meet any standards I am not planning to spend the money on one. But we have identified leaks and closing those should bring the figure down to about 1. That is not quite Passivhaus but getting close.
We worked hard on plugging the gaps because air leakage would reduce the efficiency of the air-source heating and the mechanical heat recovery ventilation. Several people told me British workers could not build air tight. We have shown that they can given the right design and by ensuring that everyone working on the site was aware of the importance of blocking every possible leak.
But still major construction firms are apparently often struggling to meet even the inadequate English standard. The fact that on new estates only a sample of buildings are tested and the developer gets to choose which ones are does not help improve things.
With the news today that EU leaders have agreed a pact to reduce greenhouse gas emissions by 40% by 2030 improved standards in the construction industry become increasingly important. For anyone who tells me British workmen are the problem I now have the experience to respond: “Rubbish. They just need the right plans and committed managers.”