Warksburn Old Church massively beats key Passivhaus benchmark!
It was a great privilege to present an in-depth progress report on our globally unique project to convert a former church to a domestic space to Passivhaus standards for airtightness, insulation and ultra energy efficiency.
It was a pleasure to share the stage with Channel 4 Grand Designs presenter Kevin McCloud and his fellow property expert, writer & broadcaster, Kunle Barker.
Appearing on the main stage, Alan was delighted to be able to reveal the news that Warksburn Old Church has now received its formal airtightness certificate, a key requirement for Passivhaus certification. We are delighted not just to have met the required standard, but to have smashed it out of the park.
A little background is helpful. The value which was measured is Air Changes Per Hour (ACH). This is a measure of how many times the total cubic volume of air inside a building will be exchanged with air from outside the building, in a single hour. Obviously, the higher the ACH number, the less airtight a building is. And the less airtight it is, the more it carbon and money it will cost to heat, because all the energy expended to heat the interior is wasted, when the heated air leaks out to the outside world.
- A typical ‘ordinary’ UK house is relatively inefficient, with values typically between around 10 and 15 ACH, depending on the type of construction and the era of the building.
- The required standard for a Passivhaus retrofit of an existing building is 1 ACH, which is, of course, between 10 and 15 times better than typical UK housing stock.
- Given the complexity of making an 1875 building airtight, whilst preserving its key heritage features, we would have been delighted to hit the ultra-demanding standard for a new build Passivhaus. This is 0.6 ACH or lower.
- We were therefore simply blown away when Ian Ritchie, the independent expert from specialist airtightness testers Ritchie & Ritchie, confirmed Warksburn Old Church had achieved 0.19 ACH. That translates as around 52 to 79 times more efficient than typical UK legacy housing stock.
Coupled with Mechanical Ventilation Heat Recovery (MVHR) system now being installed, and the multiple layers of super-insulation built in to the floor, walls, roof, windows. and doors, this astounding airtightness result will enable Warksburn Old Church to operate as one of the most energy efficient buildings in the UK.
Achieving 0.19 ACH is testimony to the extraordinary and painstaking attention to detail which our lead contractor, David Reed, and his team have put in to the job. The image below shows the moment all their hard work was officially recognised, as Ian Ritchie delivered his verdict. A true milestone moment in the life of the building.
