Sustainability Talk: Passivhaus - what's the hold up?

Last week Cullinan Studio asked an expert panel to discuss Passivhaus for our monthly Sustainability Talk. The main question of the night was - what's the hold up? Why has the UK not quite embraced the system as readily as our continental cousins? Our panel argued that digging a little deeper into the issue reveals there a number of misconceptions about Passivhaus to be blamed for stalling its popularity.

Architect Justin Bere refuted the common argument that Passivhaus means a sentence to architectural banality. Bere suggested it's more useful to see Passivhaus as a tool to ensure quality and comfort rather than a stringent aesthetic style. In the face of the extra costs associated with the system, he called upon some research his practice has been involved in, which demonstrates the capacity of Passivhaus to reduce whole life costs (with the caveat of an economic context of low to middle interest rates).

Justin Bere of Bere Architects

Also addressed by Bere were common misconceptions about MVHR interfering with relative humidity. He cited performance feedback which showed MVHR to consistently enable optimum relative humidity levels of 30-60%. As for the question of whether UK builders are up to the challenges of building Passivhaus, Bere believes the architect  can go some way to help. From ensuring the detailing rigour starts at their drawings, to choosing specifications that harmonise with the system (for example specifying window fixing that required predrilled holes) and appointing an "airtightness champion" on-site.

Will South, of Passivhaus specialist consultants Cocreate, agreed, saying that the architect should be willing to teach the contractor. He also advocates Passivhaus courses for the whole team, including the client: the fact is that even well-designed Passivhaus buildings are overheating, so its as much about education as design.  He believes that Building Control represents the minimum standard - this "bottom" isn't where we want to be: longevity and quality are more readily on offer with Passivhaus. In this way, Passivhaus is as much about quality assurance as it about comfort, of course through meticulous detailing. In response to the issue raised that the airtightness values required are excessively low, South conceeded this is a case of overdesign, but doing so to allow for the building to change and grow without adversely affecting the whole system.

Will South from Cocreate

Ivan Christmas, Senior Development Manager at the London Borough of Camden, has been at the helm of what is currently the UK's largest residential Passivhaus project: Chester Balmore, in Highgate New Town. The project only began to aim for Passivhaus certification at tender when contractors Willmott Dixon were brought on board, demonstrating that the system can be designed in at a later stage. Bear in mind this change did also mean a change in architect (from competition winners Rick Mather Architects to specialists Architype) in order to achieve the redefined design goals. Both Christmas and Ben Shuster of Willmott Dixon pointed out the project's fanned bays and adherence to conservation constraints show that a real design dialogue has been allowed to take place - unaffected by Passivhaus requirements.

Chester Balmore in Camden - currently on site

It was particularly useful to have wisdom shared from the perspective of several members of the team that would be responsible for delivering a certified building - the architect, client, contractor and specialist consultant. As the evening devolved into Q&A, it was clear that although achieving the full certification may be a stretch, even with some deviation, Passivhaus is definitely a better baseline to leap from. The real hold up lies in practicing the balancing act of rigourous Passivhaus detailing and wider architectural design choices.