[UKPHC Part 1] The UK Passivhaus Conference discussed the many lessons which can be learnt from completed Passivhaus projects
Last week Footprint attended this year’s Passivhaus Conference, held at Nottingham University.
One of the opening sessions of the conference focused on the lessons which could be learnt from completed Passivhaus projects. Three different typologies and projects were discussed; large scale residential, Passivhaus schools and refurbishment projects.
The Wimbish Passivhaus scheme by Parsons + Whittley was completed in 2011. It features 14 homes; 6 flats and 8 houses, all completed to both Passivhaus and Code for Sustainable Homes Level 4 standards.
The project used a design and build contract, but the designers held on to the project until RIBA Stage F, allowing a lot of the work to be carried out at detailed design stage, before the project was tendered. It was questioned as to whether design and build contracts were really suitable for Passivhaus projects. The onus of the detailing and airtightness is put on the contractor who may not necessarily be that up to speed with Passivhaus construction techniques. At Wimbish they maintained the architects to monitor the work on site.
Jane Barnes of Davis Langdon said ‘using Passivhaus certified designers who understand the details of Passivhaus fully and can use PHPP is key’.
Another important point which came out of the Wimbish project was collating the information required for certification. Hastoe said if they were to do the project again they would incentivise the contractor to ensure that all the material required for Passivhaus certification was available before practical completion.
The uplift in cost from Code for Sustainable Homes Level 4 to also achieving Passivhaus at Wimbish was 12 per cent. But due to the lessons learnt from this project they have managed to reduce this to 6 per cent on their next Passivhaus scheme at Ditchingham.
Jonathan spoke of the practice’s routes in Segal style self-build architecture, and about how this had led them to create buildings which are buildable and simple. Creating projects with a simple form and section allows the building to perform efficiently. He saw their delivery of Passivhaus as the ‘logical next step’, believing ‘Passivhaus frees up the architect to create sustainable well designed buildings’, but stressed the need to keep simple form, plans and detailing in order to achieve the standard at no extra costs.
Through their Passivhaus projects they recognised the importance of focusing on thermal bridging, and recommended keeping the structure outside the thermal envelope. This helps to avoid any thermal bridges and makes air tightness detailing simpler.
They spoke of the importance of modelling, in order to fully understand the detailing of a Passivhaus project.
It was concluded that co-ordination was most important in a retrofit project, as continuity had to be provided and often the projects have to be planned around peoples lifestyles and movements within the property.
A common theme running through all these projects was the importance of training contractors and those working on site in the details and specifics of Passivhaus construction. Successful Passivhaus construction projects engage the supply chain and it is not possible to create high levels of airtightness and thermal efficiency if those working on site do not understand what they are trying to achieve.