Jon Bootland is chief executive of the Passivhaus Trust, which promotes the adoption of the international Passivhaus eco-design standard in the UK
Passivhaus is on the rise in the UK, with the Scottish Government developing a Passivhaus-equivalent policy for the energy efficiency of new-build housing, and local authorities and social housing providers similarly pursuing large-scale projects, including schools, housing and even swimming pools.
“The feedback is that contractors are not finding the switch to Passivhaus as difficult as they expected”
Passivhaus projects require better standards of onsite quality assurance than typical builds. Contractors tendering for such schemes for the first time might find the prospect daunting. However, the feedback the Passivhaus Trust is getting is that contractors are not finding the switch to Passivhaus as difficult as expected. It is more about a shift in mindset than a huge overhaul of practices.
Our recently updated How to Build a Passivhaus guide shares some useful lessons for contractors taking on a Passivhaus project for the first time.
Key stage design reviews
Structured reviews, analysing every aspect of the design and the construction, are hugely beneficial, particularly for less-experienced project teams. These reviews examine the buildability, sequencing and construction programme, identify and expose risks that could impact upon project delivery, and allow the project team to formulate strategies that resolve the risks in an open and collaborative fashion.
Toolbox talks
Each trade, from foundations to roof, has a part to play in the successful completion of a project. Training plays a key role in the success of a Passivhaus project and helps to bring all site operatives on board. One of the best techniques is to hold a series of toolbox talks that all site personnel are required to attend. New or replacement personnel should also receive an induction.
Typically, these toolbox talks examine each detail, the sequence in which it will be constructed, the technologies that will be used when forming the detail, and trades that will impact upon the successful completion of the detail. The talks work best when there is an atmosphere of collaboration, allowing any sceptics to voice their concerns and hopefully bringing them on board.
Site inspections and feedback
The design team and Passivhaus designer/consultant will undertake site inspections periodically. Detailed site reports that support a useful, practical feedback loop are invaluable to ensure a successful outcome. Discussing the contents of the reports with site managers, rather than simply handing over the document, is essential to establishing this feedback loop. The best site reports also record the lessons learned from the site visit so that they are fed forward to subsequent phases of the project and for future projects.
Dedicated onsite quality-assurance champion
Successful Passivhaus projects almost always have a dedicated onsite quality-assurance champion appointed to ensure that the building satisfies its airtightness target and that the correct insulation system is installed properly. This vital role involves undertaking day-to-day site inspections of the work and instructing improvements as required.
Typically, a quality-assurance champion will review the buildability of the air barrier, wind barrier and insulation systems, look at the sequencing of the build process and try to pre-empt challenges before they become obstacles. Their role generally covers ensuring that the interface between insulation products has a good butt joint, and that insulation is encapsulated between the air barrier and the wind barrier. They would also check that the wind barrier system is complete.
Another important responsibility is to ensure that only the specified materials are used in the construction. This helps to avoid the use of ad hoc substitutes being introduced at the last minute through value engineering, without prior consultation and agreement with the designer. Quality-assurance champions also often organise and arrange pressure tests, and arrange toolbox talks for all trades.
Passivhaus training
The Passivhaus Trust offers a free online ‘Introduction to Passivhaus’ course, as well as its freely downloadable How to Build a Passivhaus guide. It is also possible to undertake a short course of training to become a certified Passivhaus tradesperson.
