The number of construction projects built to achieve the Passivhaus standard is on the rise. Currently, Passivhaus projects make up around 1% of all UK housing projects. The Passivhaus Trust aims to increase that to 10% in the next decade.
The standard is not just for homes either, with larger projects increasingly seeking certification. At Proctor Group, we have seen our membranes used on the world’s first Passivhaus-certified leisure centre (St Sidwell’s Point in Exeter) and, in Ireland, on large residential developments.
In Scotland, new ‘Passivhaus equivalent’ energy efficiency standards are being developed. This is alongside an innovative funding model promoting the standard’s adoption on a range of school and community campus projects across the country – many of them also featuring our membranes.
What distinguishes a certified project from one ‘following principles’?
The Passivhaus Trust defines eight principles of the Passivhaus standard. Five of these relate to fundamental aspects of buildings and their fabric:
• insulation;
• airtightness;
• ventilation;
• minimal thermal bridging; and
• high-performance windows.
The other three are principles of approach, or what projects need to deliver a building that, typically, does not suffer from a performance gap between as-designed and as-built. They are:
• detailed criteria for performance and comfort;
• accurate design modelling; and
• rigorous quality assurance.
At the same time, there has been a rise in projects that state they have adopted Passivhaus principles, but which do not complete the journey to full certification.
This can be a controversial area. It is one thing to implement the five building-related principles of the standard. But without the principles of approach then how can you be sure the building will perform as expected?
For specifiers and contractors alike, it is worth understanding the distinction between aiming for certification and seeking to follow principles alone. It could significantly alter the scope of the work you do on any such project, and how you do it.
Certified components can aid specification for Passivhaus buildings
To support the selection and use of products that contribute to meeting the Passivhaus standard’s criteria, the global Passive House Institute (PHI) independently certifies products for reliable performance values.
Certified components are assessed for important performance values, including airtightness. In the words of the PHI, “products can be seamlessly integrated into Passive House projects.”
Proctor Group offers two PHI certified components. Wraptite® is an external air barrier that provides airtightness and vapour permeability. Procheck® Adapt is an airtight vapour control layer with variable vapour resistance to suit seasonal changes in moisture levels.
Membranes must fulfil all project requirements
Working with certified components can give added confidence that a product is well-suited to the requirements of the Passivhaus standard. However, as with any construction project, the most important thing is to choose the right product for the right reasons.
For example, if certain levels of fire safety performance are required from a membrane, then it is important to use a product that provides that – even if it is not a PHI certified component.
Other products in the Proctor Group range include Procheck® A2 (an airtight vapour control layer) and Probreathe® A2 (an airtight, vapour permeable membrane). Both provide a reaction to fire classification of A2,s1-d0 alongside airtightness, and can be integrated into build-ups for Passivhaus projects.
Look for manufacturer support around installation
What sets Passivhaus-certified projects apart is their focus on quality assurance. Ultimately, it doesn’t matter if a design meets Passivhaus principles, or how well the chosen products perform. If the construction quality is poor, then the building will suffer from a performance gap.
Therefore, it can pay dividends to work with manufacturers who provide on-site support and toolbox talks. This is exactly what Proctor Group offers to projects across the UK, and has demonstrated on many of the Scottish Passivhaus school projects.
For several of those schools and community campuses, contractors were working on a Passivhaus project for the first time. By supplying on-site training on how to install Wraptite, we helped to set them up for success and ensure the installation met the required levels of quality.
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