Scotland’s First Passivhaus-Certified Primary School, Featuring Wraptite® External Air Barrier, Nominated for Multiple Awards

A key component in the building fabric specification was the A. Proctor Group’s Wraptite® airtightness membrane. Installed to the external side of the structural frame, the fully self-adhered membrane contributed to an overall airtightness test result of 0.53 air changes per hour (ach) at 50 Pascals. The Passivhaus standard requires 0.6 ach or lower.

Meeting the Passivhaus standard was key to unlocking funding from the Scottish Futures Trust Learning Estates Investment Programme. By achieving the target, the school can be expected to use 50% less energy than a similar school that doesn’t meet the standard. Post-occupancy monitoring is taking place to measure in-use performance against expectation.

As well as pioneering Passivhaus school construction in Scotland, Riverside Primary was also one of the first steel-framed Passivhaus projects in the whole of the UK. Steel frame construction introduces specific technical challenges, especially in terms of minimising heat loss through the frame members and guarding against any risk of interstitial condensation.

Using Wraptite moves the airtightness barrier to the exterior face of the wall, avoiding complex detailing around services and other typical penetrations at the internal face. As it is also vapour permeable, Wraptite helps to achieve high standards of airtightness without increasing condensation risk in the structure.

Kevin Dickson, Regional Managing Director at main contractor Robertson Construction Tayside, said:

“We consistently deliver high-quality projects for our customers, and our supply chain plays a key role in that success. The membrane used, Wraptite, was part of the construction for the Passivhaus school and provided several benefits.

“Membranes work best with a consistent surface, which posed a challenge given the steel-framed construction of the school. However, as a business committed to continuous improvement, we saw this as an opportunity to advance our Passivhaus knowledge and learn from this project alongside the architect Architype.”

A benefit of choosing Wraptite was that it supported a local supplier. The membrane was supplied by A. Proctor Group from nearby Blairgowrie, contributing to the local economy.

“Architype originally specified a loose-applied, taped membrane solution,” explained Kevin Dickson, “but as a local contractor, we prioritise using a local supply chain to deliver benefits in the areas where we work, so chose A. Proctor Group and its Wraptite product. As a fully-adhered solution, it removed the need for tape, making it less labour intensive, quicker to install and more economical.”

Overall, the Wraptite solution lent itself to the on-site quality checks required for Passivhaus accreditation.

Writing in the Architect’s Journal, Sam Boyle, associate at Architype, said:

“Technical expertise was required to ensure delivery, both in detailing and upskilling the contractor team. A collaborative and no-blame culture was fostered throughout the project by all.”

As part of this, Architype presented toolbox talks as part of their project support.

“Riverside Primary set the benchmark in Scotland for Passivhaus schools, and we look forward to continuing our successful delivery of Passivhaus projects for our customers,” said Kevin Dickson.

Robertson Construction Tayside is currently working on three more new-build Passivhaus school projects:

• Perth High School
• East End Community Campus in Dundee
• Monifieth Learning Campus

Find out more about Wraptite.