A first-year assessment of Riverside Primary School, Scotland’s first Passivhaus-certified primary school, has revealed actual energy operational performance to be significantly below the Passivhaus primary energy demand target.

With an energy assessment of just 43 kWh/sqm/annum, Riverside is significantly outperforming the classic Passivhaus target of 60 kWh/sqm/annum.

Riverside Primary School is part of Perth & Kinross Council’s capital programme of school upgrades and improvements through hub East Central Scotland Limited.

And Perth & Kinross Council appointed BakerHicks Motherwell to provide mechanical and electrical design services on the project for principal contractor, Robertson Tayside.

In Scotland, local authorities are required to pay upfront for the delivery of new schools, with Scottish Government providing funding through the Scottish Futures Trust (SFT) on an outcomes-based funding approach over 25 years.

And projects need to meet a clear delivered energy target of 67kWh/m²/yr for core hour/facilities with energy performance and outcome monitored at set intervals.

Where the energy target is not achieved in full, funding is reduced correspondingly.

David Coulter, associate engineer and certified Passivhaus designer at BakerHicks said: “Achieving the energy target was absolutely crucial, both to achieve Passivhaus accreditation and to ensure SFT funding for the council.

“When designing the system, the hot water strategy was one of the main challenges as we needed to avoid large-scale energy usage and heat losses.

“We wanted to explore using all-electric point-of-use solutions that would only generate energy when required, for example during break or lunch times.”

Key to this approach was the use of Baxi’s Heatrae Sadia point-of-use electric water heaters (pictured below).

These can be an efficient solution to an immediate supply of hot water for washbasins and kitchen areas in buildings like schools.

And they incorporate anti-legionella functionality, water pasteurisation, and anti-tamper design to ensure that water is adequately stored, cycled, and distributed.

Coulter said: “A key benefit of these water heaters is that the units are sized, thereby providing more flexibility to meet the required volume. This meant that we could look to design down to avoid oversizing, where appropriate and so ensure the most-efficient operational performance.”

To achieve Passivhaus certification, Riverside Primary School needed to undergo a rigorous quality assurance compliance process to ensure the targets would be met.

Coulter said: “It was an exacting process.

“We needed to supply detailed calculations and evidence relating to the energy values of the selected technologies.”

With the recent report on energy operational performance demonstrating the success of the solution, BakerHicks now uses this design as a template for future projects, even where Passivhaus standards are not applied.

Coulter said: “We are pleased to see these energy results and are delighted that the building is operating far more efficiently than initially projected.

“The data shows significantly-lower energy consumption, which demonstrates the importance of strong operational performance and effective energy management.

“The client team and end users have adapted well to the Passivhaus strategies, learning valuable lessons learned along the way and this marks a promising step forward for future projects and building services solutions.”