The focus on closing the performance gap for more energy-efficient newbuild schools is causing a rethink of the hot water strategy to avoid large scale energy usage. Rob Erwood, Commercial Sales and Specification Director at Baxi, discusses the uptake of Passivhaus standards for newbuild school programmes and the options for meeting the hot water demand efficiently.
In the drive to meet tighter efficiency requirements for newbuild schools, focus has intensified on designing buildings that achieve reliably high comfortable levels all year round with consistently reduced energy use. This had led to an uptake of Passivhaus design standards to deliver local authority newbuild school programmes – particularly in Scotland where 35 Passivhaus schools are underway.
On the surface, Passivhaus school buildings will look no different to other schools. But their future proof design, optimised for net zero with reduced heat losses, results in ultra-low energy demand and an excellent indoor environment. The challenge, arguably, lies in the hot water design.
Point of use solutions
When it comes to heating, school buildings built to the Passivhaus standard are designed to require less energy for heating. But the hot water design is central to achieving buildings that are truly energy efficient, environmentally friendly and economical to run.
One option to meet the hot water demand is to use point-of-use electric water heaters or cylinders in areas like washrooms and kitchens as they only use energy when hot water is required. This makes it much easier to monitor, measure and control hot water usage as well as keeping any hot water pipework runs to an absolute minimum to avoid heat transfer losses.
Reducing the kilowatt rating and capacity, increasing control and lowering flow rates will be further considerations. Selecting products with enhanced controls such as a smart thermostat can also help with energy management as it can learn the pattern of hot water usage in the school building over a period of time.
Mind the gap
Take Riverside Primary School, one of the first Passivhaus standard primary schools in Scotland and the first to achieve certification. Rigorous and continual quality verification, which must be evidenced to achieve independent certification, means that this Passivhaus building operates as predicted, with no gap in efficiency levels at the design stage and real-world operation.
The new multi-million-pound school is part of Perth and Kinross Council’s ongoing capital programme of school upgrades and improvements through hub East Central Scotland Limited (hubco) to enhance the environment for learning and teaching across the area.
Instrumental in forming the energy strategy for Riverside Primary School was the multi-disciplinary design, engineering and project delivery company BakerHicks Motherwell, appointed by Perth and Kinross Council to provide mechanical and electrical design services for principal contractor Robertson Tayside.
Avoiding large scale energy usage
Riverside Primary School is designed to be well suited to low-carbon heating. Air Source Heat Pumps (ASHPs) provide the primary heat energy for the school building with separate systems for the heating services, including radiators and underfloor heating and the kitchen domestic services, where the ASHPs provide preheat to a Megaflo Eco hot water cylinder.
“The hot water strategy was one of the main challenges when designing the system as we needed to avoid large scale energy usage,” explained David Coulter, Associate Engineer and Certified Passivhaus Designer at BakerHicks. “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. So, we asked Baxi for help with the solution.”
Baxi’s Public Health technical sales and specification team, headed up by Stephen Lynch, worked with David to identify the selection of equipment required to meet the hot water demand efficiently at Riverside Primary.
“A key benefit of the Heatrae Sadia water heaters is that the units are sized, thereby providing more flexibility to meet accurately the required volume,” David added.
In total, seven Heatrae Sadia Multipoint 15 units, six Multipoint Eco 30, three Hotflo 10, two Hotflo 15, 24 Aquaheat 7 as well as the Megaflo Eco cylinder have been installed within the new school building.
Educational process
Using the Passivhaus standard brings major advantages to schools, making them more efficient and cost-effective to operate and maintain, and helping them meet sustainability goals and lead by example.
However, the concept calls for outside-the-box thinking to achieve the most energy-efficient hot water design strategy. This makes it an educational process for designers and school estates managers alike, as it encourages a rethink of hot water consumption to avoid large scale energy usage and prioritise energy savings.
With Passivhaus certification successfully achieved at Riverside Primary School, which is now nearing the end of its first term, Perth & Kinross Council has achieved its commitment to enhance education provision for children north of Perth and taken a step closer to its net zero carbon ambitions – with the hot water strategy and point-of-use electric water heaters playing a critical part in its success.
Heatrae Sadia is part of Baxi. For more information on the Heatrae Sadia point of use water heater range, visit: https://www.heatraesadia.com/products/