Trial / Demo
This pioneering Welsh school campus is a Net-Zero Carbon in operation (NZCio) facility. Designed with IESVE software by the Arup building physics team, it sets a new benchmark for sustainable educational environments and future climate resilience, backed by a rigorous 25-year performance commitment.
The new Mynydd Isa Campus is an ambitious project, providing a modern learning environment for 43 nursery pupils, 600 full-time primary pupils and 700 secondary students. Arup successfully bid for this significant programme in 2021 and subsequently worked with the Welsh Education Partnership Company (WEPCo), Sheppard Robson Architects and Robertson Construction Group. The project was developed under the Mutual Investment Model (MIM), part of the Welsh Government’s Sustainable Communities for Learning Programme. The design for the two-storey, 10,500m² campus was delivered in 2023, and the construction was completed in 2025.
Building Physics and Climate Resilience
The exacting brief stated that the building must perform optimally for a further 25 years, with a Project Company (Project Co) setup at Financial Close to lifecycle and provide hard FM. Using IESVE to perform dynamic simulation modelling, Arup focused on building physics, particularly energy and thermal comfort, comparing actual performance against the design and adjusting parameters accordingly with real-world data. Beyond standard BB101, the scheme met CIBSE TM52 for preventing overheating and proved resilient against future weather file changes up to 2050, anticipating a two-degree temperature increase in that time. IESVE was used to establish overheating risks under various climate scenarios, including typical years, warm summers and prolonged heatwaves.
With mechanical cooling essentially off the table in pursuit of NZCio, Arup also tested the early designs parametrically to include air tightness, driven by contractor build quality, and analyses of glazing and system efficiencies.
Optimising Energy Efficiency with Dual-Mode Ventilation
The use of IESVE helped to find the optimal ventilation solution for energy efficiency, leading to a dual-mode operation. In winter, windows and chimneys remain closed, with the space conditioned via Mechanical Ventilation Heat Recovery (MVHR) units. These units recover heat from outgoing air, significantly reducing heating energy demand. In summer, the MVHR switches off, and the building shifts to natural ventilation mode with windows and chimneys open. A ‘traffic light system’ in classrooms alerts teachers when to fully open the windows if overheating is detected.
The campus design brings together the primary and secondary schools as separate ‘finger’ blocks, joined by a shared entrance, secure reception and kitchen. The finger-block formation provides separation between primary and secondary teaching areas, while enabling a balanced relationship between external learning and recreation spaces. The design inherently maximises natural ventilation and daylighting, while minimising overheating through east-west orientation.
Net-Zero Carbon in Operation (NZCio) building
From the early concept stage, Arup and the team made the bold step in agreeing that the NZCio definition should be all-encompassing, to include regulated energy (used in operating the building) as well as unregulated energy consumption (energy by building users). Educational buildings have an advantage in having lower energy consumption generally due to reduced hours of occupation, which made achieving NZCio more viable.
Working closely with architects, the building's two-storey layout was optimised to maximise roof space for PV panels. 1,080 solar panels were installed across 2,500 m² of rooftop space and the system is expected to produce over 500,000 kWh of electricity annually, cutting carbon emissions by more than 100 tonnes each year.
The team continuously developed and refined the sophisticated and complex IESVE model to maintain NZCio status. Cross-ventilation had to be integrated within the spaces, ensuring airflow between façade windows and out through specially designed chimneys that facilitate air movement. Extensive testing and scenario modelling through IESVE was performed ensuring a better understanding of the building's long-term performance. The software also proved invaluable in highlighting the need for airtightness testing, a critical aspect given the building's pressure testing requirements.
“I feel honoured to have worked on this project from the very beginning and take it through to completion. IESVE modelling helped play a significant role in the design of the scheme, from developing the complex cross ventilation chimney concept to achieving NZCio. It’s an incredible achievement that the building generates as much energy as it will consume over the course of a year.”
Steven Burrows, Associate Building Physics Engineer, Arup
Performance Insights and Promising Results
This project not only achieves Net Zero Carbon in operation (NZCio) but also boasts a BREEAM 'Excellent' rating, demonstrating a strong commitment to sustainability. Looking ahead, the project aims to meet a maximum embodied carbon target of 800kgCO2/m², further solidifying its sustainable credentials.
Since its opening in April, the school building has received very positive feedback. IESVE software was instrumental throughout the project, particularly in the detailed and process-driven phases. It allowed for comprehensive parametric testing early on, which then transitioned into refined ventilation design for optimal thermal comfort. This led to crucial energy modelling and validation, highlighting sensitivities and any areas needing attention.
A fascinating insight from the detailed energy model, as illustrated by the energy breakdown Sunburst chart is the significant weighting of unregulated energy in a low-energy building of this nature. For example, small power equipment and computers account for 25% of total electricity consumption and, when combined with catering and server consumption, this figure jumps to 45%. This information is vital to understand the broader scope of energy consumption beyond the building's operational systems.
“I was delighted to represent the Council’s Climate Change committee and see this remarkable project coming to life. It not only reflects our commitment to high-quality education but also to a greener, more sustainable future for our children.”
Councillor Mared Eastwood, Flintshire’s Cabinet Member for Education, Welsh Language, Culture and Leisure
"We're delighted with the net zero carbon solution for this project. A first of its kind for MIM, we are thrilled with the completed building which demonstrates how state of the art education facilities can be built responsibly. Together with our construction partners, WEPCo is proud to have been entrusted with delivering this special 3-16 education campus for Flintshire County Council and the communities of Mynydd Isa, now and into the future. Diolch yn fawr."
Neil Cutting, General Manager, Flintshire Schools Limited (Project Co)
