Passivhaus Targeted Student Accommodation
The Purdown View project for the University of the West of England is set to be one of the world’s largest student accommodation schemes designed to Passivhaus standards. QODA Consulting is the Lead Passivhaus Designer on the project.
Below, Principal Sustainability Engineer Alex Bunn explains QODA’s influence as Passivhaus designers on this exciting project.
In 2020, the University of the West England (UWE) in Bristol declared a climate and biodiversity emergency. Shortly after, UWE published the ‘University Strategy 2030’, which included a key target to become carbon neutral as an organisation with net-zero emissions by 2030.
Targeting Passivhaus Classic Certification
Working with UWE early in the project’s conception, QODA helped to define the sustainability aspirations of the University’s newest student accommodation scheme. During these discussions with key stakeholders, it was agreed that the new development should target Passivhaus Classic Certification.
Passivhaus buildings provide a high level of occupant comfort while using very little energy for heating and cooling. They are built with meticulous attention to detail and rigorous design and construction according to principles developed by the Passivhaus Institute in Germany.
Concentration on form factors at early stages starts the building design on a path to energy-efficiency performance and can reduce construction complications and costs.
The Purdown View scheme comprises three buildings, providing beds and communal areas for 900 students over 26,000m2 in a mix of four, six, and eight-bed clusters. With a gross development value of £77m and an estimated construction value of £60m, the construction work started in 2021 and is due to be completed in December 2023.
3D image of southern elevation produced by Architects Stride Treglown, showing that large windows are possible in Passivhaus design with summer overheating mitigated by passive features.
Pioneers of large-scale Passivhaus
Passivhaus projects of this scale were not common at the time of design, therefore QODA worked closely with Architects Stride Treglown using simple geometries to create low-form factors for the buildings, an important feature for Passivhaus buildings.
Low-form factor buildings are designed to use energy more efficiently. The shape has been designed to minimise the outside surface area of the building compared to the amount of space inside, relatively reducing the amount of heat that can escape through external surfaces in cold weather.
Low-form factors in buildings also help reduce complexity when designing for airtightness and minimising thermal bridges. This is due to the simplicity of low-form-factor buildings having a reduced number of construction junctions. Concentration on form factors at early stages starts the building design on a path to energy-efficiency performance and can reduce construction complications and costs.
The rigorous standards of Passivhaus Certification were one of the reasons UWE chose to target the standard for their new student accommodation.
The primary principle behind Passivhaus is a highly efficient building shape and envelope. The envelope consists of well-insulated walls, roofs, and floors, along with high-performance triple-glazed windows. These significantly reduce the heat transfer between the interior and exterior of the building. Additionally, the building is designed to be airtight, minimising air leakage and ensuring that the indoor climate remains stable.
Key features of the Passivhaus design
Building Services for energy efficiency and comfort
Whole building ventilation systems at Purdown View have been designed to operate constantly at a low rate, providing fresh filtered air while extracting stale air. The Heat Recovery Ventilation system also recovers the heat from the outgoing air to preheat the incoming fresh air. This approach helps maintain a healthy indoor environment whilst minimising heat losses.
The building has been designed without energy-intensive air conditioning systems, as the high-performance envelope will also reduce peak summer temperatures experienced internally. This approach is supported by the natural ventilation strategy, which was extensively tested for each room using thermal modelling software. The models demonstrated that the building will be able to maintain comfortable temperatures in summer as well as winter. Large windows can be opened by building occupants to increase airflow into the building and improve internal comfort levels if temperatures get high.
In winter, warm, stale air is extracted from the rooms and passed through a heat exchanger to warm the fresh air from outside. The fresh air is then passed over a heater battery to further warm it before being introduced to the rooms.
In summer, warm, stale air is extracted from the rooms and replaced with fresh air from outside. Occupants can increase airflow to rooms with large opening windows to maintain thermal comfort.
Rigorous modelling approach
The rigorous standards of Passivhaus Certification were one of the reasons UWE chose to target the standard for their new student accommodation; the buildings are required to meet strict energy efficiency criteria, including a maximum annual heating demand and a maximum air leakage rate. Etude has acted as the Passivhaus Certifier on this project, and QODA has worked closely with Etude to develop the Passivhaus modelling of the buildings. This has been achieved via specialist software from the Passivhaus Institute. The PHPP (Passivhaus Planning Package) has been used to verify the design and takes into account every facet of the design and construction of the buildings.
This project sets an example for large-scale Passivhaus developments and stands poised to redefine the possibilities of campus living.
Teaming up with the Contractor
Vinci Construction was appointed as the Principal Building Contractor and has collaborated with QODA to understand the importance of detail and quality in Passivhaus construction. A key area of concern was the stringent Passivhaus air tightness limit of 0.6 air changes per hour (under building air-testing conditions), which was identified as a key priority from the beginning. QODA and Vinci worked together to design and install a façade that could achieve the required airtightness rating. In support of this goal Vinci performed airtightness testing on façade mock-ups at their Technology Centre, providing confidence in the proposed installation.
The University of West England’s Net Zero Carbon targets have driven this ground-breaking project, which puts sustainability and innovation at the heart of student accommodation design. By embracing demanding Passivhaus standards and weaving energy efficiency principles into every facet of its design, UWE has demonstrated a steadfast commitment to a low-carbon future.
This project sets an example for large-scale Passivhaus developments and stands poised to redefine the possibilities of campus living, offering a glimpse into a more sustainable and comfortable future for students while reducing operating costs for the University.
The student accommodation has been designed to provide comfortable internal conditioning in both summer and winter, and the University is predicted to find reduced costs of 40% and reduced emissions of 71%, associated with space heating demand when compared with regulation student accommodation built to the current Building Regulations.
QODA are excited about the imminent completion of Purdown View and will work closely with UWE to understand and fine-tune the building’s in-use performance as part of our ongoing Soft Landings work.