Global Health Building
Client: University of Oxford
The brief
The University of Oxford challenged CPW to deliver the design of one of the University’s first certified Passivhaus buildings, providing:
detailed MEP consultant duties
Passivhaus designer services, including registration and engagement with the Passive House Institute
Energy and sustainability consultant services, including circular economy and whole lifecycle carbon analysis
Passive engineering services, including climate-based natural daylight analysis, thermal bridge detailing and thermal comfort studies
The Global Health Building will bring together the Centre for Tropical Medicine and Global Health with some of the Oxford Population Health department, aiming to improve treatments and save lives across the world. The development will support the University’s roadmap to operational net zero carbon and overall positive impact on biodiversity by 2035.
The design
Constructed across four floors, the 4,700m² building will accommodate around 400 members of staff with high-standard facilities including an agile-enabled, open-plan office setup, seminar spaces, global video conferencing facilities and SMART-connected amenities.
This building is set to be an exemplar for future developments and is designed to achieve Passivhaus Classic certification and go beyond Building Regulations and the Oxford Local Plan.
The development targets sustainability in all elements of its design, providing occupants with exceptional thermal comfort and air quality control, maintaining floorplan flexibility, while balancing this with optimised plant and services operation, high performance building fabric design, and the use of high efficiency building systems. These efficient design concepts are further complemented by an effort to minimise embodied carbon and utilise natural and renewable energy sources wherever possible.
Effective structural solutions
A research-led design process has dictated the final structural solution through iterative testing.
Four structural solutions were examined by our Digital Engineering team, ranging from heavyweight cast in-situ concrete to lightweight timber. Extensive dynamic modelling enabled us to understand the impact on the internal environment, level of MEP services complexity required to achieve project success criteria, and the resultant operational carbon emissions.
This quantitative analysis explored the following factors to determine best value for the University:
thermal comfort
embodied carbon
operational carbon
operational energy and utility costs
complexity of services
capital cost
buildability
Our findings pointed to a heavier construction approach being preferred. Plenty of built-in thermal mass meant that the building was able to retain heat in the colder months, and maintain thermal inertia throughout the night, until the occupants return the next day. Likewise in the hotter months, the benefits of cooling the exposed thermal mass in the building via night purge, dramatically reduced operational energy required to cool the spaces. This led to the leanest building services design, and overall best performance and return on investment.
Optimised building services
A lean building design has resulted in negligible building heat loss. A comfortable temperature within the building is maintained through heat recovery utilising the waste heat generated by occupants, equipment and lighting, for example, while during the colder months the building can benefit from trapping free solar heat.
The central atrium acts as a regulator for the wider building’s environment. We can cleverly manipulate this space through natural or mechanical ventilation, to either trap or release heat from the building, which then influences the environment of the surrounding spaces.
The office accommodation takes advantage of a displacement ventilation strategy, maximising the temperature and air quality control capabilities of the mechanical ventilation system. Climatic sensors throughout the structure monitor internal and external environmental criteria and guiding the transition between natural and mechanical ventilation, resulting in the most efficient approach to maintaining good indoor air quality.
We designed and specified a heating strategy that comprised Air Source Heat Pumps as the primary heat source, which are 4-6 times more carbon efficient than gas-fired combined heat and power. The design also incorporates solar photovoltaic panels to contribute to building electrical loads, solar thermal panels to feed a solar hot water system and a solar reservoir to harness generated heat via high efficiency heat exchangers.
Achieving Passivhaus standard
The Global Health Building is meticulously designed to meet the stringent requirements of the Passivhaus Classic certification.
Our building physics team explored various architectural designs and orientations, incorporating wind and solar irradiance analyses to optimise energy efficiency with minimal heat loss through the building's envelope. The team simulated multiple façade options to achieve a delicate balance between capturing winter sun, reducing summer overheating, enhancing daylight entry, minimising heat loss through solid structures, and using materials with minimal carbon footprint.
To create an exceptionally airtight structure, the building has been designed to surpass the Passivhaus requirement of 0.6 air changes per hour by using detailed architectural products, robust components, and airtight sealing techniques. This level of air tightness is five times greater than that of typical Building Regulation compliant buildings.
The design features components such as triple-glazed windows and materials with very low thermal conductivity to reduce heat transfer.
Our Passivhaus designers also conducted extensive thermal bridge analysis to mitigate heat loss at critical points where continuous insulation is unachievable, such as at service penetrations, floor intersections, and external building junctions. Addressing thermal bridges is crucial to prevent condensation and ensure even internal surface temperatures.
To meet a specific primary energy demand target, detailed user profiles were created that include expected use of electrical devices and IT equipment, and account for flexible working patterns, allowing us to estimate an average energy consumption per user, enhanced by automated lighting systems that adjust based on daylight and occupancy.
Our team developed several PHPP models—detailed tools for calculating a building's final energy requirements and evaluating different components and usage scenarios. These models were adjusted for various energy sources, material performance, building orientations, and operational patterns.
Ultimately, the building achieves a remarkably low heat demand, significantly below the Passivhaus Classic limit of 15 kWh/m²/annum, with projected values around or less than 10 kWh/m²/annum.
Tackling embodied carbon
Our dedicated team has conducted comprehensive embodied and operational carbon assessments, setting a milestone as the University’s first application of a Life Cycle Carbon Assessment (LCA). The results of this assessment were used to inform the University’s 2019/2020 Emissions Accounting Report, highlighting the longer-term impact of our work on the University’s processes.
Embodied Carbon Life Cycle Assessments have been undertaken throughout the design process to inform low carbon design and specification. After examining the results of the total predicted CO2 emission figures, it was clear to our team that grid decarbonisation would have a massive impact on an all-electric building over a 60-year life-cycle. The Stage 4 assessment estimates the embodied carbon as 891 kgCO2e/m², which shows more than a 10% improvement compared to the GLA target for education buildings.
Stakeholder engagement
Through close engagement with University of Oxford stakeholders from the Estates and Medical Science departments, we have ensured that the design is future proofed, accommodating for remodelling and repurposing, as well as ensuring a clear understanding of the Estates’ pipeline to extend the usable life of the building.
The outcome is a spatially coordinated design, aligned to project stakeholder consultation feedback, incorporating lessons learned and the review of precedents.
Targeting Passivhaus Classic Certification
Targeting Oxford City Council Local Plan compliance
Predicted EPC A
On track for 40% reduction in carbon emissions compared with 2013 Building Regulations
Images courtesy of Associated Architects.
Want to find out our net zero carbon offering? Visit our service page.