Article - Issue 13, August 2002
Design for green – Jubilee campus, Nottingham
John Berry, Special Professor in Building Technology at University of Nottingham John Thornton, Visiting Professor in Structural Engineering Design at University of Newcastle
The new Jubilee Campus at the University of Nottingham is designed as an environmentally friendly development, incorporating such features as photovoltaic cells in the roof and use of recycled newspaper for insulation. The 18 acre site was developed on a budget comparable with similar academic building projects with the objective of keeping energy costs low and ensuring a good fit with the surroundings. It houses facilities for three departments in addition to halls of residence for some 300 students, as well as new bulidings for support services. John Berry and John Thornton describe the ideas behind the new campus.
Sustainable development is one of the biggest challenges facing our generation. People in Europe spend more than 90% of their lives in buildings and over 30% live in urban settlements. The building sector accounts for almost 50% of the developed world’s energy consumption and gives rise to the majority of the greenhouse gas emissions. The impact of the built environment is thus profound. It is easier to talk about these issues than to act, but engineers are well-placed to take the lead in the innovative thinking necessary to translate idea to reality.
The Jubilee Campus is an example of what can be achieved when client, architect and engineer have the same objectives. A design competition was held by the University of Nottingham in 1996, to choose a design team of architect and engineer for their new Millennium Campus. An enlightened brief placed a strong emphasis on environmental issues, in choice of materials, emissions of the buildings and the landscape within which the buildings sit. Choice of site was important in the context of the goal of sustainable development. Aware that further development of the current Highfield Campus would upset the balance between buildings and parkland, the University decided to develop a new campus one mile away. Also conscious of the current strength of opinion against greenfield development, in 1996 it acquired a derelict 18-acre industrial site which was once the Raleigh Cycle factory. The client brief called for an exemplary low-energy and environmentally cohesive development, which would, by example, disseminate environmental awareness and demonstrate the viability of practical, affordable and sustainable regeneration as part of the educative process. This brief, as well as the site, presented an opportunity for our team of Michael Hopkins & Partners (architects) and Arup (engineers) to develop our thinking and experiences from earlier low-emission/ low-energy buildings and research studies. The Inland Revenue Centre in Nottingham, Portcullis House at Westminster and two European Commission research studies under the Joule II programme informed our approach.
Features of the first phase
The budget at £1000 per m2 was no different from other university projects and called for a clarity of approach to satisfy these ambitions. Initially, there was to be a master plan for the entire 18 acre site, comprising three faculty buildings of Education, Computing Science and Management & Finance. In addition, there would be a Learning Resource Centre, a central lecture theatre complex, central catering facilities and halls of residence for 300 students – in total, an area of some 40,000 m2 of academic space. The first phase was to comprise a School of Management & Finance, a central lecture theatre and a post-graduate hall of residence for 150 students. These were to be completed in October 1999, to mark the Golden Jubilee of the university.
The university set ambitious goals for ground management, including promoting new habitats for wildlife and ecology, while preserving the diversity in the existing woodland. The belt of mature trees at the boundary with the adjacent houses was the key to the organisation of the site. A new lake was formed next to these trees, which distances the university buildings from the houses and is an essential part of the water management scheme. It collects and cleans rain-water and car park run-off. The faculty buildings face south-west onto the lake, taking advantage of the prevailing winds and optimising passive solar gains. The buildings are restricted to three storeys, to optimise daylight to the spaces in and around the buildings and to encourage the use of stairs, rather than lifts.
The university is committed to using products from renewable sources and to recycling waste. This policy touched all parts of the construction process, from the cedar redwood cladding with its recycled newspaper insulation, to the cut and fill balance of the lake, which ensured that all excavated material remained on site. The lake makes a significant contribution to the wildlife habitat; less obvious is that of the ‘green’ roofs to the buildings.
Integrating engineering and architecture
The underlying concept of our design integrates the often contradictory requirements of architecture and engineering. Architectural and engineering elements are combined to fulfil more than one function, such as: exposed concrete soffits to dampen internal temperature swings, photovoltaic cells laminated into clear glass as shade devices and the use of stairways, corridors and floor voids as low-pressure air paths. This holistic approach made the most of the budget, as well as providing the principle which guided the development of the design. A successful outcome from such an approach is a team effort. The engineer has a view on the architecture, the architect has a view on the engineering and they share the vision of the project as a whole.
The engineer’s role in the design of these buildings is interesting in that much of the thermal engineering is realised in architectural components, but the ultimate performance in terms of indoor climate, energy and CO2 emissions depends on a comprehensive analysis of the total system: the building fabric and the mechanical and electrical systems. There can also be difficulties when components are used differently from usual and workers do not fully appreciate the importance of additional requirements, such as, for example, restrictions on leakage through a raised floor when it is used to supply air.
Integrated environmental design is a combination of active and passive systems and, in these terms, the structure is a passive thermal element, as well as the principal means of support. The expressive structures of our other projects were replaced by the simplest possible solution of a flat slab supported by columns on a 6 m x 6 m grid. Both sides of the structure are in contact with the air supply, to optimise the thermal behaviour. With this approach, we achieve the lowest cost structure with the optimal thermal performance, while satisfying the architectural needs.
We decided, at the competition stage, to use mechanical rather than natural ventilation. An innovative feature is the ‘super efficient ventilation system’ operating in mixed mode. Feedback from the Inland Revenue building, also in Nottingham and the conclusion of two successive EEC Solar House Joule II research projects into the low-energy workplace indicate that both internal comfort and energy consumption are improved by adding mechanically assisted ventilation with heat recovery.
The addition of air distribution systems with low pressure components and heat exchangers provides adequate minimum ventilation to deep plan areas and partitioned cellular rooms, while minimising energy loss through heated or cooled ventilation exhaust air. If the fresh air intake is placed at roof level, avoiding street level pollution, the addition of dynamic non-ionizing electrostatic filters and a thermal heat recovery wheel enables 100% fresh air to be supplied to all interior volumes without recourse to recirculation. The faculty buildings incorporate tracking wind cowls to reduce the requirement for electric fan power for air exhaust. The use of the building itself provides low-pressure air paths via corridors, stair towers, builders-work supply shafts and the raised floor.
In summer, the exposed thermally massive concrete floor slabs store ‘coolth’ from night to day, creating cooler internal conditions than outside. Evaporative wet pack humidifiers, integrated with the low-pressure air plant, provide additional passive cooling via the thermal heat recovery wheel in peak summer conditions.
Thermal wheels are rotary heat exchangers. In winter, the heat of the exhaust air is absorbed by an aluminium rotor, which then delivers the heat to the supply air; and vice versa, in summer. Rotary heat exchangers are used when the supply and exhaust air ducts converge at one point. Low velocities through the rotor ensure optimum heat exchange efficiency of 84% and pressure loss of 60 Pa. Typically, each thermal wheel is 2.4 m diameter, 400 mm deep, weighs 0.58 tonnes and has a heat exchange surface area of 2,300 m2.
The mixed mode ventilation system combines the advantages of natural and mechanical ventilation, without the high electrical consumption penalty of standard mechanical ventilation systems. The unique combination of low pressure-loss components results in a building that uses no more electricity than a naturally ventilated building, recovers heat to minimise the thermal energy loss through ventilation in winter, stays cooler in summer through passive evaporative cooling and provides significantly improved conditions year round.
The ventilation units and tracking wind cowls are integrated into the roofs of the stair towers to give a direct connection to the supply ducts on either side of the stair and the exhaust duct, which is the stair itself. These specially designed and manufactured units are an innovative design, providing energy-efficient performance. A principal area of innovation is the component arrangement, using very low pressure-drop devices, bypassing components when not in use and avoiding the pressure loss of heating and cooling coils in the supply train. The total power of 0.4 W per litre per second of air delivered and extracted compares with the 1.0 accepted as excellent by the Scandinavians, who lead in many areas of environmental managements, and the 2.5 for a typical system.
Light shelves in the façade reflect light up to the ceiling, to enhance internal daylight levels, while shading the floor to reduce overheating from solar gain in summer. Daylight and movement sensors minimise the use of artificial light, reducing the cooling load and electrical consumption.
Active renewable energy sources tend to be associated with conservation measures and the very low-input fan powers make it feasible to supply them using photovoltaics. Some 450 m2 of photovoltaic cells are integrated into the roofs of the atria. The monocrystalline cells are installed between two 6 mm sheets of toughened glass, the upper sheet is a low iron glass. Providing shade as well as power, the installation delivers 51 MWh per annum with a peak output of 54.3 kW. This is a significant contribution to the annual electrical consumption of the supply and extract fans.
Working with others
Support for our ideas came in the form of an EU THERMIE grant for 1.3 million Euros, which enabled us to develop and incorporate the innovative sustainability features of the development. A spin-off from the grant was performance monitoring, which started six months after completion and lasted for one year. This provided the opportunity to work closely with the School of the Built Environment at the University and to take full advantage of the information available, which has led to an enduring partnership.
The project was awarded the RIBA 2001 Sustainability Award and has become symbolic of a forward-looking institution.
SPECIAL PROFESSOR IN BUILDING TECHNOLOGY, UNIVERSITY OF NOTTINGHAM
VISITING PROFESSOR IN PRINCIPLES OF ENGINEERING DESIGN, UNIVERSITY OF NEWCASTLE
John Berry is a Director at Arup and holds a Special Professorship in Buidling Technology at the University of Nottingham. He is a Building Services Engineer with interests in integrated design, energy conservation and green buldings. He advises the EU on energy strategy under the ENERBuilD programme and is currently working in Copenhagen.
John Thornton, Structural Engineer, is a Director at Arup and a Visiting Professor in Principles of Engineering Design at the University of Newcastle. He has worked on many award-winning buildings and has particular interests in membrane structures, precast concrete and integrated design.