Civil Engineering Building, University of Cambridge

The Civil Engineering building provides approximately 5000m² of laboratory, research and office space and includes a test laboratory with a large structural “strong floor”. This area is located at the heart of the building with its activity visible to visitors and academics. Daylight design combined with dynamic modelling helped to ensure that exemplary levels of natural daylight can enter the building without causing overheating, and the use of natural passive ventilation is promoted wherever appropriate.

The building was not connected to the site-wide district heating network, as this was not deemed compatible due to its low heat demand, instead a GSHP meets the minimal cooling and heating demands and allows inter-seasonal storage (the annual heat balance with ground is close to zero). A very high energy efficiency is achieved (COP=4, EER=5, SCOP=8). Photovoltaics were maximised. The rainscreen cladding insulation thickness was optimised at 300mm, for embodied energy, operational energy and cost (U=0.15W/m²K) compared to early stage proposals of 480mm (U=0.1W/m²K). A blue/green roof is used for storage and attenuation of rainwater and four large wind cowls, which are part of the natural ventilation strategy, also serve to house future ventilation exhausts or flues.

The Civil Engineering Building achieved a BREEAM ‘Excellent’ rating and an ‘A’-rated EPC. Analysis of its first year of operation is currently under review.

The building is designed to minimise energy use throughout its lifecycle, from concept through to demolition and has a number of key circular economy features:

• Choice of structural frame based on minimum life cycle energy calculations

• Design for longevity and/or adaptability

• Design for disassembly and reuse

Introducing new structure:

The ground floor raft provides an extremely flexible foundation solution and can support additional structure. It should be possible to build additional structure supported by the existing building, e.g. providing a roof over the second-floor terrace, within the residual strength of the structure. Although this will be subject to detailed analysis at the time of any future extensions.

Removal of sections of upper floor:

The upper floor’s 200mmm thick pre-cast pre-stressed hollow core concrete planks (spanning 7.2m) can be removed without compromising the overall structural stability, the steel frames can be retained. Although the slab can be removed in the future, specialist access for safe lifting and removal will be required and suitable options for reuse would need to be found.

Future expansion:

The University wanted to retain the potential to add future terraced extensions, to form a series of similar buildings. To facilitate this, shear connectors were cast into the north and south ends of the ground floor raft foundation; to limit relative settlement at the junction between buildings and transfer a limited load into the raft foundation.

Steel columns on the north and south facades can double the design axial load required for the existing building and have bolts holes for future connections; allowing the potential connection of another similar beam into the columns. Details for building movement joint and connection details to new structure will need to be developed to manage relative movements between the buildings.

The design was developed to facilitate in-use adaptation and reuse at the end of the building’s life. Design options included specification of concrete slabs that could be reused by adopting bespoke precast planks on a steel frame that was bolted together. Costing exercises resulted in the use of industry standard hollow core planks. Time was then spent developing connection details that maximised the opportunity for steel reuse at end of life. The final design focused on maximising reuse of the primary steel columns and beams, representing 45% of steel used in the building.

Instead of the usual practice of burying column baseplates in concrete, a pocket was left so that the covering can easily be removed, and the bolts undone. The same philosophy was applied to other connections so that the entire primary structure could be salvaged and re-used. This contrasted with the usual situation where major alterations or demolitions cause so much damage that steel components are sent for scrap.

Details were developed between the post-tensioned hollow-core planks and the steelwork to allow removal without damaging the steelwork, increasing the possibility of reuse. The openings in the beam webs for future services were rationalised; therefore, limiting any additional fabrication of primary steel sections which might limit reuse in future.

Mechanical and electrical services are not embedded in the building but left accessible for easy adaption in the future. Services arranged in modular grid bays allowing for labs and office spaces to be reconfigured to reflect the changing research works as well as changing groups and sizes within individual departments. Main electrical cabling is on 'hangman' service units from high level enabling ease of dismantling and reconfiguration.