his project for Jesus College, Cambridge University, provides high-quality, exemplary commercial accommodation on a site in the centre of Cambridge. It is the ‘greenest’ office building in Cambridge, achieving BREEAM ‘Excellent’ and following BCO standards.
Gort Scott and the design team delivered all aspects of the project from concept through to internal fit out. This project demonstrates use of innovative design and building technologies to create a highly sustainable building that responds to its historic urban context in a bold yet sensitive manner. The requirement was to make a building that would serve as a lasting asset to the College and make a positive contribution to the surrounding area, much of which is also owned by the College.
The design responds respectfully to its neighbours but also has a distinct identity that is not compromised by the onerous planning requirements of the Conservation Area, and Listed buildings on three sides.
Inside, Gort Scott has delivered a series of high-quality, environmentally comfortable, naturally ventilated and flexible open-plan office spaces that are made of robust and long-lasting materials. Within one modest scaled building a variety of different internal spaces have been created and end users are very positive about the comfort, atmosphere and design of the building.
The brief was for a speculative commercial office building, for rent, on a site in the centre of Cambridge. The building had to achieve BREEAM Excellent, follow BCO standards and demonstrate excellence in terms of design. The building had to be made of robust, long-lasting and sustainable materials.
3 key challenges
• Planning:
The site is in a Conservation Area with Listed Buildings on three sides. Consent was achieved through careful consideration of the context and history of the area.
• Conflict of acoustics with natural ventilation strategy:
The entire office is passively ventilated – there is no mechanical plant. However, it was not possible to utilise cross ventilation due to the noisy high street location, therefore vertical stacks were integrated into the design and in themselves became key to the expression of the building.
• Flexibility:
There was no pre-let agreement with tenants, and the College intends to maintain ownership for many years. Therefore, flexibility in allowing the building to be divided into multiple and changing ownerships was important. This was achieved through careful planning of the building and management systems.
Innovation
• Environmental integration:
The key innovation was the seamless integration of the environmental strategy into the design and delivery of the building, avoiding ‘bolt-ons’, resulting in a high-quality, unique and characterful building. The natural ventilation stack chimneys located on the corners of the building, are expressed on the facade with the bespoke, snapped header brickwork.
• Scale of spaces:
The modest scaled office building occupies a gap in the market for quality office accommodation in Cambridge. The majority of office space on the market is in stacked, deep plan buildings which are more generic in nature.
• A good High Street building: Gort Scott has taken the context of the building very seriously. The building has a clear front, flank and rear. The entrance is through a colonnade past a small walled garden which provides visual amenity to the street and a break out space for the offices.
The key to delivering the client’s demanding brief was to ensure that the environmental strategy was fully integrated into the building. For example, the need for thermal mass drove the structural strategy of an in-situ concrete frame utilising the exposed concrete soffits and walls in the common parts to provide thermal mass to even out yearly temperatures. In turn, careful detailing and coordination of services with the in-situ concrete elements was required to ensure that the quality of the building was maintained.
Long-term vision
Multiple-occupancy was considered early on, as the end tenant was not known and is likely to change in the future. The building plan and servicing allows for the property to host up to seven independent small/medium sized businesses, or each floor could function independently, or the whole building could be occupied by a sole tenant equally well.
The entrance area can function as a general entrance for multiple units, or be used as a manned reception. Lift access is provided to all floors.
The raised access floor with fully adaptable servicing, provision of solar shading and lighting and acoustic attenuation on the soffit, ensures that the open-plan spaces are flexible to any layout and alternative use, while still being an environmentally comfortable place of work.
Concrete soffits and exposed conduits will allow for re-positioning of lights should this be required. The location of the stacks and ventilation louvres allow for the open plan arrangement to be divided into cellular offices or meeting spaces should this ever be desired.
Technical solutions
The need for thermal mass drove the structural strategy of an in situ-concrete frame utilising the exposed concrete soffits and walls in the common parts to even out yearly temperatures. This also drove the raised access floor (with underfloor heating), servicing strategy of surface mounted conduit and lighting, and the requirement for acoustic panels.
Natural ventilation for the majority of the offices is driven by the open chimney stacks, that are expressed in decorative snapped header brickwork externally. Fresh intake air was provided via louvres at the quiet rear (garden area) of the building, which have timber screens to conceal them. To maintain the open vents at the top of the chimney, rather than closing with louvres, Max Fordham and Gort Scott developed a series of shelves with external drip trays to catch any driving rain.
Intake air from the rear was not possible in one ground floor office, meaning the added complexity of getting intake air from the noisy Hills Road side. This was integrated by creating acoustically attenuated ‘cupboards’ internally with the air coming through hit and miss brickwork. This is a practical and decorative means of achieving the environmental strategy.
All of the details were worked through to achieve an air tightness of 5 pascals and a high U-value.
BREEAM certification
The building is the highest scoring BREEAM ‘Excellent’ building in Cambridge City. The interim assessment rates the building as BREEAM ‘Excellent’, achieving a high 77 points (the threshold being 70). The final assessment is being processed by BREEAM currently. This is likely the highest score that could reasonably be achieved on this constrained site. In order to achieve ‘Outstanding’ more renewables would be required for which there is physically not enough space.
Specific environmental measures
As part of the Considerate Constructors Scheme and for BREEAM recycling measures were put in place throughout the works. The Green Lease for future tenants also includes this.
Renewable energy sources used are Gas Source Heat Pump and Photo-voltaic panels on the roof. The green guide was used when specifying finishes, fixtures and fittings. Water-saving sanitaryware fittings are used throughout. Embodied energy was considered from an early stage. A key consideration was the concrete frame, adding a high percentage of GGBS to reduce the overall environmental impact of the concrete. Due to the benefits of the thermal mass of the concrete and its importance for the environmental strategy, the use of concrete is the most sustainable frame strategy, when considered over the building’s lifetime.
Areas of landscaping with trees, green roof to the cycle shelter and public seating and planting, benefit the end users and neighbours to the building, along with vastly improving the ecology of the site, which was a contaminated brownfield site.
The main contractor, Ashe, is based in nearby Hitchen and it has an established network of local direct labour and subcontractors. Local specialist subcontractors included MJS for the concrete and Anglian Brickwork.
Gort Scott’s client is hopeful that in setting a high environmental standard for the building it may encourage more sustainable buildings within Cambridge.
