One of British Land’s first buildings on the Broadgate estate to undergo a full refurbishment has been completed
The 13,600m² office space was originally completed in 1989 by Skidmore Owings and Merrill. Less than twenty-five years old, the building has undergone a major refurbishment.
John Robertson Architects implemented a number of strategies to improve environmental performance, including innovative lighting, high performance glazing, and the replacement of plant and services.
Plant has been centralised and relocated to the roof space, where previously there was a plant room on each individual floor. They found that if they were to successfully achieve their target of BREEAM Excellent, the answer was to not just refurbish the existing plant, but to replace it, making it as efficient as possible.
The lighting within the building was carefully considered in order to further reduce energy demands. The architect, Festus Moffat said ‘really efficient lighting is a key to the buildings success’. The lights within the building dim according to daylight levels - lights towards the edge of the floor plates sense the levels of daylight and dim in response.
The impacts of the buildings glazing were carefully modelled; it was believed the impact of the façade over performing could cause problems. A careful balance had to be met between high g-values and low u-values, balancing daylight with heat transmittance and both the future needs and users of the building.
New cladding has been installed at both ground and mezzanine level, using black anodised aluminium and full height glazing to provide a contemporary identity to the building. The original cladding was kept at the upper levels, in order to reduce the amount of new materials being used. This cladding was tested for air permeability before work commenced in order to highlight any issues with failing seals or junctions. These tests showed the existing façade to have an air tightness level similar to that of a new building, and therefore confirmed the decision to retain it.
Modelling was used from the start of the project. The building services engineer, Chapman Bathurst, created an energy model of the building which was used in the decision making process. This model has also enabled British Land to predict future occupier’s energy consumption, allowing greater planning in ways to reduce this.
The building has been achieved without the use of renewables, which could have been challenged by the Greater London Authority. Yet they were receptive of this approach, due to the focus on reducing the energy usage within the building before using add on technologies.
Festus said that ‘nothing innovative has been done; it is about finding the right solutions and proving that they work’. He highlighted that it was about planning for future use within the refurbishment, adding: ‘we don’t work the way we did twenty years ago, and we don’t know how we will work in the future. So the building has to be flexible and able to adapt’.
Source: British Land
A key to the buildings success is the British Land’s support of sustainability from the outset with a focus on reducing users demand for energy. Strongly led by the developer the energy efficiency and sustainability of the refurbishment was a key driver for the project. Reducing its carbon emissions by sixty per cent, the retrofit has achieved BREEAM Excellent and an EPC rating of B.
Roof u-value: 0.18W/m2K
Wall u-value: 0.69W/m2K
Floor u-value: 0.22W/m2K
Window u-value: 1.3W/m2K
Window g-value: 56%
Annual CO2 emissions: 19.0kgCO2/m2
Predicted annual energy consumption: 90.4kg/m2
Air permeability: 9.84m3/hr/m2 @ 50pa
Client: British Land
Architect: John Robertson Architects
Project Manager: M3 Consulting
Main Contractor: Como Interiors Ltd
Structural Engineer: Meinhardt
Building Services Engineer: Chapman Bathurst
Sustainability Consultant: Environmental Perspectives
CDM: Capita Symonds
Strip Out Contractor: H Smith (Engineers) Ltd