Renovation of the derelict 1960s iconic headquarters of the Imperial Tobacco Company to create over 400 residential units. All apartments are designed with individual mechanical heat-recovery ventilation serving bathrooms and kitchens. This innovative, low-energy form of ventilation enables the normal trickle vents to be omitted from the windows thereby reducing heat demand by more than 50% while maintaining air quality.
Urban Splash set a very challenging brief for the team to explore all possible options for energy efficiency and the use of renewable resources. Our aim, to make this one of the most efficient developments in the country.
The apartments are heated using a closed loop ground source heat pump system. Pipework loops are installed within 88 boreholes, drilled to a depth of approximately 100m. Chilled water pumped through the pipes absorbs heat from the ground at a steady temperature of 11-14°C. The chilled water warmed by its passage through the boreholes, delivers its energy to a heat pump where a compressor cycle increases the temperature to 55°C for distribution around the building to the apartments.
Plate heat exchangers are provided to all apartments which draw energy in direct relation to demand. For every five units of energy supplied as heating, only one unit of electricity is used to drive the compressor giving a highly efficient system. When grid electricity is used, the carbon emission is 0.025kg from every unit of heat, compared to 0.053kg for a gas-fired boiler.
The borehole field generates 50% of the buildings peak energy demand for hot water and heating with a biomass boiler providing supplementary heat for the winter months where the demand exceeds the capacity of the ground source heat pump system. Back-up central gas boilers are provided to allow maintenance of the ground source heat pump and biomass systems.
The existing building has very deep floor plans, typical of corporate offices of the period. The creation of a central atrium with an ETFE roof provides a circulation route within the building supporting apartments of manageable dimensions. The atrium brings daylight to apartment facades that open into the space while the ETFE roof provides a thermally effective buffer space effectively converting an external facade into an internal thus reducing an apartment’s exposed external wall area.
High-performance low ‘E’ double glazing with selective coatings minimises heat loss and solar gain while allowing daylight into the space. All external glazing is set-back from the structural line providing protective shading from high-angle radiation in summer. Lighting to apartments maximises the use of integrated low-energy light sources, with lighting to common areas managed via daylight and movement sensors.
The project achieved an ‘Excellent’ Eco-Homes rating.