UK Headquarters Extension
Client: Spirax-Sarco
The brief
Industrial engineering group Spirax-Sarco was looking to replace the 1950s extension to their Grade II listed Charlton House headquarters in Cheltenham. The new 3,000m² extension needed to be sympathetic to the adjacent listed building and at home within the leafy, suburban area alongside residential houses.
CPW were appointed to provide MEP and Sustainability Consultancy up to RIBA Stage 3, and from there acted as the Client’s Technical Advisor. Alongside the building services design, CPW undertook detailed thermal and energy modelling to inform the building envelope design, prioritising a fabric first solution to minimise carbon emissions.
The final design was a sustainable, contemporary, four-storey office providing 180 workstations, flexible working spaces, a gym, breakout spaces, and an auditorium.
Sustainable features
Sustainability was at the heart of our design and aligned closely with the sustainability objectives of Spirax-Sarco, achieving BREEAM Outstanding – putting it in the top 1% of UK non-domestic buildings for sustainability.
A range of environmentally friendly features were implemented such as solar control glass and highly efficient heat pump technology. In the office areas, an exposed concrete soffit was utilised to regulate heat through exposed thermal mass, alongside a multi-service chilled beam for heating, cooling, ventilation and lighting to provide a neat, and efficient solution. This passive measure reduces the overall cooling demand in peak summer periods.
By using variable air volume control we were able to ensure that our ventilation efforts weren’t being wasted on empty spaces and only in use when there was demand, thereby using intelligent building management features to reduce energy usage. The mechanical ventilation system incorporates high efficiency heat recovery as a means of utilising the waste heat from the building generated by the occupants, equipment, solar reservoirs and lighting which would otherwise be lost to atmosphere and its associated energy wasted.
Electrical vehicle charging points were also added to the car park to further encourage staff to move away from fossil fuels and help on their journey towards decarbonisation.
Solar PV was provided on the roof to offset the buildings carbon emissions, resulting in nearly 25% net reduction in CO₂.
Utilising solar
Artificial lighting in office buildings often accounts for between 25 and 30% of a building’s total CO₂ emissions. Maximising daylight is an essential tool to conserve energy, as well as being important for the end user’s wellbeing.
A detailed daylight modelling exercise was undertaken to see how the building’s structural form, elevation design and material specifications interact to provide an efficient daylight design.
However maximising daylight, such as with the full-height glazing used in the building, has the potential to significantly increase the risk of overheating.
CPW used thermal modelling to assess the impact of solar gain in summer and test the effectiveness of passive design measures. Providing an air-tight, well insulated building with measures to passively control the impact of solar gains on the internal environment such as external shading devices, as well as highly efficient lighting and HVAC system control measures was essential to providing a low energy building.
Artificial lighting
The CPW Lighting team were engaged to provide interior lighting concepts for the front of house areas of the building, as well as practical, external illumination to pedestrian zones highlighting water features and trees. The internal lighting needed to provide practical light levels, establish a sense of arrival in the main atrium, as well as distinguish key breakout zones from the more functional office areas of the building.
The team selected an automatic control system for the lighting with occupancy detection and daylight linking, ensuring artificial lighting was only used when necessary and so reducing energy consumption. Simple, scene selection wall plates were used in multi-functional spaces such as meeting rooms, auditoriums and presentation spaces.
Once complete, the all-electric building was rated EPC A and BREEAM Outstanding, making it one of the top performing new builds in the country for sustainability.
BREEAM Outstanding
Top 0.5% of sustainable new builds
EPC A
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