Case Study: The National Trust Central Office - RIBA Product Selector

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secontrols.com headquarters building would possess all the same sustainable and responsible credentials as its work ethos. Inherent sustainability With staff spread across four different sites, some teams having three or four locations, The National Trust needed a new central office – one that could house everyone under one roof and provide its members with a better, more integrated service. As well as streamlining working practices and cross-team communication, The Trust also wanted to reduce costs and pollution with a smaller carbon footprint. Rather than choosing a typical country house, The National Trust sought better value for money in the former railway town of Swindon. It chose to occupy a large brownfield site in the Great ‘ The success of our sustainable initiatives is down to managing expectations. Every member of staff has had training on the natural ventilation system. ‘ Liz Adams National Trust Property Manager Western Railway Works, an area of significant architectural heritage undergoing major regeneration. Sustainability was a key issue for The Trust and its move to Swindon. As such, the new build had to meet stringent and high quality benchmarks for sustainable design – as well as providing an open plan space conducive to interactive team working between departments. The benchmark of green building The resulting building, headquarters named Heelis, was created by developers Kier Ventures and architects Feilden Clegg Bradley in collaboration with The National Trust, natural ventilation specialists SE Controls / NVS and Max Fordham LLP . Cutting edge in its design, Heelis beautifully complements the surviving buildings of the Swindon Railway Works with their distinctive facades by Brunel and Gooch. Internally, the striking structure has a generous front-of-house atrium with a shop and café that is open to the public. It also comprises a two-storey deep open plan office. Two courtyards were included in the scheme, introduced by Max Fordham LLP and the architect, to enable cross ventilation. In such a deep space, the courtyards both required vents leading into them – without which the cross ventilation strategy would not be able to function effectively. A number of ‘green’ products and systems were also specified for the project, including a bank of 1,554 photovoltaic solar panels on the roof. Electricity generated from these panels is used in the building. A lighting control system adjusts the level of artificial light in response to external conditions and movement sensors ensure lights are turned off in unoccupied areas. All of the timber used in construction has been harvested from sustainable woodland, much of it originating from National Trust properties. Even the carpet was specially developed using wool from Herdwick sheep grazed on National Trust farmland. Blue Staffordshire engineering bricks were used as the principal external material, blending in as a contemporary interpretation of the surrounding structures. They are laid in lime mortar to reduce cement use and facilitate recycling. Cast aluminium cladding (visible on parts of the elevation) also provides a subtle tribute to the railway works that once occupied the site.
Ensuring optimum internal temperatures Internally, the building required a ventilation strategy that would provide fresh air and generate a healthy environment for its users. It also needed an alternative method of cooling other than air conditioning – one of the largest producers of co2 emissions and incredibly expensive to run. In line with the building’s myriad sustainability credentials, air conditioning and mechanical ventilation methods were completely unacceptable. A natural ventilation system from SE Controls / NVS provided the answer. Combined with large areas of exposed thermal mass that reduce the need for cooling during warm periods (concrete panels to the first floor and roof soffit that give off ‘coolth’ to the office space during a working day), the solution works by expelling stale air and introducing fresh air through the use of climatic changes. The natural solution Consuming very little energy and with very little carbon emissions, natural ventilation systems demonstrate how buildings can be architecturally exciting while still being efficient, sustainable and, importantly, providing best value. New low energy heating and mechanical ventilation systems can offer impressive energy ratings in a Image courtesy of Max Fordham LLP similar league as natural ventilation strategies, but cost implications including capital equipment and maintenance can make them significantly more expensive. SE Controls / NVS displayed its firstrate partnering and project management approach by working with M&E engineers Max Fordham LLP, Schüco (Glazing Systems Supplier) and Parry Bowen (Glazing Fabricator) to design, install and commission a natural ventilation system that would fit perfectly with the building’s design principles. Working with the building’s sense of airiness and open plan space, the winning strategy has enabled the scheme to achieve an ‘excellent’ BRE Environmental Assessment Method rating. This is alongside providing occupants with the flexible, open plan and healthy working environment they desired from the outset. An innovative ventilation strategy Based around the company’s OSO controller and a series of different actuators, the system was fitted to the façade windows and banks of roof vents. In total, 307 actuators were installed on 213 windows and 156 actuators on 78 roof vents. The innovative OSO Controller acts as an intelligent interface between the actuators and BMS (Building Management System), with which it communicates using the LonWorks interface. As required, the BMS communicates with the OSO Control Systems and appropriately opens or closes windows and rooflights around the building, depending on the ‘ temperature signals received from the sensors placed around the offices. Though SE Controls / NVS were able to offer a full stand alone battery backed control system, there were clear technical and financial advantages in allowing the BMS to be in overall control – a flexible approach encouraged by SE Controls / NVS to give clients a best value solution. The fact that occupants could control the vents with override switches was also a very important element. Guy Nevill Max Fordham LLP ‘ As the temperature inside increases above a set parameter, the warm stale air rises. The rooflights are opened to allow this warm air to escape, rather than filling the ceiling space - and eventually the whole room - from the top down. The façade windows are opened to allow cool fresh air to be drawn in, replacing the stale air. This is a typical application of the stack ventilation principal, utilising the buoyancy effect of warm air to create low pressure areas at the bottom of the stack. This in turn draws replacement air from wherever possible – ideally, in this case, an open window. As the temperature levels return to normal, the windows and rooflights close incrementally. During the summer, a night time cooling strategy is triggered - in part due to a comparison of internal and external temperatures during the day.
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Case Study: The National Trust Central Office - RIBA Product Selector

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