Background Set in the countryside on the northern edge of Cambridge, the village of Longstanton boasts a rich and long heritage stretching back to Roman times and has been expanding rapidly over the past 10 years to become a vibrant and younger community.
Alongside the traditional village, new residents have been progressively settling in at the Home Farm housing development site to the north-west of the village, a development which has seen a necessary infrastructure investment across the region by Cambridgeshire County Council, investment that included a guided bus way and related park & ride stations along it.
Jackson Civil Engineering, the largest company within the SEH Group – one of the largest privately owned construction companies in the UK – was brought into the project to complete the guided bus route scheme.
Park & Ride The park and ride facility at Longstanton needed a terminal building and Cambridge County Council decided to create a unique exhibition centre. The building needed to meet the BREEAM Excellent rating and demonstrate how energy efficiency and renewable energy technologies could be incorporated into a building. The building was designed to set a benchmark for low Carbon properties proposed at the new Town of Northstowe and was required to showcase environmentally friendly and low carbon living to encourage local residents to go green in their own homes.
Jackson employed sister firm SEH French to handle the build of the exhibition centre which in turn contracted SEH Commercial, another key player in the SEH Group, to manage the installation of energy solutions such as solar panels, a ground source heat pump, natural ventilation systems and the windows and doors at the site.
SEH Commercial Windows and energy solutions specialists, SEH Commercial, began work on the project in June 2010. The job required a coordinated approach to ensure that the station and exhibition centre were using the best green technologies, as Julian Pennington, sales director at SEH Commercial explains:
“We were heavily involved in the initial design and concept of the building from the early stages, allowing us to make sure we had a building with a good thermal mass and insulation which enabled us to focus on delivering a number of key areas for the project. This included the Ground Source Heat pump, which uses ground energy collectors to contribute warmth to the building and provide hot water; the installation of energy efficient windows and doors which insulate the building and provide the highest security levels; the installation of 4.5kW solar panels which generate electricity to offset the power requirements of the building; the installation of a sophisticated natural ventilation system which maintains the ideal temperature through an integrated system flow-energy fans; the supply of the building management system (BMS) controlling all aspects of the control of the building systems; installing Active energy data software we are able to provide data on the energy consumed, generated and how efficiently the whole system is working so that the details could easily be seen interrogated by the client and used to educate people visiting the centre.”
Windows & Doors For this project, a special composite timber/aluminium window frame was specified along with an aluminium door product with an automatic opening system. Both products carry the Secured By Design standard. In total, 13 windows and 2 doors were installed.
The doors were powder coated to match the windows, and have multipoint locking with radar sensors inside & out, incorporating IRS safety sensors, sash-lock with cylinder and thumb-turn, overhead door closer and lever handles. The finish makes for an impressive looking building and provides security levels whilst maintaining the insulation levels required.
Solar PV The SEH Commercial energy solutions team is MCS accredited solar PV installers and specialises in commercial solar photovoltaic energy installations. For the solar PV at Longstanton a galvanised steel frame was designed and installed onto the timber frame of the building (pictured) to maintain the perfect level position for the 4.5kW system to generate energy for the premises. The Fronius inverter is located in the plant room which converts the generated DC current into useable AC charge which then gets used by the exhibitions’ systems; any surplus is fed back into the national grid and generates revenue paid through the government’s Feed in Tariff scheme (FITs).
Ground Source Heat Pump (GSHP) “The novel aspect of the ground source heat pump at Longstanton was that we wanted to be able to demonstrate it,” says Julian Pennington. “Usually, everything is hidden underground so we decided that rather than installing vertical ground energy collectors in different locations and connecting them in series, we installed three radially drilled energy collectors from a central glazed-chamber within the floor space of the exhibition centre (pictured left). This allowed us to create a display of the technology and is a novel design for this technology.”
Heat pumps take advantage of the physical properties of liquids and gases as they change from one state to another in what’s known as the refrigeration cycle. Ground source heat pumps get their energy from the ground which, in the UK, is around 10°C for most of the year. Heat pump technology extracts the useful energy from the ground and elevates its temperature to a level suitable for building heating.
“This energy is effectively inexhaustible, renewable and free,” says Julian. “We use some electricity to drive the heat pump refrigerant cycle. The key to heat pump performance is the efficiency of the overall process. In a well designed system it’s possible to get efficiency levels of greater than 400%. At this level of efficiency a heat pump provides one of the lowest energy, lowest carbon heating systems possible. By getting a good proportion of our energy from the environment we can also operate a heat pump system more cheaply than most alternatives.”
Natural Ventilation The thermal comfort of the building is maintained utilising a natural ventilation strategy that in the winter prevents useful heat energy – and the saving invested in it – being lost to the outside and pushes hot air out of the building and draws cooler air into the building through the windows in the summer months.
To do this SEH Commercial installed an E‐Stack roof‐based unit that operates in different modes in summer and winter, on-site there is a traffic light management system which indicates to the building staff when to open windows at the appropriate time, means the building breathes efficiently to optimise the energy.
When the outside temperature is above a threshold value (typically 17°C), the system works in conventional displacement ventilation mode, using low‐level (usually manually‐operated) windows or vents as well as the stack. The system operates up-flow displacement ventilation and the ventilation rate is governed by internal temperature and CO2 levels.
“What’s really clever about the E-Stack is that in winter, the system takes in cold external air at high level, mixes this air with warm room air, and returns intermediate temperature mixed air to the room,” says Julian. “Using simple thermo-dynamic principles which see cold air falling, this removes the need for pre‐heating of air entering the room in winter and additionally reduces the risk of cold draughts. The operation of the E‐Stack unit is controlled by a controller which adjusts the operation of the unit to provide comfortable interior temperatures and CO2 levels.”
With the project completed in November 2012, the SEH Commercial installations have contributed to a state of the art exhibition centre which is already being used by hundreds of people each day that pass through the Longstanton Park & Ride terminal.
