Articles & Case Studies


Posted: Wednesday 8th September 2010

Hanson Formpave, a leading UK manufacturer of specialist concrete products has recently completed an installation of its Aquaflow ThermaPaveTM system on the car parking site of Kimberley, a new sustainable commercial building, developed by Hanson UK at a former brick works site in Stewartby, Bedfordshire.

Working in conjunction with the project managers, Form4, appointed architects, tp bennett, civil and structural consultant engineers, Scott Wilson, the project’s building services designer, Waterman Group and landscape architects, Whitelaw Turkington, Hanson Formpave supplied its Aquaflow ThermaPave system – a combination of the company’s best selling permeable paving system, AquaflowTM and ground source heat pump (GSHP) technology, for use on the 6,500m2 car park, on this occasion Hanson Formpave used Geothermal International to provide the energy solution aspects of the project.

With car parking facilities accommodating 285 car parking spaces, Mark Stewart of tp bennett, wanted to fully utilise this space, “With Hanson Formpave, the engineers and Adrian Judd of Whitelaw Turkington, we researched the option of integrating the SUDS system with the geothermal heating/cooling system, to maximise the efficiency of the build.”

Encouraged by Formpave’s unique, environmental approach and its proven Aquaflow system, Mark and Geoff Arnold of Scott Wilson tasked the Hanson Formpave design team with delivering a paving and geothermal energy system, which would not only work across such a vast site but also harvest the natural benefits of the surroundings – the lakes to the left of the car park.

The Kimberley implementation required bespoke modification to the standard Aquaflow sub-base; at a reduced level, an impermeable welded membrane was laid, creating a tanked reservoir area, ensuring that the slinky pipes used in the GSHP process, 8.4 km in total, are constantly immersed in water.

Geoff Arnold, appointed highways engineer from Scott Wilson explains the construction of the car park: “We had to base the construction depth of the car park on heating capacity rather than a general construction formula. In working with Hanson Formpave we were able to fully utilise the space as well as reduce excavation costs, as it wasn’t necessary to excavate additional areas to install the slinky pipes – we simply used the base of the car park. With frost penetrating the ground upto 450mm deep we had to lay the pipes at 700mm to ensure that they didn’t freeze, in contrast to a typical car park excavation depth of 300mm.

“With the pipes one metre apart you can begin to appreciate the scale of the geothermal solution. The slinky pipes are sat within 200mm of permanently saturated stone; with any overflow directed into the lake. The wet environment allows a better heat exchange, with the pipes needing the difference in temperature to maintain an optimum level of performance. We also had to ensure that the base was flat so that the water would always remain at its 200mm peak. A slight incline or change in gradient would mean that the water would run downhill and as a result the stone would dry out and affect the moisture content surrounding the pipes and subsequently the heat exchange,” Arnold added.

Roger Garratt, renewables manager for Hanson Formpave explains further: “The five 130kW GSHPs were able to guarantee an impressive energy supply to meet the demands of the entire building! With an open plan layout it is important that there is a consistent and constant level of warmth and energy supply. To ensure this, the ground floor is heated by under floor heating – a common partner for geothermal energy as they run at the optimum efficiency level of around 45 degrees Celsius. The offices on the upper floor are supplied by specialist geothermal radiators, with a much larger surface area than a standard domestic radiator. So that these are a viable option and can work in limited spaces they are double skinned with double the amount of fins; ensuring optimum performance without the inconvenience of size.

The heating system works from a thermostat within the building, with the five GHSP working in series, each one works in turn until they achieve the desired temperature then individually shut off once this is reached. The GSHP’s can also provide both heating and cooling, this can be achieved simultaneously if need be, through the use of a ‘sliding header’ valve arrangement. This offers flexibility to the occupants, if say, where cooling may be required in the gym, while the rest of the building requires heating.

Awarded an Excellent BREEAM rating and an EPC energy efficiency rating of B, Kimberley is 30% more efficient than a typical new build with a rating of just 35kg of CO2 per m2 per year, compared to a typical new build figure of 50kg of CO2 per m2 per year.

Project manager, Andy Szymanski from Form4 concludes: “Hanson Formpave has been able to ensure that the building and its occupants will make a saving, in excess, of 26% in CO2 emissions (when comparing the Building Energy Rating with the Target Energy Rating) and of at least 42% in annual fuel costs; offering pay back within 5-6 years. With the proposed Renewable Heat Incentive (RHI) set to start in April 2011, the Government will be providing financial support for those who install renewable heating systems including GSHP, across all levels; even businesses and offices. So it begs the question, why wouldn’t you? Kimberley isn’t just an ideal representation of Hanson Formpave doing what it does best; it is a perfect prototype for the future and sets the bar for building and construction in Britain for the next ten years and beyond.”

As a modern, landmark office complex, Kimberley was built with modern methods of construction to high standards, with one ultimate consideration - sustainability. The 6,000m2 building comprises primarily of impressive open plan office space with additional accommodation, restaurant, gymnasium, crčche and other multi-purpose areas.

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