A novel approach to lighting has also been followed in the reception area, usually the best place to find poorly controlled high-energy lighting. At Solais House the reception is lit using projectors that bounce light off ceiling-mounted prismatic reflectors. The reflectors distribute light evenly around the reception. This strategy meant that only two high-powered lamps were needed as opposed to the several that would normally be required.
Space heating is provided by two ground-source electric heat-pumps that draw water from a single 120 m open-circuit borehole. A submersible pump draws out the ground water and pumps it to a heat-exchanger to separate the lphw circuits from the primary circuits. The heating circuit runs at 45°C flow, 40°C return to serve large perimeter radiators, and also an underfloor heating circuit in the reception.
A portion of the ground water serves the chilled beams in the meeting rooms and server room, and in summer used to serve the underfloor circuit in the reception area.
Domestic hot water is generated by evacuated-tube solar collectors located on the south-facing roof. The heated water goes to a pre-heat cylinder, with a gas-fired hws generator for back-up and pasturising purposes, and from there serves the building's basins, sinks and showers.
The large flat roof is used to gather rainwater for toilet flushing and window cleaning. A 15 m3 storage vessel is buried in the grounds. Water use is minimised by the use of waterless urinals and 2/4 litre dual-flush toilets.
At the innovative end of the scale Bailey took the opportunity to cover the three sides of the fully-glazed reception lobby with mono-crystalline photovoltaics (PV). These generate a nominal 5 kW of electricity. As the specification was double-glazed clear glass, the choice was between PVs or an internal blind system (which wouldn't keep out the solar gain anyway).
Rather than put in £30,000 of motorised internal shading, with all the maintenance, controls issues and zero payback that would come with it, Bailey opted for £90,000 of PV (around £750/m2) which gives the appearance of tinted glass. It also comes with a payback - albeit rather lengthy.
Although PVs loiter just outside the fit-and-manage category, it wasn't a simple case of gluing them onto the outside of a standard glazed façade, as NG Bailey's technical director Paul Hancock explains. "The PV cells required us to design the pressure plates and the glazing bars to suit the PVs, and to provide cable ways with enough depth to carry all the cables and connectors," he said. "The pressure plates tend to shade the PVs, and the way it has to be wired up means than when one cell goes off the whole lot on that side of the façade goes off."
With NG Bailey's sister company ICS acting as system integrator for the intelligent bms (ibms), it was inevitable that Solais House would be equipped with the latest in integrated controls.
There is no central supervisory computer. The while thing is network-based, with all addressable components like the hopper windows, lighting and solar panels all using various types of open communication protocols such as LonWorks, BACNET, and MODBUS TCP/IP, to communicate with the Tridium front end.
All wall-mounted controls and sensors are addressable wireless units to make them easy to reposition. This saves on installation and churn costs, but does make the capital cost of each one about £500. Hence Bailey has adopted voice over internet protocol (VOIP) for the building's network and fieldbus applications. Once the ibms system is fully commissioned, occupants will be able to override hopper windows, for example, using their desk telephone.
As all addressable components, from lighting to security access, all use open communication protocols, the scope for using one system to control another is limited only by NG Bailey's imagination. For example, the external floodlighting is linked to the night purge so that the lights come on when the windows are open. Similarly the lighting presence detectors in meeting rooms are also used to bring on the mechanical ventilation (and to set it back when the lights are turned off).
The building was occupied in August 2008, but for various reasons completion and handover was a more fraught process than NG Bailey had planned. The building only had an electrical supply four weeks before practical completion. "Commissioning was really a case of 'switch it on, and does it work,'" recalls Paul Hancock. "There's still a lot of work to be done, as well as calibrating and commissioning."
At the time of writing the controls system had not been fully handed over, and the gas meter had not been signed over by the builder. Bailey's own gas readings show the building used 3350 kWh of gas for the dhw services for the five months to the end of January 2009. However, company has yet to receive a gas bill - sadly a widespread problem.
NG Bailey has tried hard to ensure energy loads do not proliferate in the building. A lot of effort has been put into reducing plug-in power. For example, all printing is centralised, so the building only has six wireless networked printers for 120 workstations.
NG Bailey is confident that a year's environmental monitoring will justify the building's EPC rating of 13 kgCO2/m2 per annum. But the compnay has aspirations to make the site zero-carbon. That hinges on two future sources of renewable energy: a 75 kW wind turbine and a 7.5 kW (continuous output) micro-hydro scheme in a river that runs past the site. Formal approval is currently being sought, as is interest from other firms on the business park as potential customers for the power.
So there we have it: a speculative low energy building. And potentially zero-carbon too, if the extra renewables are installed. But is the building a template for other business parks?
Solais House conforms to the rule of cutting loads and raising efficiencies first before relying on renewables. On the other hand the occupier is not sweating the asset - Solais House only has 120 occupants with a normal occupancy between 50-75 per cent of that number - so its low energy use needs to be judged in that context.
On the other hand the building has lots of attention to detail that takes low energy design onto the next level - at least as far as speculative offices are concerned. In fact, if Solais House does any one thing, it's to finally eliminate the distinction between purpose-build and speculative-build in terms of sustainability. All that's left now is to prove it.