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NG Bailey's Solais House - BSRIA model projectJuly 2009

What's the best way of procuring a low energy building? Answer: build it yourself. Roderic Bunn visits NG Bailey's Solais House to find out how to turn a speculative office deep green.

The killer question in any argument about achieving low or zero carbon buildings is always: "so what about all those speculative buildings and unprincipled property developers? You can't make those low energy."

Services contractor NG Bailey would beg to differ. In August 2008 the company moved into its much-modified, spec-build regional headquarters on a Glasgow business park, and proudly put up its Energy Performance Certificate in reception with a chunky green arrow pointing to the letter A.

OK, it's only an EPC, which means the building's projected energy use of 55 kWh/m2 per annum (13 kgCO2/m2 per annum) is still theoretical. But Solais House is nevertheless shaping up to be an exemplar spec-build that could silence the low energy nay-sayers.

Proving the building's credentials though, is going to take a bit of time. It's normal for a new building to take at least one heating season and one cooling season for all the bugs to be ironed out and for the systems to settle into a consistent level of performance.

Which is why NG Bailey and BSRIA intend to monitor the building's energy use, occupant satisfaction and general usability for a full report in about a year's time.

Humble origins

Solais House is located on the Strathclyde Business Park on the outskirts of Glasgow, a small community of low-rise open-plan offices that are ubiquitous south of the border but still quite rare for this part of Scotland.

Predictably, all the buildings on the park look much the same - the architectural palette clearly struggled to break into double figures - so the huge NG Bailey signboard above Solais House is an invaluable aid to visitor navigation.

However unprepossessing it might be, the design ideology does have some essential virtues: simplicity, space efficiency, a reasonable glazing ratio, and a bold structural overhang on the first floor that has high pretensions to solar shading even if it doesn't quite cope with all conditions.

The first floor office area. Occupancy density is currently quite low, nominally at one person per 16m2 with only between 50-75 per cent of staff in at any one time. Occupant satisfaction surveys show that density is an important factor in levels of perceived comfort and productivity.

A two-storey fully glazed reception lobby faces more or less due south - a constraint that NG Bailey has turned into a virtue.

For most other clients, that would've been that. But NG Bailey became more than just a client and owner-occupier. Through its offshoot Bailey Building Services, along with various other parts of the Group, NG Bailey acted as its own m&e fitout consultant, main contractor, m&e contractor, lighting designer, ceiling and partition contractor and ICT specialist.


With this integrated delivery team, Bailey was able to take the basic speculative template offered by the developer and improve virtually every aspect of the building's construction. For example, Bailey took the building's traditional brick and block with cavity insulation and set much higher levels of thermal and airtightness performance.

The inner blockwork face has been coated with a cement render to reduce permeability. This was then sealed and bonded to the aluminium window frames. Effort was made to eliminate air gaps with bonded seals to the plasterboard and cills.

NG Bailey aimed to halve the Scottish regulatory target of 10 m3/(m2.h) at 50 pa but in the event got it down to 2.89 m3/(m2.h), once the roof membrane had been prevented from lifting and the seals between the sun pipes and the roof membrane had been improved. At sub 3 m3/(m2.h) levels, details like this loom large.

The building has fixed solar shading on the ground floor. All the windows are high-efficiency units with a low-e coating and mid-pane blinds. The upper hopper windows are motorised, while the main tilt-and-turn windows are manually operated. All the other buildings on the park have centre-pivot windows with internal linen glare-control blinds (which probably means the windows are shut most of the time, if experience is anything to go by).

NG Bailey avoided dx air-conditioning. That, along with prefabricated roof-top plantrooms, released space on the roof for lightwells and sun pipes, the latter used to illuminate the first floor toilet areas.

Environmental engineering

Solais House is a mix of passive fit-and-forget systems like sun-pipes, and innovative, very much fit-and-manage complex systems, such as ground-source heat pumps.

At the keep-it-simple end of the scale the building is fully naturally ventilated, with motorised hopper windows doing the bulk of the ventilation needs. The motorised hopper windows are controlled by Bailey's intelligent building management system (ibms). Not only are these used in a night cooling role, but they are also linked to the building's door access system so that the facade security lighting is only on when the building is unoccupied. The hopper windows will open once it gets dark.

The floor plates are almost entirely open-plan with the exception of a few perimeter meeting rooms. Even here, motorised hopper windows in the partitions maintain air paths across the floor plate. For acoustic privacy the occupants of these meeting rooms can close the Lon-controlled hoppers for a limited time via the ibms. The hopper windows in meeting rooms are also operated via buttons on the Cisco IP phone handsets to allow user override.

The raised portions of the lightwells are also equipped with motorised hopper windows for stack ventilation.

As a concession to the need for cooling in meeting rooms, chilled beams have been chosen in preference to dx air-conditioning. These beams run off a chilled water circuit supplied from an open-circuit borehole. The only mechanical ventilation is limited to toilet extract and selected cellular spaces which modelling suggested could overheat. A run-around coil in the air handling unit takes waste heat from the separate toilet airstream for pre-conditioning the meeting room supply air in winter.

The office lighting is of high frequency fluorescent downlights in a conventional suspended ceiling. These are controlled by a DALI digital dimming system. Control of the lamps follows best practice in auto control: default off, (through absence detection), with lamps programmed to come on when daylight falls below a set level. Results from NG Bailey's initial measurements indicate less than 9 W/m2 and light efficacies of greater than 80 lumens/Watt.

Bailey installed an enhanced level of detection - one detector per four workstations rather than one detector per (nominal) 40 m2. Once the desks went in the control zones were set up to mirror the layout.

Getting daylight into enclosed zones like toilet cores is always challenging (and rarely done). At Solais House NG Bailey opted for Monodraught's proprietary Sunpipe product to illuminate the toilets. The Sunpipe works by directing daylight down through mirrored aluminium tubes to a domed diffuser fitted in the ceiling. Backup electric lighting is based on a mix of 3 W light-emitting diodes and compact fluorescent fittings (the latter dimming on daylight detection).

NG Bailey made strenuous efforts to get daylight into the office spaces. Lightwells equipped with motorised clerestorey windows provide daylight to both floors and an extract path for natural ventilation.

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).

Initial operation

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.