Pitching to the green

Is the speculative office market ready for sustainable energy use? Alison Luke gets wind of changes afoot.

Think of a spec office installation and what comes to mind? Cat A fit-out? Air conditioning? A new development in County Durham is challenging such preconceived ideas, with solar power, ground source heating and a 35-metre tall wind turbine added to the services mix.

The Greenhouse is the second building to be constructed on an industrial park four miles outside Consett in the hilly Derwentside landscape. The site is part of regeneration plans outlined for an area that was decimated by the decline of the steel industry. Its construction signals change for the area, but its use of sustainable energy is also a fresh move in the speculative development market.

This is the first of a new prototype of centres from developer Groundwork West Durham, an environmental regeneration charity that was created by the Countryside Commission in the late 1970s. The £4.2 million Greenhouse project comprises two buildings joined at 90°, with a combined rentable floor space of around 3000 m2. The two-storey blocks operate individually, but share some facilities including a central plantroom.

The larger of the buildings comprises around two-thirds of the total area. This houses around 20 business start-up units of varying size that can be rented out according to demand. Within this building also is a cafe and lettable conference spaces.

During the design and build period Derwentside Primary Care Trust (DPCT) selected the smaller building as a new site for its administration staff. The Trust moved into the space in late February from its previous location in a local hospital. Notably, one of the primary factors in this decision was the building's inclusion of environmentally-friendly technologies. "One of the selling points of the building is that it uses ground source heat pumps, so the energy bills will be a lot less," explains Steve Marshall, project manager with m&e contractor Haden Young.

But the developer has not just included renewable energy sources; a holistic approach has been taken. This started with reducing the amount of energy needed to run the building and covered all aspects of the project, including the sourcing of materials and labour. "The whole ethos of the building is low energy," explains mechanical design manager David Weakford.

Power to the people

A passive ventilation strategy using a mix of side, cross and stack effect principles was incorporated into the design. Weakford confirms: "As much of the building as possible is naturally ventilated, so where there are spaces up to 7 m deep, ventilation will be by openable windows." Deeper plan areas are generally ventilated by roof-mounted Windcatchers controlled by temperature sensors on their bases connected to motorised dampers. The core of the open plan ground floor in the DPCT building needed some extra help, so here a geothermal heat pump running in reverse cools the area via fan coil units.

One of the most unusual aspects of the m&e services is this ground source heat pump system, which supplies zoned underfloor heating throughout the buildings. An energy source that is becoming popular, the vertical boreholes commonly used elsewhere were not possible here.

"It was all going to be geothermally heated via borehole heat pumps, but they found that there are some old mine workings underneath and the boreholes would be unsuccessful," says Marshall. "The client was keen to retain geothermal heating, so an investigation was made into the horizontal slinky loops system." The principle is the same, but in this case an array of coiled pipework is laid across the site at a depth of around two metres. The capacity was limited by the space available for the pipework, so gas-fired condensing boilers top-up the system.

The second energy source to be used for heating at the Greenhouse was flat plate solar collectors. "Solar collectors on the roof are the primary source of heating for the hot water," explains Alan Tingate, Haden Young's electrical design manager. This is backed up by immersion heating elements in the hot water calorifiers.

Photovoltaics were originally in the design as a sustainable means to generate electricity, however this was vetoed early in the process. The old issue of payback periods reared its ugly head at this point. "At the moment the likely output of a pv installation is in the region of 4 kW from the space available," adds Tingate. "It was not viable at today's energy costs, but space has been left on the flat roof where they could provide pvs in the future if they become more viable."

The scheme does boast increased wind power capacity, however. In the original tender the installation of a 50 kW wind turbine was included, however partway through the project this was upgraded. "An opportunity arose where [the developer] could buy a product, so they chose to do that," explains Marshall. This "product" was a second-hand 200 kW wind turbine.

Haden Young provided the electrical connections for the wind turbine in liaison with the specialist contractors installing the turbine. The system is designed so that any excess electricity produced can be exported to the grid.

With one building already leased and units in the second filling up it seems that the market is ready for change. Growing power bills and more environmentally-conscious firms are changing attitudes. It may be time for speculative developers to rethink their long-held attitude that renewable energy sources and short-term tenants do not mix.