Lean green BREEAM machine

Close attention has been paid to Vulcan House’s performance in use. All Home Office staff will be given a guide on how to use their new home.

The UK government has set out to become carbon neutral by 2012. A new headquarters for the Home
Office shows how the target might be achieved.

(Article taken from our customer magazine, Momentum)

The guard on the site gate of Sheffield’s Vulcan House takes an exceptionally keen interest in visitors to the project. Vulcan House is being built for the Home Office; security is tight. But questions are not just about the nature of your business. He wants to know where you have travelled from and how you made your journey.

On Vulcan House the Home Office is conducting a rigorous investigation. It wants to discover how much CO2 construction has generated. Based on its design, total building performance has been assessed using the Building Research Establishment Environmental Assessment Method (BREEAM). “We set out to achieve a BREEAM Excellent rating,” says Home Office project manager Phil Calvert. Every detail has been fine tuned to deliver optimum environmental performance.

Around 2000 Home Office staff are based in Sheffield, scattered across five sites. “If someone has a meeting outside their office they have to catch a bus, take a taxi or walk. Journey times can be up to 30 minutes,” Calvert says.

The Home Office wanted to centralise its operations in a brand new, purpose built headquarters. And it wanted not just to meet but exceed the government’s own environmental targets. Government has committed to becoming carbon neutral by 2012.

A design and build competition brief for construction of the super green office building was drawn up by Mott MacDonald with project manager and architectural consultant Drivers Jonas and property advisor Donaldsons, recently bought by DTZ.

Tours and workshops are planned before occupation takes place early in 2008“BREEAM ratings are won or lost in the first 10% of the design phase,” notes Mott MacDonald technical director Eddie Murphy. “We asked bidders to look at integrating building services with the fabric. “It’s not enough to put up a building and slot services into it afterwards. You have to treat the building as a whole from the moment you start.

“If you have a building that’s well insulated, protected from solar gain and airtight you create an internal environment that’s stable and passive."
Eddie Murphy

"Put people on the north and east sides of the building, where solar gain is least, rather than south and west where it’s greatest. You quickly start reducing the amount you need to cool the building. You get a much more efficient, cost effective environment.”

Vulcan House’s blockish shape was dictated by the desire to put 10 100m2 of workstation space, a 515m2 public area, training facilities, toilets, tearooms, kitchens and a restaurant, arranged over seven floors, into as efficient an envelope as possible. “A cube offers the best external area per internal square meterage in terms of regulating the building’s climate,” Murphy says. The block is punctured by a central light well, “to get lots of daylight into it”.

Though highly prescriptive, the Home Office was interested in seeing how contractors would interpret the brief for construction.

“We asked bidders to create virtual thermal models of their design and subject it to a year’s worth of local weather data. By changing the orientation of the building we found we could save 5% energy,” Murphy recalls. The models also established the amount of glazing to be used on each face of the building – 75% on the east and north walls and 50% on the south and west.

Construction was awarded to speculative developer and contractor Wilson Bowden, with structural engineer White Young Green, architect Hadfield Cawkwell Davidson and services consultant Hannan Associates.

“Setting out to attain the BREEAM Excellent environmental rating added a 5%-10% premium to the construction cost compared to a conventional spec-built office,” notes Murphy. When Vulcan House was awarded BREEAM Excellent status in May 2006, there were only 560 office buildings that had attained a BREEAM rating of any kind. “Only 132 of those had achieved Excellent,” he adds. Using conventional economics the building would not normally have got further than the drawing board. Including fit out and finishing, the 13,400m2 building has a capital cost of £40 million. Murphy says: “To enable the project to happen we had to work out a rental cost embracing lifecycle costs, and the government signed a covenant guaranteeing that rent for the duration of its 15 year lease.”

Structurally Vulcan House is standard stuff – a steel frame built on bored concrete piles. Externally there are no sun screens or conservatory style thermal buffers to suggest that Vulcan House is environmentally honed. You could find the same kind of skin on modern office buildings across the UK. It is wrapped in argon-filled double glazing to minimise heat transfer through radiation. Solar protective glass is designed to allow through light but prevent heat gain. Insulated ceramic panels minimise thermal loss or gain on non-glazed areas.

And at first glance the building services are also nothing to get excited about. The building is not even naturally ventilated. But in many ways all this makes Vulcan House’s achievement of a BREEAM Excellent rating all the more remarkable.

Heat from extracted air is used to warm incoming air. Air is circulated locally rather than ducting it over large distances. “That reduces the energy needed to pump it from
2.0W/litre/second, which is what you would normally expect, down to 0.8W.”

Heating and cooling plant specification has been closely scrutinised. “There are no hydrofluorocarbons in the chillers,” Murphy emphasises. HFCs are powerful greenhouse gases. A kilogram of HFC has a global warming potential between 100 to 12,000 times greater than a kilogram of CO2.

“A typical office air conditioning system will have upwards of 30kg of HFC refrigerant in it, which leaks out and has to be topped up regularly. So instead of HFC, in Vulcan House we’re installing ammonia chillers. Ammonia is benign to the atmosphere and it’s also a better refrigerant. It’s lighter than HFCs, so it’s easier to pump around the system, which means it’s using less energy in operation.”

Wilson Bowden has chased down the global warming impact of the scheme through every part of construction. “Every material we use is checked,” says Wilson Bowden construction manager David Wragg.

All plant is prefabricated and delivered to site with minimal packaging. What protection there is gets stripped off and sent back to the manufacturer for reuse. All this reduces the project’s energy footprint.

Key sustainability facts

• Carbon emissions measured through construction
• Designed to be carbon neutral in use
• Water use 20% lower than government targets
• Increased capital cost offset against reduced operating cost

What is BREEAM?

The Building Research Establishment Environmental Assessment Method ranks each aspect of a building, including the energy embodied in its construction materials, energy used through the construction process itself, its thermal mass, insulation, lighting, heating and cooling, ventilation, water consumption, access to public transport, waste generated through construction and in use, and efficiency in operation.