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The refurbished office space is designed to offer more flexibility and energy efficiency

Tricorn House is a Landmark 12 storey office building that bears a passing resemblance to the European commission's Berlaymont building in Brussels. It stands beside Birmingham's Fiveways roundabout, and it was all set to be demolished: its floors were in a poor condition and the limited floor-to-ceiling heights meant refurbishing to modern standards would be problematical.

In the end it was saved by an innovative flooring system, which turned it into a viable commercial development. William Davies, the for developer Commercial Estates Group, says the improvement works significantly increased the rental value of Tricorn House. He says: "The refurbishment allowed us to move the rental levels up to new highs for this location."

Andrew Wilkes, a workplace engineering consultant at Andrew Wilkes Management, was hired by CEG to find a way to rescue the Tricorn.

He says: "There is no doubt that this building would have reached the end of its useful life and that eventually it would have been demolished to make way for a new structure, just like many others around the country."

One of the problems the project team identified was the difficulty of providing an effective air-conditioning solution, a raised floor for cabling and acceptable floor-to-ceiling height all at the same time.

The existing perimeter fan coils were obsolete and Davies says there wasn't space for a traditional ceiling-mounted air-conditioning system as this would have taken 600 mm out of the narrow 2.8 m floor-to-ceiling height. Furthermore, a floor or ceiling-mounted solution was necessary as CEG wanted to get rid of internal divisions so it could let each of the 13,950 m² floors to a single tenant. Another solution had to be found.

Tricorn House has been a landmark on the Birmingham skyline for more than 30 years

Wilkes worked out a way to deliver air through a floor raised by just 175 mm. He specified Hiross Flexible Space System, which is one of the few products that claim to be effective with shallow floor voids. Hiross, which is supplied by underfloor air-conditioning manufacturer AET, provides duct-free low-energy air-conditioning and ventilation to all levels from beneath a raised access floor while leaving space for cabling and power distribution.

Wilkes says: "I know from our computational fluid dynamics modelling and thermal analysis that it is not enough to merely push the air through a thin floor void. The air delivery terminals must have powered delivery - in other words, fans."

Another reason why he chose Hiross is that it includes underfloor fan units that are not restricted by duct or pipe connections as they pull conditioned air into the office space. And the units are easily interchangeable with floor panels so any changes in office layout can be easily accommodated. Wilkes says: "The concept allowed a building that might not otherwise be retained and re-used to be refurbished with an excellent internal environment."

Naturally, CEG welcomed Wilkes' suggestion as, coupled with a ceiling void of 78 mm, it allowed a floor-to-ceiling height of 2.5m.

Moreover, it enables the property developer to divide each floor of Tricorn House into air-conditioning zones depending on the potential use and occupancy density of the area, with each zone supplied with chilled or warmed air by a conditioned air module.

Davies says that this "very efficient and flexible system becomes a selling point when marketing space".

Air is drawn into the occupied space by fan-assisted terminals, which are recessed into the floor, plugged into an underfloor power source, and connected by data cabling for intelligent control