Next generation

Leasing office space is highly competitive, with building owners constantly looking for the edge that sets their project apart. Today, that advantage is most likely to come down to green factors. Does the building have a Green Star rating? What energy savings can be expected? Does the design maximise the space and is it a comfortable, user-friendly workspace?

Ken Wimsett, managing director of Latitude Group, the developer of a new 5-Star Green Star office building in Christchurch, says Green Star ratings will be expected as standard in the not-so-distant future.

"Latitude Group has been one of the pioneers of the Green Star rating system," he says. "It has long been evident that having such a rating will be a critical factor in attracting tenants, and it was our first priority in developing the design brief for Club Tower. As this was to be the first new-generation, A-grade office tower to be built in Christchurch for 20 years, it had to set the benchmark."

Designers Robert Weir and Jason Walker of WeirWalker Architecture say the building's central, landmark location was also a key design influence.

"With adjacent historic buildings and a height limit on the neighbouring Canterbury Club site, this building is never going to be built out," says Walker. "This was an opportunity to provide a distinctive, modernist architectural form that would sit comfortably in the landscape for years to come."

To maximise the site, the building sits to the boundaries, with a setback from the second floor. This provides space for a landscaped podium on the roof of the ground-floor cafe.

"The podium features attractive seating and trees, so people working in the building haven't lost a sense of connection with the ground," says Walker.

The architects say providing retail space at ground level has several advantages. It disguises the carparking levels at the rear of the building, and the cafe facilities provide a breakout space for office workers.

Upper levels are defined by substantial cantilevered balconies that are staggered to soften the exterior facade treatment, and to add visual interest.

"The balconies also provide shade for the floors below, which contributes to the Green Star rating," says Weir. "In addition, they add value to the tenancies staff can use the balcony space for breakout areas. The balcony space is leased as a separate entity, but at a slightly lower rate than the rest of the floors."

Another key feature of the exterior is a box-like element that appears to pop out from one side of the building. Weir calls it positive-negative detailing.

"On the one hand there is a glass box projecting out from the solid form of the building. But as the glass carries no visual weight, you see through into the interior, like a negative detail."

The foyer is a double-height space with a mezzanine bridge linking the top floor of the car park to the lifts. Stone and timber veneers were specified to provide an enduring look. A large accent wall features granite squares laid in two directions to create a woven pattern. There is also a large window in the foyer, which was designed to provide a visual link to the new tree-lined pedestrian boulevard of the Christchurch civic building. Temporarily covered, the window will be exposed once the adjacent building is completed.

In keeping with the need to maximise the floorplates, the interiors are column free. Services are positioned on the west side of the building, to reduce the heat loadings from the afternoon sun. To ensure the views in all directions are maintained, windows have been positioned to allow glimpses either side of the lift core. Glass office partitioning also allows workers to see through walls to the views outside.

Thermal modelling helped determine the precise specifications of the double-glazed window and door joinery. Walker says extra insulation was provided in the spandrels to balance any potential heat loss through the expansive glazing.

The building also features energy-efficient lighting and a daylight harvesting system. Sensors measure the amount of natural light coming into the office and lighting levels are automatically ramped up or down to ensure there is a constant level of 400 lux over the work surfaces.

Other green features include extensive recycling facilities. Rubbish can be sorted prior to council pick-up. Rainwater and grey water are also recycled, treated and used to irrigate the gardens.

"We used low-VOC and low-maintenance materials wherever possible," says Weir. "Sealants, paints and carpets, for example, are all low VOC, and the furniture was selected for its environmentally friendly design and manufacture. The building exterior features composite Alco aluminium panels that will never need painting. The concrete base is also an eco-friendly option, due to the materials being constantly replenished and close at hand in Christchurch."

As the first 5-Star Green Star office building in Christchurch, Club Tower is providing tenants with significant cost savings resulting from the design and energy efficiency of the building.

Story by: Colleen Hawkes