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Case study: Office building

Office - CentrePort / Statistics New Zealand Building, Wellington

Photo of Statistics New Zealand Building.

Summary

Client

CentrePort / Statistics New Zealand

Site address

Hinemoa Street, CentrePort, Wellington

Total floor area

9,300m2 (NLA)

Cost/m2

Yet to be finalised

Conventional cost/m2

$2000

Contract value

Yet to be finalised

Economics

Unfortunately final construction costs are yet to be determined and are subject to commercial sensitivities at this stage. However, as part of the design process a detailed cost/benefit study was carried out to assess the suitability of several sustainability features. Some, such as the high-performance glazing, were found to have significant benefits, not only in terms of energy use but also in equipment sizing for air conditioning. Other sustainable features, such as solar water heating, were not included in the final fit-out (due to the relatively low hot water demand in commercial buildings).

Energy modelling predicts that the building will save around $14.7/m2 in energy costs. With water savings included the sustainable benefits would be around $15/m2. Using overseas examples as a precedent it can be expected that the ecologically sustainable development (ESD) premium would be around 5%, this gives a simple payback of under seven years.

For office buildings in general, results of overseas studies show that returns from ESD are best for owner/occupiers; for speculative commercial buildings the increased cost of sustainable building will need to be reflected in increased rentals. It has been found that for tenants, the rental premium is likely to be repaid by a factor of three over a 20-year lease period. This includes a modest productivity benefit which may arise from having a more comfortable working environment.

Environmental summary

  • Energy used - 102 kWh (predicted).
  • Stormwater design - swales used to control rainwater run-off.
  • Site - re-use of redundant wharf area.
  • Waste - 80% of construction waste re-used or recycled.

Client brief

The client wanted a modern working environment that would support the 'whole of business' objectives. The building design was to provide a high quality internal environment that would satisfy Statistics New Zealand's objective to create a place of work that encouraged collaboration, professionalism and a united culture.

As part of the process, Statistics New Zealand and its consultants developed a highly specific brief that required features such as large floor plates, regular plan shape, minimal core to glass distances, and a high level of modular coordination.

Process

Statistics New Zealand established the criteria, which included sustainable design, energy efficiency and a high-quality working environment.

The selected design team worked with Statistics New Zealand's consultants to develop the building that best reflected the initial planning intentions proposed within the brief.

Late in the design phase DEGW, Statistics New Zealand's interior design consultants, reviewed the base building design. The main result of this review was to separate the core area to form a 'gathering space'. Although this moved the design away from the initial parameter, the reconfiguration was seen as a valid design improvement.

Concept

The large open-plan floor plates are designed around central hubs, which provide core facilities, vertical circulation and 'gathering spaces'.

These central spaces provide refreshment and conversation zones. An important benefit of this space, and the adjacent central stairs, is the ability for staff to get together and share knowledge across the organisation.

An attractive and spacious staircase was created to enhance the visual connection between floors. The result is a honed concrete and steel staircase within a three-sided floor-to-ceiling fire-rated glass enclosure.

Three lifts serve the building, but its low-rise structure means the stairs should be popular for moving between floors.

Facilities

  • Secure covered car parks within the building.
  • Office accommodation for approximately 500 staff.
  • Truck dock / loading bay.
  • Showers / lockers / bike racks.
  • Café and commercial kitchen.
  • Open deck with glazed canopy.

Site

The building is on land previously used by CentrePort for car parking and bulk storage. It is close to Parliament and other key Government agencies and stakeholders.

The long axis of the building lies north to south, maximising views of the Wellington CBD, Mt Victoria and Matiu (Somes) Island, while maintaining view corridors from city to sea.

Materials

The building's fabric has been designed to enhance comfort and reduce energy consumption (thermal performance).

A fully glazed curtain wall using high-performance double glazing allows high levels of natural light, while the narrow floor plates and office space planning give staff good access to daylight and views.

The internal floors generally use a 'shell and core' format with little or no internal finishing or with the fit-out integrated with the base structure.

Transport

The building is a five-minute walk from Wellington's main railway station. Employees can use both rail and bus services to the central city using the station terminus.

Cycling facilities ('parking' space, showers and lockers) are provided for employees and visitors.

Water

Water saving measures within the building include low-flow fittings for showers and taps, and dual low-flow flush cisterns for toilets. The landscaping uses a water-efficient irrigation system with drip feeders and automatic timers.

Energy

The building and its services are designed to achieve a high quality internal environment, and energy efficient solutions.

The client included an energy performance target of 145 kWh/m2/year (of net lettable area) in the design brief. A preliminary energy study using modelling based on the Australian GreenStar method - backed by EECA - predicted an energy use of 102 kWh/m2/year.

The model assumes good management of the lighting only - not daylight dimming. However, modelling does tend to underestimate actual usage due to longer operating hours and higher than predicted plug loads.

Despite this, it is likely that the building will perform below the client's benchmark level in terms of energy use.

The predicted energy use compares well with the National Energy Efficiency and Conservation Strategy target for new buildings of 100 kWh/m2/year.

A low-pressure system (VAV) was picked as the most suitable heating, ventilation and cooling (HVAC) system for the building. The VAV system is designed to achieve good internal environmental quality. The system includes economiser cycles, CO2 control, and free-cooling controls to take advantage of Wellington's mild climate. These features, along with the building management system (BMS), reduce the demands on the ventilation fans and pumps to mimimise energy consumption.

The office lighting systems are designed to take full advantage of natural lighting. Energy efficient dimmable lamps (T5) and daylight compensation controls take advantage of natural lighting, giving a lighting power density of around 12.5 W/m2.

Occupancy sensor control of the lighting is provided to appropriate areas.

The BMS monitors and controls the building services to balance comfort and energy use. It also allows the energy consumption of separate features and areas to be monitored, enabling features and areas of high energy consumption to be identified and fixed.

Energy-saving strategies used include:

  • variable speed drives for fans and pumps
  • low-flow water fittings, reducing hot water usage
  • building management system with control of out-of-hours usage
  • economy cycle control for free cooling has been incorporated in the chiller plant
  • higher-than-code levels of insulation.

Graph showing that estimated energy use is just above the NEECS Target and significantly lower than the Brief Target.

Credits

Client CentrePort Limited

Contractor Fletcher Construction

Tenant Statistics New Zealand

Project manager - client Rawlinsons

Project manager - tenant Mallard Cooke

Architect JASMAX Wellington

Fitout architect - tenant Studio of Pacific Architecture/DEGW

Structural engineer Dunning Thornton

Services engineer Beca Carter Hollings & Ferner

Acoustic consultants Marshall Day Acoustics (Wellington)

Surveyor Spencer Holmes

Fire engineering Spencer Holmes