Building Design
Post design and construction strategies
Building envelope and orientation
Mechanical ventilation, cooling and heating
Plan of Darling Park complex Level 10.5
Spatially, the basic concept for the 3.5 hectare site was for three office towers, public open space and a waterfront restaurant / entertainment area. The development site spanned five roadways, which was resolved by building over and under them, this providing a connection between the city and Darling Harbour. The towers are triangular and grouped around a circular raised garden, which is actually built over a vehicular freeway, though this has been executed in such a way that it is not apparent when in the space. The triangular shape and the disposition of Towers 1 and 2 allow them to have frontages and entrances from Sussex Street (thus a CBD street presence) as well as articulating with, and defining the form of, the shared garden. The garden has been designed with a variety of levels of open and enclosed spaces to provide different settings from public to semi-private.
The designers of Darling Park set out to create a prestige business environment more akin to a five star hotel than an office tower. The lavish foyers, lush garden and the Cockle Bay Wharf restaurant precinct are all intended to provide a 'total lifestyle and work experience' to attract blue chip tenants. So too are the 700 parking spaces promoted to potential tenants as approximately three times the average car parking of other Sydney CBD office towers. The seven basement levels of car parking are all below sea level, and given the close proximity to the harbour, they required additional strengthening against water pressure and potentially unstable marine sediments.
Interior of Building Foyer
Underground parking, foyers and gardens are shared between the towers. A distinguishing feature of Darling Park is the street level foyer, with polished timber floors, leather lounges, artworks, mood lighting and coffee bars. This generously proportioned and opulently fitted out space forms a public interconnection between the two towers and through to the garden, as well as articulating with the separate foyers that some of the larger tenants like Fairfax have. The common foyer is a 'live space' used by both building tenants and the public. This civic approach (Kuhne & Associates' contribution to the project) is in stark contrast to the more typical corporate foyer: a vast, empty marble space of security surveillance where no-one is inclined to linger.
Publicly acessible luxury is Darling Park's most attractive feature. The downside of this space is the environmental cost: timbers sourced from old growth forests; plants from around the world; energy required to transport and transform marbles, metals, leathers and timbers into finely wrought, decorative objects and finishes; chemicals, water and energy required to maintain the foyer and gardens in a permanently pristine condition. Then, over and above this, are the reverberating impacts of the development's sign value. Darling Park upped the stakes for prestige commercial developments in Sydney. To be part of the image, Darling Park's big corporate tenants have fitted out luxury entry lobbies on their own floors. This high impact palatial style (previously the preserve of mansions and expensive hotels) then gradually insinuates itself as normality for those inhabiting such spaces on a daily basis.
Reception area on a tenant floor (Fairfax)
The building's systems were also designed to high performance specifications, though this is contradictory. On the one hand the HVAC system is very reliable and operates with great efficiency, on the other, it has been designed for very high loads, which means that tenants are not constrained in their use of heat-generating office equipment and lighting because the system can cope with it.
View of Darling Park: Western Elevation
Building height
was required by the Darling Harbour Authority to be lower than core CBD heights,
so as to create a step down to the waterfront. Therefore:
1. Towers 1 and
2 are 27 storeys above ground (plus 3 top levels for plant)
2. Tower 3 will be 19 storeys
Each tower is triangular with champfered corners. The core structure, floor
system and support structures are reinforced concrete. There is a column frame
around the perimeter.
Typical high rise floor plan (high density)
The floor plan consists of a triangular service core surrounded by three modules of column free, open-plan office space. Each floor averages 1900m2 of lettable space. Some floors are linked by interconnecting stairs, a feature used for dramatic effects by some of the corporate tenants (e.g. Price Waterhouse Cooper's Hollywood style grand sweeping staircase).
Detail showing Price Waterhouse Cooper's sweeping staircase
Post design & construction strategies
For large and complex developments to be commercially viable, the building systems have to go through a commissioning and testing process, while the building managers have to be provided with documentation and hand-over manuals. With tenants on long leases paying premium rent, it is vital to ensure that building functions as designed. But of course the story doesn't end there, because highly engineered buildings like Darling Park are not simple containers for tenants' activities, they are in fact assembled technological systems that have to be operated and maintained - in this sense they are more akin to industrial plants. The most important post design and construction strategy for commercial developments like Darling Park, therefore is to ensure the appointment of building managers with expertise in facility care and energy management. They should ensure that performance actually improves over time.
A large air-conditioning system, for example, needs to be 'run-in' and its operation periodically reviewed and fine-tuned, especially as occupancy and loads vary over time. Darling Park's building managers, Jones Lang Lasalle have taken on this responsibility, using feedback from the Building Management System (BMS) which controls air conditioning and common area lighting, to learn how to get the most efficient and cost-effective operation out of the buildings' technical systems.
Design Strategies: Energy
Building envelope and orientation
Basic building design and orientation was driven by the desire to maximise flexible lettable space and take advantage of the views over Darling Harbour to the west and southwest. The chamfered triangular design, chosen because it allowed column-free space, resulted in three long sides facing east, west and south, which is not optimal in terms of daylighting or protection against glare and heat. Added to this, windows are floor to ceiling height - a design practice that the Property Council of Australia now generally advises against (PCA, 2001) because of glass's poor insulating properties.
To offset the thermal disadvantages of the building footprint and envelope (a problem common to many tower blocks), Darling Park's windows are double glazed (which has half the heat transmission properties of single glazing) and the facades have been treated differently. The western facade has full sun hoods of a slightly different 'dropped down' design, while the south facade of Tower 2 has external fixed vertical louvres.
Detail of Western facade showing 'dropped down' sun hoods
Mechanical ventilation, cooling and heating
Air conditioning is supplied by a central plant that provides constant air volume at the perimeter and variable air volume (VAV) for the rest of the space. Three air-handling units (AHUs) at the top of the building and three in the basement deliver pre-cooled or pre-heated air. The floors are divided into three zones with six to eight VAV outlets per zone. The VAV system is programmed to supply higher volumes and rates of airflow as internal temperatures rise. There are shut-off dampers on each floor operated according to tenant use patterns.
As is typical with Sydney office buildings, cooling far outweighs heating needs, this because of the mild climate and radiated heat from density of occupation, lighting and office equipment loads. The chillers are therefore crucial. Located in the basement, the refrigerant activated chillers provide chilled water, which is pumped to the AHUs located on basement level B2 and up to rooftop level 28. The AHUs blow air through heating and cooling coils distributing it through the building. There are two large capacity centrifugal chillers and one smaller capacity screw chiller. These have four modes of operation according to load demand:
1.Screw chiller
only
2.One centrifugal chiller
3.Screw + centrifugal chiller
4.Two centrifugal chillers
Modes 1 and 2 are applied for 99 percent of the time, and the building has never needed to operate in mode 4. Switching between modes is automated via the BMS, as is switching between the two large chillers to equalise their operational lives.
The system has been programmed to deliver a temperature range between 21.5 and 23.5 degrees C, with 22.5 as the mean target. Summer and winter set points are different, with winter being set lower to take into account that occupants will be dressed more warmly. An outside air economy cycle is used, introducing larger amounts of external air on a controlled basis for cooling the building according to balance between external and internal temperatures.
Winter heating is supplied by gas-powered boilers that operate typically between April and October. Two boilers are available, configured in an alternating duty/standby arrangement, however only one of the boilers needs to operate to provide the required level of heating.
The HVAC system has been designed for a maximum equipment load of 45W/m2; a lighting load of 15W/m2 and a population density of one person per 10m2 NLA. The lighting load is at the upper limit of current practice (PCA 2001, p.46). The equipment load is extraordinarily high, given that the office equipment target load for energy efficient buildings in the early 1990s, when Darling Park was first occupied, was only 5W/m2 (BOMA,1994). This fact, along with the specification of the chillers, suggests that Darling Park's HVAC system was deliberately over-specified in anticipation of increasing IT equipment usage. The ability to cope with high lighting loads and large personnel energy take-up has attracted high energy using tenants.
Lighting is a significant consumer of energy in commercial buildings and has been identified as a priority area for abatement by the Australian Greenhouse Office. On average it accounts for 21 percent of greenhouse gas emissions of commercial buildings (AGO, 1999). This is the context in which to consider the design and operation of Darling Park's lighting systems.
Common area lighting at Darling Park is BMS controlled and is programmed to vary in intensity according to time of day. The BMS has the capability to control the lighting on tenanted floors, however this functionality has not been elected for implementation by the tenants.
The lighting design for office floors has been specified to provide illumination to office areas of 500 lux, which is higher than the current Australian Standard of 320 lux (AS 1680.2.2-1994 Interior Lighting: office & screen-based tasks). Some technical energy efficiency measures were incorporated (light fittings each comprise 2X36W fluorescent units, dimmable electronic ballasts and low brightness diffusers; light boxes can be moved within the ceiling grid allowing flexibility in fit-outs).
The design of the basic lighting controls is not optimal for energgy conservation, however. There is only one switch panel per floor and switching is organised into three lighting zones corresponding with the 'wedges' of the floorplates. This zoning configuration works against the advantage of the daylighting from floor to ceiling windows, because perimeter lighting cannot be switched off when daylight is adequate, unless controls have been modified. According to Building Managers Jones Lang Lasalle, most tenancy fit-outs have installed greater levels of control. As yet, Fairfax, the largest tenant has not, but is considering a major lighting control retrofit, given that after hours, frequently whole floors remain lit even though only a few people might be working.
Interior of Star Court
Darling Park has one of the highest recycling rates of any CBD building. A centralised service is provided to tenants with separate bins provided for paper and general waste to every desk in the building and a separate bin for glass collection on each floor. Any contamination of the recyclable waste results in a note being left at the offending desk.
The garden terrace is somewhat ambiguous in environmental terms, being very resource intensive and requiring irrigation. The 3,000m2 garden is basically a very big 'plant pot' on a shallow concrete slab (though soil depth is 1 metre). Soil was custom designed to hold moisture and nutrients, to provide good drainage and prevent seepage onto the roads and car parks below. The garden comprises over 1000 trees and plants sourced from around the world and chosen for their ability to tolerate a west-facing aspect, intense sunlight, strong salty winds and air pollution. Perrenials, grasses and super-advanced trees feature.
Darling Park Garden Terrace