This article was published in High Performing Buildings, Summer 2010. Copyright 2010 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Posted at www.hpbmagazine.org. This article may not be copied C A S E S T U D Y LATITUDE EAST and/or distributed electronically or in paper form without permission of ASHRAE. For more information about High Performing Buildings, visit www.hpbmagazine.org. A Positive Sydney’s Latitude East ranks among Australia’s five most efficient buildings. Latitude East’s performance stems from relatively standard building systems that are designed, implemented and controlled for maximum energy savings rather than green bells and whistles such as trigeneration, wind power or solar photovoltaics. LatitudeBY SCOTT WALKDEN-BROWN AND GODFREY FREDERICK he National Australian BUILDING AT A GLANCE Built Environment Rating System (NABERS) gave Name Latitude East Latitude East its top rat- Location Ting, five out of five stars. Its energy- 52 Goulburn Street, Sydney, Australia saving strategies have led to a build- Owner Brookfield/Credit Suisse Real ing that emits 40% less carbon diox- Estate Fund International (CSREFI) ide than the benchmark required for Principal Use Commercial Office the top NABERS rating. Employees/Occupants 1,400 (approx.) Latitude East is the final building Conditioned Space 247,578 ft2 built at World Square near the heart Substantial Completion/Occupancy of Sydney’s commercial business 2007 district. World Square is a city block Occupancy 100% bounded by George Street, Liverpool Street, Pitt Street and Goulburn Street. The site consists of a large multilevel underground parking operational efficiency requirements area, a shopping center, restaurants, to receive a 4.5 NABERS rating. cafes, hotels, office buildings and Waterman designed the mechani- residential apartment towers. cal, electrical, plumbing and fire Latitude East has nine levels of protection services. We were com- commercial office space with a missioned by Brookfield for these central atrium and approximately consulting services and worked 247,578 ft² of air-conditioned space. closely with them and the rest of the It is built on top of a large common design team. basement and two retail levels. The Energy modeling firm AECOM plant room is located on the top floor. conducted energy simulations The building team sought to build using IES Virtual Environment a high quality, energy-efficient software according to the NABERS office building that would meet the Energy Commitment Agreement for predicting the energy use of the building. IES software is compli- Latitude East’s central atrium with glass ant with ANSI/ASHRAE Standard elevators, exposed elevator structure and 140–2001, Standard Method of Test Drew glass-enclosed stairs results in a dramatic for Evaluation of Building Energy central space and helps unify the nine floors Analysis Computer Programs. Richard of commercial office space. 6 HIGH P ERFORMING B UILDINGS S ummer 2 0 1 0 S u m m e r 2 0 1 0 HIGH P ERFORMING B UILDINGS 7 Energy-Efficient Design The key design elements that con- tribute to the energy efficiency of the building fall into two categories: • The building form, including a central atrium and the façade and • The air conditioning, ventilation, building management control sys- tem (BMCS) and lighting design. Waterman worked together with Brookfield, the architect, façade engineer and energy modeling con- sultant to: • Maximize natural light via the external façade and via the central atrium; Drew • Provide adequate shading to reduce solar loads and glare; and Richard The central atrium of Latitude East • Reduce heat transmission. provides natural light to the lobby and building. The shade from the exist- surrounding offices. The building team checked dif- ing buildings adjacent to Latitude ferent shading configurations and East prompted the team to mini- façades. The architectural concept glazing options for their effect on mize external shading elements, design also strongly influenced the the cooling and heating loads of the particularly on the north and west shading decision. The team selected glazing that offers a reasonable shading fac- tor, but does not reduce daylight- ing (see Lighting Design, p. 20). Double glazing improves the glazing R-value and reduces heat transmission. Air-Conditioning Systems Central chillers, an air-handling plant located in the roof plant room, and boilers serve the building. The system includes: • Two high-efficiency water-cooled screw chillers with variable-speed drives (VSDs); A lighting control system uses photo- electric cells to adjust high-efficiency T5 fluorescent lights based on the amount HPB.hotims.com/30305-2 Drew of available daylight. The building team selected glazing that provides some shad- Richard ing, but does not reduce daylighting. 8 HIGH P ERFORMING B UILDINGS S ummer 2 0 1 0 • Variable-speed chilled water, Chillers. Cooling load calculations heating water and condenser indicated that the building load at T A B L E 1 water pumps; Latitude East was in the vicinity of Load % COP • Three cooling towers with 3,000 kW, prompting a design using variable-speed fans; two chillers at 1,500 kW cooling 100 6.2 90 6.8 • Two gas-fired hot water heaters; capacity each. 80 7.8 Higher chiller set- • • Central air-handing units (AHUs) The team based its chiller selec- point improved effi- 70 8.7 for each perimeter zone and the tion on the following energy-effi- ciency at all loads. 60 9.6 center zone with VSDs; and ciency specifications: It also reduced 50 10.8 pump motor power. • Return/relief air fans with VSDs. • A chilled water operating setpoint of 59°F to 45°F; 40 10.2 30 9.1 • A condenser water temperature of 85°F; and 20 7.6 10 5.7 Latitude East is part of Sydney’s World • A minimum coefficient of perfor- Square, a city block that includes retail mance (COP) at various load The higher chiller setpoint rep- stores, restaurants, office buildings, apart- ments and hotels. The site was previously conditions from 100% to 10% resents a slight shift from tradi- home to the Anthony Hornden & Sons (Table 1). tional practice in Australia where department store, which opened in 1905 and was called The Palace Emporium. Richard Drew 1 0 HIGH P ERFORMING B UILDINGS S ummer 2 0 1 0 HPB.hotims.com/30305-27 chilled water design temperatures Second, using a higher chilled BUILDING ENVELOPE are typically 54°F to 43°F. The water ΔT makes it possible to Roof higher chilled water temperatures reduce the flow rate for the chilled Type Concrete, air gap, insulation improved energy efficiency in water pumps. The team determined Overall R-value R-11 Reflectivity 0.5 two areas. that the 46°F split was a good solu- First, the higher chilled water sup- tion for chiller and AHU coil opera- Walls ply temperature directly increases tion allows for a reduction in the Type Concrete, air gap, insulation, plasterboard the efficiency of the refrigeration chilled water pump motor power by Overall R-value R-11 cycle and chiller COP. The building approximately one-third. Glazing percentage 98 team selected the highest possible Windows chilled water supply setpoint that Air Distribution. Ductwork ris- U-value 0.35 (average) did not adversely affect the dehu- ers deliver air to each floor from Solar Heat Gain Coefficient (SHGC) 0.4 (average) midification ability of the air-han- the central air-handling units. dling unit cooling coils or the over- Latitude 33°55' South all cooling coil selection including Three electrical submeters track energy Outdoor Design Conditions air and water pressure drop. used by the building’s elevators and escala- 90°F dry bulb, 73°F wet bulb tors. Additional submeters track building systems’ energy consumption, providing data that helps building managers identify and resolve problems. Richard Drew 1 2 HIGH P ERFORMING B UILDINGS S ummer 2 0 1 0 HPB.hotims.com/30305-33 ENERGY AT A GLANCE Energy Use Intensity (Site) 24 kBtu/ft2 Natural Gas 10 kBtu/ft2 Electricity 14 kBtu/ft2 Annual Source Energy 58 kBtu/ft2 NABERS Energy Rating f five out o five stars (valid through May 2011) Latitude East uses standard light air boot/troffer type air dif- fusers. Laboratory testing and the calculation of the Air Diffusion Performance Index (ADPI) helped determine the optimum diffuser performance in accordance with Drew ASHRAE Standard 113-2005. Richard Some areas were designed to suit ten- ant requirements, such as the ceiling in this area. ELECTRICITY USE 2 0 0 7 – 2 0 0 8 ( CUMULATIVE) Multiple variable air volume ter- minal boxes (VAVs) on each floor then modulate the airflow to con- trol zone temperatures. In Australia, VAV systems are generally designed for a minimum airflow rate of approximately 0.98 cfm/ft2 with the VAV boxes at full capacity. This design aims to ensure reasonable air movement when the VAV boxes are at minimum turndown (airflow). However, often this practice G A S U S E 2 0 0 7 – 2 0 0 8 ( CUMULATIVE) allows for a minimum VAV turn- down of only approximately 70%. The turndown rate could vary based on diffuser manufacturer, selection, spacing and layout. Unfortunately, this typically means that the VAV boxes do not always have enough modulation range to control temper- ature unless the VAV boxes are also fitted with electric zone reheat. 1 4 HIGH P ERFORMING B UILDINGS S ummer 2 0 1 0 HPB.hotims.com/30305-38 Left This view looking up from the atrium This enabled lower VAV turndowns, WHILE YOU WERE SLEEPING, Drew lobby shows the large skylight, which pro- resulting in two energy benefits: vides natural light to internal offices. Richard • Electric reheats were not Below Various glazing treatments were OTHERS WERE MAKING ICE! selected based on building orientation and required in the VAV boxes for shading from other buildings.