District (or central) cooling systems, which distribute chilled water or other media to multiple buildings for air-conditioning, have been used in commercial buildings for decades. While district cooling systems are most widely used in downtown business districts and institutional settings, such as college campuses, they offer tremendous benefits to building owners and should be considered by developers planning large office complexes or mixed-use properties.In traditional construction, the chiller is typically the largest energy load in any given building. In fact, heating, ventilating, and air-conditioning (HVAC) account for more than 30 percent of the energy consumed in U.S. commercial buildings. Individual buildings, and even individual segments of a building, usually have separate cooling systems, but by planning appropriately on the front end – before construction even begins – developers can create an efficient infrastructure that provides environmental and economic benefits.At Atlantic Station, a 140-acre, mixed-use development in midtown Atlanta, developers partnered with Southern Company Energy Solutions, a business unit of Atlanta-based Southern Co., to create a 50,000-square-foot central cooling plant to cool buildings throughout the property.The Benefits of District CoolingThe fully built-out plant at Atlantic Station will save building owners more than $35 million in construction costs, while operating more than 25-percent more efficiently than traditional building HVAC systems. This will result in emissions savings equaling 2 million gallons of gasoline. This energy efficiency will result in lower energy bills for building owners and will help reduce heating of the local atmosphere.Individual building HVAC systems emit thermal heat that warms the local atmosphere. By using energy-efficient, centralized cooling, developments, such as Atlantic Station, have the opportunity to reduce this atmospheric warming and thus improve quality of life and preserve the environment.The district cooling system will also reduce building maintenance and save the enormous square footage required for more conventional building cooling systems. The amount of leaseable floor space is increased by eliminating the need for on-site mechanical equipment rooms, including chillers, cooling towers, pumps, and refrigerant-monitoring systems. The absence of cooling units at each building will even provide aesthetic benefits, eliminating the need for the typical (and sometimes architecturally challenging) rooftop cooling unit.How District Cooling Systems WorkWater is chilled at a central plant to about 38 degrees F. and delivered to the buildings where it circulates through refrigeration coils. Fans blow the building’s air across the coils, which cool the air.At Atlantic Station, the system will use a two-mile-long network of 36-inch pipes to deliver chilled water from the central cooling plant to the 12 million square feet of office, residential, and retail space as the buildings are constructed at the development. The system will circulate approximately 40,000 gallons of chilled water per minute at peak times to control the temperature in these buildings.Engineering of Atlantic Station’s district cooling system, with Southern Company Energy Solutions, commenced two years before the development’s projected 2003 opening. Such foresight stands to benefit not only the developer, its partners, and tenants, but the environment, too.James Jacoby is president of Atlantic Station LLC, and chairman, chief executive officer, and founder of Atlanta-based Jacoby Development (www.jacobydevelopment.com).