ENERGY SAVINGS THROUGH TREATING BUILDINGS AS SYSTEMS

Much of the analysis of the potential to save energy and reduce emissions of greenhouse gases in thebuildings sector has focused on the energy savings that can be achieved through incrementalimprovements in the efficiency of individual energy-using devices (motors, fans, pumps, boilers,chillers) but without changing the way in which they are put together as systems. However, muchlarger savings are possible through changes in building systems, and further, these savings can beachieved at much smaller incremental investment cost and sometimes at lower first cost. This paperwill focus on the savings that can be achieved through a systems approach to buildings. The systemsapproach begins with a consideration of building shape and form and the specification of a highperformanceenvelope so as to minimize heating and cooling loads. This leads to a number ofsynergies that further reduce energy requirements, such as permitting cooler temperatures fordistributing heat and warmer temperatures for distributing coldness (which leads to greater efficiencyin the operation of heating and cooling equipment), the use of displacement ventilation (which reducesventilation energy requirements), and chilled-ceiling cooling (which improves the efficiency of chillers).Use of warmer temperatures for cooling also permits greater use of ambient air or direct use of coolingtowers for cooling, giving yet further cooling-energy savings. Separation of cooling fromdehumidification functions permits use of solar thermal energy in desiccant dehumidification andcooling systems. In desiccant dehumidification systems without the use of solar energy, efficiencies ofindividual components do not appear to be any better than that of conventional vapour-compressionsystems, but overall system efficiency can be much better. Altogether, heating and cooling loads innew buildings can be readily reduced by a factor of three to four, and sometimes more, compared tocurrent practice in most jurisdictions of the world. With regard to lighting, system-level considerations(layout, controls, sensors, placement of sensors, daylighting) are at least as important as theefficiencies of individual devices. Finally, the building occupants are part of the building energy system,and are an important consideration with regard to operable windows and fans, use of an adaptivethermal comfort standard, demand-controlled ventilation, the operating strategy with passive andhybrid passive/mechanical ventilation systems, and occupancy sensors for lighting systems.