energy design resources design brief air conditioning ventilation Using the whole systems approach Summary Air conditioning and ventilation systems have a large impact on building profitability Not only do they consume about one to building design designers around the world have succeeded fourth of an office building s electricity but they have a large influence on worker productivity Nonetheless considerable evi at creating highly efficient air con dence indicates that air conditioning systems receive less attention than they deserve Opportunities to cost effectively improve the energy efficiency of these systems frequently go overlooked ditioning systems that provide excellent workspace comfort and surveys of office workers have shown that one third to onehalf of those questioned find their offices too hot or too cold This state of affairs is both unnecessary and uneconomical Using the whole systems approach designers around the world have succeeded at crafting highly efficient air conditioning systems that also provide excellent workspace comfort They begin by minimizing unwanted heat gains to reduce cooling loads Next they design air distribution systems and cooling plants to contents meet those reduced cooling loads taking advantage of both capital and operating cost savings Finally they specify highly Introduction 2 efficient cooling plants Reducing Cooling Loads 5 In one exemplary building that benefitted from this approach Improving the Efficiency of Air Distribution Systems 8 Choosing High Efficiency Unitary Equipment 11 Designing High Efficiency Chilled Water Systems 14 ever to produce such extraordinary results Virtually any air Replacing Refrigerative Cooling with Evaporative Cooling 19 conditioning and ventilation design can be incrementally For More Information 22 improved through the use of the whole systems problem solv Notes 24 worker productivity improved by 16 percent while electricity consumption went down by 40 percent Another building s clever design made it possible to maintain thermal comfort in a hot climate without any electrically powered air conditioning and ventilation system Designers need not feel pressured how ing approach Introduction Air conditioning and ventilation systems have a tough assignment Although they work tirelessly to make buildings comfortable and healthy they are rarely noticed unless they aren t working well That s a shame because these systems have a huge impact on the bottom line for building owners and operAir conditioning and ventilation systems consume nearly one fourth of the electricity used in commercial buildings in the five state Pacific region that includes California ators For example air conditioning and ventilation systems consume nearly one fourth of the electricity used in commercial buildings in the five state Pacific region that includes California 1 Although the minimum efficiency of these systems is prescribed by local and national codes and standards such as the California Energy Commission s Title 24 there are often many economically justifiable opportunities for reducing air conditioning energy costs that go overlooked The impact that air conditioning systems have on worker productivity is also frequently overlooked by owners and operators As Figure 1 shows in a single year office worker salaries equal about 130 per square foot That is about one and one half times the cost of constructing the building nearly 100 times the annual electric bill and about 160 times the operating cost of the building s space cooling and air handling system 2 Is it worthwhile to spend more money on a high quality air conditioning and ventilation design that yields a more comfortable building and improved worker productivity Judging from studies showing that one third to one half of the office workers questioned find their offices to be too hot or too cold the answer would appear to be yes 3 Productivity gains need not be large to quickly pay for the additional design and construction costs of improving these systems For example assuming that a new commercial air conditioning system costs about 10 per square foot to design and install if a 10 percent increase in the cost of that system resulted in only a one percent increase in productivity the additional cost would be paid for sometime during the first year of operation page 2 air conditioning ventilation Because productivity improvements have the potential to produce far greater returns than energy efficiency improvements we also need to ask whether it might make sense to improve productivity at the cost of increased energy consumption If one had to choose between these two attributes the obvious choice would be productivity Fortunately building designers do not have to settle for that kind of trade off It is possible to design If forced to choose between improving highly efficient air conditioning systems that also provide excel productivity or energy efficiency the lent workspace comfort yielding lifetime economic benefits for obvious bottom line choice would be owners and well modulated temperatures for occupants productivity Fortunately designers don t have to settle for that kind of trade off For example when the West Bend Mutual Insurance Company built its new 150 000 square foot headquarters in West Bend Wisconsin several years ago the building design incorporated many energy efficient features such as upgrades to lighting and window systems The finished all electric building uses 40 percent less electricity than West Bend s old building which was gas heated 4 Figure 1 Annual operating costs per square foot for a medium size office building In a medium size office building one year s worth of office worker salaries is roughly equivalent to one and a half times the entire cost of constructing the building Office workers salaries 130 Gross office rent 21 Total energy use 1 81 Electricity use 1 53 Repair and maintenance 1 37 Space cooling and air handling electricity 0 61 Space cooling and air handling electricity and maintenance 0 82 Total building operations and management salaries 0 58 0 20 40 60 80 100 120 140 Source E SOURCE air conditioning ventilation page 3 But the savings didn t end there The advanced air conditioning system designed for the building also included personal environment modules for 430 of West Bend s 500 employees The modules feature adjustable desktop diffusers that allow employees to control both the airflow and the temperature right at their
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