THE AIR UP THERE Effects of ductwork leakage on HVAC systems By Josh Lewis
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roperly designed and operated HVAC systems are critical to ach ieve com for t , adequate indoor air quality and energy efficiency in healthcare facilities. These systems are governed primarily by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standard 170, Ventilation of Health Care Facilities, which sets out temperature and humidity levels that must be maintained; minimum outdoor air and total air changes per hour; filtration levels; whether recirculated air can be used; and room pressure relationships to adjacent areas. The standard has evolved as ongoi ng resea rch has shown it’s necessary that HVAC systems effectively filter, dilute, purify and humidify air to reduce the risk of healthcare acquired infections (HAIs). As a result, healthcare facilities often
36 CANADIAN HEALTHCARE FACILITIES
have some of the largest HVAC systems, which consume a high amount of energy per square metre compared to most commercial buildings. Since no price can be put on the health and safety of patients and staff, energy ef f iciency has historically taken a backseat to the minimum design and operational requirements of HVAC systems. (If the standard is not followed, there is potential increased risk of HAIs and legal liability.) But now, with Canada’s commitment to reduce greenhouse gases to achieve net-zero emissions by 2050, solutions must be found to address these compet i ng pr ior it ies a nd t hen systematically implemented. THE X-FACTOR
There are many factors that determine both the operating state and energy efficiency of an HVAC system. They
include the necessary fan speed and power to move the air through the system; the heating and cooling energy input to achieve the desired temperature; and the effort needed to humidify or dehumidify the air to maintain the space conditions required by standard 170. Many of these factors can be optimized through commonly used strategies, such as variable frequency drives (VFDs), parallel fans, high-efficiency boiler and chiller systems, heat recovery equipment and building automation, as well as tuning the systems to operate at the optimal level. This is primarily achieved with testing and air balancing by professional service providers. There is another factor that can greatly impact the operation and efficiency of these systems — ductwork leakage. Most people easily recognize the waste produced by leakage in other types of systems like a steady drip com-
