Improving Indoor Environmental Quality and Energy Performance of Modular Classroom HVAC Systems
The factory-built relocatable classroom (RC) is a dominant force in the school facility construction industry in the United States (U.S.) and elsewhere. It is estimated that there are approximately 650,000 RCs currently occupied in the U.S., housing about 16 million students. RCs receive public attention due to complaints about poor indoor environmental quality (IEQ). Both measured data and anecdotal evidence in California have suggested excessive acoustical noise from heating, ventilation, and air conditioning (HVAC) equipment as a central factor leading to degraded IEQ. In the U.S., RCs are typically equipped with unitary exterior wall-mount HVAC systems, and interior acoustical noise due to structural and airborne transmission can reach levels of about 58dB(A) with compressor cycling, under unoccupied conditions. Due to these noise levels teachers often simply choose to turn off the HVAC, leading to inadequate ventilation, as well as poor thermal conditioning, and thus to poor indoor air quality. Elevated levels of carbon dioxide and volatile organic compounds including formaldehyde are common. We discuss the acoustic component of our efforts to develop and test energy efficient HVAC systems that address the ventilation, controls, and acoustic requirements necessary to ensure high quality indoor environments in RCs.