The V in Classroom HVAC

Briefly notes the commonly applied minimum outdoor air ventilation rates for school classrooms in the US over the last 100 years and outlines the provisions of the current draft of the successor to Standard 62-1989. Points out that the ability of an HVAC system to provide acceptable thermal conditions and air quality are often overlooked. Examines and compares the performance capabilities of several classroom HVAC systems of maintaining space relative humidity and controlling risk of microbial infection transmission. Also evaluates the effect of different outdoor ventilation rates on classroom humidity during warm weather. The systems compared are - unit ventilators, VAV single duct, single zone rooftop units, conditioned outdoor air supply system and dual fan, dual duct.