Effect of Residential Ventilation Techniques for Hot and Humid Climates on Indoor Concentrations of Volatile Organic Compounds

Mechanical ventilation may be necessary to provide adequate ventilation in new houses due to the relatively low rates of infiltration achieved in new construction. However, in hot and humid climates, increased ventilation may raise indoor humidity to an undesirable level. A study was undertaken by the Florida Solar Energy Center (FSEC) to evaluate the humidity effects of different mechanical ventilation strategies for such climates. The study was conducted in a new 141-m2 manufactured house sited at the FSEC campus. Six mechanical ventilation strategies were evaluated for their ability to control indoor humidity levels over 14-day periods with simulated occupancy. A base case with no extra ventilation served as a control. The strategies consisted of spot exhaust ventilation, use of an energy recovery ventilator, and four configurations of a dedicated outdoor air supply system, one of which included use of a room dehumidifier. The objective of the study described here was to determine the impacts of the ventilation techniques on the concentrations and emission rates of indoor-generated formaldehyde and other volatile organic compounds (VOCs). Measurements of indoor and outdoor VOCs were made both by active and passive sampling during each ventilation condition. The emission factors of most VOCs remained relatively constant across all experiments with mechanical ventilation. The case with the dehumidifier and the outside air supply fan programmed to be on at least one-third of the time was shown to provide the generally lowest indoor VOC concentrations because it was able to operate at a higher ventilation rate while maintaining 50% indoor relative humidity.