Vent Right And Then? Mechanical Ventilation, Dehumidification And Energy Use In Humid Climates

Report Number




Ventilation; Dehumidification; Hot Humid Climates; Humidity; Buildings


The desirability of mechanical ventilation in homes and acceptable infiltration rates are sometimes contentious topics' particularly in humid climates. We present preliminary results of two monitored lab homes constructed to represent the thermal characteristics of typical existing Florida homes. They are configured for the ventilation study with tight and leaky envelopes and with and without mechanical ventilation. We also present simulation results of high performance new homes with mechanical ventilation and typical older existing homes with and without air tightening and mechanical ventilation to provide added context.

Lab home test results indicate that mechanical supply ventilation of the tight home (2 ach50) in accordance with ASHRAE 62.2-3013 increased average indoor relative humidity by 2.2% as compared with the leaky home (8 ach50) without mechanical ventilation in the hot, humid climate of central Florida. However, cooling energy use was increased by about 27% due to substantially increased air conditioner moisture removal ( > 63%). Results also indicate that failure to ventilate the tight home during winter results in excessive indoor relative humidity due to typical internal moisture gains.

To explore other conditions and climates, highly-efficient new tight homes (1.5 and 3 ach50) were simulated in twelve TMY3 weather files representing five U.S. climate zones. Existing leaky homes (11 ach50) were also simulated for one TMY city. Parametric analysis was accomplished using different ventilation system types with and without dehumidification.

Date Published



This paper published in the Proceedings of the 2014 ACEEE Summer Study on Energy Efficiency in Buildings,

© 2014 American Council for an Energy Efficient Economy

Local Subjects

Buildings - Dehumidification; Hot Humid Climates; Humidity; Buildings - Ventilation


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