Ventilation requirements in hot, humid climates

In 2003 ASHRAE approved the nation's first residential ventilation standard, ASHRAE Standard 62.2. Meeting this standard in new construction requires the use of mechanical ventilation, which in turn can often significantly increase the latent load faced in new homes. As the thermal performance of houses improves, sensible loads have decreased and existing equipment may not be able to deal with the remaining latent load. Failure to take this load into account can result in poor indoor air quality and moisture-related problems. As part of work through the Building America program, LBNL has simulated the effects of mechanical ventilation systems that meet ASHRAE Standard 62.2 on ventilation, energy use and indoor humidity levels. In order to capture moisture related HVAC system operation, such as the lack of dehumidification from typical air conditioning systems at the beginning of each cycle, we developed a simulation tool that operates on a minute-by-minute basis and utilizes a dynamic model of air conditioner performance. This paper looks in depth at the implications of these simulations in humid climates.