Computer simulation software was used to study the impacts of ASHRAE Standard 62-1989 on small Florida offices. The simulation tool was selected due to its unique ability to model both moisture transport/storage in typical building materials and the effect of continuous supply fan operation on air conditioner latent capacity. A typical building was modelled for three cities (Miami, Orlando, and Jacksonville). The performance of a conventional heating, ventilating, and air-conditioning (HVAC) system and commercially available alternative technologies was simulated to determine their ability to mitigate the impacts of increased ventilation while maintaining acceptable indoor humidity levels. The installed first costs and life-cycle costs of the HVAC systems were compared to identify cost-effective options for meeting the new ventilation requirements. A conventional air conditioning system, with a sensible heat ratio (SHR) of 0.78, was unable to keep the indoor humidity below 60% RH for a significant number of hours when the outdoor air flow rate was increased from 5 to 20cfm (2.5 to 10.0 L/s) per person. While reducing humidity levels to a certain extent, simply selecting a conventional air conditioner with a slow SHR (0.73) still allowed humidity levels in excess of 60% RH for 8% to 15% of the total occupied hours. Alternative HVAC systems are currently available to meet the increased dehumidification loads resulting from ASHRAE Standard 62-1989 ventilation rates. Of the alternative systems evaluated for this study, demand-controlled ventilation and enthalpy recovery wheels minimised both the energy and economic impacts of the increased ventilation requirements.

KEYWORDS: year 1996, standards, ventilation, USA, offices, relative humidity, calculating, moisture, unit air conditioners, performance, air conditioning, air flow rate, humidity, dehumidifying, demand controlled ventilation, heat recovery, computer programs, comparing