Demand-Controlled Ventilation in a Multi-Zone Office Building

Abstract

This study applies indoor air quality modelling to investigate the potential advantages and drawbacks of demand-controlled ventilation as an indoor air quality control strategy. The study uses a multiple zone pollutant transport model to evaluate the performance of several indoor air quality control strate gies under a variety of conditions. The pollutant transport model is incorpo rated into the TRNSYS simulation program to allow simultaneous calculation of both building pollutant concentrations and building energy use. A specific office building situation consisting of a main zone and a conference room was studied. The simulations showed that a carbon dioxide-based demand con trolled ventilation system can provide better control of indoor air quality than a constant outdoor airflow at the ASHRAE Standard 62-1989 prescribed level under a wide range of building conditions. The constant outdoor air approach lacks the capability of providing additional outdoor air when required by poor building conditions such as a low pollutant removal effectiveness and a high occupant density. The demand-controlled ventilation system saves energy compared to the constant outdoor air approach under all conditions consid ered. It was also found that a demand-controlled ventilation strategy consist ing of a step controller combined with scheduled 100% outdoor air purges can protect building occupants from exposure to high concentrations of non-occu pant-generated pollutants while still providing energy savings.