Improvement in demand-controlled ventilation simulation on multi-purposed facilities under an occupant based ventilation standard

The objective of this paper was to find an effective way of improving demand-controlled ventilation (DCV) simulation performed under an occupant based ventilation standard established in many countries. Two attractive DCV approaches, CO2–DCV and RFID–DCV, were applied to DCV simulations for a theoretical public assembly space served by a dedicated outdoor air system (DOAS) with an enthalpy recovery device. A numerical model for predicting the real-time occupant number, required ventilation amount, CO2 and formaldehyde (HCHO) concentrations under given conditions was developed using a commercial equation solver program. The current ventilation standard used in Korea was applied as a case of occupant based ventilation standards. It was found that the current standard might cause unstable DCV simulation results, especially under CO2–DCV. This is because the ventilation rate (per person) indicated in the standard is the sum of the outdoor air required to remove or dilute air contaminants generated by both occupants and the buildings themselves, and not a pure function of occupant numbers. Finally, it makes DCV control unstable when ventilation flow is regulated only by the number of occupants. In order to solve this problem, the current occupant based ventilation standard was modified as a form of ASHRAE Standard 62.1-2007 showing good applicability to various DCV approaches. It was found that this modification enhances applicability of the current ventilation standard to CO2–DCV significantly and can maintain acceptable HCHO concentrations during the entire time of operation. Fan energy reduction can also be expected from DCV operations.