Demand controlled ventilation : Impact on energy use and indoor environmental quality

European buildings account for a significant share of the energy-related emissions in Europe. Addressing the increasing energy use and its contribution to greenhouse gases (GHG) is internationally recognized as crucial, and emissions must be halted. Heating, ventilation, and air conditioning (HVAC) systems responds to a substantial share of the energy use in buildings. Demand controlled ventilation (DCV) is a technique designed to improve the energy efficiency. DCV operates by adjusting the air flow rates and settings of ventilation to the actual demand in buildings. DCV systems can be based on detected levels of i.e., relative humidity (RH), carbon dioxide (CO2), and volatile organic compounds (VOC) and it is valuable to understand what parameters that are most significant for the control. This study aimed to investigate how different control parameters and settings affected the energy use of ventilation and indoor environmental quality (IEQ). A case study was implemented in an educational building and monitoring was done during the operation of different cases. From the measured data, four different IEQ parameters, and energy use were evaluated. Energy usage was both calculated from energy equations in Excel and simulated in software called TRNSYS based on inputs of measured airflows. The results showed that using DCV instead of constant air volume (CAV) ventilation resulted in 10-65% energy use reductions. The majority of measured IEQ parameters occurred within the scope of good levels according to standards. Energy savings of 56% was achieved when conducting settings on wider temperature intervals, letting the temperature fluctuate between (20±3˚C), and the result indicated that it did not affect the IEQ negatively. Also, it was possible to reduce energy use by implementing VOC control instead of CO2. Some of the cases showed that RH conditions were positively affected when implementing DCV. It was also shown that the answers in the questionnaire survey did not always interact with the measured values. This indicates that the experienced IEQ does not necessarily represent the measured values and differences between individuals will have an impact as well