Distributed Demand Controlled Ventilation for Improving Indoor Air Quality

The interest in controlling Indoor Air Quality (IAQ) stems from the desire to create and maintain healthy and safe work environments for the many people around the world who work in office buildings. This means being able to immediately detect the presence of pollutants and contaminants, alert those in charge, and mitigate the problem or reduce the impact on the indoor environment.

The Syracuse Center of Excellence headquarters includes a Total Indoor Environmental Quality (TIEQ) laboratory for research in this area. But the new building also serves as an example of the latest technology in IAQ and “intelligent built environmental systems.” An intelligent system is designed and built to monitor the environment, perceive changes in conditions, and make automatic adjustments to the indoor environment to achieve optimal performance.

Current HVAC (heating, ventilating, and air conditioning) technology exists for demand-controlled ventilation (DCV). This regulates the amount of fresh air brought into a building based on the carbon dioxide (CO2) generated by the occupants’ activities. DCV provides good IAQ and is more energy efficient than older systems.

However, a recent study by the National Institute of Standards and Technology, a federal government technology agency, shows that DCV may result in higher levels of unhealthy air pollutants such as the volatile organic compounds (VOC) that are emitted in an office environment from plastics and other synthetic materials, cleaning chemicals, and copying and other office equipment. These “passive emissions” can accumulate in the building during unoccupied periods, when the CO2 levels are expected to be low, prompting the DCV to shut off or drastically reduce the supply of fresh air. Some of them cannot be eliminated from the office environment, so controlling  them becomes important.

Researchers at Syracuse University are taking DCV one step further by investigating distributed demand controlled ventilation (DDCV). In this project, investigators are testing methods that rely on a network of distributed sensors and environmental control systems to adjust the supply of fresh air for each occupant based on local conditions. This approach ensures that each occupant will receive the correct amount of fresh air indicated by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) at reduced energy consumption. The DDCV approach will also address such important considerations as occupancy, activity, floor area, passive emissions and ventilation efficiency in individual occupied spaces. To this end, a mathematical model and experimental methods have been developed to evaluate practical design and control methods, and optimize the mechanical equipment for improved IAQ and lower energy consumption.

The new system, operating at a higher level of intelligence, monitors individual offices and cubicles as well as the interaction of the air throughout larger office spaces. Regulation of fresh air control and contaminant detection is then based on the conditions or needs in the individual areas. This distributed approach to IAQ will achieve maximum comfort, health, and safety for workers throughout a building.