With the increasing advancements in ventilation technologies, demand controlled ventilation (DCV) systems have become a major factor for indoor air quality. Demand controlled ventilation systems are particularly beneficial in meeting rooms, where occupancy and pollutant accumulation may reach harmful levels.
The Basics of Demand Controlled Ventilation
Demand controlled ventilation can enhance heating, ventilation, and air conditioning (HVAC) systems and building performance. Such technology adjusts the ventilation airflow according to the actual demand and is applicable to variable air volume (VAV) systems. Note that this technology is an energy efficient air-handling system which can meet the varying temperature and humidity needs of buildings. In contrast, constant air volume (CAV) configurations operate at full capacity regardless of occupancy or contaminants.
The design of demand controlled ventilation relies on precise sensors and accounts for occupancy, activity rates, and pollutants. In fact, as the number of people correlates with carbon dioxide (CO2) concentrations, CO2 sensors are among the most used promising methods to build a boost demand controlled ventilation efficiency. Such detectors surpass sensors of occupancy which detect presence but not the number of occupants. The DCV system we built at Foobot goes even beyond by monitoring five airborne pollutants in addition to CO2.
Demand controlled ventilation benefits not only fresh air supply but thermal comfort and energy costs. Since such systems provide ventilation airflow on demand, they are cost-efficient, particularly in office buildings where occupancy. Additionally, the use of an economizer can contribute to costs reductions and energy efficiency by using outside air ventilation when the weather conditions allow it. Economizers also regulate the mixed air temperature according to its setpoint improving thermal comfort levels.
Demand Controlled Ventilation in Meeting Rooms
As indoor air quality is essential for human health and building performance, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has introduced standards for HVAC optimization and high-occupancy areas, such as office buildings, classrooms, meeting rooms, correctional facilities, theaters, lobbies, medical centers, conference rooms, and areas with high levels of pollutants (e.g., beauty salons and labs).
To set an example, the 126.96.36.199 Ventilation Controls for High-Occupancy Areas section states that demand control ventilation is required for areas bigger than 500 sq. ft. and with design occupancy for ventilation of more than 40 people per 1000 sq. ft.. Note that standards are changing and improving on a regular basis. The initial ASHRAE standards 62 and 62.1, for instance, stated that the required ventilation for conference and meeting rooms (cfm per 1,000 sq. ft.) was 1,000 and 310 cfm per 1,000 sq. ft., respectively. Now, the modified ASHRAE standard 62.1-2016: Ventilation for Acceptable Indoor Air Quality is accepted globally.
Office buildings and meeting rooms, in particular, require special consideration as they impose high health risks. Data showed that people spend up to 90% of their time indoors, sealed in cubicles and transport. To improve HVAC efficiency in meeting rooms, the following sensor equipment can be employed:
- Time-based controls
- Occupant counters
- Occupancy sensors
- Air pollution sensors
Demand Controlled Ventilation in Meeting Rooms and Health Outcomes
The US Environmental Protection Agency (EPA) reveals that indoor air can be more detrimental to human health than outdoor air pollution. Thus, demand controlled ventilation in meeting rooms is essential to improve air quality, thermal comfort, and cost efficiency. Relying on reduced fan power and air cfm, demand controlled ventilation results in energy reductions between 25-55%, compared to CAV systems, and longer longevity. Additionally, such systems allow the use of smaller ducts, which will lead to reductions in the spaces required for installation.
Moreover, with the implementation of a CO2, humidity, pressure or temperature sensor, demand controlled ventilation systems can lead to better health outcomes:
- Research shows that poor air quality has a negative effect on work performance. Note that dampness, bad odor, and thermal comfort also influence performance and may lead to work errors. To set an example, typing speed can decrease by 10% due to poor office environments. Demand controlled ventilation systems, however, can improve employee performance and productivity by adjusting airflow to the actual demand. In 2003, the US Green Building Council conducted a meta-study and concluded that delivery of fresh air and reduced levels of pollutants improve productivity by 11%.
- Air quality affects cognitive abilities. A survey showed that 68% of office workers experience cognitive problems and difficulties concentrating, 67% suffer from fatigue at work, and 54% experience decreased productivity. In addition, mental acuity and the completion of complex tasks may deteriorate. High accumulations of CO2 (1,400 ppm) lead to a decrease in concentration of 20%. Complex tasks performance, such as information acquisition, crisis response, and planning strategies, also decreases.
- Poor air quality causes adverse physical symptoms and long-term effects. Headaches, watery eyes, and nausea are common in 41% of office workers. Note that although the human breathing increases CO2 levels, people are not the only factor for air pollution. In office spaces and meeting rooms, gas emissions from laser printers and pollutants from clogged filters can also lead to negative health outcomes, such as allergies, respiratory diseases, and even premature birth. The Royal College of Physicians revealed that in the UK alone, bad air quality accounts for 40,000 premature fatalities annually.
- Air quality at work also impacts subjective well-being, such as life satisfaction, optimism, and happiness. Note that subjective well-being has been linked to job satisfaction, attendance, and loyalty.
Demand Controlled Ventilation: The Key to Better and Green Work Environments
Demand controlled ventilation is an innovative technology which can lead to improved air quality and energy efficiency. Demand controlled ventilation systems are essential in office buildings and meeting rooms, where the concentrations of pollutants can reach harmful levels. Interestingly, demand controlled principles can be applied to lighting controls in office buildings and satisfactory integration between lighting and HVAC systems can be achieved. Efficiency is also required regarding water and material. We should note that the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) is one of the main bodies that provide certifications for sustainable and green facilities. Evidence shows that green buildings with good indoor air quality, daylight, acoustic privacy, and greenery can improve employees’ performance and well-being.
Improving green building principles, work environments and air quality in meeting rooms is an essential step to ensure human safety, productivity, and well-being. Demand controlled ventilation systems, emerging in the US and in California in particular, are to have become the key to better working environments and building performance.