Demand Controlled Ventilation

Green building initiatives, like the US Green Building Council’s LEEDv4, British BREEAM and Australian Energy Rating all encourage commercial constructors and building operators to reduce their impact on environment by increasing their energy efficiency. Especially LEED v4 stresses the importance of precise ventilation automation control using accurate sensors. Also the ASHRAE Green Standard 189.1 (USA) and the European standard EN 13779 recommend using demand-controlled ventilation (DCV) primarily to reduce energy usage while promoting healthy indoor air.

Demand-Controlled Ventilation and Energy Efficiency

Demand-controlled ventilation (DCV) is proven to have a huge impact on HVAC systems’ energy efficiency. The US Department of Energy conducted a research on energy savings and economics of advanced control strategies for HVAC in 2011. The research concluded that DCV contributes to the biggest energy savings in HVAC in small office buildings, strip malls, stand-alone retails and supermarkets compared to other advanced automated ventilation strategies. Average cost savings of using demand-controlled ventilation were calculated to be 38% for all commercial building types, which is a very significant number. The amount depends on the climate, of course; demand-controlled ventilation is most efficient in cold climates, and coupling it with multi-speed fan control will bring more benefits also in hot climates.

Demand-Controlled Ventilation and Employee Productivity

Studies indicate that better indoor air and ventilation also has a positive impact on employee productivity. The Continental Automated Buildings Association (CABA) conducted a comparison between better buildings and other employee strategies, like workplace health programs and bonuses. With a meta-study of 500 different studies, they found  that better buildings increase productivity by 2%–10%. The Federation of European Heating, Ventilation and Air Conditioning (REHVA) state that decreased ventilation lowers productivity, for example, typing speed, by 10%. The US Green Building Council conducted a meta-study in 2003 and concluded that delivery of fresh air and reduced levels of pollutants improve productivity by 11%. According to the analysis of the Carnegie Mellon University, better ventilation improves productivity by 3%–18%. To sum it up, the productivity gains of better ventilation range between 2% and 18%, according to many studies.

A study conducted by the National Institute of Environmental Health Sciences (NIEHS) in 2015 focused on the effects indoor air quality has on employees’ cognitive abilities. The extensive study setting simulated office conditions and compared conventional offices to WWF Green and Green+ offices. Cognitive scores in crisis response, information usage and strategy, among other variables, were evaluated on the test subjects. The results of the NIEHS study show how cognitive skills are decreased by the increase of carbon dioxide in indoor air. This finding shows that strategic skills, for example, are decreased only to 20% in indoor air with a 1,400 ppm concentration of CO₂ compared to the normal outdoor level of 400 ppm. Some of the more mechanical skills, like information seeking and task orientation, were not affected much. However, cognitive skills that require more advanced application of information, such as crisis response, information usage, and strategy, are affected the most. The study shows clearly that handling more advanced tasks becomes much more difficult when the carbon dioxide levels rise in indoor air.

How Does Demand-Controlled Ventilation Work?

In DCV the ventilation intensity is adjusted to correspond to the true need in order to save energy. It has clear advantages especially when occupancy varies widely, such as in schools, conference centers, and auditoriums. The CO₂ level in a space indicates human presence and can be used to control ventilation. The efficiency of DCV can only be optimized by accurate carbon dioxide sensing.

Vaisala CARBOCAP® technology delivers maintenance-free accuracy and performance that lasts. The CO₂ sensors can be used in a wide variety of applications, including variable outdoor CO₂ levels or facilities with around-the-clock occupancy such as hospitals, workplaces, and residential buildings.