Residential Smart Ventilation: A Review
Air ventilation is one of the top energy users in residential buildings. Smart ventilation equipment and controls help to reduce the amount of energy use attributable to ventilation in homes while maintaining high indoor air quality. Ventilation can also be used as a resource for utility grid demand response if done intelligently. A key component of the smart ventilation concept is the use of controls to ventilate more when doing so provides an energy or air quality advantage and/or a resource to the power grid, and less when it provides a disadvantage. Unlike demand-controlled ventilation, other smart ventilation concepts involve the addition of several new inputs into control algorithms—namely measured or modeled concentrations of pollutants and signals from the electricity grid. And, unlike demand-controlled ventilation, smart ventilation uses the “equivalent ventilation” principle in the selection of the control strategy, which allows anticipation of future ventilation needs and retroactive compensation for previous ventilation needs.
To determine the best means of controlling ventilation in residences, this study first reviewed literature relating to the:
- Suitability of common environmental variables (pollutants of concern, humidity, odors, CO2, occupancy) for use as input variables in smart ventilation applications
- Availability and reliability of relevant sensors
- Different control strategies used for a smart ventilation approach.
Results of the review showed that the suitability of each environmental variable is specific to each smart ventilation application, and also that pollutant sensors are currently not robust or accurate enough to be relied upon for residential ventilation controls.
Next, this research assessed the regulatory context in which smart ventilation strategies might be implemented most effectively. The assessment showed that many countries already have a regulatory structure that is favorable for the development of smart ventilation strategies. These countries have regulations and standards in place that propose “equivalence methods” that offer a path to compliance including the use of smart ventilation strategies. These compliance paths have allowed for the development and availability of demand-control ventilation systems in the marketplace; more than 30 such systems have been approved and are available in countries including Belgium, France, and the Netherlands. It seems likely that the more complex smart ventilation strategies would follow a similar path to market acceptance.
Results of the review of smart ventilation in residential buildings is used to:
- Determine and discuss performance of smart ventilation in terms of energy and indoor air quality
- Gather data on occupant behavior
- Assess the suitability of automatically controlled ventilation systems
- Assess the applicability of a multi-zone approach for ventilation.
This meta-analysis of 38 studies of various smart ventilation systems with controls (on either CO2, humidity, combined CO2 and TVOC, occupancy, or outdoor temperature) shows that ventilation energy savings of up to 60% can be obtained without compromising IAQ—and sometimes even improving it. In some cases, the smart ventilation strategies did not reduce energy use (showing an increase in energy use of up to 26%).
Occupant behavior was also examined in the review. The examination showed that occupants are rarely aware of the quality of their indoor air, particularly with regard to health issues, and do not necessarily operate the ventilation systems when recommended for optimal indoor air quality or energy efficiency. The applicability of a multi-zone approach is also demonstrated by studies showing a disparity in concentrations between different rooms of a home, and differences between single-zone and multi-zone modeling in residential buildings.
Finally, this report summarizes ongoing developments in smart ventilation strategies and applications, including research into indoor air quality metrics, feedback on the lack of quality in ventilation installations, and source control (filtration and air cleaning) issues.