Meeting residential ventilation standards through dynamic control of ventilation systems

Abstract

Existing ventilation standards, including American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) Standard 62.2, specify continuous operation of a defined mechanical ventilation system to provide minimum ventilation, with time-based intermittent operation as an option. This requirement ignores several factors and concerns including: other equipment such as household exhaust fans that might incidentally provide ventilation, negative impacts of ventilation when outdoor pollutant levels are high, the importance of minimizing energy use particularly during times of peak electricity demand, and how the energy used to condition air as part of ventilation system operation changes with outdoor conditions. Dynamic control of ventilation systems can provide ventilation equivalent to or better than what is required by standards while minimizing energy costs and can also add value by shifting load during peak times and reducing intake of outdoor air contaminants. This article describes the logic that enables dynamic control of whole-house ventilation systems to meet the intent of ventilation standards and demonstrates the dynamic ventilation system control concept through simulations and field tests of the Residential Integrated Ventilation-Energy Controller (RIVEC).

Advanced Controls for Residential Whole-House Ventilation Systems

“…The larger value for lim R allows the ventilation device to be off for longer periods while the house is unoccupied, as the inhabitants will not be exposed to the higher levels of indoor contaminants, while limiting the peak levels that a returning occupant is exposed to at the beginning of the occupancy period. Previous work by Sherman and Walker (2011) has shown that a fan sized to 125% of the ASHRAE 62.2 minimum ventilation rate is required for a fan that will be switched off for at least four hours every day (the peak energy demand period).…”

“…The controller does this by shifting the ventilation load of the whole-house mechanical ventilation system off-peak and taking into account auxiliary mechanical ventilation by other systems (Sherman and Walker, 2011). Other ventilation controllers are available, but unlike RIVEC they do not i) account for the contributions of other systems that mechanically ventilate a home, ii) have the ability to avoid times of peak energy and monetary ventilation cost, or iii) have the capability to track IAQ levels only during occupied hours.…”

“…The RIVEC control algorithm was first outlined by Sherman andWalker (2011) andSherman et al (2009). This work further develops the control algorithm in response to the results and recommendations from those reports. The main modifications are to eliminate the pre-peak and post-peak shoulder periods, to remove minimum and maximum ventilation rates and to include occupancy sensing.…”

“…So the RIVEC-controlled device does not need to operate at the same time (although it can operate at the same time, due to subtle intricacies of the control algorithm). To prevent rapid cycling or switching of the whole-house ventilation fan, the controller makes decisions every 10 minutes (also based on Sherman and Walker (2011)). Note that RIVEC monitors the ventilation devices and performs IAQ calculations on much short timescales, so that short duration fan operation (such as bathroom exhaust fans) can be captured.…”

“…Building from previous work (Sherman and Walker, 2011), the control algorithms for RIVEC are optimized and additional control facilities, such as occupancy are developed.…”