We express the performance benefits of “Smart Ventilation” in comparison to continuous whole-building ventilation. The ASHRAE ventilation standard 62.2 specifies continuous ventilation as its primary option. LBNL scientists use continuous ventilation as a baseline for ventilation energy use and for assessments of indoor air quality. We refer to this comparison between intermittent smart ventilation and continuous ventilation as “equivalence”.
Smart Ventilation and Airtightness
To meet zero net energy (ZNE) requirements, the industry must reduce natural infiltration-related energy use. This involves reducing envelope air leakage by half – from roughly 4 ACH50 in current production homes to below 2 ACH50. This air-leakage reduction represents about 15% energy savings from conventional new homes. Previous studies have estimated about 1,000 kilowatt-hours/year energy savings in a typical ZNE home.
We anticipate even greater savings for new homes that use economizers. Title 24 requires economizers in Climate Zones 8-14, where the majority of new construction in the state currently happens. If California doesn’t meet these IAQ requirements, then these natural infiltration-related savings won’t happen. This will make it very difficult, if not impossible, for California to meet its ZNE targets.
Reducing natural air leakage in new construction is an important step in getting to the state’s 2020 goal.
Smart Ventilation and IAQ
Concern about adverse impacts of airtight buildings on IAQ is a major barrier to industry and the utilities to enhance building energy efficiency. The concern is that reducing natural infiltration will cause health problems and reduce building durability. The SVACH research will lower this barrier by providing both the quantitative and qualitative information to demonstrate how to achieve acceptable IAQ while reducing natural infiltration.
California homes must achieve and maintain good IAQ, or California utility ratepayers will bear considerable additional healthcare costs. IAQ studies generally show that health-related IAQ costs are greater than the energy-related costs of ventilation. However, it is difficult to determine exact values. Nevertheless health costs would likely exceed the $1 billion California-energy-savings estimate from the RESAVE ventilation study (another LBNL/CEC research project). Thus, health costs are a barrier that seriously limits the State’s ability to air-tighten buildings, which in turn limits the state’s ability to achieve ZNE homes.
Energy Savings and Peak-Load Reduction
Heating and cooling electricity peak demand occurs only at certain times. Peak demand is one aspect of ZNE that can cause peak-demand problems for utilities. The peak demand is about 15% of the heating and cooling load for a conventional home, however a higher fraction for a ZNE home. A smart ventilation system can reduce the peak by shifting ventilation operation to off-peak hours.
Previous LBNL studies indicated that simple timer controls avoid ventilation on summer afternoons or winter nights. This can save about 40% of ventilation peak load. Smart ventilation systems that respond to utility peak demand/load-shed signals should make it possible to reduce potential grid reliability problems.
Current smart-ventilation systems reduce peak load, save energy, and control pollutant levels compared to continuous ventilation using these strategies.
- Using timers or temperature sensors to determine when ventilation occurs so that the energy impact is smallest. For example, shifting ventilation from times of high temperature difference to times of low temperature difference. This control strategy is particularly valuable as a peak-demand-reduction strategy.
- Accounting for operation of other ventilation systems, such as kitchen and bathroom exhaust fans and clothes dryers. For example, if the close dryer operates for an hour, the ventilation system’s controls reduce its operating time to compensate for the clothes dryer’s air exchange.
- Reducing ventilation during times when the building is unoccupied.
- Ventilating more at some times to compensate for other times when ventilation is reduced. For example, ventilating more when the outdoor air is cleaner and less when the outdoor air is dirtier.
Summary of Smart-Ventilation Benefits
- Optimize energy efficiency and IAQ for Zero Net Energy (ZNE) homes
- Reduce electricity consumption – by 15% of HVAC energy use
- Reduce electricity demand – by a least 15% of HVAC load
- Enhance occupant respiratory health
- Maintain IAQ equivalence compared to ASHRAE 62.2
- Respond to high outdoor pollutant levels by temporarily reducing ventilation operation
- Account for other air exchange — local exhaust fans and clothes dryers