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Proper ventilation of residences is essential for occupant health and comfort, and is responsible for a significant portion of energy consumption in homes. This study examines a method for providing adequate ventilation in homes while reducing energy consumption and peak demand: "smart" control of ventilation through sensing of occupancy and modulation of ventilation fans. We first conducted a detailed simulation study of advanced California homes with several occupancy-based ventilation control strategies. We then look at how general these results are nationally through a second simulation campaign in 15 ASHRAE climate zones. All simulations compared equivalent indoor air quality situations and assessed energy savings benefits. A key difference from previous demand-controlled ventilation strategies is that our study includes the effects of building related contaminants that are continuously emitted, irrespective of occupancy status, consistent with the requirements in ASHRAE Standard 62.2–2016. Under this new assumption, it is very difficult to extract substantial energy savings using only occupancy sensing. For the baseline strategy, savings were less than 10% of ventilation energy and sometimes negative in all cases analyzed other than leakier 2-story homes. Addition of a pre-occupancy flush period increases savings somewhat, but savings are still less than 15% other than in 2-story leakier homes. • Accounting of exposure to pollutants emitted by a home is crucial for accurately determining the efficacy of a given strategy. • Large savings are very difficult to achieve through occupancy-based smart ventilation in residences. • Efficacy of occupancy-based smart ventilation strategies is very climate-dependent and most effective in the hottest climates. • Efficacy of strategies is highly dependent on concentrations to which occupants are exposed immediately upon returning home. [ABSTRACT FROM AUTHOR]

We present a study of natural ventilation design during the early (conceptual) stage of a building's design, based on a field study in a naturally ventilated office in California where we collected data on occupants' window use, local weather conditions, indoor environmental conditions, and air change rates based on tracer-gas decay. We performed uncertainty and sensitivity analyses to determine which design parameters have most impact on the uncertainty associated with ventilation performance predictions. Using the results of the field study along with wind-tunnel measurements and other detailed analysis, we incrementally improved our early-design-stage model. The improved model's natural ventilation performance predictions were significantly more accurate than those of the first draft early-stage-design model that employed model assumptions typical during initial design. This process highlighted significant limitations in the EnergyPlus software's models of occupant-driven window control. We conclude with recommendations on key design parameters including window control, wind pressure coefficients and weather data resolution to help improve early-design-stage predictions of natural ventilation performance using EnergyPlus. [ABSTRACT FROM AUTHOR]

Abstract: This study examines the human health implications of natural ventilation in California office buildings. We modeled work-time exposures using field data on indoor and outdoor ozone and particulate matter from four case studies in naturally ventilated offices and published data from mechanically ventilated offices. We also modeled the amount of time that windows would be open in the naturally ventilated office and used the results to estimate the difference in pollutant exposures for occupants of naturally ventilated versus mechanically ventilated, air-conditioned offices. Based on published concentration–response equations, we estimated the incremental changes in health outcomes that resulted from the difference in exposures for occupants in the two types of offices. We also estimated the differences in sick building symptom rates based on symptom prevalence rates in naturally ventilated and air-conditioned offices. Finally, we developed first-order estimates of the health-related costs and benefits of retrofitting 10 percent of California's current office space to use natural ventilation. Findings included an increase in annual health-related costs from increased exposure to ozone and particulate matter of between $130 million and $207 million, and a reduction in sick building syndrome symptom costs, valued between $4.3 million and $11.5 million. Our estimates have a high degree of uncertainty and exclude potentially significant health-related costs and benefits of both naturally ventilated and air-conditioned buildings. Nonetheless, these estimates indicate that health-related costs of natural ventilation are significant and warrant further study. We also explore several mitigation options that could limit the health and economic impacts of natural ventilation. [Copyright &y& Elsevier]

Peak power demand strains electrical grids and increases cost of electricity generation, transmission and distribution infrastructure. Many studies have examined ways of reducing peak power demand, including modification of room air temperature setpoints or reduction of lighting levels. However, very few or no studies have examined the peak power reduction resource offered by temporary curtailment of building ventilation systems. For this reason, we conducted a simulation campaign in which we examined the resource offered by temporary ventilation curtailment in commercial buildings of different use types across the United States and in residences in the state of California, with the essential constraint that any changes resulted in air quality acceptable to occupants through additional ventilation to compensate for the curtailment. To do this, we employed previously validated building models implemented in the airflow and contaminant transport tool CONTAM and building thermal and systems modeling tool EnergyPlus, in some cases co-simulated. Results show savings are highly dependent on building type and climate but range from 0–2 W/ft2 and up to 40% of total peak building power demand. Depending on building type, this power shed can be conducted for 1.5–8 h before acute exposure or odor concerns are expected, assuming a safety factor of 2. This reduction is of the same magnitude as that offered by thermal control strategies such as setpoint increase, or from lighting reduction strategies. [ABSTRACT FROM AUTHOR]