Limited evidence associates inadequate classroom ventilation rates (VRs) with increased illness absence (IA). We investigated relationships between VRs and IA in California elementary schools over two school years in 162 3rd-5th-grade classrooms in 28 schools in three school districts: South Coast (SC), Bay Area (BA), and Central Valley (CV). We estimated relationships between daily IA and VR (estimated from two year daily real-time carbon dioxide in each classroom) in zero-inflated negative binomial models. We also compared IA benefits and energy costs of increased VRs. All school districts had median VRs below the 7.1 l/s-person California standard. For each additional 1 l/s-person of VR, IA was reduced significantly (p<0.05) in models for combined districts (À1.6%) and for SC (À1.2%), and nonsignificantly for districts providing less data: BA (À1.5%) and CV (À1.0%). Assuming associations were causal and generalizable, increasing classroom VRs from the California average (4 l/s-person) to the State standard would decrease IA by 3.4%, increase attendance-linked funding to schools by $33 million annually, and increase costs by only $4 million. Further increasing VRs would provide additional benefits. These findings, while requiring confirmation, suggest that increasing classroom VRs above the State standard would substantially decrease illness absence and produce economic benefits. Practical ImplicationsThese findings suggest a potentially large opportunity to improve the attendance and health of elementary school students in California through provision of increased classroom ventilation. The majority of classrooms in this study provided less ventilation than specified in current State guidelines. If the relationships observed here (and in several prior studies) and the costs and benefits estimated here are confirmed, it would be advantageous to students, their families, and school districts, and highly cost-effective, to ensure that ventilation rates in elementary school classrooms not only meet but substantially exceed current ventilation guidelines. Because specific exposures and response mechanisms involved have not been determined, it is possible that more energy-efficient alternatives to increased ventilation, such as filtration and reduced indoor emissions, might provide similar benefits. Nomenclature

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Limited evidence has associated lower ventilation rates (VRs) in schools with reduced student learning or achievement. We analyzed longitudinal data collected over two school years from 150 classrooms in 28 schools within three California school districts. We estimated daily classroom VRs from real-time indoor carbon dioxide measured by web-connected sensors. School districts provided individual-level scores on standard tests in Math and English, and classroom-level demographic data. Analyses assessing learning effects used two VR metrics: average VRs for 30 days prior to tests, and proportion of prior daily VRs above specified thresholds during the year. We estimated relationships between scores and VR metrics in multivariate models with generalized estimating equations. All school districts had median school-year VRs below the California VR standard. Most models showed some positive associations of VRs with test scores; however, estimates varied in magnitude and few 95% confidence intervals excluded the null. Combined-district models estimated statistically significant increases of 0.6 points (P = 0.01) on English tests for each 10% increase in prior 30-day VRs. Estimated increases in Math were of similar magnitude but not statistically significant. Findings suggest potential small positive associations between classroom VRs and learning.

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Spatial prediction is an important problem in many scientific disciplines. Super Learner is an ensemble prediction approach related to stacked generalization that uses cross-validation to search for the optimal predictor amongst all convex combinations of a heterogeneous candidate set. It has been applied to non-spatial data, where theoretical results demonstrate it will perform asymptotically at least as well as the best candidate under consideration. We review these optimality properties and discuss the assumptions required in order for them to hold for spatial prediction problems. We present results of a simulation study confirming Super Learner works well in practice under a variety of sample sizes, sampling designs, and data-generating functions. We also apply Super Learner to a real world dataset.

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This document summarizes a research effort on demand controlled ventilation and classroom ventilation. The research on demand controlled ventilation included field studies and building energy modeling. Major findings included: The single-location carbon dioxide sensors widely used for demand controlled ventilation frequently have large errors and will fail to effectively control ventilation rates (VRs). Multi-location carbon dioxide measurement systems with more expensive sensors connected to multi-location sampling systems may measure carbon dioxide more accurately. Currently-available optical people counting systems work well much of the time but have large counting errors in some situations. In meeting rooms, measurements of carbon dioxide at return-air grilles appear to be a better choice than wall-mounted sensors. In California, demand controlled ventilation in general office spaces is projected to save significant energy and be cost effective only if typical VRs without demand controlled ventilation are very high relative to VRs in codes.Based on the research, several recommendations were developed for demand controlled ventilation specifications in the California Title 24 Building Energy Efficiency Standards.The research on classroom ventilation collected data over two years on California elementary school classrooms to investigate associations between VRs and student illness absence (IA). Major findings included: Median classroom VRs in all studied climate zones were below the California guideline, and 40% lower in portable than permanent buildings. Overall, one additional L/s per person of VR was associated with 1.6% less IA. Increasing average VRs in California K-12 classrooms from the current average to the required level is estimated to decrease IA by 3.4%, increasing State attendance-based funding to school districts by $33M, with $6.2 M in increased energy costs. Further VR increases would provide additional benefits. Confirming these findings in intervention studies is recommended. Energy costs of heating/cooling unoccupied classrooms statewide are modest, but a large portion occurs in relatively few classrooms.iii

This document summarizes a research effort on demand controlled ventilation and classroom ventilation. The research on demand controlled ventilation included field studies and building energy modeling. Major findings included: The single-location carbon dioxide sensors widely used for demand controlled ventilation frequently have large errors and will fail to effectively control ventilation rates (VRs). Multi-location carbon dioxide measurement systems with more expensive sensors connected to multi-location sampling systems may measure carbon dioxide more accurately. Currently-available optical people counting systems work well much of the time but have large counting errors in some situations. In meeting rooms, measurements of carbon dioxide at return-air grilles appear to be a better choice than wall-mounted sensors. In California, demand controlled ventilation in general office spaces is projected to save significant energy and be cost effective only if typical VRs without demand controlled ventilation are very high relative to VRs in codes.Based on the research, several recommendations were developed for demand controlled ventilation specifications in the California Title 24 Building Energy Efficiency Standards.The research on classroom ventilation collected data over two years on California elementary school classrooms to investigate associations between VRs and student illness absence (IA). Major findings included: Median classroom VRs in all studied climate zones were below the California guideline, and 40% lower in portable than permanent buildings. Overall, one additional L/s per person of VR was associated with 1.6% less IA. Increasing average VRs in California K-12 classrooms from the current average to the required level is estimated to decrease IA by 3.4%, increasing State attendance-based funding to school districts by $33M, with $6.2 M in increased energy costs. Further VR increases would provide additional benefits. Confirming these findings in intervention studies is recommended. Energy costs of heating/cooling unoccupied classrooms statewide are modest, but a large portion occurs in relatively few classrooms.iii