Person:

Pendleton, Joseph

Background Past work demonstrating an association between indoor air quality and cognitive performance brought attention to the benefits of increasing outdoor air ventilation rates beyond code minimums. These code minimums were scrutinized during the COVID-19 pandemic for insufficient ventilation and filtration specifications. As higher outdoor air ventilation was recommended in response, questions arose about potential benefits of enhanced ventilation beyond infection risk reduction.

Objective This was investigated by examining associations between indoor carbon dioxide concentrations, reflective of ventilation and building occupancy, and cognitive test scores among graduate students attending lectures in university classrooms with infection risk management strategies, namely increased ventilation.

Methods Post-class cognitive performance tests (Stroop, assessing inhibitory control and selective attention; Arithmetic, assessing cognitive speed and working memory) were administered through a smartphone application to participating students (54 included in analysis) over the 2022–2023 academic year in classrooms equipped with continuous indoor environmental quality monitors that provided real-time measurements of classroom carbon dioxide concentrations. Temporally and spatially paired exposure and outcome data was used to construct mixed effects statistical models that examined different carbon dioxide exposure metrics and cognitive test scores.

Results Model estimates show directionally consistent evidence that higher central and peak classroom carbon dioxide concentrations, indicative of ventilation and occupancy, are associated with lower cognitive test scores over the measured range included in analysis ( ~ 440–1630 ppm). The effect estimates are strongest for 95th percentile class carbon dioxide concentrations, representing peak class carbon dioxide exposures.

Impact statement As the COVID-19 pandemic eased, questions emerged on the benefits of increased outdoor air ventilation beyond infection reduction. This work assesses associations between carbon dioxide concentrations, indicative of ventilation and occupancy, and cognitive test scores among students in university classrooms with increased outdoor air ventilation. Although not causal, models show statistically significant evidence of associations between lower carbon dioxide concentrations and higher cognitive test scores over the low range of carbon dioxide exposures in these classrooms. While the underlying mechanisms remain unknown, higher outdoor air ventilation appears to provide additional benefits by reducing indoor air exposure and supporting student performance.

Few studies have examined associations between indoor conditions and creativity, despite its importance to knowledge work. Accordingly, we investigate associations between indoor air and thermal conditions and divergent creative thinking scores among 86 young adult knowledge workers in office buildings across four countries over approximately six months. Indoor environmental monitors at participant workstations provided measurements of indoor carbon dioxide and fine particulate matter concentrations, temperature, and relative humidity. Hourly averages of these environmental parameters were paired with participant responses to the Alternative Uses Test, a validated assessment of divergent creative thinking, for incorporation into mixed effects statistical models. The models show statistically significant evidence that higher indoor carbon dioxide concentrations, altered by ventilation and occupancy, are associated with lower divergent creative thinking scores. A 100-ppm increase in CO2 is associated with a 3 % (95 % CI: 0–5 %), 4 % (95 % CI: 1–6 %), and 11 % (95 % CI: 5–16 %) negative difference in the expected fluency, flexibility, and originality count scores, respectively; and an 11 % decrease (95 % CI: 5–16 %) in the expected elaboration score. There is suggestive evidence of lower divergent creative thinking scores with higher fine particulate matter concentrations; however, concentrations and sensor accuracy were low and limit these findings. The thermal estimates suggest a temperature range of roughly 22–26 ◦C to be associated with higher divergent creative thinking scores. Overall, this study suggests that maintaining temperatures within a normative range and focusing on ventilation, to lower concentrations of carbon dioxide and unmeasured but correlated pollutants, can help promote creative thinking in working environments.

Motivated by limitations with the use of temperature and thermal comfort models in relation to occupant health outcomes, this work investigates numerous characterizations of thermal conditions and associations among these thermal variables, cognitive performance, and thermal perceptions. Measurements of classroom dry-bulb temperature and relative humidity were used to calculate a suite of eleven thermal variables, which were paired with thermal sensation votes and cognitive test responses from graduate students attending classes in these monitored spaces, resulting in an analysis dataset of 273 observations from 54 participants. Results from Spearman Rank correlation coefficients, factor analysis, and principal component analysis suggest that the eleven thermal variables cluster into three groups that reflect variations in indoor temperature, indoor relative humidity, and indoor-outdoor differences. While several variables appear to reflect variations in only air temperature (e.g., PMV estimates) or moisture, indoor enthalpy appears to reflect variations in temperature and RH in the most balanced manner. A series of mixed effects statistical models suggest that higher values of indoor enthalpy appear to be associated with improved cognitive test scores and warm sensations, and warm sensations appear to be associated with improved cognitive test scores. The collective results posit new considerations for the importance of indoor moisture with respect to occupant outcomes and how commonly used modelling approaches may not reflect this. Additional research that incorporates diverse populations, varied built environments, and causal methods could help further our understanding of the effects of air temperature and moisture on occupant outcomes in varied built environment settings.