The unprecedented levels of urbanization in the last century have led to significant social housing populations in cities across the world. Housing conditions in social housing units are usually ...substandard, which often correlates with higher exposure to indoor pollutants, and ultimately negative health effects. We reviewed 49 articles in the literature documenting indoor environmental quality (IEQ) conditions in social housing which were focused on air pollutant concentrations, thermal comfort, or health effects associated with living in these units. We found evidence that social housing residents may be disproportionately exposed to higher levels of PM2.5, which is heavily influenced by the presence of cigarette smoking in the building. However, we found no evidence that they are disproportionately exposed to higher levels of other pollutants such as formaldehyde and dampness. Poor thermal comfort was also found to be a prevalent issue in social housing, but there are not enough data on comparable non-social housing to make a definitive statement about relative prevalence. We also found that there are strong indicators that residing in social housing is associated with negative health effects, with high prevalence of respiratory problems. Lastly, we found that green retrofits have the potential to improve the IEQ conditions, but these retrofits must be tailored to the specific context of each building. Given the increasing importance of social housing to most urban areas, and the potential vulnerability of social housing inhabitants, it is imperative that we maintain healthy environments for these occupants.
•Review encompasses 49 articles documenting IEQ in social housing.•High exposure to PM2.5 and poor thermal comfort were common issues reported.•Living in social housing was consistently associated with poor health.•Green retrofits offer an opportunity to improve the IEQ and the health of occupants.
This study explores the impact of filtration on energy use in residences based on yearlong measurements in 19 homes in Toronto, Canada. Results show that permanent split capacitor (PSC) motor fans ...drew approximately 40% more power than electronically commutated motor (ECM) fans and the median efficacy (flow divided by power) of ECM fans was 43% higher than that of PSC motor fans. In response to a pressure drop of 150 Pa, ECM fans drew more power (46% − 58% increase) and generally tended to maintain airflow rate, while PSC motor fans drew less power (10% − 23% decrease), but generally tended to reduce airflow rate. Filter pressure drop was not strongly correlated with filter nominal efficiency; thus, the use of higher-efficiency filters may not impact fan power draw. Fan energy consequences of high-efficiency filters are negligible in our sample, and because HVAC runtimes were generally low (median = 11%), the difference between the energy consumption of ECM and PSC motor fans at typical runtimes was small (less than 10 kWh per month). Filters in systems with ECM fans have higher effectiveness per unit of power draw than those in systems with PSC motor fans.
Poor indoor air quality indicated by elevated indoor CO2 concentrations has been linked with impaired cognitive function, yet current findings of the cognitive impact of CO2 are inconsistent. This ...review summarizes the results from 37 experimental studies that conducted objective cognitive tests with manipulated CO2 concentrations, either through adding pure CO2 or adjusting ventilation rates (the latter also affects other indoor pollutants). Studies with varied designs suggested that both approaches can affect multiple cognitive functions. In a subset of studies that meet objective criteria for strength and consistency, pure CO2 at a concentration common in indoor environments was only found to affect high‐level decision‐making measured by the Strategic Management Simulation battery in non‐specialized populations, while lower ventilation and accumulation of indoor pollutants, including CO2, could reduce the speed of various functions but leave accuracy unaffected. Major confounding factors include variations in cognitive assessment methods, study designs, individual and populational differences in subjects, and uncertainties in exposure doses. Accordingly, future research is suggested to adopt direct air delivery for precise control of CO2 inhalation, include brain imaging techniques to better understand the underlying mechanisms that link CO2 and cognitive function, and explore the potential interaction between CO2 and other environmental stimuli.
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•Continuous filtration systems operation maximizes exposure reduction and energy use.•Operation strategies based on monitoring and cycling can optimize filtration.•Concentration ...threshold can reduce runtime while causing little increase in exposure.•The benefits come from synchronizing operation with high concentration periods.•Benefits depends on outdoor concentration, infiltration, HVAC sizing, and emissions.
Particle filtration systems are widely used indoors to reduce particle concentration. Increasing the runtime, the fraction of time a system operates, can improve the removal performance but also comes at a greater energy cost. Thus, operation strategies are needed to improve performance while conserving energy. In this work, we used exposure reduction, a metric for filtration effectiveness, and removal efficacy, the ratio of exposure reduction to runtime to provide a quantitative assessment on four operation strategies including strategies sensitive to concentration and/or presence of emission events, pulsing the system regardless of concentration, and pulsing during elevated concentration periods. A time-varying mass balance model is used to estimate indoor concentration with stochastic emission events. The results show that the concentration strategy, which synchronizes the system operation with high indoor concentrations has the highest removal efficacy. It could achieve a comparable level of concentration reduction as continuous operation at runtimes as low as 80%. The runtime of this strategy can be further reduced by increasing its concentration threshold. This strategy provides opportunities to regulate indoor concentration while conserving fan energy use, especially in regions with relatively low ambient concentrations and strong episodic sources.
In this study, we explore different filter and contextual characteristics that influence effectiveness of high‐efficiency filters in 21 residences in Toronto, Canada. The in situ effectiveness was ...assessed with decay tests at the beginning and the end of filter life with four different filters (MERV 8‐14 from ASHRAE Standard 52.2) installed in operational HVAC systems, compared with either the system off or with no filter installed. There was considerable difference between median PM2.5 effectiveness of the non‐electret filters when compared to electret filters (16% vs. 36%) of the same nominal efficiency (MERV 8). However, median PM2.5 effectiveness of electret filters only slightly improved (between 5% and 9% absolute increase) as MERV increased from 8 to 14. There was more variation in filter effectiveness between the same filter in different homes than there was between different filters in the same home. Variations in filter performance arose because home‐specific particle loss rates (eg, ventilation rate) vary greatly in different buildings. The higher the loss rates due to non‐filter factors, the lower the effectiveness of a filter. Given the relatively large variation in effectiveness for a given filter over time and in different homes, increasing system runtime may be a productive way to improve filter performance in many homes.
Behavior can account for significant differences in building energy use. Monitoring and reporting of building energy use may induce occupants to conserve energy. The goal of this study was to assess ...the behavioral impact of providing building occupants with personal electricity utilization data contextualized with different social frames of reference. We installed monitoring equipment on the electrical meters for 83 rooms of a six-floor residential dormitory building and formulated three study groups and a control group from the building occupants. One study group was provided with their own electricity use, a second group was provided their own electricity use contextualized with average building occupant utilization, and a third group was provided with their own electricity use contextualized with both average occupant utilization and the electricity use of their peer network in the building. The only group that significantly reduced their electricity use when compared to the control group was the study group that could view peer network utilization. All three study groups exhibited response–relapse patterns after viewing their electricity consumption raising important questions about the sustainability of energy conservation and monitoring efforts.
Effectiveness is commonly used to evaluate the particle removal performance of residential filtration systems. Previous investigations have used various effectiveness metrics to assess system ...performance through modeling efforts. However, the model assumptions often lead to an overestimation of effectiveness. Further, none of the studies considered the impact of realistic residential heating, ventilation, and air conditioning (HVAC) system operation patterns. In this investigation, we evaluated the strength and limitations of various effectiveness metrics. We identified exposure reduction as the most appropriate metric for modeling analyses because it does not rely on any steady-state assumptions. A time-varying mass balance model that accounts for system operation parameters including runtimes and cycle on-times, and the impact of indoor emission sources is used to simulate the changes in indoor particulate matter smaller than 2.5 μm (PM2.5) concentration with and without system operation. The effectiveness results show that runtime has the biggest impact on exposure reduction. At a fixed runtime, short cycle on-times and the coincidence of system operation with emission events can further improve the removal performance of the system. Thus, the particle removal performance of a filtration system can be optimized by changing its operation pattern while still maintaining similar fan energy use.
•Existing effectiveness metrics could overestimate HVAC filtration performance.•We present a framework to directly assess filtration performance.•The simulation results suggest runtime has the biggest impact on effectiveness.•Shorter cycle on-times bring more filtration benefit.•Filtration performance can be optimized by synchronizing operation with emissions.
The dynamics of indoor environmental conditions, human occupancy, and operational characteristics of buildings influence human comfort and indoor environmental quality, including the survival and ...progression of microbial communities. A suite of continuous, long-term environmental and operational parameters were measured in ten patient rooms and two nurse stations in a new hospital building in Chicago, IL to characterize the indoor environment in which microbial samples were taken for the Hospital Microbiome Project. Measurements included environmental conditions (indoor dry-bulb temperature, relative humidity, humidity ratio, and illuminance) in the patient rooms and nurse stations; differential pressure between the patient rooms and hallways; surrogate measures for human occupancy and activity in the patient rooms using both indoor air CO2 concentrations and infrared doorway beam-break counters; and outdoor air fractions in the heating, ventilating, and air-conditioning systems serving the sampled spaces. Measurements were made at 5-minute intervals over consecutive days for nearly one year, providing a total of ∼8×106 data points. Indoor temperature, illuminance, and human occupancy/activity were all weakly correlated between rooms, while relative humidity, humidity ratio, and outdoor air fractions showed strong temporal (seasonal) patterns and strong spatial correlations between rooms. Differential pressure measurements confirmed that all patient rooms were operated at neutral pressure. The patient rooms averaged about 100 combined entrances and exits per day, which suggests they were relatively lightly occupied compared to higher traffic environments (e.g., retail buildings) and more similar to lower traffic office environments. There were also clear differences in several environmental parameters before and after the hospital was occupied with patients and staff. Characterizing and understanding factors that influence these building dynamics is vital for hospital environments, where they can impact patient health and the survival and spread of healthcare associated infections.
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