Search

Tracer gas experiments were conducted in a 158 m3 room with overhead supply diffusers to study dispersion of contaminants from simulated speaking in physically distanced meeting and classroom configurations. The room was contained within a 237 m3 cell with open plenum return to the HVAC system. Heated manikins at desks and a researcher operating the tracer release apparatus presented 8-9 thermal plumes. Experiments were conducted under conditions of no forced air and neutral, cooled, or heated air supplied at 980-1100 cmh, and with/out 20% outdoor air. CO2 was released at the head of one manikin in each experiment to simulate small (5× perfectly mixed conditions. Operation of two within-zone air cleaners together moving ≥400 cmh vertically in the room provided enough mixing to mitigate elevated exposure variations.

Tracer gas experiments were conducted in a 158 m3 room with overhead supply diffusers to study dispersion of contaminants from simulated speaking in physically distanced meeting and classroom configurations. The room was contained within a 237 m3 cell with open plenum return to the HVAC system. Heated manikins at desks and a researcher operating the tracer release apparatus presented 8-9 thermal plumes. Experiments were conducted under conditions of no forced air and neutral, cooled, or heated air supplied at 980-1100 cmh, and with/out 20% outdoor air. CO2 was released at the head of one manikin in each experiment to simulate small (5× perfectly mixed conditions. Operation of two within-zone air cleaners together moving ≥400 cmh vertically in the room provided enough mixing to mitigate elevated exposure variations.

Assessment of integrated personal exposure (PE) to airborne particulate matter (PM) across diverse microenvironments (MEs) over 24 hours under different exposure scenarios is necessary to identify appropriate strategies to improve urban air quality and mitigate the health effects of PM. We carried out a collaborative study in a densely populated city-state (Singapore) to assess the integrated PE to fine particles (PM2.5), ultrafine particles (UFPs) and black carbon (BC) across diverse indoor and outdoor urban MEs, estimate related health risks and make suitable recommendations for healthy living in cities. Two volunteers with different lifestyles participated in the study by tracking their PE to particulate air pollution and the time-activity patterns over 24 hours using portable PM monitoring devices and recording their whereabouts using GPS coordinates. Home, transport and recreation (i.e., food court) MEs represented pollution hotspots of PM2.5 (21.0 μg/m3), BC (3.4 μg/m3) and UFP (33.0 × 103 #/cm3), respectively. Among the different modes of transport used by the participants (walking, cycling, e-scooter, mass rapid transport (MRT), bus, car and taxi), the air pollutants had elevated concentrations while commuting by public transport (bus and MRT) as well as during active modes of transport (walking and cycling). Air-conditioned cars and taxis, equipped with air filtration systems, represented the lowest PE. The health risk assessment revealed that there are potential carcinogenic risks associated with the long-term exposure to elevated levels of PM2.5-bound toxic trace elements. These risks can be mitigated with the introduction of low-carbon and active modes of transport in place of internal combustion engines and the use of indoor air pollution exposure mitigation devices.

BACKGROUND: It has long been known that nasal inoculation with influenza A virus produces asymptomatic to febrile infections. Uncertainty persists about whether these infections are sufficiently similar to natural infections for studying human-to-human transmission. METHODS: We compared influenza A viral aerosol shedding from volunteers nasally inoculated with A/Wisconsin/2005 (H3N2) and college community adults naturally infected with influenza A/H3N2 (2012-2013), selected for influenza-like illness with objectively measured fever or a positive Quidel QuickVue A&B test. Propensity scores were used to control for differences in symptom presentation observed between experimentally and naturally infected groups. RESULTS: Eleven (28%) experimental and 71 (86%) natural cases shed into fine particle aerosols (P

The use of smiley-face polling stations has had a rapid growth as a means of automatically and efficiently collecting user satisfaction verdicts in airports, restrooms, museums, and retail. Their advantages are that they are low cost, efficient for both respondents and analysts, in addition to having higher response rates than other survey types. Their main disadvantage is the lack of control with who is voting, meaning both repeat voters and non-voters may lead to biased results. The aim of this study is to assess the representativeness and functioning of such publicly located satisfaction polling stations (SPSs) in an indoor climate setting, and to evaluate their potential for real-time evaluation of occupant's satisfaction with the indoor climate. We carried out continuous field tests in two office buildings for more than two months where the results of SPSs were compared with 473 survey results collected in 10 rounds during the tests. To assess how sensitive the instrument was to changing conditions, we deliberately changed temperature setpoints on selected days in one of the buildings. We found that the SPSs had a high and variable non-response bias which could result in a low accuracy for benchmarking of building indoor climate satisfaction. Results also showed a high correlation between SPS complaints and complaints recorded in the surveys for the thermal comfort aspect of indoor climate, including thermal comfort induced by temperature interventions. SPSs can provide valuable continuous recordings of the occupant's satisfaction with the indoor climate.

Uncertainty about the importance of influenza transmission by airborne droplet nuclei generates controversy for infection control. Human challenge-transmission studies have been supported as the most promising approach to fill this knowledge gap. Healthy, seronegative volunteer 'Donors' (n = 52) were randomly selected for intranasal challenge with influenza A/Wisconsin/67/2005 (H3N2). 'Recipients' randomized to Intervention (IR, n = 40) or Control (CR, n = 35) groups were exposed to Donors for four days. IRs wore face shields and hand sanitized frequently to limit large droplet and contact transmission. One transmitted infection was confirmed by serology in a CR, yielding a secondary attack rate of 2.9% among CR, 0% in IR (p = 0.47 for group difference), and 1.3% overall, significantly less than 16% (p

Inhalation exposure to pure and metabolic elevated carbon dioxide (CO2) concentration has been associated with impaired work performance, lower perceived air quality, and increased health symptoms. In this study, the concentration of metabolic CO2 was continuously measured in the inhalation zone of 41 subjects performing simulated office work. The measurements took place in an environmental chamber with well-controlled mechanical ventilation arranged as an office environment. The results showed the existence of a personal CO2 cloud in the inhalation zone of all test subjects, characterized by the excess of metabolic CO2 beyond the room background levels. For seated occupants, the median CO2 inhalation zone concentration levels were between 200 and 500 ppm above the background, and the third quartile up to 800 ppm above the background. Each study subject had distinct magnitude of the personal CO2 cloud owing to differences in metabolic CO2 generation, posture, nose geometry, and breathing pattern. A small desktop oscillating fan proved to be suitable for dispersing much of the personal CO2 cloud, thus reducing the inhalation zone concentration to background level. The results suggest that background measurements cannot capture the significant personal CO2 cloud effect in human microclimate.

Radiant cooling and heating systems provide an opportunity to achieve significant energy savings, peak demand reduction, load shifting, and thermal comfort improvements compared to conventional all-air systems. As a result, application of these systems has increased in recent years, particularly in zero-net-energy (ZNE) and other advanced low-energy buildings. Despite this growth, completed installations to date have demonstrated that controls and operation of radiant systems can be challenging due to a lack of familiarity within the heating, ventilation, and air-conditioning (HVAC) design and operations professions, often involving new concepts (particularly related to the slow response in high thermal mass radiant systems). To achieve the significant reductions in building energy use proposed by California Public Utilities Commission’s (CPUC’s) Energy Efficiency Strategic Plan that all new non-residential buildings be ZNE by 2030, it is critical that new technologies that will play a major role in reaching this goal be applied in an effective manner. This final report describes the results of a comprehensive multi-faceted research project that was undertaken to address these needed enhancements to radiant technology by developing the following: (1) sizing and operation tools (currently unavailable on the market) to provide reliable methods to take full advantage of the radiant systems to provide improved energy performance while maintaining comfortable conditions, (2) energy, cost, and occupant comfort data to provide real world examples of energy efficient, affordable, and comfortable buildings using radiant systems, and (3) Title-24 and ASHRAE Standards advancements to enhance the building industry’s ability to achieve significant energy efficiency goals in California with radiant systems. The research team used a combination of full-scale fundamental laboratory experiments, whole-building energy simulations and simplified tool development, and detailed field studies and control demonstrations to assemble the new information, guidance and tools necessary to help the building industry achieve significant energy efficiency goals for radiant systems in California.

High CO2 concentration in inhaled air has been shown to negatively impact work performance and increase acute health symptoms. As respiratory CO2 is constantly exhaled, it may not dissipate in surrounding air in absence of adequate air movement and is instead re-inhaled into the airways (breathing in a CO2-rich bubble). In this study, we explored the impacts of context-dependent factors such as office activities, desk settings, and personal differences on the inhalation zone CO2 concentration and on concentrations at a below-neck wearable sensor. While all factors were found to significantly impact measurements at both measuring points, desk settings (empty desk, desk with a fan, desk with laptop, desk with monitor) was found to be the most dominant factor. Presence of a small portable desk fan was found to significantly reduce the CO2 concentration. On average, we observed a 177 ppm reduction in CO2 concentration when using a fan, which is 25 ppm higher than the background CO2 measurement (650 ppm). Among 41 test subjects, we found distinct relationships between the inhalation zone CO2 concentration and the wearable sensor measurements and, by applying a hierarchical clustering algorithm, we found 4 clusters of relationships. While below-neck wearable sensors could be used as an exact measure of inhalation of CO2 concentration for 29% of the subjects, we identified a boundary point (917 ppm) separating high and low inhalation zone CO2 concentration measurements.

The current standard procedure for design sizing of cooling systems is not well suited for design of buildings with radiant cooling. There are several reasons that the standard design procedure for radiant cooling systems (ASHRAE Systems & Equipment 2016 Chapter 6: Radiant Heating and Cooling) is flawed, including that the current standard definition of space cooling load (ASHRAE Fundamentals 2017 Chapter 18: Nonresidential Cooling and Heating Load Calculations) omits fundamental principles that are essential to the operation of radiant cooling. This report identifies several specific shortcomings with the current standard cooling load definition and with the standard cooling system design sizing procedure. We explain the fundamental flaws with each, discuss why addressing these shortcomings is especially important to the optimal design and operation of radiant cooling systems, and provide general recommendations for how the procedures ought to be improved. The issues and recommendations presented in this report have been informed by several research projects conducted as part of the CEC EPIC research program Optimizing Radiant Systems for Energy and Comfort (EPC-14-009). In addition to identifying specific flaws with standard cooling load and design sizing procedures, we also discuss how each aspect of our research has provided evidence about or potential solutions to each issue.

The goal of this study was to (1) propose changes to Title 24 to support improved modeling capabilities and help achieve significant energy efficiency goals for radiant systems in California, and (2) propose changes, as needed, to relevant ASHRAE Standards, Handbooks, and Guidelines to provide new information and guidance on radiant systems. The current version of California Building Energy Efficiency Standards, Part 6 of the California Building Standards Code (Title 24) does not address factors specific to high thermal mass radiant systems within the body of the Standards. The alternative compliance method references some limited aspects relating to radiant systems but it is incomplete and not practically applicable, and has not yet been implemented in the associated compliance software. In addition, there are some modeling limitations for radiant systems in EnergyPlus, which is the simulation engine underlying the compliance software for the Title 24 performance approach. Updates to the Title 24 alternative compliance method are needed to ensure that modeled performance accurately reflects proposed designs, and to properly allow buildings with radiant systems to take appropriate credit for their performance. This study provided a background and roadmap of the steps needed to provide effective coverage of radiant systems for Title 24 compliance. Listed below are topics that are recommended to be added to the ASHRAE Standards and Handbooks.• Provide consistent definitions for different radiant system types in ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).• Provide comfort data in real radiant buildings in ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).• Provide revised cooling load definitions and calculations in ASHRAE Handbook Fundamentals, Chapter 18 (Nonresidential Cooling and Heating Load Calculations) and ASHRAE Handbook Fundamentals, Chapter 19 (Energy Estimating and Modeling Methods).• Provide revisions to account for effect of night cooling for buildings conditioned by radiant system in ASHRAE Handbook Fundamentals, Chapter 18 (Nonresidential Cooling and Heating Load Calculations), ASHRAE Handbook Fundamentals, Chapter 19 (Energy Estimating and Modeling Methods), ASHRAE Guideline 36-2018 (High-Performance Sequences of Operation for HVAC Systems), and ASHRAE Handbook Systems & Equipment, Chapter 6 (Radiant Heating and Cooling).• Provide new design guidance to account for the impacts of direct solar radiation on chilled radiant floors in ASHRAE Handbook Applications, Chapter 54 (Radiant Heating and Cooling), and ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).• Provide new design guidance to account for the impacts of acoustical ceiling panels and clouds on cooling capacity of radiant ceiling slabs in ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).• Provide new design guidance to account for the impacts of air movement from ceiling and other fans on cooling capacity for both radiant ceilings and floors in ASHRAE Handbook System and Equipment, Chapter 6 (Radiant Heating and Cooling).

Radiant cooling systems extract heat from buildings differently than all-air cooling systems. These differences impact the time and rate at which heat is removed from a space, as well as the total amount of thermal energy that a mechanical system must process each day. In this article we present measurements from a series of multi-day side-by-side comparisons of radiant cooling and all-air cooling in a pair of experimental testbed buildings, with equal heat gains, and maintained at equivalent comfort conditions (operative temperature). The results show that radiant cooling must remove more heat than all-air cooling – 2% more in an experiment with constant internal heat gains, and 7% more with periodic scheduled internal heat gains. Moreover, the peak sensible space heat extraction rate for radiant cooling (heat transfer at the cooled surface, not the cooling plant) must be larger than the peak sensible space heat extraction rate for all-air systems, and it must occur earlier. The daily peak sensible space heat extraction rate for the radiant system was 1–10% larger than for the all air system, and it occurred 1–2 hours earlier. These findings have consequences for the design of radiant systems. In particular, this study confirms that cooling load estimates for all-air systems will not represent the space heat extraction rates required for radiant systems.

Little is known about the amount and infectiousness of influenza virus shed into exhaled breath. This contributes to uncertainty about the importance of airborne influenza transmission. We screened 355 symptomatic volunteers with acute respiratory illness and report 142 cases with confirmed influenza infection who provided 218 paired nasopharyngeal (NP) and 30-minute breath samples (coarse >5-µm and fine ≤5-µm fractions) on days 1-3 after symptom onset. We assessed viral RNA copy number for all samples and cultured NP swabs and fine aerosols. We recovered infectious virus from 52 (39%) of the fine aerosols and 150 (89%) of the NP swabs with valid cultures. The geometric mean RNA copy numbers were 3.8 × 104/30-minutes fine-, 1.2 × 104/30-minutes coarse-aerosol sample, and 8.2 × 108 per NP swab. Fine- and coarse-aerosol viral RNA were positively associated with body mass index and number of coughs and negatively associated with increasing days since symptom onset in adjusted models. Fine-aerosol viral RNA was also positively associated with having influenza vaccination for both the current and prior season. NP swab viral RNA was positively associated with upper respiratory symptoms and negatively associated with age but was not significantly associated with fine- or coarse-aerosol viral RNA or their predictors. Sneezing was rare, and sneezing and coughing were not necessary for infectious aerosol generation. Our observations suggest that influenza infection in the upper and lower airways are compartmentalized and independent.

Direct solar radiation on a cooled radiant floor increases its cooling capacity. There is limited measured evidence of this phenomenon reported in the literature. We assessed the effect of solar radiation, increased air movement, and carpet on the cooling capacity of the radiant floor in a laboratory exposed to the outside environment. We performed experiments for different chilled water supply temperature. The cooling capacity of the chilled radiant floor was measured to increase from 32 up to 110 W/m2 under direct solar radiation. The surface temperature region exposed to solar radiation reached a peak temperature of 26 °C while the unexposed areas were between 20 and 21 °C. Increasing the chilled water supply temperature from 12 to 18 °C caused a decrease in cooling capacity from ~110 to ~95 W/m2. Higher air speeds along the floor created by ceiling fans increased the radiant slab cooling capacity by ~12 % (from 32 to 36 W/m2) when the operative temperature was 24 °C and, up to ~19 % (40 W/m2) when it is increased to 26 °C. The presence of thin carpet tiles reduced the radiant floor cooling capacity for ~5 % compared to an exposed floor slab.

Ceiling fans may cool room occupants very efficiently, but the air speeds experienced in the occupied zone are inherently non-uniform. Designers should be aware of several generic flow patterns when positioning ceiling fans in a room. Key to these are the fan jet itself and lateral spreading near the floor. Adding workstation furniture redirects the jet’s airflow laterally in a deeper spreading zone, making room air flows more complex but potentially increasing the cooling experienced by the occupants.This paper presents the first evaluation of the effects of tables and workstation partitions on a room’s generic air flow and comfort profiles. In a test room with a ceiling fan, we moved five anemometers mounted in a “tree” at heights of 0.1, 0.6, 0.75, 1.1, and 1.7 m to sample a dense measurement grid of 7 rows and 6 columns.  We tested five different table and partition configurations and compared them to the empty room base case. From the results we propose a simplified model of room airflow under ceiling fans, useful for positioning fans and workstation furniture.  We also present comfort contours measured in two ways that have comfort standards implications.  The measured data are publicly available on the internet.