•ISO, EN, GB/T, and ISHRAE specify multiple categories for IEQ values, while ASHRAE, SS and AS provide acceptable levels.•Reviewed standards on IEQ focus on the perception rather than productivity ...and well-being.•There is no integrated assessment of various IEQ-related dimensions in the standards.•Occupants adaptation is considered to a greater extent in thermal comfort-relates standards.•Regional differences in climate, building typology, and demographics are not adequately covered in international standards.
Quality of the indoor environment has become an important parameter to account for in new and existing buildings due to the increasing number of people spending most of their time indoors. Generally, the design and evaluation of indoor environments in buildings rely on appropriate guidelines and recommendations. National and international IEQ standards specify indoor environmental conditions considered acceptable to most occupants. This publication reviews and critically compares the requirements for indoor thermal environment and ventilation for acceptable air quality across international standards such as ISO, EN and ASHRAE and national standards of China, India, Singapore, and Australia.
The critical analysis of IEQ standards demonstrates that regional differences and diversity factors due to factors such as climate, building typology, demographics, and culture might not be appropriately addressed both in national and international standards, limiting the feasibility of universal indoor environmental criteria. In addition to that, most of the standards provide recommendations for various categories of thermal comfort and air quality by focusing on the perception of IEQ by occupants rather than productivity and wellness as quantitative criteria. The review shows that thermal comfort and air quality parameters are treated separately and without an integrated assessment of various environmental quality-related dimensions. Therefore, there is a need for a method to combine various indoor environmental factors into a combined indicator.
During the rapid rise in COVID-19 illnesses and deaths globally, and notwithstanding recommended precautions, questions are voiced about routes of transmission for this pandemic disease. Inhaling ...small airborne droplets is probable as a third route of infection, in addition to more widely recognized transmission via larger respiratory droplets and direct contact with infected people or contaminated surfaces. While uncertainties remain regarding the relative contributions of the different transmission pathways, we argue that existing evidence is sufficiently strong to warrant engineering controls targeting airborne transmission as part of an overall strategy to limit infection risk indoors. Appropriate building engineering controls include sufficient and effective ventilation, possibly enhanced by particle filtration and air disinfection, avoiding air recirculation and avoiding overcrowding. Often, such measures can be easily implemented and without much cost, but if only they are recognised as significant in contributing to infection control goals. We believe that the use of engineering controls in public buildings, including hospitals, shops, offices, schools, kindergartens, libraries, restaurants, cruise ships, elevators, conference rooms or public transport, in parallel with effective application of other controls (including isolation and quarantine, social distancing and hand hygiene), would be an additional important measure globally to reduce the likelihood of transmission and thereby protect healthcare workers, patients and the general public.
The natural ventilation potential to maintain acceptable indoor air quality (IAQ) and thermal comfort in gymnasia was investigated using a university multisport facility in northeastern United States ...as a case study building. A parametric modeling study was conducted considering the effects of opening configurations and control strategies during the summer months. The thermal accuracy of the model was verified using field measurements during August 2015. Performance metrics for IAQ and thermal comfort were the percentages of occupied hours during which ventilation rate met or exceeded ASHRAE Standard 62.1–2013 and temperature met adaptive thermal comfort criteria of ASHRAE Standard 55–2013, respectively. Wind direction was found having a major effect on cross ventilation rate. Wind and buoyancy driven forces could complement or oppose each other depending on the wind direction and opening position. Relative to the base case, larger net openings that were more evenly distributed performed better. Rooftop vents improved ventilation performance, particularly under unfavorable wind conditions. With improved opening configurations, the acceptable ventilation hours increased from 21.5% to 99.5% of occupied time for the maximum occupancy. The strictest temperature-controlled strategy had the best thermal performance. Thermal comfort conditions could be maintained during 85.3% of the occupied hours. However, the temperature rule largely shortened the opening operation time, and consequently decreased the acceptable ventilation hours to only 47.1%. Continuously natural ventilation during occupied time gave the longest combined IAQ-thermal acceptable hours, 73.9% of the occupied time, although it moderately decreased the thermal comfort hours to 74.2%.
•Natural ventilation potential to maintain acceptable air quality and thermal comfort may be significant for gymnasia.•Wind and buoyancy driven forces can complement or oppose each other depending on the wind direction and opening position.•Larger net openings that are more evenly distributed performed better.•Rooftop vents improve ventilation performance, particularly under unfavorable wind conditions.•More attention is needed to achieve the IAQ-thermal balance of controlled natural ventilation.
In-duct ultraviolet germicidal irradiation (UVGI) systems treat moving air streams in heating, ventilation, and air-conditioning (HVAC) systems to inactivate airborne microorganisms. UVGI system ...performance and costs to implement and operate the system depend greatly on the output of the UV lamps and the exposure time, which are affected by the temperature and the velocity of the air passing through the UVGI device. The type of HVAC system, the installation location of the UVGI device, and the climatic location of the building all have an impact on the air temperature and velocity the device experiences at a given time. The effects of installation location and climate were investigated using simulation of an in-duct UVGI device installed in a cooling-only VAV system operating in a hypothetical commercial building. The studied device was investigated at locations both upstream and downstream of the cooling coils of the VAV system in three climatically distinct U.S. locations. The results of the six resulting scenarios indicate that UVGI devices installed upstream of the cooling coils provide comparable if not better performance than those installed downstream. The results demonstrate the impact on performance and cost of the dynamic environment that a UVGI device could experience. It can also be observed that the generated heat of UVGI devices has a great impact on cooling and heating loads, and thus affects the overall operating cost.
•Performance and cost of in-duct UVGI systems in three climates were studied.•Effects of UVGI installation relative to the cooling coil of a VAV system were compared.•Effect of dynamic environment on the performance of UVGI system was studied with simulation.•Use of simulation supports performance-based design.•UVGI installation and operating costs were less upstream of the cooling coil.
The question of whether SARS‐CoV‐2 is mainly transmitted by droplets or aerosols has been highly controversial. We sought to explain this controversy through a historical analysis of transmission ...research in other diseases. For most of human history, the dominant paradigm was that many diseases were carried by the air, often over long distances and in a phantasmagorical way. This miasmatic paradigm was challenged in the mid to late 19th century with the rise of germ theory, and as diseases such as cholera, puerperal fever, and malaria were found to actually transmit in other ways. Motivated by his views on the importance of contact/droplet infection, and the resistance he encountered from the remaining influence of miasma theory, prominent public health official Charles Chapin in 1910 helped initiate a successful paradigm shift, deeming airborne transmission most unlikely. This new paradigm became dominant. However, the lack of understanding of aerosols led to systematic errors in the interpretation of research evidence on transmission pathways. For the next five decades, airborne transmission was considered of negligible or minor importance for all major respiratory diseases, until a demonstration of airborne transmission of tuberculosis (which had been mistakenly thought to be transmitted by droplets) in 1962. The contact/droplet paradigm remained dominant, and only a few diseases were widely accepted as airborne before COVID‐19: those that were clearly transmitted to people not in the same room. The acceleration of interdisciplinary research inspired by the COVID‐19 pandemic has shown that airborne transmission is a major mode of transmission for this disease, and is likely to be significant for many respiratory infectious diseases.
Control sequences for air distribution and terminal systems in heating, ventilating, and air-conditioning (HVAC) aim to achieve a balance in the system outputs, i.e., maintain thermal comfort and ...indoor air quality (IAQ) with minimal energy use. ASHRAE Guideline 36 (G36) – High-Performance Sequences of Operation for HVAC Systems, is the result of ASHRAE research project 1455-RP intended to develop standardized sequences of operation to achieve more effective use of existing controls. This paper complements G36 by evaluating the influence of the uncertainty inherent in the control components (e.g. sensors and actuators) on the system outputs of a multiple zone variable air volume (VAV) system. The system outputs under study were zone air temperature, relative humidity, carbon dioxide (CO2) concentration, and site electricity use. To evaluate the effects of uncertainty in HVAC systems with advanced sequences of operation, this work applies a Monte Carlo uncertainty analysis to a detailed Modelica building energy model that has been programmed with G36 control sequences. Uncertainty models were integrated with the deterministic models of the building and the control sequence at small time scales to represent frequencies in which a real-world building automation system (BAS) samples its signals. The impact of uncertainty was quantified using annual simulations. Specification of the accuracy levels in the components of the control system were evaluated by the means of: 1) uncertainty analysis for low, medium, and high severities of accuracy in the components to identify relation between performance requirements and component accuracy, and 2) sensitivity analysis to identify the sensors and actuators where the impact of uncertainty on the system outputs is most influential.
The evolution of SARS‐CoV‐2 virus has resulted in variants likely to be more readily transmitted through respiratory aerosols, underscoring the increased potential for indoor environmental controls ...to mitigate risk. Use of tight‐fitting face masks to trap infectious aerosol in exhaled breath and reduce inhalation exposure to contaminated air is of critical importance for disease control. Administrative controls including the regulation of occupancy and interpersonal spacing are also important, while presenting social and economic challenges. Indoor engineering controls including ventilation, exhaust, air flow control, filtration, and disinfection by germicidal ultraviolet irradiation can reduce reliance on stringent occupancy restrictions. However, the effects of controls—individually and in combination—on reducing infectious aerosol transfer indoors remain to be clearly characterized to the extent needed to support widespread implementation by building operators. We review aerobiologic and epidemiologic evidence of indoor environmental controls against transmission and present a quantitative aerosol transfer scenario illustrating relative differences in exposure at close‐interactive, room, and building scales. We identify an overarching need for investment to implement building controls and evaluate their effectiveness on infection in well‐characterized and real‐world settings, supported by specific, methodological advances. Improved understanding of engineering control effectiveness guides implementation at scale while considering occupant comfort, operational challenges, and energy costs.
Maintaining control system performance over the lifespan of a building offers great potential for increasing system operation efficiency. Programming the building monitoring system with control loop ...performance assessment (CLPA) indices provides a way to identify poorly performing loops. This work further advances building control monitoring by developing an approach to help prioritize control problems based on the severity of their system-level impact. CLPA indices were added to a Modelica-based small office building model programmed with advanced heating, ventilating, and air conditioning control sequences. An extensive set of unique simulations of different levels of loop detuning were implemented to generate a database that contains both system-level performance metrics and CLPA indices. A regression model was then developed that combines individual loop performance to assess the impact on system-level outputs. Loops of the zone with higher heat gains and the air handling unit supply air temperature loop produced the greatest system-level impact.
•Control loop tuning was prioritized by linking CLPA indices and system performance.•Harris index is appropriate for CLPA, but is not intended for system assessment.•Cooling load diversity among zones influences which loops have the largest impact.
PDF
