Ventilation Rate Requirements Research Articles

Relationships between Acoustics, Thermal, Indoor Air Quality, and Lighting Conditions on Student Achievement in K-12 Classrooms

Data on acoustic, thermal, indoor air quality, and lighting conditions have been collected from 220 classrooms in the midwestern United States. Gathered acoustic data include sound levels logged every 10 seconds and room impulse responses from which reverberation times were extrapolated. K-means clustering was used to group the logged sound data into times when speech was or was not occurring; then acoustic metrics were calculated from the clustered data. When comparing the measured acoustic conditions to ANSI S12.60, 91% of the classrooms did not meet the recommended maximum background noise level for unoccupied conditions, while 15% did not meet the recommended maximum reverberation time. The field measurements also revealed that only 20% of the classrooms met ASHRAE Standard 62.1 ventilation rate requirements, while all classrooms met recommended IES illuminance level for reading and writing. Multivariate linear regression analyses between the environmental conditions and student achievement data, while controlling for student demographics, have identified a number of significant relationships. This presentation summarizes key results, describes how acoustic conditions were correlated to building mechanical systems, and considers how indoor environmental quality may be optimized to benefit occupants in educational settings. [Work supported by the United States Environmental Protection Agency Grant Number R835633.]

A pre-assessment and pollution prevention tool for indoor volatile organic compound simulations during the interior design stage

Volatile organic compounds (VOCs) are common indoor pollutants that can deteriorate indoor air quality. The pre-assessment of VOC concentrations aimed at pollution prevention during the interior design stage is effective in terms of time and expense for VOC control, as required by engineering applications. In this study, we introduce the concept, framework, and mathematical models of a pre-assessment and pollution prevention tool for VOC simulations. This tool considers multiple emissions sources and sinks, the interior construction schedule for the building materials, internal and external airflows, and air cleaning. The emissions/adsorption patterns from building materials were numerically coupled with the combined effects of the thermal environment, ventilation, indoor VOC concentrations, and emissions/adsorption from other materials at each time step, thereby improving the accuracy of the tool in engineering applications. The proposed tool was applied in an office building with multiple rooms and building materials to illustrate the simulation procedures and validate its effectiveness at VOC preventive control. The main emissions sources were determined and the selection of building materials was modified based on the simulation results. Field measurements were performed and the measured data were compared with the simulation results after construction completion. Differences between the simulated and measured results were predominantly within 0.02 mg/m3. The normalized mean square error was 0.11 and the mean relative standard deviation was 16.9%. This method can be used for indoor VOC concentration estimations, source contribution analysis, interior design scheme optimization, and ventilation rate requirement estimation, among other applications.

Numerical investigation on indoor environment decontamination after sneezing

More than 320 million people worldwide were affected by SARS-CoV-2 or COVID-19, which already caused more than 5.5 million deaths. COVID-19 spreads through air when an infected person breathes, coughs, or sneezes out droplets containing virus. Emerging variants like Omicron with positivity rate of 16 (highest among others) present a greater risk of virus spread, so all types of indoor environments become critically important. Strategically adopted Heating Ventilation and Air Conditioning (HVAC) approach can significantly reduce the virus spread by early removal of contaminated aerosolized droplets. We modeled different HVAC configurations to characterize the diffusion of contaminated droplets cloud through Computational Fluid Dynamics (CFD) simulations of sneeze in standard hospital room as indoor scenario. Injection of saliva droplets with characteristics of exhaled air from lungs was applied to mimic real sneeze. CFD simulations have been performed for three HVAC configurations at two Air Change per Hour (ACH) rates; 6 and 15 ACH. For the first time, use of air curtain at low flow rate has been examined. Simulations provide high fidelity spatial and temporal droplets cloud diffusion under different HVAC configurations, showing spread in room indoor environment up to 360 s. Over 92% of ejected sneeze mass is removed from room air within seconds while the remaining 8% or less becomes airborne with droplets (<50 μm size) and tends to spread uniformly with regular HVAC configuration. Low-speed air curtain accelerates decontamination by efficiently removing aerosolized 1–50 μm size droplets. Study investigates role of droplets removal mechanisms such as escape, evaporation, and deposition on surfaces. Interestingly, results show presence of contaminated droplets even after 5 min of sneeze, which can be effectively removed using low-speed air curtain. Study finds that high ventilation rate requirements can be optimized to modify earlier and new hospital designs to reduce the spread of airborne disease.

Residential dual core energy recovery ventilation system for ventilation of northern housing

Heat/energy recovery ventilation systems are types of HVAC that can reduce energy consumption and improve the ventilation rate of housing in cold climates. Their performance achieved to date has been inadequate due to equipment failures (freezing of cores, noise, etc.). Freezing of cores is common in extremely cold climates. Single core HRV/ERV units are usually equipped with defrost strategies such as recirculation of exhaust stale air across the heat exchanger and back into the supply air to the house. These defrost strategies can undermine ventilation standards (ventilation rate requirement not being met during recirculation). This paper presents a rigorous investigation on the performance of dual core energy recovery system that provided a continuous ventilation rate at outdoor temperatures below -10°C without frost protection. The dual core ERV had higher apparent sensible effectiveness (up to 12% more) and apparent total effectiveness (up to 9% more) than a conventional single core ERV. It showed no sign of frost problems after four weeks of winter testing, continuously provided outdoor air without stopping to defrost, unlike the conventional single core ERV which required up to 7.5 hours defrosting per day, and also provided a higher supply air temperature (up to 3°C) to indoors with a total whole-house energy saving of 4.7%.

Wind energy and natural ventilation potential of a wind catcher in Yazd – Iran (a long-term measurement)

ABSTRACTWhen designing energy efficient buildings it is useful to study existing climate—responsive building typologies. The wind towers or wind-catchers of Yazd city in Iran are typical examples of such a typology. Although many previous studies have investigated the performance of various types of wind catcher systems, studies based on a long-term real-life measurement can be rarely found. In this study a long-term whole year monitoring campaign on an existing full scale four sided wind catcher in Yazd was carried out in 2014–2015. Three prevailing wind directions were identified and the measured on-site wind speeds were used to estimate the wind induced natural ventilation potential of the tower. A shaft/tower airflow performance index was developed. The monitoring results were compared to the ASHRAE Standard 62:2001 ventilation rate requirement. Results show that the total ventilation rate of the wind tower surpasses the ASHRAE Standard requirements. Furthermore it shows that the shafts are exposed to the prevailing wind directions perform better. For more effective natural ventilation a wind tower with adaptable openings/shafts are proposed.

A practical method and its applications to prioritize volatile organic compounds emitted from building materials based on ventilation rate requirements and ozone-initiated reactions

Volatile organic compounds emissions from building materials can be a major pollution source in low-occupant-density spaces. Composite-style indoor air quality references, which reflect the combined effects of multiple volatile organic compounds, can be used to determine ventilation rate requirements based on building material emissions. The lowest concentration of interest concept was adopted to implement the idea. Twenty-eight building materials selected from the National Research Council of Canada database were subjected to emission modelling, resulting in 101 volatile organic compounds as a starting volatile organic compound pool. A method was proposed to generate a volatile organic compound priority list that determines ventilation rate requirements while considering ozone-initiated reactions. Three priority lists were obtained based on three lowest concentration of interest schemes, i.e., AFSSET, AgBB and EU-LCI, with each consisting of 17–21 volatile organic compounds that were most likely to attribute to large ventilation rate requirements. Also, analyses of selected volatile organic compounds showed that the changes in the composition of the priority lists due to ozone-initiated reactions could be ignored at a typical indoor ozone concentration level. The application of priority lists was discussed for source control and air cleaning device testing. This paper provides a method to prioritize the chemicals based on ventilation rate requirements with a goal of developing volatile organic compound control strategies at building design stage.

Ammonia and Hydrogen Sulfide Concentrations and Emissions for Naturally Ventilated Freestall Dairy Barns

<abstract> <b><sc>Abstract.</sc></b> Concentrations and emissions of ammonia (NH₃) and hydrogen sulfide (H₂S) data for two naturally ventilated freestall dairy barns, within a one-year window of a two-year measurement effort, are presented in this article. Barn 1 (B1) had a capacity of 400 fresh-lactating Holstein cows, while barn 2 (B2) had a capacity of 850 non-fresh-lactating Holstein cows. The 10 min mean concentrations of NH₃ in the barns ranged from 0.16 to 2.85 ppm, while the concentrations of H₂S ranged from 0.0 to 135.8 ppb. The concentrations of NH₃ and H₂S in the barns were significantly below the OSHA permissible and NIOSH recommended exposure levels with respect to safety and health concerns of farm workers. Air exchange rates ranged from 7 to 74 h^-1 during all measurement periods, which met and exceeded the standard minimum ventilation rate requirements for dairy barns. Ammonia emissions ranged from 15.1 to 36.7 g d^-1 AU^-1 (20.3 to 49.5 g d^-1 cow^-1) with a mean of 21.6 g d^-1 AU^-1 (29.0 g d^-1 cow^-1). Emissions of H₂S, on the other hand, ranged from 0.0 to 1.5 g d^-1 AU^-1 (0.0 and 2.0 g d^-1 cow^-1) with an overall mean of 0.51 g d^-1 AU^-1 (0.69 g d^-1 cow^-1). In general, NH₃ emissions correlated fairly well with temperature (R² = 0.29 to 0.51). However, the relationships between NH₃ emission and wind speed were mixed, ranging from zero to moderately positive (R² = 0.01 to 0.46). Regression analyses did not indicate any significant relationships between H₂S emissions and these environmental parameters.

Contaminant levels, source strengths, and ventilation rates in California retail stores.

This field study measured ventilation rates and indoor air quality in 21 visits to retail stores in California. Three types of stores, such as grocery, furniture/hardware stores, and apparel, were sampled. Ventilation rates measured using a tracer gas decay method exceeded the minimum requirement of California's Title 24 Standard in all but one store. Concentrations of volatile organic compounds (VOCs), ozone, and carbon dioxide measured indoors and outdoors were analyzed. Even though there was adequate ventilation according to standard, concentrations of formaldehyde and acetaldehyde exceeded the most stringent chronic health guidelines in many of the sampled stores. The whole-building emission rates of VOCs were estimated from the measured ventilation rates and the concentrations measured indoor and outdoor. Estimated formaldehyde emission rates suggest that retail stores would need to ventilate at levels far exceeding the current Title 24 requirement to lower indoor concentrations below California's stringent formaldehyde reference level. Given the high costs of providing ventilation, effective source control is an attractive alternative. Field measurements suggest that California retail stores were well ventilated relative to the minimum ventilation rate requirement specified in the Building Energy Efficiency Standards Title 24. Concentrations of formaldehyde found in retail stores were low relative to levels found in homes but exceeded the most stringent chronic health guideline. Looking ahead, California is mandating zero energy commercial buildings by 2030. To reduce the energy use from building ventilation while maintaining or even lowering formaldehyde in retail stores, effective formaldehyde source control measures are vitally important.

A preliminary ventilation rate determination methods study for residential buildings and offices based on VOC emission database

Ventilation is commonly used as a basic means to supply outdoor air to indoor environment to achieve better indoor air quality. To reduce harmful effect due to indoor pollutants such as formaldehyde and VOCs emitted from building materials, proper ventilation should be maintained to meet a minimum ventilation rate at least. Two new methods, i.e., characteristic and two-stage ventilation rate method, were proposed to predict ventilation rate based on building material emissions. Scenarios involving four standard rooms and different material loadings were analyzed to study adequate ventilation rates for residential buildings and offices. The study followed the IAQ procedure recommended by ASHRAE. The emission source data were from the National Research Council Canada (NRC) database. The building material emissions and consequent VOC concentrations were predicted by using two approaches called the characteristic emission rate method and the two-stage emission rate method. The ventilation rates were calculated for ten scenarios to meet the thresholds given by seven indoor air quality references. The results showed that the ventilation rate depended on the selection of reference standard, material and emission area. The dominating chemical substance in determining ventilation rate in various cases was not unique. The time to take for the emission to complete was 2.5–5 years for all cases. Due to the inherent nature of the characteristic emission rate method for over-estimating long-term emissions, replacing the characteristic ventilation rate with steady-state ventilation rate could lead to the ventilation rate requirement reduced by approximately half.

Effects of different air inlets on indoor air quality and ammonia emission from two experimental fattening pig rooms with partial pit ventilation system – Summer condition

It has previous been demonstrated that a pit ventilation system could improve indoor air quality and reduce ammonia emission significantly from pig production if an air purification system was installed to treat the pit exhaust air. However, the knowledge about the influence of a partial pit exhaust unit treating a small part of the ventilation (10%) in a ventilation system with different types of air inlets on indoor air quality and ammonia emission from pig house is still lacking. In this study, two rooms, both with partial pit exhaust and ceiling-top room exhaust units, were used. One room was equipped with ceiling air inlet (system C) and another room was equipped with wall jet air inlet (system W). Each room had 32 fattening pigs. The maximum ventilation rate in each room was set as 3200 m3 h−1. Room ventilation rate was automatically controlled by a climate control strategy based on indoor thermal conditions, while pit ventilation rate was fixed at 10% of the maximum ventilation rate. Ammonia concentrations were measured in air inlet, room exhaust and pit exhaust for both systems. Air flow rates and ammonia concentrations were measured and recorded continuously. Results showed that ventilation rate requirement was higher in system C than in system W (22.3%, p < 0.001) to maintain the setup indoor thermal condition during the whole fattening period. In the meantime, significant higher ammonia concentrations and emissions in both pit and room exhausts were found in system W than in system C (p < 0.001). The ammonia emission ratio of pit exhaust, defined as the emission via pit exhaust divided by the total emission, in systems C and W was 48% and 47%, respectively. If applying an effective air purification system, a significant reduction of ammonia emission could be achieved. The gap of ammonia concentration difference between system C and W increased in the later stage. Higher room ventilation rate led to smaller difference of ammonia concentration in room air. Slurry depth had a positive effect on the ammonia emission from pit exhaust. No significant difference in the pigs' activity was found between the two ventilation systems.

A novel approach of integrating ventilation and air cleaning for sustainable and healthy office environments

Abstract A wise integration approach using well-developed and innovative existing scientific/engineering tools can be a good answer to rising core questions of sustainability science. Many research works have been conducted to protect and satisfy occupant health and comfort in a sustainable way. The present study investigates a novel approach to the control of ventilation, dynamically integrated with the use of air cleaning technology toward a substantial reduction of building energy/cost with cleaner indoor air than what the standard provides. To demonstrate the proposed methodology, a low energy office building was used as a testbed, subject to the variation of outdoor pollution due to nearby traffic. A detailed building model was constructed by utilizing DesignBuilder and ContamW based on the building design/actual construction documents for the analyses of combined IAQ and energy benefits. Target contaminants included formaldehyde, other 16 representative VOCs and CO 2 for IAQ analysis. Dynamic profiles of outdoor pollution were based on actual monitoring data and EPA_2008_AirData. By setting up a suite of usage scenarios under four representative climate and outdoor air quality conditions throughout the U.S. including Syracuse (cool), Los Angeles (mild), Houston (cooling dominant) and Duluth (heating dominant), the approach of dynamic integration of ventilation and air cleaning was assessed. Results showed that the minimum ventilation rate requirements in ASHRAE 62.1-2010 might not be sufficient for meeting the exposure limit constraints for IAQ (especially for formaldehyde) at all times. The integration strategy would provide satisfactory IAQ, and also could bring most energy/cost benefits (∼11% annual savings) for the case building.

A cross-sectional study of schools for compliance to ventilation rate requirements

The use of continuous data logging instruments recorded levels of carbon dioxide (CO2) exhaled by students in schools. This allowed a check of a large data set in order to determine ventilation rates from the rate of its decay (ΔCO2). Data collected on CO2 levels through time was a useful tool for determining the effect of mechanical equipment to ventilation rates as part of a larger study on indoor air quality. Calculation of the air exchange rate (AER) used ASTM tracer gas methods applied to a regression analysis where the data showed a logarithmic decay rate. Ventilation measured in this study was total ventilation including mechanical ventilation from heating ventilation and air conditioning (HVAC) units, replacement air from exhaust fans and infiltration through outside walls.

風圧力発生頻度に基づく常時換気システムの設備された集合住宅の換気量充足度評価に関する研究 : 第2報-片廊下型高層集合住宅に対する検討

風圧力発生頻度に基づく常時換気システムの設備された集合住宅の換気量充足度評価に関する研究 : 第2報-片廊下型高層集合住宅に対する検討

風圧力発生頻度に基づく常時換気システムの設備された集合住宅の換気量充足度評価に関する研究 : 第1報-センターコア型超高層集合住宅に対する検討

風圧力発生頻度に基づく常時換気システムの設備された集合住宅の換気量充足度評価に関する研究 : 第1報-センターコア型超高層集合住宅に対する検討

Ventilation requirements in non-domestic buildings and energy efficiency

This paper focuses on the importance of the level of ventilation requirements on the energy demand of non-domestic buildings. At present, we observe a tremendous difference in the ventilation requirements in various countries as well as at the European level. Variations by a factor of 10 of the ventilation rate requirement can be found in the proposal for European standard CEN (European Committee for Standardisation) prENV 1752 depending on the ‘cleanness’ of the building. The present paper develops these problems and makes a comparison with the situation in other areas like thermal comfort and lighting requirements. Results of a practical case study are included.

The effects of temperature on broilers: Ventilation rates for the application of temperature control

1. Application of the temperature recommendations from experimental evidence necessitates knowledge of the minimum ventilation rate requirements of the birds, since control of house temperature for finishing broilers in practice is through modulation of ventilation rate in insulated buildings. 2. The minimum ventilation rate requirement was found to be 1.5(( 10‐4 m3/s per kgW 0–75 (W = body weight), or 2 m3/s per tonne of food used per day, in three experiments using a total of 33 280 broilers. 3. The first limiting factor governing ventilation rate is often the ammonia concentration in the house air, and under British climatic conditions, the minimum ventilation rate may need to be exceeded after the birds are about 5 weeks of age.