Outdoor Ventilation Rate Research Articles

Estimation of children's CO2 generation rates in naturally ventilated educational buildings

Indoor CO2 concentration serves as an indicator of indoor air quality, which is mainly influenced by occupants' CO2 generation rate, outdoor ventilation rate and outdoor CO2 levels. Determining the CO2 generation rate is fundamental to design effective ventilation systems that ensure good indoor air quality. The ASTM D6245 standard offers a method to estimate human CO2 generation based on sex, age, body mass, and activity level. However, due to the limited number of studies on CO2 generation rate for children and adolescents in daily scholarly activities, accurated values are difficult to estimate. This research uses a stochastic grey box modelling approach to estimate CO2 generation rates in naturally ventilated schools and compares it with the standard approach. This method can address the complexities and variations in real educational environments. The proposed model was verified through an experimental campaign including 32 classrooms with students aged 4, 10, 13 and 16 years. The model provided a detailed description of the indoor CO2 dynamics in 72% of the studied cases. Estimated CO2 generation rates were found to be in line with the expected standard value of between 1.0 MET to 2.0 MET activity levels (7.07–12.65 L/h for a 4-year-old, 9.63–13.29 L/h for a 10-year-old, 14.54–19.32 L/h for a 13-year-old, and 12.11–20.53 L/h for a 16-year-old). These findings not only bridge the gap in children's CO2 generation rates but also introduce a novel approach to assess human CO2 generation rates under uncontrolled conditions.

Development of a Bayesian inference model for assessing ventilation condition based on CO2 meters in primary schools.

Outdoor fresh air ventilation plays a significant role in reducing airborne transmission of diseases in indoor spaces. School classrooms are considerably challenged during the COVID-19 pandemic because of the increasing need for in-person education, untimely and incompleted vaccinations, high occupancy density, and uncertain ventilation conditions. Many schools started to use CO2 meters to indicate air quality, but how to interpret the data remains unclear. Many uncertainties are also involved, including manual readings, student numbers and schedules, uncertain CO2 generation rates, and variable indoor and ambient conditions. This study proposed a Bayesian inference approach with sensitivity analysis to understand CO2 readings in four primary schools by identifying uncertainties and calibrating key parameters. The outdoor ventilation rate, CO2 generation rate, and occupancy level were identified as the top sensitive parameters for indoor CO2 levels. The occupancy schedule becomes critical when the CO2 data are limited, whereas a 15-min measurement interval could capture dynamic CO2 profiles well even without the occupancy information. Hourly CO2 recording should be avoided because it failed to capture peak values and overestimated the ventilation rates. For the four primary school rooms, the calibrated ventilation rate with a 95% confidence level for fall condition is 1.96±0.31 ACH for Room #1 (165 m3 and 20 occupancies) with mechanical ventilation, and for the rest of the naturally ventilated rooms, it is 0.40±0.08 ACH for Room #2 (236 m3 and 21 occupancies), 0.30±0.04 or 0.79±0.06 ACH depending on occupancy schedules for Room #3 (236 m3 and 19 occupancies), 0.40±0.32,0.48±0.37,0.72±0.39 ACH for Room #4 (231 m3 and 8–9 occupancies) for three consecutive days.

Development and application of an indoor carbon dioxide metric.

Indoor carbon dioxide (CO2 ) concentrations have been considered for decades in evaluating indoor air quality (IAQ) and ventilation, and more recently in discussions of the risk of airborne infectious disease transmission. However, many of these applications reflect a lack of understanding of the connection between indoor CO2 levels, ventilation, and IAQ. For example, a single indoor concentration such as 1000ppmv is often used as a metric of IAQ and ventilation without an understanding of the significance of this or any other value. CO2 concentrations are of limited value as IAQ metrics, and a single concentration will not serve as a ventilation indicator for spaces with different occupancies and ventilation requirements. An approach has been developed to estimate a space-specific CO2 level that can serve as a metric of outdoor ventilation rates. The concept is to estimate the CO2 concentration that would be expected in a specific space given its intended or expected ventilation rate, the number of occupants, the rate at which they generate CO2 , and the time that has transpired since the space was occupied. This paper describes the approach and presents example calculations for several commercial, institutional, and residential occupancies.

REAL TIME MONITORING OF INDOOR ENVIRONMENT QUALITY AND ENERGY CONSUMPTION IN A RESIDENTIAL BUILDING

Several theoretical studies were oriented towards the relationship between the main two building design estimators (building energy consumption and indoor environmental quality) but very little experimental research has been carried out in order to underline the correlation between this two parameters. This paper is focused towards the experimental study of the correlation between these two design estimators. Several indoor comfort parameters (air temperature, radiant mean temperature, sound pressure level, outdoor ventilation rate and lighting level) as well as energy consumption were monitored in different rooms inside a laboratory experimental house at real scale located in Bucharest, Romania. Time variations of these parameters and space distribution maps inside the house were analysed in order to understand the indoor comfort variations. Four comfort indexes (thermal comfort index, acoustic comfort index, indoor air quality index and visual comfort index) were determined and their time variations were used to emphasize the correlation between the indoor environment quality and the energy consumption. The overall indoor environment quality was found to be inversely correlated with the energy consumption and that this general trend can be easily influenced by the weight of the four comfort types.

Cooling load and noise characterization modeling for photovoltaic driven building integrated thermoelectric cooling devices

Photovoltaic driven thermoelectric cooling devices are investigated for installation in a modular outdoor test-room. Because of Peltier effect in a thermoelectric cooling (TEC), heating and cooling is achieved by applying a voltage difference across the thermoelectric module. Theoretical design modeling of cooling load and noise characterization of building integrated Thermoelectric (TEC) Devices is analyzed. System design of photovoltaic driven TEC devices is investigated with varying fresh outdoor ventilation rates. Building integrated design of TEC devices inside ceiling suspended duct along with TEC devices mounted on wall driven by rooftop and active façade photovoltaic devices is considered in the analysis. In this way, two-stage dehumidification is achieved by two different sets of TEC devices. The investigation is conducted for effect of voltage, air flow rate and height of fin heat transfer surface. Expressions along with results for noise characterization in photovoltaic driven building integrated TEC devices are also provided.

Method for the determination of optimal work environment in office buildings considering energy consumption and human performance

• A model was proposed to obtain economically optimal environment conditions. • Energy and staff performance were integrated in office environment design. • Optimal conditions vary with practical factors such as salary and energy price. • Optimal conditions for an office in Shanghai as a prototype were achieved. How to balance the contradiction between energy saving and improvement of indoor environmental quality which consequently affects human performance has always been a problem. We put forward the economically optimum condition as a concept that maximized economic benefit in terms of regulation of office environment parameters. The calculation method was provided by which energy consumption could be reduced without compromise of human performance. A regression model predicting the energy consumption of a typical office building was illustrated as a function of two indoor environment parameters, i.e., indoor air temperature and air ventilation rate. Practical factors including salary and electric price, which have impact on the condition determination, were discussed. As a prototype, an office building in Shanghai achieved its economically optimal conditions at an air temperature of 25.1 °C and an outdoor ventilation rate of 17.9 L/s-person in summer.

Influence of ventilation and filtration on indoor particle concentrations in urban office buildings

This study aimed to quantify the efficiency of deep bag and electrostatic filters, and assess the influence of ventilation systems using these filters on indoor fine (<2.5 μm) and ultrafine particle concentrations in commercial office buildings. Measurements and modelling were conducted for different indoor and outdoor particle source scenarios at three office buildings in Brisbane, Australia. Overall, the in-situ efficiency, measured for particles in size ranges 6–3000 nm, of the deep bag filters ranged from 26.3 to 46.9% for the three buildings, while the in-situ efficiency of the electrostatic filter in one building was 60.2%. The highest PN and PM2.5 concentrations in one of the office buildings (up to 131% and 31% higher than the other two buildings, respectively) were due to the proximity of the building's HVAC air intakes to a nearby bus-only roadway, as well as its higher outdoor ventilation rate. The lowest PN and PM2.5 concentrations (up to 57% and 24% lower than the other two buildings, respectively) were measured in a building that utilised both outdoor and mixing air filters in its HVAC system. Indoor PN concentrations were strongly influenced by outdoor levels and were significantly higher during rush-hours (up to 41%) and nucleation events (up to 57%), compared to working-hours, for all three buildings. This is the first time that the influence of new particle formation on indoor particle concentrations has been identified and quantified. A dynamic model for indoor PN concentration, which performed adequately in this study also revealed that using mixing/outdoor air filters can significantly reduce indoor particle concentration in buildings where indoor air was strongly influenced by outdoor particle levels. This work provides a scientific basis for the selection and location of appropriate filters and outdoor air intakes, during the design of new, or upgrade of existing, building HVAC systems. The results also serve to provide a better understanding of indoor particle dynamics and behaviours under different ventilation and particle source scenarios, and highlight effective methods to reduce exposure to particles in commercial office buildings.

Impacts of heat recovery ventilators on energy savings and indoor radon level

Purpose – This paper aims to investigate the impact of heat recovery ventilators (HRVs) on the energy use and indoor radon in a one family detached house. Heat recovery ventilation systems, because of reducing ventilation loss through recovered exhaust air, can play a good role in the effectiveness of ventilation to reduce energy use. In addition HRVs can maintain pressure balance and outdoor ventilation rate at a required level to mitigate indoor radon level.

Characterization and performance evaluation of a full-scale activated carbon-based dynamic botanical air filtration system for improving indoor air quality

A dynamic botanical air filtration system (DBAF) was developed for evaluating the short and long-term performance of botanical air cleaning technology under realistic indoor conditions. It was a fan-assisted with controlled airflow, activated-carbon/hydroculture based potted plant unit. The DBAF was first tested using a full-scale stainless chamber to evaluate its short-term performance. It was then integrated in the HVAC system of a new office space (96.8 m 2) to study the effects of moisture content in the root bed on the removal efficiency, and the long-term performance. The results indicated that 5% outdoor air plus botanical filtration lead to the similar indoor formaldehyde/toluene concentration level as 25% outdoor air without filtration, which means that the filtration system was equivalent to 20% outdoor air (476 m 3/h). The DBAF was effective for removing both formaldehyde and toluene under 5–32% volumetric water content of the root bed. It also performed consistently well over the relatively long testing period of 300 days while running continuously. The reduction in outdoor ventilation rate while using the botanical filtration system to maintain acceptable air quality would lead to 10–15% energy saving for the cold climate (Syracuse, NY), based on simulation analysis using EnergyPlus. For winter condition, the filter was also found to increase the supply air RH by 20%, which would decrease the dryness of air. For summer condition, the increase of RH in summer would be within 15% of the RH condition when no botanical air filtration is present.

Survey of ventilation rates in office buildings

Building ventilation is a primary determinant of indoor air quality in buildings as it impacts indoor contaminant concentrations and occupant comfort. However, relatively few measurements of office building ventilation performance have been conducted, and those data that exist generally have not employed consistent measurement methods and have not involved representative collections of buildings. The US Environmental Protection Agency (EPA) Building Assessment Survey and Evaluation (BASE) study involved indoor environmental measurements, including ventilation, in 100 US office buildings using a standardized protocol. This paper presents an analysis of the measured outdoor air ventilation rates, including comparisons with the requirements in the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Standard 62-2001 (2001). The outdoor ventilation rates measured using duct traverses at the air handler intakes are higher than might be expected, with a mean value of about 55 litres/second (l/s) per person. However, these elevated values are not so unexpected given the low occupant density (mean of about four persons per 100 m2) and the high outdoor air fractions (mean of about 35%). Air change rates based on peak carbon dioxide concentrations in the space are lower than the volumetric values with a mean of about 20 l/s per person. Questions exist regarding these peak carbon dioxide values based on the assumptions on which the determinations are based. La ventilation des bâtiments est un facteur décisif fondamental de la qualité de l'air intérieur des bâtiments car elle a des incidences sur les concentrations de contaminants à l'intérieur de ces bâtiments et sur le confort des occupants. Or, on a fait peu de mesure des performances en matière de ventilation des immeubles de bureaux; les données qui existent n'ont généralement pas été obtenues à partir de méthodes de mesure cohérentes et elles ne sont pas représentatives d'ensembles de bâtiments. Aux Etats-Unis, l'Agence de Protection de l'Environnement (EPA) a procédé à une étude et à une évaluation de bâtiments (BASE); ces travaux incluaient des mesures environnementales relevées en intérieur selon un protocole normalisé, notamment des mesures de la ventilation, dans une centaine d'immeubles de bureaux. Cet article analyse des débits de ventilation relevés à l'extérieur et établit notamment des comparaisons avec les exigences de la norme 62-2001 (2001) de l'ASHRAE (Société américaine des ingénieurs en chauffage, réfrigération et climatisation). Les débits de ventilation en extérieur mesurés au moyen de conduits transversaux par rapport aux prises d'air sont plus élevés que ce à quoi on pouvait s'attendre, avec une valeur moyenne d'environ 55 litres/seconde par personne. Ces valeurs élevées ne sont pourtant pas aussi inattendues que cela, compte tenu de la faible densité d'occupation (en moyenne quatre personnes par 100 m2) et des fractions élevées d'air extérieur (moyenne d'environ 35%). Les débits de changement d'air basés sur des concentrations maximales de dioxyde de carbone dans l'espace sont inférieurs aux valeurs volumétriques avec en moyenne 20 litres/seconde par personne. Il reste à répondre à la question concernant ces valeurs maximales de dioxyde de carbone qui sont basées sur les hypothèses sur lesquelles ces déterminations sont fondées. Mots clés: dioxyde de carbone; base de données; mesures; immeubles de bureaux; ventilation; Etats-Unis

Occupational Health: Will Work for Air

Vol. 114, No. 6 EnvironewsOpen AccessOccupational Health: Will Work for Air John Manuel John Manuel Search for more papers by this author Published:1 June 2006https://doi.org/10.1289/ehp.114-a345aCited by:1AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit Indoor air specialists Olli Seppänen of the Helsinki University of Technology and William Fisk and Q.H. Lei of the Lawrence Berkeley National Laboratory are not the first to establish a link between work performance and ventilation—for several decades, researchers have seen an association between an inadequate supply of outdoor air and discomfort and illness among building occupants. But Seppänen and colleagues, in a meta-analysis published in the February 2006 issue of Indoor Air, are the first to present a model showing the quantitative relationship between these two variables. Their findings are simple: if you want your workers to perform, you have to let them breathe fresh air.Ventilation rates vary considerably within and among commercial buildings due to such factors as equipment design and operation. Experts say these rates are often below levels recommended by groups such as the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). However, says Charlene Bayer, a principal research scientist at Georgia Tech Research Institute, the results seen by Seppänen and others suggest that even the ASHRAE standard is probably not high enough. Further, with the recent spike in oil and natural gas prices, building managers may be keeping ventilation rates intentionally low to save on energy bills—a practice that robs Peter to save Paul, as worker productivity can end up dropping.The researchers subjected the data from nine earlier studies to statistical analysis to compare the results across studies. Five studies collected data from call centers, one was conducted in school classrooms, and three were conducted in a controlled simulated office setting. Each study compared performance at a minimum of two different ventilation rates.From each study, Seppänen and colleagues calculated a “performance change” parameter by subtracting performance at the lower ventilation rate (expressed in liters of air per second [L/s]) from performance at the higher ventilation rate and dividing the difference by performance at the lower ventilation rate. (The performance figures were expressed in terms of speed of work, and the change in speed was expressed as a percentage.) The resulting parameter was further normalized by dividing by the difference between the two ventilation rates and multiplying by 10.Results typically showed increases in average work performance in the range of 1–3% for each 10 L/s-per-person increase in outdoor ventilation rate. The performance increase was greater when ventilation rates were initially low (below 20 L/s per person, which is twice the ASHRAE standard) and almost negligible when ventilation rates were already high (above 45 L/s per person). The authors speculate that the improvement of performance was related to reducing levels of indoor air pollutants.Will this analysis encourage those who design and manage office buildings to let more outside air flow to their occupants? Not in the short run, says Bayer. “Concerns are still primarily with energy conservation, and are increasing due to continually increasing energy costs.” But, she says, this new analysis provides those who are interested with a tool to better balance the needs of energy conservation and worker health and performance.No air, no workReducing ventilation to save money ends up costing more in lost productivity.FiguresReferencesRelatedDetailsCited by Hassim M, Pérez A and Hurme M (2010) Estimation of chemical concentration due to fugitive emissions during chemical process design, Process Safety and Environmental Protection, 10.1016/j.psep.2010.01.006, 88:3, (173-184), Online publication date: 1-May-2010. Vol. 114, No. 6 June 2006Metrics About Article Metrics Publication History Originally published1 June 2006Published in print1 June 2006 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Energy consumption and ventilation performance of a naturally ventilated ecological house in a cold climate

In this paper, the thermal and ventilation performance of an ecological house in Helsinki, Finland are presented. The single-family dwelling has a well-insulated, wooden frame construction with no plastic vapour retarder. The measured and simulated results show that the energy consumption of the house is low and that the outdoor ventilation rate is generally satisfactory based on the measured CO 2 concentrations. Extrapolating the measured ventilation data shows that, when the operable windows are closed, the ventilation rate is expected to be about 0.45 air-changes-per-hour (ach) in the winter and about 0.25 ach in the summer. The consumption of total primary energy and space heating energy were measured to be 30% less (162 kWh/(m 2 a)) and 36% less (76 kWh/(m 2 a)) than in typical Finnish houses, respectively. The paper also uses a numerical model to investigate the sensitivity of energy consumption to the insulation level, household electricity and domestic hot water consumption, window area, ventilation rate and heat recovery effectiveness.

The outdoor air ventilation rate in high-rise residences employing room air conditioners

Ventilation is important because it affects indoor environmental conditions, including air pollutant concentrations that may modify the health of the occupants of a building, or their perceptions and comfort. This paper reports, first of all, on field studies monitoring indoor overnight CO 2 levels and outdoor ventilation rates in bedrooms employing room air conditioners (RACs), so the current situation of ventilation in actual high-rise residential buildings in Hong Kong can be appreciated. This is followed by a report of the results of laboratory experiments where two typical RACs were used in an examination of outdoor air ventilation characteristics in rooms employing RACs. The results of field studies showed that the outdoor ventilation rates in the measured bedrooms equipped with RACs in high-rise residential buildings in Hong Kong could not meet the ventilation requirement specified in the ASHRAE standard 62-2001 even if there was only one occupant in a bedroom. Although the use of a window-type air conditioner (WRAC) may provide a higher outdoor ventilation rate than the use of a split-type air conditioner (SARC), this may be ascribed to the fact there is more natural infiltration when a WRAC is used. The ventilation damper currently available in a WRAC does not significantly affect the outdoor ventilation rate. Therefore, such a damper cannot be expected to provide the ventilation rate as required by a ventilation code and its intended function of controlling ventilation is limited. In addition, the air exhausted from indoors to outdoors through the ventilation outlet in a WRAC is air that has just been cooled by the cooling coil (evaporator). This is unreasonable, because exhausting just-cooled and dehumidified air is a waste of energy. Therefore, an improved design for a WRAC has been suggested. Finally, the outdoor ventilation requirement for bedrooms at nighttime, when occupants are asleep, is discussed. A new ventilation rate of 3.0 l/s per person for the sleeping environment in high-rise residential buildings is proposed.

Effect of energy conservation by controlled ventilation: Case study in a department store

The outdoor-air load in a large building uses 30 to 40% of the total cooling or heating energy. It can be highly effective, therefore, to reduce the outdoor-air load to save energy when air-conditioning a building. One way of doing this is to control the outdoor ventilation rate in relation to the occupancy rate (persons/m 2) since in many conventional buildings, the supply rate of outdoor air is fixed. This report refers to the energy saving in a department store through control of the outdoor-air ventilation rate. The analysis was made by computer simulation on a given department store located in Tokyo (floor area 30,000 m 2, seven storeys above and two storeys bellow ground). The number of visitors was recorded by actual observation.