Occupancy density and benefits of demand-controlled ventilation in Norwegian primary schools

One hundred and fifty-seven classrooms for fourth form pupils were inspected at 81 randomly selected schools in Oslo, Norway. Primary school classrooms in Oslo have on average 22 occupants present, while the maximum capacity is 30. Classrooms are typically used 4 h daily for normal school activities. The corresponding ventilating air volume and energy use has been analysed for three ventilation strategies: (a) constant air volume [CAV], (b) CO₂ sensor based demand-controlled ventilation [DCV-CO₂], and (c) infrared occupancy sensor based demand-controlled ventilation [DCV-IR].DCV-CO₂ and DCV-IR reduce the energy use due to ventilation in the average classroom to 38% and 51%, respectively, compared to the corresponding energy use for a CAV system operating with full airflow from 7:00 am to 5:00 pm.     

Air flow rates and energy saving potential in schools with demand-controlled displacement ventilation

Demand control is particularly energy efficient and reliable when combined with displacement ventilation (DCDV). In order to investigate how much DCDV in practice reduce the ventilation air volumes and the energy demand, two Norwegian schools with CO₂-sensor based demand controlled displacement ventilation (DCDV-CO₂), Jaer School and Mediå School, are analysed and compared with traditional constant air volume (CAV) mixing ventilation. During daytime operation with normal school activity, DCDV-CO₂ reduces the ventilation air volume by 65–75% in both schools compared to CAV. For Mediå School, both the airflow rates and the energy performance were analysed through measurements and use of a detailed, calibrated simulation model. The analysis period was 11–17 November, 2002. It was found that during this week, DCDV-CO₂ daytime operation weekdays reduce the total heating energy demand by 21%, the amount of unrecovered heat in the exhaust ventilation air by 54%, and the average airflow rate by 50%. Presuming constant fan efficiency it was also found that DCDV-CO₂ daytime operation weekdays reduce the fan energy consumption by 87% the analysed week.     

In-situ implementation and validation of a CO2-based adaptive demand-controlled ventilation strategy in a multi-zone office building

This paper presents the in-situ implementation and validation of a CO₂-based adaptive demand-controlled ventilation (DCV) strategy in a super high-rise building in Hong Kong. The adaptive DCV strategy employs a dynamic multi-zone ventilation equation for multi-zone air-conditioning systems, in which a CO₂-based dynamic occupancy detection scheme is used for online occupancy detection. This strategy is implemented in an independent Intelligent Building Management and Integration platform (IBmanager), which communicates with the main station of the Building Management System (BMS) through a communication protocol and interface. The performance of this DCV strategy is practically tested and validated by comparing with that of the original fixed outdoor air flow rate control strategy used in site. The implementation architecture and test results including energy and environmental performances represented. Since the accuracy and reliability of the major measurement instrumentations affect the actual performance of the DCV strategy significantly, the commissioning and calibration of major measurement instrumentations are presented as well.     

A novel and dynamic demand-controlled ventilation strategy for CO2 control and energy saving in buildings

Although conventional CO₂-based demand-controlled ventilation strategies, such as proportional and exponential controls, can ensure buildings/spaces meeting the minimum requirements of outdoor air by industry standards, they are operated under the assumption of equilibrium condition which can hardly be reached in practice and therefore there is still much space to improve on conventional strategies in terms of energy saving. In this paper, a novel and dynamic control strategy was developed for hourly scheduled buildings. The strategy utilized schedules by setting a base ventilation rate for unoccupied periods and calculating ventilation rate dynamically at each occupied period by solving the CO₂ mass balance equation to keep indoor CO₂ near the set point during the occupied period. Experimental simulations were made over a sports training center using both simulated and experimental CO₂ generation rates. Results show that the new strategy can save +34% of energy related to ventilation air compared to proportional control. The new strategy was also extended to common buildings which are occupied for almost all opening hours. In the case of common buildings, the new strategy can save about +26% of energy related to ventilation air compared to proportional control. The new strategy is simple, dynamic, flexible and efficient.     

The ventilation problem in schools: literature review

Based on a review of literature published in refereed archival journals, ventilation rates in classrooms often fall far short of the minimum ventilation rates specified in standards. There is compelling evidence, from both cross‐sectional and intervention studies, of an association of increased student performance with increased ventilation rates. There is evidence that reduced respiratory health effects and reduced student absence are associated with increased ventilation rates. Increasing ventilation rates in schools imposes energy costs and can increase heating, ventilating, and air‐conditioning system capital costs. The net annual costs, ranging from a few dollars to about 10 dollars per person, are less than 0.1% of typical public spending on elementary and secondary education in the United States. Such expenditures seem like a small price to pay given the evidence of health and performance benefits.     

关键区温度重设定的自适应按需新风控制

针对多区域变风量空调系统,提出一种关键区温度重设定的自适应按需新风控制策略,以最少的能耗满足各区的室内空气质量要求。该策略实时检测各区人员负荷,识别关键区,充分考虑关键区的新风需求,在进行新风设定时充分考虑循环空气中没有使用完的新风。关键区的温度重设定可以加大输送到关键区的送风量从而加大关键区的新风量,新风比减小,从而达到节能目的。利用多区域变风量空调系统的动态仿真平台对该控制策略进行了测试,对其动态控制性能、能耗特性及空气质量特性进行了评估,同时将该控制策略与其他按需新风控制策略进行了比较。     

A review of ventilation and the quality of ventilation air

Ventilation is pivotal in terms of securing optimum indoor air quality. In addition, it also has a major impact on energy use in buildings. It is important, therefore, that the role and impact of ventilation is fully understood and that ventilation is employed efficiently. The purpose of this paper is to review these aspects with particular reference to recent research and developments. Key aspects are concerned with identifying the role of ventilation and reviewing this role in the context of the other measures that must be taken to secure a healthy indoor environment. References are particularly made to the development of standards and recent related research. Although good progress is being made, areas that still need to be addressed include maintaining good outdoor air quality and preventing contaminated outdoor air from entering buildings. The outcome of recent research must also be disseminated in practical ways to policy makers, building occupiers and practitioners. Good indoor climate can be achieved, not so much by introducing expensive concepts, but by developing a rationale approach to identifying needs and applying the necessary tools to deal with each need.     

How home ventilation rates affect health: A literature review

This paper reviews studies of the relationships between ventilation rates (VRs) in homes and occupant health, primarily respiratory health. Five cross‐sectional studies, seven case‐control studies, and eight intervention studies met inclusion criteria. Nearly all studies controlled for a range of potential confounders and most intervention studies included placebo conditions. Just over half of studies reported one or more statistically significant (SS) health benefits of increased VRs. Wheeze was most clearly associated with VR. No health outcomes had SS associations with VRs in the majority of statistical tests. Most studies that reported SS health benefits from increased VRs also had additional health outcomes that did not improve with increased VRs. Overall, the number of SS improvements in health with increased VRs exceeded the anticipated chance improvements by approximately a factor of seven. The magnitude of the improvements in health outcomes with increased VRs ranged from 20% to several‐fold improvements. In summary, the available research indicates a tendency for improvements in respiratory health with increased home VRs; however, health benefits do not occur consistently and other exposure control measures should be used together with ventilation. The research did not enable identification of a threshold VR below which adverse health effects occur.     

A review on wind driven ventilation techniques

Natural ventilation has gained prominence in recent times as a bespoke method of ventilating buildings. The two fundamental principles of natural ventilation are stack effect and wind driven ventilation. This paper reviews miscellaneous wind driven ventilation designs with respect to traditional means such as wind towers and more modern techniques including turbine ventilators and wind catchers. A distinction is made between specific types of wind driven ventilation techniques depending on their operation and mode of engagement with the wind. For example, a static wind catcher is classified as passive; a rotating wind cowl as a directed passive technique and a rotating turbine ventilator is classified as outright active due to its constant rotation with the wind. A table summarising the review is presented at the end with corresponding references.     

The ventilation of multiple-bed hospital wards in the tropics: A review

Hospital and healthcare facilities have diverse indoor environment due to the different comfort and health needs of its occupants. Currently, most ventilation studies revolve around specialised areas such as operating rooms and isolation rooms. This paper focuses on the ventilation of multiple-bed hospital wards in the tropical climate, taking into account the design, indoor conditions and engineering controls. General ward layouts are described briefly. The required indoor conditions such as temperature, humidity, air movements and indoor air quality in the ward spaces are summarized based on the current guidelines and practices. Also, recent studies and engineering practices in the hospital indoor environment are elaborated. Usage of computational fluid dynamics tools for the ventilation studies is discussed as well. As identified during the review, there is an apparent knowledge gap for ventilation studies in the tropics compared with temperate climates, as fact studies have only been published for hospital wards in countries with a temperate climate. Therefore, it is highlighted that specific tropical studies along with novel engineering controls are required in addressing the ventilation requirements for the tropics.     

Constructed wetlands: a review

The first aim of this invited literature review is critically to review and evaluate hydrological, physical and biochemical processes within natural and constructed wetlands. The second aim is to contribute the thoughts of the authors to the discussion with the help of a case study focusing on gully pot liquor treatment. The performances of constructed treatment wetlands with and without macrophytes, and aggregates of different adsorption capacities will be assessed, principle findings highlighted and conclusions, also relevant to the literature review, will be drawn. The relationships between aggregates, microbial and plant communities as well as the reduction of predominantly biochemical oxygen demand, suspended solids and heavy metals are investigated. After maturation of the biomass, which dominates the litter zone, organic and inorganic contaminants are usually reduced similarly for all wetland types. There appears to be no additional benefit in using macrophytes and expensive adsorption media in constructed wetlands.     

主动弯曲网壳结构综述

主动弯曲网壳结构的成形方式极为特殊,其初始形态为由剪式铰连接的双向通长平面网格,通过对平面网格的弯曲实现结构曲面造型.由于剪式铰允许发生平面内转动,因此结构可通过四边形网格角度的变化来适应自身形态的变化.主动弯曲网壳结构最早由德国著名工程师Frei Otto于上世纪六十年代提出,但由于找形复杂、施工困难等因素,全球仅有...     

Role of ventilation in airborne transmission of infectious agents in the built environment - a multidisciplinary systematic review

There have been few recent studies demonstrating a definitive association between the transmission of airborne infections and the ventilation of buildings. The severe acute respiratory syndrome (SARS) epidemic in 2003 and current concerns about the risk of an avian influenza (H5N1) pandemic, have made a review of this area timely. We searched the major literature databases between 1960 and 2005, and then screened titles and abstracts, and finally selected 40 original studies based on a set of criteria. We established a review panel comprising medical and engineering experts in the fields of microbiology, medicine, epidemiology, indoor air quality, building ventilation, etc. Most panel members had experience with research into the 2003 SARS epidemic. The panel systematically assessed 40 original studies through both individual assessment and a 2-day face-to-face consensus meeting. Ten of 40 studies reviewed were considered to be conclusive with regard to the association between building ventilation and the transmission of airborne infection. There is strong and sufficient evidence to demonstrate the association between ventilation, air movements in buildings and the transmission/spread of infectious diseases such as measles, tuberculosis, chickenpox, influenza, smallpox and SARS. There is insufficient data to specify and quantify the minimum ventilation requirements in hospitals, schools, offices, homes and isolation rooms in relation to spread of infectious diseases via the airborne route. PRACTICAL IMPLICATION: The strong and sufficient evidence of the association between ventilation, the control of airflow direction in buildings, and the transmission and spread of infectious diseases supports the use of negatively pressurized isolation rooms for patients with these diseases in hospitals, in addition to the use of other engineering control methods. However, the lack of sufficient data on the specification and quantification of the minimum ventilation requirements in hospitals, schools and offices in relation to the spread of airborne infectious diseases, suggest the existence of a knowledge gap. Our study reveals a strong need for a multidisciplinary study in investigating disease outbreaks, and the impact of indoor air environments on the spread of airborne infectious diseases.     

Natural ventilation in a double-skin facade

Double-skin facades are assuming an ever-greater importance in modern building practice. There is an increasing demand for higher quality office buildings. Occupants and developers of office buildings ask for a healthy and stimulating working environment.Double-skin facades are appropriate when buildings are subject to great external noise and wind loads. A further area of application is in rehabilitation work, when existing facades cannot be renewed, or where this is not desirable. Double-skin facades have a special aesthetic of their own, and this can be exploited architecturally to great advantage.However, there are still relatively few buildings in which double-skin facades have actually been realized, and there is still too little experience of their behavior in operation.In this matter, we choose to study the natural ventilation in multi-storey double-skin facades. Simulations where realized with TAS software on a building proposed in the frame of the subtask A of the Task 27 (performance of solar facade components) of the International Energy Agency, Solar Heating and Cooling Program.We decide to study a sunny summer day; and we analyze the double-skin facade behavior for various conditions: impact of the double-skin orientation and impact of the wind orientation and the degree of wind protection.     

室内可吸入颗粒物污染研究现状

简述了可吸入颗粒物对人体健康的影响以及常用的采样和分析方法，重点介绍了国外的研究成果和研究进展，分析了国内的研究现状，并对今后的研究工作提出一些建议。     

Intelligent building research: a review

Within the last two decades, substantial amount of literature on intelligent building has been generated. However, there is a lack of systematic review of existing research efforts and achievements. A comprehensive review on existing research provides great benefits to identify where more efforts are needed and therefore the future research directions. For this purpose, this paper reviews the literature related to the subject area of intelligent building. Our review indicates that previous research efforts have dealt mainly with three research aspects including advanced and innovative intelligent technologies research, performance evaluation methodologies and investment evaluation analysis. It is also identified that among the three research aspects, relatively less literature has been found addressing the issues of investment evaluation of intelligent buildings. Based on a comprehensive literature review, the paper also summarizes a few future research directions, which are useful to researchers working in this important area.     

Particle deposition indoors: a review

Particle deposition indoors has received increasing attention recently because of increasing concern about the effects of particle exposure on human health. Deposition is a positive phenomenon from the perspective of human health, as deposited particles cannot be inhaled unless resuspended. There are studies showing strong correlation between the prevalence of biological-origin airborne particles and the prevalence of some specific sick building syndrome (Menzies et al., 1998; Teeuw et al., 1994). In the literature, the amount of research effort put on particle deposition indoors which is directly related to human health and microcontamination control is far less than the amount of research on deposition in small diameter tube/channel. This is a summary of the full-length version which will appear on the home page. The full-length paper aims to provide an up-to-date revision for both experiment and modeling on particle deposition indoors. This paper summarizes the experimental studies for particle deposition indoors for non-industrial environments. In section 2, 'Background', an overview of the different mechanisms of particle deposition, focusing on indoor environments is addressed. In section 3, 'Experimental Study Review', a survey of aerosol deposition experiments in small experimental chambers and real houses (or large-scale chambers) is presented. Detailed experimental measurements are addressed for the real house studies. The experimental techniques of particle generation, particle labeling and detection methods are discussed. Although the present paper focuses on experimental studies, it would be more complete to include some discussions on the modeling of the term particle eddy diffusivity and it is reviewed in section 4, 'Modeling Review'.     

Performance validation of a hybrid ventilation strategy comprising longitudinal and point ventilation by a fire experiment using a model-scale tunnel

We examined the exhaust performance of a hybrid ventilation strategy for maintaining a safe evacuation environment for tunnel users in a tunnel fire. The hybrid ventilation strategy combines the longitudinal ventilation strategy with the point ventilation strategy which is a type of transverse ventilation strategy. The model tunnel developed by this study was scaled to 1/5 the size of a full-scale tunnel. The model-scale experiment was performed taking into consideration Froude's law of similarity. Measurement items were the distribution of temperature and concentration of smoke inside the tunnel, longitudinal wind velocity, mass flow of smoke in the point ventilation duct, and the heat release rate of the fire source. The following main conclusions were obtained. The smoke height was constant even when varying the extraction rate of smoke from the ceiling vent. The backlayering length and critical velocity of the smoke flow in the hybrid strategy could be predicted by the methodology developed by using the longitudinal strategy. The hybrid strategy maintained a safe evacuation environment on both sides of the tunnel fire.     

Natural ventilation of multiple storey buildings: The use of stacks for secondary ventilation

The natural ventilation of buildings may be enhanced by the use of stacks. As well as increasing the buoyancy pressure available to drive a flow, the stacks may also be used to drive ventilation in floors where there is little heat load. This is achieved by connecting the floor with a relatively low heat load to a floor with a higher heat load through a common stack. The warm air expelled from the warmer space into the stack thereby drives a flow through the floor with no heat load. This principle of ventilation has been adopted in the basement archive library of the new SSEES building at UCL. In this paper a series of laboratory experiments and supporting quantitative models are used to investigate such secondary ventilation of a low level floor driven by a heat source in a higher level floor. The magnitude of the secondary ventilation within the lower floor is shown to increase with the ratio of the size of the openings on the lower to the upper floor and also the height of the stack. The results also indicate that the secondary ventilation leads to a reduction in the magnitude of the ventilation through the upper floor, especially if the lower floor has a large inlet area.     

Organoleads in the environment: a review

The automobile and its use have been proposed as major sources of environmental organolead compounds. However, confirmation of this proposition was not possible until analytical technology evolved to give sufficient sensitivity to detect small quantities of lead species in small samples of environmental materials. It was further hypothesized that various biochemical pathways could convert inorganic lead ion to organolead species, a proposal which has been examined by several groups over many years. Once it was unequivocally established that organolead species can occur in the environment as a result of anthropogenic activity or naturally occurring biotic or abiotic processes, our group and others have examined the possible and likely biochemical effects associated with the environmental processes of organolead species. Research in this area has focused on examining the interactions of certain algae with a variety of organolead species. This paper discusses the evolution of environmental organolead biogeochemical research over the past 15 years.