Impact of airflow profile on indoor air quality—a tropical study

The validation of the concentration levels of indoor contaminants and the measurement of ventilation parameters with CFD simulation results often poses considerable difficulty due to the effect of several confounding factors. Whilst a building in dynamic operation with varying operating characteristics in terms of the air-conditioning system and the activities of the occupants renders the possibility of a continuous measurement of IAQ and ventilation data, it is almost impossible to simulate such dynamic changes in the CFD environment. It then becomes imperative that steady-state measurements in buildings be used as representative data for the purposes of CFD simulation. This paper reports the findings of a study, in which the simulation of airflow pattern in an office building in Singapore is based on the indoor environmental conditions and the corresponding ventilation parameters measured on a typical day. Boundary conditions are obtained through hood measurements to determine the airflow rate from each diffuser. The findings of this study clearly support the critical impact of airflow on pollutant pathways in the building as a result of air supply volume, arrangement of air inlet and outlet devices, space design and the presence of heat sources.     

Is solar air conditioning feasible?

This paper examines the feasibility of desiccant cooling in UK climates, using gas-solar hybrid technology for regeneration. Desiccant cooling is a heat driven system. It has potential to reduce energy costs and environmental pollution, when compared with conventional vapour compression systems. The regeneration of the desiccant can be provided by any low temperature warm air or water source including waste heat, CHP, gas or solar. Heat recovery is also available. Gaia Research worked with Napier University to develop computer codes for the simulation of solar energy collection and hot water delivery to drive the desiccant cooling system, based on real meteorological data. A solar desiccant computer model was developed with the University of Leeds which analysed the energy consumption and costs associated with desiccant cooling using meteorological data for an inner London site in 1994. The study demonstrates that coupling the desiccant system to solar collectors produces significant savings in both running cost and CO2 emissions. The existing models of solar contribution and desiccant cooling will be refined. This will enable an assessment to be made of the UK opportunities for energy conservation and CO2 emission reduction in relation to latitude, internal design conditions, and real loads. Cet article traite des possibilites de realisation de systemes de refroidissement par deshydratation dans les conditions climatiques propres au Royaume-Uni, en faisant appel a la technologie hybride gaz-energie solaire pour la regeneration. Compares aux solutions classiques de compression de vapeur, de tels systemes de refroidissement, bases sur la puissance thermique, permettent de reduire les couts energetiques et de diminuer la pollution environnementale. La regeneration du deshydratant peut etre assuree par toute source d'eau ou d'air chauffee faiblement: chaleur perdue, CHP, gaz ou energie solaire. Le Groupe Gaia Research et l'Universite Napier ont travaille ensemble au calcul de codes informatiques pour simuler le captage de l'energie solaire ou la fourniture d'eau chaude pour alimenter le systeme de refroidissement par deshydratation en fonction de donnees meteorologique brutes. Avec l'Universite de Leeds, ils ont mis au point un modele de deshydratant solaire qui analyse la consommation energetique et les couts du refroidissement par deshydratation; ce modele utilise des donnees meteorologiques recueillies a Londres en 1994. Cette etude demontre que l'association d'un systeme deshydratant a des capteurs solaires degage des economies non negligeables au niveau des couts d'exploitation et reduit sensiblement les emissions de CO2. Les modeles existants, bases sur la contribution de l'energie solaire et du refroidissement par deshydratation, seront ameliores et serviront a evaluer les possibilites pour le Royaume-Uni de faire des economies d'energie et de reduire les emissions de CO2 en fonction de la latitude, des parametres de conception et des charges reelles.     

Is day natural ventilation still possible in office buildings with a double-skin façade?

Double-skin facades are assuming an ever-greater importance in modern building practices. But there are still relatively few buildings in which they have actually been realized, and there is still too little experience of their behaviour in operation.To preserve comfort and reduce cooling loads, it is important to apply natural cooling strategies.This article examines the efficiency of the natural day ventilation in relation to the double-skin orientation and the speed and orientation wind.     

Indoor air quality and the associated health risk in primary school buildings in Central Europe – The InAirQ study

The indoor air quality (IAQ) was investigated in sixty-four primary school buildings in five Central European countries (Czech Republic, Hungary, Italy, Poland, and Slovenia). The concentration of volatile organic compounds, aldehydes, PM_2.5 mass, carbon dioxide, radon, as well as physical parameters were investigated during the heating period of 2017/2018. Significant differences were identified for the majority of the investigated IAQ parameters across the countries. The median indoor/outdoor ratios varied considerably. A comprehensive evaluation of IAQ in terms of potential health effects and comfort perception was performed. Hazard quotient values were below the threshold value of 1 with one exception. In contrast, 31% of the school buildings were characterized by hazard index values higher than 1. The maximum cumulative ratio approach highlighted that the concern for non-carcinogenic health effects was either low or the health risk was driven by more substances. The median excess lifetime cancer risk values exceeded the acceptable value of 1 × 10⁻⁶ in the case of radon and formaldehyde. PM_2.5 mass concentration values exceeded the 24 h and annual guideline values set by the World Health Organization in 56 and 85% of the cases, respectively. About 80% of the schools could not manage to comply with the recommended concentration value for carbon dioxide (1000 ppm).     

Comfort,perceived air quality,and work performance in a low-power task–ambient conditioning system

Zhang's thermal comfort model [Zhang H. Human thermal sensation and comfort in transient and non-uniform thermal environments, Ph.D. thesis, UC Berkeley; 2003. 415 pp.] predicts that the local comfort of feet, hands, and face predominates in determining a person's overall comfort in warm and cool conditions. We took advantage of this in designing a task–ambient conditioning (TAC) system that heats only the feet and hands, and cools only the hands and face, to provide comfort in a wide range of ambient environments. Per workstation, the TAC system uses less than 41 W for cooling and 59 W for heating. We tested the TAC system on 18 subjects in our environmental chamber, at temperatures representing a wide range of practical winter and summer conditions (18–30 °C). A total of 90 tests were done. We measured subjects' skin and core temperatures, obtained their subjective responses about thermal comfort, perceived air quality, and air movement preference. The subjects performed three different types of tasks to evaluate their productivity during the testing. The TAC system maintains good comfort levels across the entire temperature range tested. TAC did not significantly affect the task performance of the occupants compared to a neutral ambient condition. Whenever air motion was provided, perceived air quality was significantly improved, even if the air movement was re-circulated room air. In our tests, subjects found thermal environments acceptable even if they were judged slightly uncomfortable (−0.5). By reducing the amount of control normally needed in the overall building, the TAC system saves energy. Simulated annual heating and cooling energy savings with the TAC system are as much as 40%.     

Is it possible to estimate atmospheric deposition of heavy metals by analysis of terrestrial mosses?

Here we present a critical review of diverse research studies involving estimation of atmospheric deposition of heavy metals from the concentrations of the contaminants in terrestrial moss. The findings can be summarized as follows: i) significant correlations between the concentrations of contaminants in moss and bulk deposition were observed in only 40.1% of the cases in which the relationship was studied and in only 14.1% of the cases, the coefficient of correlation was > 0.7; ii) some method-related problems were identified (i.e. small sample sizes, elimination of some data from the regression analyses, large distances between the moss sampling sites and the bulk precipitation collectors, differences in times of exposure of the moss samples and collection times for the bulk precipitation), so that the results of the studies may not be completely valid, and iii) evidence was found in the relevant literature that moss does not actually integrate the atmospheric deposition received. We also discuss the reason why, in accordance with the published data, bulk deposition cannot be correctly estimated by determination of the final concentrations of contaminants in the organism, such as the existence of different sources of contamination, the physicochemical characteristics of the sources of deposition, physicochemical processes to which the organism is subjected and the biological processes that take place in the moss. Taking into account the above findings, it was concluded that, except for certain elements and specific cases (i.e. Pb and Cd), atmospheric deposition of elements cannot be accurately estimated from the concentrations of metals and metalloids in moss tissues. However, the analysis of moss does provide information about the presence of contaminants in the atmosphere, their spatial and temporal patterns of distribution and how they are taken up by live organisms. Use of mosses is therefore recommended as a complementary (rather than an alternative) technique in the conventional analysis of bulk deposition of contaminants.     

Developing a risk assessment model for PPP projects in China — A fuzzy synthetic evaluation approach

Earlier research works on PPP showed that an objective, reliable, and practical risk assessment model for PPP projects is essential to the successful implementation of PPP projects. However, actual empirical research studies in this research area are rather limited. This paper reports the second stage of a funded research study, which aims to develop a fuzzy synthetic evaluation model for assessing the risk level of a particular critical risk group (CRG) and the overall risk level associated with PPP projects in China. At the first research stage, thirty-four risk factors were identified through a comprehensive literature review and 3 new risk factors were proposed during a two-round Delphi questionnaire survey. The most critical 17 risk factors were selected through the calculation of normalized values. The correlation of these 17 critical risk factors (CRFs) was further analyzed via factor analysis and 6 CRGs were formulated, namely: (1) Macroeconomic Risk; (2) Construction and Operation Risk; (3) Government Maturity Risk; (4) Market Environment Risk; (5) Economic Viability Risk; and (6) Government Intervention. On the basis of the research works conducted at the first research stage, the weightings for each of the 17 critical risk factors (CRFs) and 6 CRGs were determined through the two-round Delphi questionnaire survey. A set of knowledge-based fuzzy inference rules was then established to set up the membership function for the 17 CRFs and 6 CRGs. The empirical research findings showed that the overall risk level of PPP highway projects is between “moderate risk” and “high risk”. Hence it could be construed that investment in PPP highway projects in China may be considered as risky. In fact, the Delphi survey respondents perceived that “Government Intervention” is the most CRG; with “Government Maturity Risk” being the second; “Economic Viability Risk” the third; “Market Environment Risk” the fourth; “Construction and Operation Risk” the fifth; and “Macroeconomic Risk” the last. These findings revealed that government intervention and corruption may be the major hurdles to the success of PPP highway projects in China. These may be caused by inadequate law and supervision system and poor public decision-making process. Although the fuzzy synthetic evaluation model was primarily developed for PPP projects in general, the research method could be replicated in a specific type of PPP project, such as water treatment projects and hospital projects, to produce similar models for inter-type comparisons. By doing so, it provides an opportunity for practitioners to assess the risk level of different types of PPP projects based on objective evidence rather than subjective judgment. The most CRG for different types of PPP projects could be identified and both precautionary and remedial actions could be taken as soon as possible. Such an extension would provide a deeper understanding of managing different types of PPP projects.     

Performance evaluation of solar air heater having V-ribs with symmetrical gaps in a rectangular duct of solar air heater

An investigation has been carried out to evaluate the performance of a solar air heater duct roughened with V-ribs with symmetrical gaps to enhance heat transfer. The roughness produced for enhancing heat transfer from the absorber plate also enhances pressure drop due to increased friction. Heat transfer enhancement of the absorber plate has been experimentally determined by using V-ribs with symmetrical gaps. The duct has a relative roughness height (e/D) of 0.0433, a relative roughness pitch (P/e) of 10 and an angle of attack (α) of 60°. Relative gap width (g/e) and number of gaps (N_g) were varied in the range of 1–5. The maximum enhancement in the Nusselt number and friction factor is observed to be 2.59 and 2.87 times, respectively, as compared to the smooth duct. The relative gap width of 4 and the number of gaps of 3 show the maximum value of thermohydraulic performance parameter.     

Is fluoridation a fraud?

During the past 15 years tooth decay rates have declined markedly amongst children in many parts of the industrialised world. Over the same period, however, decay rates have increased dramatically in children in developing countries. For many years it has been claimed that water fluoridation is the most important and cost-effective method for controlling dental caries. A series of recent papers in the scientific literature have challenged the 'fluoridation hypothesis', since the decline in decay reported in the developed countries has occurred in both fluoridated and unfluoridated areas. In some countries of the developing world, tooth decay is now reaching crisis proportions, hence it is important to know whether fluoridation really can "reduce tooth decay by about 60 per cent", or if the dental profession has been promoting a 'flawed' hypothesis for more than 40 years.     

On the application of a membrane air—liquid contactor for air dehumidification

This paper deals with a new approach to absorption air-handling systems working with liquid desiccants. A hydrophobic synthetic membrane, permeable to vapour but not to liquid, acts as a porous barrier between a hygroscopic solution and moist air. The results of a first series of experiments performed on a microfibre polyethylene membrane are presented and discussed in relation to an analytical model developed to analyse non-isothermal vapour flux through a hydrophobic membrane. Theoretical analysis is carried out to study the influence of different parameters affecting vapour mass flux through the membrane. The results show that considerable vapour flux can be exchanged to/from a liquid desiccant and an air stream through the membrane, suggesting the feasibility of using compact-membrane absorber and desorber units in air handling. Furthermore, membrane contactors can achieve energy saving by performing desiccant reactivation at moderate temperatures (310–330 K).     

Can we use indoor fungi as bioindicators of indoor air quality? Historical perspectives and open questions

Microbiological analysis of atmospheres witnessed substantial technical improvements in the 1940s to 1960s. May's cascade impactor and Hirst's spore trap allowed the counting of total cells but had limited capacity for identification of the spores. Bourdillon's sampler enabled the counting of cultivable fungi and their identification. A great step forward was given with the Andersen's six-stage impactor, which allowed discrimination of particles by size, counting of cultivable cells, and species identification. This period also witnessed the development of impingers, namely, the AGI-30 described by Malligo and Idoine, and the three-stage model designed by K. R. May. The 1990s to 2000s witnessed innovative discoveries on the biology of indoor fungi. Work carried out in several laboratories showed that indoor fungi can release groups of spores, individual spores and fungal fragments, and produce volatile organic compounds and mycotoxins. Integrating all findings a holistic interpretation emerged for the sick building syndrome. Healthy houses and buildings, with low indoor humidity, display no appreciable indoor fungal growth, and outdoor Cladosporium dominates. On the contrary, in sick houses and buildings, high indoor humidity allows fungal growth (mainly of Penicillium and Aspergillus), with concomitant release of conidia and fragments into the atmosphere. The intoxication probably results from a chronic exposure to volatile organic compounds and mycotoxins produced by Penicillium, Aspergillus, and Stachybotrys.Very clean atmospheres are difficult to study by conventional methods. However, some of these atmospheres, namely, those of hospital rooms, should be monitored. Sedimentary sampling, chemical methods applied to impinger's collection liquid, and selected molecular methods can be useful in this context.It was concluded that fungi can be useful indicators of indoor air quality and that it is important to deepen the studies of indoor atmospheres in order to promote air quality, the health and well-being of all, and a better understanding of the biology of indoor fungi.     

Sustainability assessment of dwellings – a comparison of methodologies

Building sustainability assessment tools (BSATs) aim to promote and rank the sustainability of building stock. This paper makes a deep comparative analysis on how dwellings are evaluated by five BSAT and one performance-based design tool. The comparison is based on: (i) the purpose of assessment; (ii) sustainability dimensions considered; (iii) indicators addressed; (iv) life cycle phases considered by the indicators; (v) type of indicators; (vi) measurements; (vii) aggregation processes; and (vii) life cycle phases during which the assessment was carried out. The evaluation showed that the scope of BSAT varies significantly as well as the life cycle phases addressed in the assessment. Financial issues are often excluded from the assessment. None of the schemes is totally quantitative or qualitative in their measurement system; all have different types of indicators and different ways to assess them. This research provides researchers and stakeholders with important inside knowledge on the tools that allow the development and construction of more sustainable buildings.     

Is crime in Mexico a disamenity? Evidence from a hedonic valuation approach

Since Roback’s seminal work (J Polit Econ 90(6):1257–1278, 1982), the literature on hedonic prices has evaluated the role of amenities in equilibrating regional differentials in nominal wages and prices. While these studies generally find evidence for traditional amenities and disamenities in developed countries, there remains little research on how characteristics such as violence affect the equilibrium in less developed countries. This article explores violence and other local characteristics as an amenity or disamenity for Mexico and employs the hedonic wage and rent theory proposed by Roback. This research uses a multilevel estimation technique using data from the Mexican Household Income and Expenditure Survey, along with other information from the municipal and state levels. This article finds evidence to suggest that illegal earning opportunities outweigh crime disamenity by inhabitants of some traditional drug-trafficking regions, because such crime appears to be the modus vivendi in those regions in a way that does not reduce economic performance.     

Private financing of roads and optimal pricing: Is it possible to get both?

Road pricing has been defended by economists as a useful instrument to internalize the costs that road users impose upon other users and the rest of society, with the aim of allocating scarce space and to reduce congestion to an efficient level. More recently, private participation in the construction, maintenance and operation of road infrastructure has been growing all over the world to face the challenge of tight budget constraints and increasing demand for additional road capacity. Fixed term concessions have been the standard contract between the public sector and private operators. Demand uncertainty and fixed term contracts have made impossible to fulfill the concession agreement in many cases, and contract renegotiation has been used to restore financial equilibrium. This has some undesirable economic consequences: selecting the most efficient concessionaire is not longer guaranteed and prices lose their role as signals for allocative efficiency. This paper addresses the problem of giving that role back to pricing, analyzing the possibility of achieving efficient pricing and cost recovery without contract renegotiation.We gratefully acknowledge the financial support of Fundación Fondo para la Investigación Económica y Social (FIES, Madrid) and Secretaría de Estado de Educación y Universidades. We are also in debt with Alejandro Lago, Gustavo Nombela and the referees for useful comments.Received: January 2003 / Accepted: July 2003     

What do we know about effects of desert dust on air quality and human health in West Africa compared to other regions?

This study aims to compare, on the one hand, the geographical distribution of the desert dust source areas, their contribution to quantities emitted into the atmosphere, the trajectories and the quantities deposited, with on the other hand the areas of research interest focused on the desert dust impacts on air quality and/or human health. Based on a systematic review of the literature using the ISI Web of Knowledge database, we found 231 articles published over the last decade on the desert dust impacts on air quality. Of these, 48% concerned Asian dust and 39% Saharan dust, with the remaining 13% divided between the other dust source areas. However, only one of these studies addressed the worsening air pollution in West Africa, even though it is very close to the Sahara, the greatest contributor to the global dust budget. Moreover, there have been very few studies (41) looking at the direct links between desert dust and human health; in this context too, no interest has been shown in West Africa. Yet this region is also among the areas in which morbidity rates have been noted to be far higher than those found in other regions of the world, and where respiratory infections alone account for more than 20% of the causes of infant mortality. This survey highlights a clear imbalance between those areas most exposed to dust and the most studied areas in terms of dust impacts. Given these findings and the often alarming results published about other regions of the world, we advocate a revival of interest in research on West Africa in order to achieve a better understanding of the desert dust impacts on air quality and health among the populations of this region.     

Is planning delay really a constraint in the provision of housing? Some evidence from Israel

This paper revisits the claim that a causal link exists between the inflexibility of land-use planning and low elasticity of housing supply. A theoretical model of factors impacting district-level planning is presented alongside a model of the impact of planning delay on housing supply. The models are estimated for the Tel Aviv district using detailed data covering a 12-year period. Results show significant impacts on planning delay due to plan, municipality and district planning commission characteristics. House prices exert a positive effect on planning speed and municipal funding acts as a supply constraint. While planning delay does not impact housing supply, delay uncertainty has a negative impact and acts as a constraint.     

What Is a Forecast for?

Abstract

Problem, research strategy, and findings: The forecasts transit agencies submit in support of applications for federal New Starts funding have historically overestimated ridership, as have ridership forecasts for rail projects in several countries and contexts. Forecast accuracy for New Starts projects has improved over time. Understanding the motivations of forecasters to produce accurate or biased forecasts can help forecast users determine whether to trust new forecasts. For this study I interviewed 13 transit professionals who have helped prepare or evaluate applications for federal New Starts funds. This sample includes interviewees who have had varying levels of involvement in all 82 New Starts projects that opened between 1976 and 2016. I recruited interviewees through a snowball sampling method; my interviews focus on the interviewees’ perspectives on how New Starts project evaluation and ridership forecasting has changed over time. Interview results suggest that ridership forecasters’ motivations to produce accurate forecasts may have increased with increased transparency, increased influence on local decision making, and decreased influence on external (federal) funding.

Takeaway for practice: Planners can evaluate the likely trustworthiness of forecasts based on transparency, internal influence, and external influence. If forecast users cannot easily determine a forecast’s key inputs and assumptions, if the forecaster has been tasked with producing a forecast to justify a predetermined action, and if an unfavorable forecast would circumvent decisions by the forecaster’s immediate client, forecasts should viewed with skepticism. Planners should seek to alter conditions that may create these conflicts of interest. Forecasters seem to be willing and able to improve forecast accuracy when the demand for accurate forecasts increases.