Available online 2 April 2013 Publication year: 2013 Source:Building and Environment
Wind-driven rain (WDR) is one of the most important moisture sources for a building facade. Therefore, a reliable prediction of WDR loads is a prerequisite to assess the durability of building facade components. However, current state of the art Heat-Air-Moisture (HAM) models that are used to assess the moisture behaviour of building facades are still based on several simplifications. Important phenomena of WDR such as raindrop impact, absorption, evaporation and runoff are not yet taken fully into account. This paper presents the implementation and application of a rainwater runoff model coupled to a 2D HAM model. In the first part of the paper, the runoff model itself is briefly described and implemented. In the second part, the coupled runoff-HAM model is used to calculate absorption and runoff of WDR during a two-shower rain event on two different types of porous facades with different capillary absorption coefficient and capillary moisture content. The calculation is performed with a realistic distribution of the impinging WDR intensity, based on CFD simulations, and with meteorological data, on a 10- minute basis. The impinging rain water that cannot be absorbed by the material develops a water film on the surface and runs down along the wall. It is shown that runoff of WDR can have significant influence on the moisture behaviour of the facade, e.g. materials with low capillary absorption coefficients may absorb almost double the amount of impinging wind-driven rain when including runoff. Also the moistening time of the facade was to be found extended. To conclude some important notes are given for future development of runoff models.
Available online 2 April 2013 Publication year: 2013 Source:Building and Environment
The post-industrial European city is characterized by dispersed urbanization, resulting in increased travel, substantial use of land, social disparities and costs that are unsustainable in the long term. Consequently, most European countries have set the goal of limiting urban sprawl by prioritizing increased density in already built-up areas. To achieve this goal, it is not enough to build new buildings in the urban lots that are still available. Efforts to increase the density of existing neighborhoods are also needed. These actions represent an important opportunity for ensuring sustainability through the simultaneous integration of socio-cultural, economic, and environmental criteria in our cities. This paper presents the evaluative approach applied to a case study carried out in the Fleurettes neighborhood, located near the train station in Lausanne, Switzerland. It demonstrates how carrying out a structured sustainability assessment of an existing neighborhood as well as a multi-criteria comparison of three possible scenarios using a tool recently developed known as SméO may truly help the decision-making process when choosing an operational strategy.
June 2013 Publication year: 2013 Source:Building and Environment, Volume 64
Living Walls, a type of vertical greenery system, are relatively light structures for architectural green cladding. They embed a thick curtain of plants nurtured by an automated watering system. Three Living Wall field tests are presented for investigating potential effects of the energy behavior on building envelopes. In particular, Living Walls were monitored in a Mediterranean temperate climate context at the latitudes of Northern and Central Italy.As a result, the dependence on the solar radiation forcing came out clearly. During sunny days, difference in temperature (monitored on the external surface) between the bare wall and the covered wall ranges from a minimum of 12 °C (case C) to a maximum of 20 °C (case A). The analysis was extended also to heat flux. The incoming (positive) heat flux through the bare wall was found to be higher compared to the Living Wall. Considering an overall thermal balance during the monitoring period, the outgoing heat flux through the Living Wall was higher. These results indicate that the use of green architectural cladding can significantly contribute to cooling energy reduction and offer a valuable solution for retrofitting existing buildings.
June 2013 Publication year: 2013 Source:Building and Environment, Volume 64
Microalgal growth largely affects the aesthetical properties of building façades worldwide. It causes biodeterioration of building materials and, in a later stage, it can compromise integrity of the elements and their durability. Recently, the use of nanotechnology to prevent the growth of microalgae is rising. One of the most widespread and promising material is titanium dioxide (TiO2). Photocatalytic properties of TiO2 inhibit biofouling of microalgae when this coating is stimulated by UV radiation coming from the sun or from artificial light. In this study, the biocide effect of TiO2 coatings applied on clay brick specimens under weak UV radiation was assessed. Results revealed that TiO2 nanocoating was not able to fully prevent microalgal biofouling, but under optimal UV exposure conditions for the growth of microalgae it efficaciously prevented the adhesion of these microorganisms on the treated substrates through the formation of a superficial water film. This property resulted in a good self-cleaning efficiency of TiO2.
June 2013 Publication year: 2013 Source:Building and Environment, Volume 64
Volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs) constitute important classes of indoor air contaminants and characterizing their emissions from building materials and consumer products is of interest for risk assessment and the development of environmentally benign products. Compared with emission chamber studies, emission models provide a more cost effective and powerful way to examine the emission behavior of VOCs and SVOCs. The objective of this paper is to review existing mechanistic models for predicting VOC and SVOC emissions from various sources, investigate their differences and similarities, and discuss the mass-transfer mechanisms on which the models are constructed. Because the usefulness of the emission models largely depends on the availability and reliability of model parameters, techniques for estimating key model parameters are also reviewed. The models covered in this review fall into three categories: models for VOC emissions from solid materials; models for VOC emissions from liquid materials; and models for SVOC emissions. VOC and SVOC emissions can be modeled within a consistent mass-transfer framework with the three model categories being intimately related. While substantial advances have been made in developing predictive models and understanding emission mechanisms, large knowledge gaps exist and further research is needed.
Highlights
► Mechanistic models for predicting VOC and SVOC emissions are reviewed. ► Covers VOC emissions from liquid and solid materials and SVOC emissions from solid materials. ► Techniques for estimating key model parameters are also reviewed. ► VOC and SVOC emissions can be modeled within a consistent mass-transfer framework.
Available online 6 April 2013 Publication year: 2013 Source:Building and Environment
Flow fields in commercial airliner cabins are crucial for creating a thermally comfortable and healthy cabin environment. The study of flow fields in cabins could be achieved by numerically solving Navier-Stokes equations with a suitable turbulence model. This investigation evaluated three turbulence models in different categories: the RNG k-ε model, LES, and DES for the steady-state flow in the first-class cabin of a functional MD-82 commercial airliner. The measured flow fields under unoccupied and fully-occupied conditions in the first-class cabin were used for validating the turbulence models. The flow in the unoccupied cabin was isothermally forced convection created by air jets from the diffusers, while the flow in the fully-occupied cabin was mixed convection driven by both the jets and thermal plumes from the thermal manikins used to simulate passengers. This study found that the RNG k-ε model gave acceptable accuracy in predicting the airflow in the unoccupied cabin where the flow was simple, but not for the complicated flow in the fully-occupied cabin. The DES gave acceptable flow fields for both cabins. The LES performed the best and the results agreed well with the experimental data. Comparing the measured flow fields in the two cabin conditions, this study found that the thermal plumes from the heated manikins had a significant influence on the flow fields, but little influence on the turbulence.
Available online 6 April 2013 Publication year: 2013 Source:Building and Environment
Airborne pathogens pose a significant threat to human health and this is especially the case in hospital environments which house patients with weakened immune systems. Good ventilation design can reduce risk, however quantifying ventilation performance and its influence on infection risk is difficult, particularly for large naturally ventilated environments with multiple openings. This study applies a pulse-injection gas tracer method to assess potential infection risk and local ventilation rates in a naturally-ventilated environment. Experiments conducted in a 200 m3 cross-ventilated Nightingale ward show that local external wind speeds in the range 1-4 m/s lead to indoor ventilation rates of between 3.4 and 6.5 air changes per hour (ACH). Natural ventilation is shown to be effective in open wards with an even distribution of potential airborne infection risk throughout patient locations. Comparison with a partitioned ward highlighted the potential for protecting neighbouring patients with physical partitions between beds, however, higher tracer concentrations are present in both the vicinity and downstream of the source. Closing the windows to represent winter conditions dramatically increases infection risk, with relative exposure to the tracer increased fourfold compared to the scenarios with the windows open. Extract fans are shown to alleviate this problem suggesting that a hybrid approach utilising the respective strengths of natural and mechanical ventilation may offer the best year-round solution in this and similar settings.
Publication date: Available online 9 April 2013 Source:Building and Environment
The urban functional zone (UFZ) is the basic unit of urban planning, which is defined as an area of similar social and economic functions. Despite the importance of UFZs, the stability of their annual temperature between winter and summer has seldom been investigated. With an understanding of the thermal impacts that planning decisions can have, it is essential to know how UFZs can be designed to regulate temperatures in the urban environment. 690 UFZs were identified using ALOS images in 2009 in Beijing. Land surface temperature (LST) was extracted from daytime Landsat TM (2002) and ASTER (2009) images. The regional LST variation of 31 district-sized sub-regions was correlated to the types of UFZs in the region and structural features of the region such as area, size, diversity, complexity and connectivity. Results showed that: (1) UFZ types, in order from highest to lowest LST variation, were commercial, campus, high density residential, water, recreational, low density residential, road, preservation, and agricultural zones; (2) the regional LST variation was positively correlated with the area of campus, commercial, high density residential, water, and road zones, but negatively correlated with the area of agricultural and low density residential zones; (3) increased connectivity and complexity decreased regional LST variations. The results indicated that the stability of annual temperatures was determined not only by the UFZ type and size but also by the connectivity and complexity. These results are clearly useful and essential pieces of information that can be applied in urban planning to improve climate adaptability.
Publication date: June 2013 Source:Building and Environment, Volume 64
Optimizing an indoor flow pattern according to specific design goals requires systematic evaluation and prediction of the influences of critical flow control conditions such as flow inlet temperature and velocity. In order to identify the best flow control conditions, conventional approach simulates a large number of flow scenarios with different boundary conditions. This paper proposes a method that combines the genetic algorithm (GA) with computational fluid dynamics (CFD) technique, which can efficiently predict and optimize the flow inlet conditions with various objective functions. A coupled simulation platform based on GenOpt (GA program) and Fluent (CFD program) was developed, in which the GA was improved to reduce the required CFD simulations. A mixing convection case in a confined space was used to evaluate the performance of the developed program. The study shows that the method can predict accurately the inlet boundary conditions, with given controlling variable values in the space, with fewer CFD cases. The results reveal that the accuracy of inverse prediction is influenced by the error of CFD simulation that need be controlled within 15%. The study further used the Predicted Mean Vote (PMV) as the cost function to optimize the inlet boundary conditions (e.g., supply velocity, temperature, and angle) of the mixing convection case as well as two more realistic aircraft cabin cases. It presents interesting optimal correlations among those controlling parameters.
Publication date: June 2013 Source:Building and Environment, Volume 64
Occupant use of interior shading devices is one of the most influential factors in the admission of daylight into the buildings. Based on a number of observations, occupants don't adjust shading devices frequently, and once lowered, the blinds are left in place for days or even weeks leading to reduced energy savings from daylight. Previous shade control behavior studies focus on environmental conditions such as transmitted vertical irradiance to predict the deployment of the shades; while there have been very few studies focusing on the factors that affect the raising of the interior shading devices by the occupants. This paper examines the effect of an interior lightshelf system on occupants' use of blinds and electric lighting. The results suggest that in identical environmental conditions, occupants whose workstations were located within the lightshelf zone demonstrated a lower window occlusion than those who were located in the area with conventional windows. Additionally, occupants in the lightshelf zone used less electric lighting than those in regular window design area.
Highlights
► Shade raising events are very difficult to predict. ► Window shading design may have an effect on occupants' use of venetian blinds. ► Subdivided windows with lightshelves can reduce lighting energy use in buildings.
Publication date: Available online 10 April 2013 Source:Building and Environment
The aim of this study was to explore how the remote control of appliances/lights (active energy management system) affected household well-being, compared to in-home displays (passive energy management system). A six week exploratory study was conducted with 14 participants divided into the following three groups: active; passive; and no equipment. The effect on well-being was measured through thematic analysis of two semi-structured interviews for each participant, administered at the start and end of the study. The well-being themes were based on existing measures of Satisfaction and Affect. The energy demand for each participant was also measured for two weeks without intervention, and then compared after four weeks with either the passive or active energy management systems. These measurements were used to complement the well-being analysis. Overall, the measure of Affect increased in the passive group but Satisfaction decreased; however, all three measures on average decreased in the active group. The measured energy demand also highlighted a disconnect between well-being and domestic energy consumption. The results point to a need for further investigation in this field; otherwise, there is a risk that nationally implemented energy management solutions may negatively affect our happiness and well-being.
Publication date: Available online 10 April 2013 Source:Building and Environment
The potential systemic differences in performance of natural, exhaust and mechanical ventilation in dwellings is the object of relentless debate among scientists, industry and policy makers, although comparisons found in literature often fail to compare the different systems on an equal basis. Presenting the results from a multi zone simulation based optimization study of residential ventilation design flow rates and sizing of the system components, this paper aims to provide a benchmark for achievable performance for the different systems for moderate climate regions (eg. Western Europe), as well as point to possible sizing strategies for future standards. The results clearly demonstrate that, considering average occupant exposure to metabolic carbon dioxide, there are small differences in the optimal performance for the 3 system approaches, with an increase of about 13% in ventilation heat loss for equal exposure for the natural ventilation system compared to the mechanical ventilation system. These differences are more marked (up to 26%) when peak exposure is considered. For typically household activity related sources, the mechanical and exhaust ventilation systems provide substantially better optimal performance, while building tighter improved the performance of all 3 system approaches. Exhaust ventilation benefits from small trickle ventilators and large transfer devices. The latter also improves the performance of natural ventilation systems, while slightly higher supply flow rates provide the best results for mechanical ventilation.
Publication date: Available online 10 April 2013 Source:Building and Environment
This study examined the effects of personally controlled air movement on human thermal comfort and perceived air quality (PAQ) in warm-humid environments. At temperatures 26, 28, and 30°C, and relative humidity (RH) 60% and 80%, sixteen human subjects were exposed to personally controlled air movement provided by floor fans in an environmental chamber. The subjects reported their thermal sensation, thermal comfort, and PAQ during the tests. Two breaks periods with elevated metabolic levels were used to simulate normal office activities. Results show that with personally controlled air movement, thermal comfort could be maintained up to 30°C and 60% RH, and acceptable PAQ could be maintained up to 30°C 80% RH, without discomfort from humidity, air movement or eye-dryness. Thermal comfort and PAQ were resumed within 5 minutes after the breaks. The 80% acceptable limit implicit in comfort standards could be extended to 30°C and 60% RH. The average energy consumed by the fans for maintaining comfort was lower than 10W per person, making air movement a very energy-efficient way to deliver comfort in warm-humid environments.
Publication date: June 2013 Source:Building and Environment, Volume 64
A large scale estimation of mean radiant temperature (tmrt) is conducted at two sites using customised globe thermometers. The measurement points cover a variety of urban typologies such as high-rise offices, parks, large water bodies and housing apartments. Data is derived using a tmrt formula calibrated to the local climate. Measurements for clear, sunny days are used for the analysis of the average diurnal tmrt profile.The diurnal tmrt profile shows that the tmrt differential between points is most evident during daytime, and is affected most significantly by shade cast by trees and buildings. Results also show that common urban constituents such as greenery and large water bodies, while proven to effectively reduce the ambient temperature of its surroundings throughout the day, do not affect tmrt significantly after nightfall. Further analysis reveals a correlation between sky view factor and tmrt in the day. Measurement points in different parks exhibit contrasting trends in tmrt reduction.Results of the study also provide a realistic threshold for the lowering of outdoor tmrt. Trees, shrubs and green walls may be introduced into the outdoor environment with the intention of reducing tmrt to a desirable level for a specific time range.
Publication date: June 2013 Source:Building and Environment, Volume 64
Building construction in India is estimated to grow at a rate of 6.6% per year between 2005 and 2030 resulting in a continuous increase in demand for building materials. Fired clay bricks are the most widely-used walling materials in the country. However, over the past few decades, the development of other materials such as concrete blocks, fly ash bricks, stabilized mud blocks, etc., has created viable alternatives to bricks. There is limited understanding of the broader environmental consequences of these building materials addressing natural resource depletion, energy, environment and socio-economic impacts.The main objective of this paper is to present a comprehensive assessment of materials used for wall construction by comparing one square meter of constructed wall for each of the materials. A composite Environmental Index was developed by weighting and aggregating normalized numerical scores of several parameters making use of a Multi-Criteria Decision Analysis (MCDA) framework. The Environmental Index was then ranked to determine walling systems that are best suited in the context of India.Our analysis shows that wall assemblies that use non-fired products as masonry units are ranked higher compared to fired masonry unit wall assemblies. Clay fired masonry wall assemblies exhibit poorer environmental performance compared to non-fired masonry wall assemblies. When a more efficient form of construction such as the Rat-trap bond wall construction is considered, the environmental performance of clay fired brick walls is significantly improved.
Publication date: June 2013 Source:Building and Environment, Volume 64
This paper presents an exhaustive overview of the field studies carried out in the past few decades on human thermal comfort. To get a better grasp of patterns in observed data and to facilitate comparison across investigations, the thermal comfort field studies are grouped using the Köppen–Geiger climatic classification of their locations. Effects of relevant environmental, physiological, and other aspects that can have an effect on thermal comfort are reviewed and discussed. Field studies across the board show that people have considerable capacity to adapt to their surroundings provided they have sufficient adaptive opportunities. This observation holds good for both air-conditioned as well as free running buildings. However, studies show that conditioned spaces have narrower comfort zones compared to free running buildings. Across climatic zones, most popular means of adaptation are related to the modification of air movement and clothing. The ease, economy, and effectiveness (the 3 ‘E’s) of adaptive opportunities play a major role in occupants' adaptation to the surroundings. Studies show that individuals are likely to perceive the same thermal environment differently and environments lacking adaptive avenues normally receive poor comfort ratings. Studies also indicate that for adaptive comfort equations, the running mean temperature may be a better outdoor index compared to the monthly mean temperature.
Highlights
► Köppen's climate classification is used to group thermal comfort field studies. ► Trends of comfort temperatures in different climate zones are examined. ► Evolution of field survey methodologies and questionnaires is discussed. ► Patterns and hindrances in use of adaptive opportunities are reviewed.
Publication date: June 2013 Source:Building and Environment, Volume 64
In Europe, high energy consumption in built environments has raised the need for developing low energy heating systems both in new building and in retrofitting of existing buildings. This paper aims to contribute by presenting annual results of calculated and measured energy consumption in five new-built semi-detached dwellings in Stockholm, Sweden. All buildings were equipped with similar low temperature heating systems combining under-floor heating and ventilation radiators. Exhaust ventilation heat pumps supported the low temperature heating system. Buildings were modeled using the energy simulation tool IDA Indoor Climate and Energy (ICE) 4, and energy consumption of the heat pumps was measured. Results showed that calculated and measured results were generally in agreement for all five dwellings, and that the buildings not only met energy requirements of the Swedish building regulations but also provided good thermal comfort.
Highlights
► A ventilation radiator is one type of low temperature heating systems. ► Energy performance in buildings with ventilation radiators was investigated. ► Dwellings with ventilation radiator met Swedish energy requirements for buildings. ► Ventilation radiators provided a good level of thermal comfort.
Publication date: June 2013 Source:Building and Environment, Volume 64 Author(s): Xiaosai He , Yi Liu , Tianwei Li , Jining Chen The exponential development of the urban real estate sector has become one of the main forces behind the development of China's urban economy. The massive development of urban buildings, however, aggregates domestic environmental pressures. This study develops a four-quadrant matrix to elaborate the direct and indirect impacts on the construction and operation of urban residential buildings and applies a hybrid life cycle assessment (LCA) method to quantify the overall impacts. The results show that the total energy consumption, water consumption, chemical oxygen demand (COD), ammonia nitrogen (NH3–N), sulphur dioxide (SO2), and nitrogen oxides (NOx) emissions of the overall life span of the urban residential buildings accounted for 5.4%, 5.6%, 3.0%, 3.5%, 3.9%, and 4.0%, respectively, of the national total in 2010. The indirect productive impacts accounted for 76.2% of the energy consumption, 86.4% of the water consumption, and 81.6% of the air pollution emission in 2010. With respect to the potential mitigation alternatives in the next five years, a scenario analysis suggests that a moderate slow-down of the construction of new buildings should be the highest priority, and promoting the application of greener housing materials and more advanced construction techniques should also be desired.
Publication date: Available online 16 April 2013 Source:Building and Environment Author(s): B.L. Gowreesunker , S.A. Tassou , M. Kolokotroni This paper reports on the energy performance evaluation of a displacement ventilation (DV) system in an airport departure hall, with a conventional DV diffuser and a diffuser retrofitted with a phase change material storage heat exchanger (PCM-HX). A TRNSYS-CFD quasi-dynamic coupled simulation method was employed for the analysis, whereby TRNSYS® simulates the HVAC and PID control system and ANSYS FLUENT® is used to simulate the airflow inside the airport terminal space. The PCM-HX is also simulated in CFD, and is integrated into the overall model as a secondary coupled component in the TRNSYS interface. Different night charging strategies of the PCM-HX were investigated and compared with the conventional DV diffuser. The results show that: i) the displacement ventilation system is more efficient for cooling than heating a space; ii) the addition of a PCM-HX system reduces the heating energy requirements during the intermediate and summer periods for specific night charging strategies, whereas winter heating energy remains unaffected; iii) the PCM-HX reduces cooling energy requirements, and; iv) maximum energy savings of 34% are possible with the deployment of PCM-HX retrofitted DV diffuser.
Publication date: June 2013 Source:Building and Environment, Volume 64 Author(s): Jan Gunschera , Sibel Mentese , Tunga Salthammer , Jan Rud Andersen Materials like building products or furnishing present in climatically controlled or uncontrolled indoor environments influence the indoor air quality (IAQ) significantly. In this study, the contribution of formaldehyde emissions from building materials and influences of adsorption/desorption behavior to indoor air pollution is investigated in a custom-made test house environment, located in a climate-controlled 48 m3 stainless steel chamber. The complete test house study comprised three experimental cycles applying different types of ceiling tiles as target building materials. In each cycle one type of ceiling tile was used, while the housing construction and fittings were left unchanged. One cycle was divided into three steps to differentiate the contribution of each material to the overall IAQ: after the background monitoring of the empty housing frame (Step I), ceiling tiles were installed in the house and the air quality was monitored for one week (Step II). Finally, furniture and carpet were introduced into the house and the air was again monitored for one week (Step III). Additionally, gypsum boards and ceiling tiles were characterized by determination of their emission, diffusion and adsorption/desorption rates with regard to formaldehyde. It is the most important finding of this study that the resulting formaldehyde concentration does not simply result from additive emissions from the materials involved. In fact, it can only be explained accurately when taking into account multiple parameters.
Highlights
► Formaldehyde adsorption/desorption properties of ceiling tiles and gypsum boards. ► Factors influencing the overall formaldehyde concentration in indoor air. ► Formaldehyde diffusion in building materials. ► Effects of measures on fabrication of ceiling tiles with regard to emission reduction.
