Available online 5 January 2013 Publication year: 2013 Source:Building and Environment
The thermal resistance (R-value) of an enclosed airspace depends on the emissivity of all surfaces that bound the airspace, the size and orientation of the airspace, the direction of heat transfer through the airspace, and the respective temperatures of all surfaces that define the airspace. A table is provided in the 2009 ASHRAE Handbook of Fundamentals (Chapter 26) that contains the R-values of enclosed airspaces. The ASHRAE table is extensively used by modellers, architects and building designers in the design for thermal resistance of building enclosures. This table provides R-values for enclosed airspaces for different values of airspace thickness, effective emittance, mean airspace temperature, and temperature differences across the airspace. The effect of the airspace aspect ratio (length/thickness) on the R-value is not accounted for in the ASHRAE table. However, in previous studies, it was shown that the aspect ratio of the airspace can affect its R-value.In this paper, previous studies undertaken by the author that focused on determining the R-value for vertical enclosed airspaces and horizontal enclosed airspaces with downward heat flow are extended to investigate the effect of the aspect ratio on the R-value of horizontal enclosed airspaces under an upward heat flow condition for different airspace thicknesses and having a wide range of values for effective emittance, mean temperature, and temperature differences across the horizontal airspaces. The R-values predicted from numerical simulation are compared with those provided in the ASHRAE table. Considerations were also given to investigate the potential increase in the R-values of enclosed airspaces when a thin sheet is placed horizontally in the middle of the airspace and whose surfaces have different values of emissivity. Thereafter, practical correlations are developed for determining the R-values of horizontal enclosed airspaces for future use by modellers, architects and building designers. The simplicity of these correlations for horizontal airspaces with upward heat flow along with those that were previously developed for vertical airspaces and horizontal airspaces with downward heat flow suggests that these correlations could be included in the ASHRAE Handbook of Fundamentals.
Highlights
► The dependence of R-value of horizontal enclosed airspace on its aspect ratio was investigated. ► The aspect ratio has more effect on the R-value of enclosed airspace of larger thickness. ► Practical correlations are developed for determining the R-values of enclosed airspaces. ► The developed correlations can be easily used by modellers, architects and building designers. ► R-value could be tripled due to installing thin sheet in the middle of enclosed airspace.
Available online 8 January 2013 Publication year: 2013 Source:Building and Environment
Photocatalysis is a promising technique for remediation of indoor air pollution. This study focuses on the enhancement of the effectiveness of the photocatalytic process by the introduction of artificial roughness on the interior reactor surface. Artificial roughness elements on the catalytic surface could enhance the turbulence intensity close to the catalytic surface. The enhanced turbulence intensity would translate to an increased in the mass transfer of airborne contaminants to the catalyst surface, improving the efficiency of photocatalysis.Air flow properties in a model photoreactor channel with transverse rib roughness on the wall are investigated by the “realizable k-epsilon ()” model. The investigation includes different shapes, sizes, and arrangements of the roughness elements for determining the maximum enhancement of turbulence intensity in the photoreactor channel. The optimum roughness has been determined to be an isosceles triangle shape with the bottom angle (α) equal to 75o, the relative height (e/h) equal to 0.05, and the pitch ratio (p/e) equal to 10. An experimental study was also carried out, which verified that the photocatalytic reactor performance for indoor air cleaning is significantly improved by a roughness pattern on catalyst surface compared to a reactor with a smooth catalyst surface.
Highlights
► The study focuses on the effectiveness of the photocatalytic process. ► A rough surface enhances wall turbulence and convective mass transfer. ► Photocatalytic reactor performance is greatly improved by rough catalyst surface. ► The paper presents analysis of turbulence intensity by CFD modeling. ► The experimental measurements are also carried out.
March 2013 Publication year: 2013 Source:Building and Environment, Volume 61
A two-storey typical family house was built in the mid-western part of Greece, comprising a load bearing steel skeleton and dry wall systems. Its walls consist of multiple layers of insulation materials and gypsum plasterboard panels containing Phase Change Materials (PCMs) for thermal energy storage purposes. A detailed matrix of sensors was installed in different locations of all external walls of the house, as well as indoors, in order to provide detailed temperature measurements and thus lead to a thorough depiction of the house's thermal behaviour. In this work, experimental data obtained during the first year of monitoring (2011) are presented. Throughout this particular monitoring period the house purposely remained closed, unoccupied and no energy systems were installed. Hence the presented analysis focuses on the thermal characterization of the house's walling system. Average monthly temperature, decrement factor and time lag values are presented for each room–wall and are discussed with respect to their orientation and exposure to the external weather conditions. Furthermore, measurements conducted on different layers of the living room's east wall aim to examine the influence of PCMs in the wall's thermal response. It is shown that within the adopted conditions (unoccupied house/no energy systems), the thermal mass of the walling system is enhanced during late spring, early summer and autumn, due to the PCM implementation, resulting also in a decrease of the decrement factor by a further 30–40% and an increase on the time lag of approximately 100 min.
Highlights
► A demo house built in the western part of Greece was monitored during 2011. ► Phase Change Materials are implemented on the house's walling system. ► The building's geometry and the implemented measuring devices are reported. ► Average monthly temperature, decrement factor, time lag values are presented. ► The influence of PCMs in the house's thermal behaviour is investigated.
March 2013 Publication year: 2013 Source:Building and Environment, Volume 61
Three different basic mixtures were prepared, by mechanical compaction, with different types of clays: quarry fine, kaolinite, and bentonite. Two groups of mixtures were studied, the first group without lime and the second with the addition of 5% hydrated lime. A comparison between the measured hygrothermal performances of the mixtures and their microstructural composition was performed. Microstructural morphology and chemical composition was characterised using SEM with EDS, mineralogy using XRD, and porosity using gravimetrics/He pycnometry and N2 physisorption with BET and BJH analysis. Hygrothermal functional properties were characterised as moisture-dependant thermal conductivity, moisture-dependent heat capacity, vapour sorption isotherms, and water vapour permeability. The hygrothermal behaviour of a TESTROOM in a Mediterranean climate was simulated using WUFI Plus v2.1. The model simulated was repeated for three different internal surface types; an earth-bentonite panel, unpainted gypsum plaster, and an acrylic stucco plaster. Results demonstrated that the earth-bentonite gave the best hygric performance in terms of humidity buffering and, when used in conjunction with an HVAC system, achieved a significant (30%) operational energy saving in terms of humidification/dehumidification.
Highlights
► Three different types of clays were tested: quarry fine, kaolinite, and bentonite. ► Two mixtures were studied: without lime and with the addition of 5% hydrated lime. ► Hygrothermal functional properties were characterised. ► The hygrothermal behaviour of a TESTROOM in a Mediterranean climate was simulated. ► Results demonstrated that the earth-bentonite gave the best hygric performance.
March 2013 Publication year: 2013 Source:Building and Environment, Volume 61
Wind-driven rain (WDR) is one of the most important moisture sources with potential negative effects on hygrothermal performance and durability of buildings. The impact of WDR on building facades can be understood in a better way by predicting the surface wetting distribution accurately. Computational Fluid Dynamics (CFD) simulation with the Lagrangian particle tracking (LPT) method has been widely used and validated by several researchers for different isolated building configurations. In this paper, Eulerian Multiphase modeling (EM) for WDR assessment is applied and validated for a monumental tower building (St. Hubertus building in The Netherlands). The LPT and EM models show comparable results and EM is validated by comparison of the calculated catch ratio values with available experimental data on windward facade. The deviations between the experimental and the model results at low rain intensity and wind speed are attributed to the absence of turbulent dispersion in both LPT and EM models. EM has the advantages, first, of less computational complexity and faster pre-processing and post-processing in terms of raindrop trajectories and WDR catch ratios, and second, of allowing the calculation of catch ratios on all surfaces of a complex geometry over the domain at once. The user time spent for the simulation decreases by at least a factor of 10 using EM instead of LPT for a single building. Additionally, the EM is expected to provide a sound basis for future WDR studies incorporating more accurate calculation of the wind flow field, e.g. by LES and the inclusion of turbulent dispersion.
Highlights
► Wind-driven rain on a tower building is studied with Eulerian multiphase model. ► The results are validated with available measurement data from the literature. ► Eulerian multiphase model is more efficient in terms of user time spent.
March 2013 Publication year: 2013 Source:Building and Environment, Volume 61
Complex buildings such as hospitals and laboratories require intensive ventilation and cooling loads in order to meet operational demands. One way to reduce energy use while meeting these demanding requirements in complex buildings is the incorporation of hybrid ventilation in areas that do not require high and continuous loads such as public spaces. This research establishes an experimental approach to test and analyze various hybrid ventilation strategies in an occupied, complex building utilizing hybrid ventilation in public spaces. To optimize the use of hybrid ventilation, this research focuses on tracking three performance criteria: energy savings, occupant comfort and indoor-air quality. The framework establishes a variety of hybrid ventilation strategies to test, and outlines how to analyze results graphically and through linear regression modeling. This experimental approach is illustrated through a case study example of a laboratory building located in Madison–Wisconsin. The selection of the ideal hybrid ventilation strategy for the public space studied resulted in 56 percent average savings in ventilation and cooling load when HV is in use, and established a potential to use hybrid ventilation for 28 percent of the 111 day cooling season (20 percent savings in mechanical cooling over the summer).
Highlights
► This case-study tracks the performance of a hybrid ventilation system in a complex building. ► Hybrid ventilation optimization was achieved through experimental method rather than modeling. ► Three performance metrics were tracked: thermal comfort, indoor-air quality and energy savings. ► Results showed significant energy savings using hybrid ventilation while meeting other metrics.
Available online 11 January 2013 Publication year: 2013 Source:Building and Environment
The purpose of this study is to evaluate the unsteady wind effects on the airflow rates of naturally ventilated buildings. A mock-up was built on the roof of a seven story building, and was designed to be ventilated with two openings by wind-driven force. The time histories of wind speed and direction, static pressure difference across the two openings, and airflow rate were monitored simultaneously in field measurement. The field measurement was conducted during one year, from June 2010 to May 2011. The pressure coefficient at the openings is significantly influenced by the fluctuating components of the wind speed and direction, and the unsteady airflow rates are also sensitive to the fluctuating components. The differences between the unsteady state airflow rates and the quasi-steady airflow rates are significantly increased when the fluctuating component is larger than the mean component. It can also be seen that if the fluctuating component is larger than the mean component, the quasi-steady airflows model is not applicable to the unsteady airflow rates. A statistical expression for the unsteady wind effects on the unsteady airflow rates is proposed from statistical analysis.
Highlights
► We evaluate the effects of unsteady wind flow on natural ventilation rate. ► The fluctuation of wind direction is independent of wind speed. ► Directional fluctuations strongly influence the pressure coefficient. ► The statistical model for prediction of unsteady wind effects is proposed.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
Rainwater runoff from building facades is a complex process governed by a wide range of urban, building, material and meteorological parameters. Given this complexity and the wide range of influencing parameters, it is not surprising that despite research efforts spanning over almost a century, wind-driven rain and rainwater runoff are still very active research subjects. Accurate knowledge of rainwater runoff is important for hygrothermal and durability analyses of building facades, assessment of indirect evaporative cooling by water films on facades to mitigate outdoor and indoor overheating, assessment of the self-cleaning action of facade surface coatings and leaching of particles from surface coatings that enter the water cycle as hazardous pollutants. Research on rainwater runoff is performed by field observations, field measurements, laboratory measurements and analytical and numerical modelling. While field observations are many, up to now, field experiments and modelling efforts are few and have been almost exclusively performed for plain facades without facade details. Field observations, often based on a posteriori investigation of the reasons for differential surface soiling, are important because they have provided and continue to provide very valuable qualitative information on runoff, which is very difficult to obtain in any other way. Quantitative measurements are increasing, but are still very limited in relation to the wide range of influencing parameters. To the knowledge of the authors, current state-of-the-art hygrothermal models do not yet contain runoff models. The development, validation and implementation of such models into hygrothermal models is required to supplement observational and experimental research efforts.
Graphical abstract
Highlights
► Rainwater runoff is responsible for rain penetration, surface soiling, biocide leaching, etc. ► Extensive review of rainwater runoff research by observations, measurements and modelling. ► Review is based on knowledge of wind-driven rain impingement patterns and wind-blocking effect. ► Review contains 235 papers, reports and books, mainly from the past 5 decades. ► Information for future research, building design and improvement of hygrothermal models.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
Despite the significant impact that the position of movable shading devices has on building energy use, peak loads, and visual and thermal comfort, there is a high degree of uncertainty associated with how building occupants actually operate their shades. As a result, unrealistic modeling assumptions in building performance simulation or other design methods may lead to sub-optimal building designs and overestimation or underestimation of cooling loads. In the past 35 years, researchers have published observational studies in order to identify the factors that motivate building occupants to operate shading devices. However, the diversity of the study conditions makes it is difficult to draw universal conclusions that link all contributing factors to shade movement actions. This paper provides a comprehensive and critical review of experimental and study methodologies for manual shade operation in office buildings, their results, and their application to building design and controls. The majority of the many cited factors in office buildings can be categorized into those affecting visual comfort, thermal comfort, privacy, and views. Most office occupants do not operate their shades more than weekly or monthly and they do so based on long-term solar radiation intensity and solar geometry trends rather than reacting to short-term events. They generally operate them to improve visual conditions rather than thermal conditions. Occupants in offices with automatically-controlled heating and cooling tend to be less diligent about using shading devices to improve their comfort.
Highlights
► Manually-operated window shade movement is complex and a function of at least 20 variables. ► Most of these variables can be reduced to the magnitude and geometry of solar radiation. ► Lack of HVAC systems cause occupants to control their shades more actively. ► Future experimental and observation studies are needed to fully understand occupant behavior.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
Guidelines for isolation rooms in hospitals require keeping these rooms at a negative pressure differential, but the guidelines do not suggest a particular ventilation strategy for how to meet this requirement. In principle, one strategy could use variable air volume (VAV). However, VAV boxes are often set to deliver constant air volume (CAV), perhaps due to a lack of confidence in the controllability of the VAV.In this paper, an adaptive VAV operation is introduced in response to a concern that the current operation is not adequate, as it leads to excessive fan energy consumption. The adaptive VAV temporarily increases the volume offset before the door is opened, and thus induces a higher negative pressure differential. Otherwise the negative pressure differential is kept at an acceptable minimum.This paper evaluates the current practice of the VAV being set to CAV in comparison to the adaptive VAV operation, which will help the facility manager make a decision. A rationale of ventilation operation is chosen by a set of objective performance evaluation criteria: normalized energy consumption, potential exposure to contamination, and thermal comfort. Analysis results show that the two operation modes do not exhibit noticeable differences in their ability to control the spread of contaminants or in their maintenance of thermal comfort. However, the adaptive VAV mode consumes significantly less energy.As transitioning between low and high pressure differentials of the adaptive VAV may result in momentary contamination exposure, caregivers can be asked to pause at the door until the required negative pressure differential is achieved in order to secure a safe transition. As this new process requires a change of the protocol for caregivers in isolation rooms, an additional performance aspect concerning potential loss of care time is incorporated into the decision analysis.A Bayesian decision theory is applied to support multi-criteria decision-making. A decision model is developed that considers stakeholders' different preferences for performance, and risk attitudes are compiled in terms of utility. Case studies emphasize that the ultimate decision should be reached based on multi-criteria comparisons of building environmental and organizational outcomes in a multidimensional and comprehensive manner. Due to the uncertainty of the performance model and the decision model, however, the choosing the decision model without accounting for uncertainty may not be always warranted; in particular, when utilities of decision options do not exhibit significant differences over the utility of the chosen decision option. Besides uncertainty analysis, this study also emphasizes an importance of significant difference testing for decision alternatives as key supplemental measures for the decision support framework under uncertainty.
Highlights
► VAV boxes in isolation rooms are often set to deliver constant air volume (CAV). ► An adaptive VAV operation temporarily increasing the volume offset is introduced. ► Performances of the current practice against the adaptive VAV are evaluated. ► The decision option chosen without considering uncertainty may not be warranted. ► Both uncertainty analysis and significant difference testing for alternatives are critical.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
This work describes the research conducted in order to assess possible changes and uncertainties in future energy performance of the residential building stock in Stockholm. The investigation is performed on a sample of 153 existing and statistically selected buildings and covers the period of 1961–2100. Four uncertainty factors of the climate have been considered: global climate models, regional climate models, emissions scenarios and initial conditions; thereby, 12 different scenarios have been created. Energy performance of the building stock is studied by looking at the overall heating and cooling demand and the indoor temperature. Three cooling strategies of the building stock were evaluated: natural, natural and mechanical (hybrid mode) and only mechanical. To decrease the number of simulations, a method for sampling the climate data has been developed and tested against Sobol quasi-random sampling method.Results of the investigation show that for all the climate scenarios the future heating demand will decrease at the end of the studied period, i.e. around 30kWh/m2 (30%) lower than before 2011, while the cooling demand will increase. Results for the heating demand can differ for about 30% between the scenarios and even more for the cooling demand. Since the current and future cooling demands are rather low, the natural cooling can be the safe choice for mitigating overheating. Uncertainties of the climate data can affect the energy simulation results, but it is possible to rank them and introduce margins to the design based on the importance of the uncertainty factor.
Highlights
► Energy simulation of the building stock in Stockholm is performed considering the climate change. ► Four climate uncertainties are considered: GCMs, RCMs, emissions scenarios and initial conditions. ► A method for sampling the climate data was developed and tested against Sobol quasi-random sampling method. ► Three cooling strategies are evaluated: natural, natural and mechanical and only mechanical. ► Heating demand will decrease in the future but climate uncertainties play an important role
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
This paper describes a practical investigation into the indoor air quality of a fully air-conditioned eight-storey healthcare facility in the East Malaysia region before and after vapour decontamination. East Malaysia is located in a hot and humid climate, which favours the growth of bacteria, yeasts and moulds. The main purpose of the investigation is to identify the potential of tea tree oil vapour decontamination to improve the indoor air quality by reducing the active bacteria, yeast and mould concentrations in indoor air. A total of 336 samples have been taken inside the building for indoor air at 84 different locations and 24 samples have been taken for outdoor air at 12 locations, which are near the fresh air intakes of the air handling units. The vapour decontamination method is used in the present study.Results show that the humidity levels remain high during the entire study period, exceeding 60% relative humidity, favouring the growth of bacteria, yeasts and moulds. By applying vapour decontamination from the air handling units to the ventilated air serving areas, the average bacteria, yeast and mould count is successfully reduced to below the recommended threshold of 500 CFU m−3 for normal zones, and 35 CFU m−3 for critical zones. The decontamination study result strongly suggests that the very real potential for applying tea tree oil vapour as air treatment in tropical countries like Malaysia for indoor air quality management in healthcare facilities.
Highlights
► The overall results show that tea tree oil can use as an alternative agent for vapour decontamination. ► This gaseous method is very useful for decontaminating complex furniture and equipments. ► Tea tree oil decontamination is easier to be applied compared to vapour decontamination. ► The final findings can be used as an important building services guide for M&E engineers.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
Size- and time-dependent aerodynamic behaviors of airborne allergen particles were evaluated in a 30-m3 chamber, both with and without the operation of air-cleaning devices: a dehumidifier and an air conditioner. In-situ real-time measurements were taken using an optical particle counter. Removal efficiencies obtained from the counter, based on particle number and volumetric concentrations, were compared to values from the conventional ELISA method, which is time-consuming and requires off-line measurements. The log of clean-air delivery rates (CADR) was linearly proportional to the log of particle size. When a dehumidifier and an air conditioner were used, CADRs against airborne allergen particles increased by 4 and 7 times, respectively, compared with conditions without air-cleaning devices. The settlement of the particles smaller than 1 μm was hardly affected by gravity, but concentrations of these particles decreased to nearly 50 and 30% of the initial concentrations with the operation of a dehumidifier and of an air conditioner, respectively. Moreover, the concentration of particles with a peak size of about 5.7-μm decreased to 9 and 0.3% of the initial value after only 30 min of operation of a dehumidifier and of an air conditioner, respectively. Comparing removal performance results between analyses that used a particle counter and the ELISA method, our new simple test method, which used an optical counter and was based on total volume concentrations, could easily predict the removal efficiency of airborne allergen particles, and the results were consistent with those obtained using the ELISA method.
Highlights
► A simple method is suggested for allergen aerosol removal by air-cleaning devices. ► Artificial allergen particles, an in-situ particle counter, and a chamber were used. ► Aerodynamic removal by a dehumidifier and an air conditioner was clearly discriminated. ► Removal efficiency by ELISA could be predicted by an optical particle counter.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
This paper analyses and compares environmental and acoustic measurements taken from 12 contrasting schools in England. The 203 classrooms measured ranged in age, style (open plan, semi-open plan and cellular) and external noise levels. The occupied environmental measures were: CO2 count, relative humidity, temperature and light intensity. The occupied acoustic measures taken were: LAeq, L1, L10 and L90. In addition, ventilation strategy, room dimensions and student numbers were also recorded. Lesson averages were compared to remove fluctuations observed in some parameters during lessons. Large variations in CO2 levels were observed between schools with 39% exceeding recommended guidelines. Lighting levels were predominantly below the recommended level required for demanding tasks. Classrooms with mechanical ventilation had higher background noise levels than those using natural ventilation. Most environmental parameters were uncorrelated with acoustic parameters. A notable exception was the correlation between LAeq and CO2 count; due to the relationships between these parameters, number of students and classroom floor area. A regression model was produced predicting a doubling in LAeq, with a 67% increase in student numbers.
Highlights
► Comparison and analysis of environmental and acoustic measurements from 12 schools in England. ► Large variations in CO2 levels were observed between schools with some exceeding recommended guidelines. ► Lighting levels were predominantly below the recommended level required for demanding tasks. ► Classrooms with mechanical ventilation had higher background noise levels than those using natural ventilation. ► A regression model was produced predicting a doubling in LAeq, with a 167% increase in student numbers.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
A bottom-up modelling approach together with a set of calibration methodologies is presented to predict residential building occupants' time-dependent activities, for use in dynamic building simulations. The stochastic model to predict activity chains is calibrated using French time-use survey data (of 1998/1999), based on three types of time-dependent quantities: (i) the probability to be at home, (ii) the conditional probability to start an activity whilst being at home, and (iii) the probability distribution function for the duration of that activity. The behaviour of the individual agents in the model is first calibrated using a generic approach, where every individual is assumed to behave the same. A refinement is then presented to account for variations in the behaviours of sub-populations, having specific individual characteristics. Furthermore, a statistical approach is introduced for the modelling of transitions between two successive activity types as a Markov process. The models are then validated using a cross-validation technique, and their predictive performance is compared at an individual level, as well as for aggregated (sub-)populations.
Highlights
► Residential activities can be reliably predicted time-dependently. ► Starting probabilities/duration distributions of activities are key models implied. ► Global activity shares are satisfactorily predicted using a generic approach. ► The predictivity is improved using an individual-dependent approach. ► Including transitions between activity types also improves predictivity.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
A potential source of energy savings in buildings is demand controlled ventilation (DCV), or dynamic modulation of the ventilation rate based on current occupancy. The impact of DCV on indoor air quality (IAQ) has not been investigated over a large range of indoor air processes or under the revised ventilation rate procedure (VRP) introduced in ASHRAE Standard 62.1-2004, which reduced per-occupant rates and added a constant per-area rate. A transient, multi-contaminant model of an area-normalized US office was created, and best estimates for distributions of model inputs across the US office sector were developed and used in a six city Monte Carlo simulation of dynamic ventilation strategies, including DCV and morning flushes. DCV implementation had a very minor effect on concentrations of ozone, particles, and carbon dioxide. The greatest effect was on daytime mean and peak concentration of total volatile organic compounds (TVOC). TVOC daytime means increased by 7–10% and peaks increased by 10–14%, depending on city. Adding a medium intensity morning flush to DCV almost completely mitigated the increase in mean concentration and reduced the peak concentration below the fixed ventilation baseline in most cases. Differences among offices due to input variations were far greater than changes observed from implementing DCV, and a sensitivity analysis indicated that the TVOC emission rate was more influential than the ventilation strategy. The distribution-based, sector-wide Monte Carlo method developed here should also be useful for assessing other ventilation strategies and input parameter impacts and informing the development of IAQ guidelines.
Highlights
► The impact on indoor air quality of DCV versus fixed ventilation was modeled for US offices. ► DCV using ASHRAE 62.1-2010 rates does not strongly affect ozone, PM, or CO2. ► The largest DCV impact is on volatile organic compound (VOC) concentrations. ► The most significant source of VOCs by far is primary emissions. ► A morning ventilation flush can mitigate DCV's impact on VOC concentrations.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
Irradiation on building vertical surfaces is a key parameter for models of building energy performance. The state of current modeling enables detailed computation of the energy balance for individual buildings. However, automating building energy performance calculations for an entire city remains a challenge due to the computational processing time and manual inputs needed to inform and execute existing models. This study presents a technique for modeling irradiance on the walls of multiple buildings by integrating spatially contiguous datasets of surrounding urban form and topography with building footprints. Point obstruction stacking, which is used to determine solar occluding features at various points across the building envelope, is validated using different configurations of point spacing. Results indicate that points spaced vertically along the edge of building walls provided the lowest error estimates of annual mean daily irradiance for both single family dwellings (RMSE: 0.84 MJ m−2 day−1) and multistory buildings (RMSE: 1.16 MJ m−2 day−1). Computational expense and application of the point obstruction stacking technique are discussed.
Highlights
► Present wall irradiance modeling techniques using common municipal datasets. ► Establish 3D modeling framework for determining solar occlusions from outdoor environment. ► Novel validation approach and comparison of computation efficiencies for each modeling technique.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
The aim of this study is to determine preferences for the environmental factors of residential buildings by using two different methods: the conjoint analysis and ranking method. We tried to identify consumers' monetary value regarding environmental performance by testing their Marginal Willing to Pay (MWTP). A survey was conducted in Seoul, Korea to clarify the preference and monetary value of four selected attributes representing environmental performance. These attributes are reduction of energy bills, reduction of CO2 emissions, reduction of volatile organic compound emissions, and application of information technology facilities. The result can be summarized as follows. The MWTP for 1% reduction of CO2 emission is estimated about $377 USD, being 2 times higher than that for reduction of VOC emissions and almost same as that for the reduction of energy bills. The energy bill is most preferred and IT facilities are least preferred in ranking method. Preferences vary according to respondents' socio-demographic factors and the numerical information in conjoint analysis makes strongly reflect them.
Highlights
► We carried out questionnaire based on ranking method and conjoint analysis. ► The willingness to pay to reduce CO2 emissions is 1.3 times higher than market price. ► This implies sustainability in the current housing market. ► According to ranking method, reduction of energy bills is most preferred. ► Numerical information in conjoint analysis makes reflect respondents' social factors.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
In this study, the Princeton ROof Model (PROM) is developed, validated and used to simulate the hygrothermal dynamics of green roof systems. PROM is embedded within the framework of the Princeton Urban Canopy Model, with a multi-layer spatially-analytical heat transfer scheme and an improved hydrological module. The model is validated by comparing simulated surface temperature and soil moisture to the measurements at two experimental sites, one in Beijing, China and the other in New Jersey, USA. The results demonstrate that PROM is able to capture the diurnal cycle of roof temperatures and the soil moisture dynamics of green roofs with high accuracy. Driven by a 30-day summertime meteorological forcing from July 2001, PROM is used to investigate the green roof thermal improvement to the urban indoor and outdoor environments, compared to conventional roofs. The impact of green roofs is significant in reducing surface temperatures, and outdoor and indoor heat fluxes during this summer period. To quantify this thermal improvement, three indices related to surface temperature, outdoor heat flux and indoor heat flux, are introduced; and the dependence of these indices on hydrological and meteorological conditions is investigated. The results indicate that incoming solar radiation and medium layer moisture are the main determinants of the green roof performance.
Highlights
► A new vertically-resolved green roof water and heat transfer model is developed. ► Validation with two different forcing datasets shows the model is highly accurate. ► Simulation results confirm green roofs improve thermal environment. ► New indices are proposed to quantify the thermal performance of green roofs. ► Solar radiation and soil moisture are the main governing hydrometeorological factors.
February 2013 Publication year: 2013 Source:Building and Environment, Volume 60
Over the past decade, efforts have been made in developing the Sustainable Building (SB) assessment tools which enable all stakeholders to be aware of the consequences of various design choices and to assess the building performance. Currently, a large variety of existing SB tools, approaches, rating systems, indices and methods of assessment are available and used in the construction industry. Despite usefulness of existing assessment methods in contributing towards a more sustainable building, some limitations have led towards a scientifically-based SB assessment tool. This paper proposes an exergy-based definition of a sustainable building, the calculation method of a new Exergy-based Index of building Sustainability (ExSI), and the rating scale. Finally, the results from five case studies are presented.
Highlights
► The paper proposes an exergy-based definition of a sustainable building. ► Develop a new prototype framework to measure the building sustainability. ► The calculation method of a new Exergy-based Index of Building Sustainability is presented. ► The methodology is applied to a few case studies.
