Forecasting simulations of indoor environment using data assimilation via an Ensemble Kalman Filter

April 17, 2013, 5:50 am

≫ Next: Occupants interaction with electric lighting and shading systems in real single-occupied offices: Results from a monitoring campaign

≪ Previous: Impact of building materials on indoor formaldehyde levels: Effect of ceiling tiles, mineral fiber insulation and gypsum board

Publication date: June 2013
Source:Building and Environment, Volume 64
Author(s): Cheng-Chun Lin , Liangzhu (Leon) Wang

Data assimilation is widely used in weather forecasting and other complex forecasting problems such as hydrology, meteorology, and fire dynamics. Among various data assimilation methods, the Ensemble Kalman Filter (EnKF) is one of the best solutions to large-scale nonlinear problems while the computational cost is relatively less intense than other forecasting methods. In this paper, a new application of EnKF to forecast indoor contaminant concentrations is presented. The first part of the paper introduces the fundamental theories of data assimilation. The second part is a case study of forecasting the concentrations of a tracer gas in a multi-zone manufactured house by using a mass balance model with an EnKF. The benefits of EnKF and several important parameters for EnKF were discussed including numbers of ensemble members and observations, time step of observations, and forecasting lead time. The EnKF method presented is one of the first studies applied to the indoor environment field. It was shown that by using EnKF, the predictability of the simple indoor air model for the multi-zone space was improved significantly.

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Occupants interaction with electric lighting and shading systems in real single-occupied offices: Results from a monitoring campaign

April 17, 2013, 5:50 am

≫ Next: Climate preferences and expectations and their influence on comfort evaluations in an aircraft cabin

≪ Previous: Forecasting simulations of indoor environment using data assimilation via an Ensemble Kalman Filter

Publication date: June 2013
Source:Building and Environment, Volume 64
Author(s): Pedro Correia da Silva , Vítor Leal , Marilyne Andersen

This study presents the results of a monitoring campaign aiming to further our understanding of occupants' behavior regarding the manual control of electric lighting in combination with shading control. It was performed on eight single-occupied offices in the city of Porto, Portugal during periods ranging from 28 to 60 days per office. A wide range of environmental variables including workplane illuminance, window and background luminance and transmitted solar radiation was measured with high frequency (20 min time steps). The study aimed to address a set of key research questions regarding typical illuminance ranges, luminance distribution and occupancy patterns found in offices and their relationship to electric lighting or shading control actions. It also enabled to compare observed behavior with predictions from benchmarking behavioral models found in the literature. The main findings were that electric lighting and shading control were influenced more by occupational dynamics (arrival and departure) than by the environmental conditions experienced over the day (daylight workplane illuminance or transmitted solar radiation), though with a large degree of variability between occupants and/or offices. It also revealed that while most of the behavioral models analyzed for comparison purposes were in qualitative agreement with field observations (e.g. more lighting switch-on actions at arrival for lower daylight illuminances), only one model (Pigg's model) predicted the frequency of observed lighting switch-off events. These findings strongly support the need for more numerous (and geographically more broadly distributed) office behavior monitoring campaigns to increase the robustness of such models.

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Climate preferences and expectations and their influence on comfort evaluations in an aircraft cabin

April 17, 2013, 5:50 am

≫ Next: Field investigation of comfort temperature in Indian office buildings: a case of Chennai and Hyderabad

≪ Previous: Occupants interaction with electric lighting and shading systems in real single-occupied offices: Results from a monitoring campaign

Publication date: June 2013
Source:Building and Environment, Volume 64
Author(s): Julia Winzen , Claudia Marggraf-Micheel

Aircraft cabins are designed with the aim of providing thermally comfortable conditions for the majority of passengers. To avoid the potential for dissatisfied customers, one focus for future design is on personalized climate zones.

In this context, the influence of individual preferences and expectations on comfort in an aircraft cabin was analysed. A study was conducted in an aircraft mock-up of a Dornier 728 using 60 subjects and a quasi-experimental design. Climate parameter sensations and personal characteristics were assessed via questionnaire; the cabin climate was measured by the use of various sensors. Two climate scenarios corresponding to cruising flight conditions (21.5 °C and 23 °C, volume flow of air 660 l/s, humidity approx. 18%) were tested to analyse thermal comfort at the lower boundary of comfort temperatures in airplanes. Results confirm that the warmer climate was preferred to the colder one. Individual preferences – especially for warmth and air movement – had significant relationships with climate parameter perceptions and evaluations. Further, flight related expectations influenced the way in which the climate situation was rated: the higher the subjects' expectations, the less comfortable the cabin climate was rated. The idea of implementing individual air conditioning is supported; practical implications of the findings are discussed.

Highlights

► Individual differences are taken into account for the analysis of thermal comfort. ► Preferences for certain climate parameters have an effect on climate sensations. ► Subjects' expectations regarding the climate in aircrafts have an effect on comfort. ► The idea of personalized climate zones in aircraft passenger cabins is supported.

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Field investigation of comfort temperature in Indian office buildings: a case of Chennai and Hyderabad

April 18, 2013, 6:35 am

≫ Next: Multiplexed Optimization for Complex Air Conditioning Systems

≪ Previous: Climate preferences and expectations and their influence on comfort evaluations in an aircraft cabin

Publication date: Available online 17 April 2013
Source:Building and Environment
Author(s): Madhavi Indraganti , Ryozo Ooka , Hom B. Rijal

India’s building energy consumption is increasing rapidly. The subcontinent does not have custom made thermal comfort standards. There is little research in this field in the last 26 years. This leaves a lot to be investigated.

We conducted a thermal comfort field study in 25 office buildings in Chennai and Hyderabad for seven months during the summer and south west monsoon seasons in 2012 and collected 2612 datasets from 1658 subjects. The comfort temperature in naturally ventilated (AC off) (NV) mode was 27.6 °C and 28.1 °C in Chennai and Hyderabad respectively. In air conditioned (AC) mode, it was 27.0°C and 26.1 °C in these two cities. These departed from the limits in the Indian National Building Code. Chennai recorded significantly higher indoor air speeds and thus higher comfort temperature. In 71% cases the air speed was less than 0.15 m/s, underscoring the need for improvement. A majority always sensed the air movement low and desired increased air speeds, despite voting comfortable.

Both the States grappled with daily outages throughout the survey period. All the buildings, excepting two were forced to run without the AC at least for two hours daily, while none were prepared well for this. Several design and non-design factors seriously impeded environmental adaptation in buildings, limiting the adaptive operation of windows and fans. Consequentially, thermal acceptability was generally low (62.5%). This calls for architect’s serious attention towards environmental and thermal adaptation in buildings, in the era of power paucity and prudent consumption.

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Multiplexed Optimization for Complex Air Conditioning Systems

April 18, 2013, 6:35 am

≫ Next: Determination of Dynamic Intake Fraction of Cooking-generated Particles in the Kitchen

≪ Previous: Field investigation of comfort temperature in Indian office buildings: a case of Chennai and Hyderabad

Publication date: Available online 17 April 2013
Source:Building and Environment
Author(s): Yongjun Sun , Gongsheng Huang , Zhengwei Li , Shengwei Wang

Optimization has been considered as an efficient tool to realize energy efficiency in the operation of air conditioning (AC) systems. With the increase of complexity of AC systems, the computational complexity of real-time optimization appears to be a challenge for practical applications. In order to overcome the challenge, this paper proposes a multiplexed optimization scheme. Unlike conventional optimization that optimizes and updates all decision variables simultaneously, the proposed scheme optimizes and updates the decision variables sequentially and one decision variable at a time. The proposed scheme is compared with a conventional optimization method (in which the genetic algorithm is adopted) as regards computational load, energy performance and system stability. Case studies show that compared with the conventional optimization method, the computational burden of the proposed scheme is greatly reduced, up to 98.3%; the energy saving achieved by the proposed scheme is 6.8%, which is comparable to that achieved by the conventional method (6.7%); and the system operation stability is significantly enhanced since the average tracking errors for several monitored variables were reduced around 50%.

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Determination of Dynamic Intake Fraction of Cooking-generated Particles in the Kitchen

April 18, 2013, 6:35 am

≫ Next: multi-objective methods for determining optimal ventilation rates in dwellings

≪ Previous: Multiplexed Optimization for Complex Air Conditioning Systems

Publication date: Available online 17 April 2013
Source:Building and Environment
Author(s): Jun Gao , Changsheng Cao , Qianfen Xiao , Bin Xu , Xiang Zhou , Xu Zhang

This paper attempts to determine the individual intake fraction of particles generated from a simplified cooking process of edible oil heating in the kitchen. First, two separate sets of experiments, utilizing real-time Malvern particle sizer and TSI aerosol monitor, respectively, are combined to obtain the size-dependent emission rate of fume particles from the cooking process. Second, a drift-flux model for particle dispersion, getting particle source-releasing conditions from the experimental data, is applied to predict the dynamic concentration in the kitchen. Third, size-dependent dynamic intake fraction of the particles by an individual in the kitchen, based on a breathing model defined, is determined from the predicted particle concentrations. It is found from the case studies that the inhaled particle concentration is highly attributed to the air distribution under different ventilation conditions of the kitchen space, even if both the ventilation rate and final capture efficiency of the exhaust system are the same. It is confirmed that different air inflow results in even different magnitude of intake fraction, ranged from ∼10^-3 to ∼10^-5. Lower intake fraction is observed under the open-door conditions because inflow from the lower-level of the door produces some effect as the displacement ventilation. Results also show that size distribution of the inhaled mass is similar to that at the source, and the dynamic intake fraction is little sensitized to the particle size, due to the short-time and short-distance particle dynamics during the cooking process. The present work quantifies the attributed fraction of cooking-generated particles taken in by exposed individual through integrating the experimental and numerical methods. It helps to evaluate the indoor air quality and understand the health risk due to cooking activity in the kitchen space.

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multi-objective methods for determining optimal ventilation rates in dwellings

April 18, 2013, 6:35 am

≫ Next: Particulate concentrations within a reduced-scale room operated at various air exchange rates

≪ Previous: Determination of Dynamic Intake Fraction of Cooking-generated Particles in the Kitchen

Publication date: Available online 17 April 2013
Source:Building and Environment
Author(s): Payel Das , Zaid Chalabi , Benjamin Jones , James Milner , Clive Shrubsole , Michael Davies , Ian Hamilton , Ian Ridley , Paul Wilkinson

The optimal ventilation rate in a dwelling is a trade-off between the requirement to minimize ventilation heat losses to help meet national greenhouse gas emission targets and the need to minimize adverse health impacts arising from exposure to cold temperatures and pollutants from indoor and outdoor origin. This paper presents approaches for exploring these trade-offs based on two implementations of multi-objective optimization that consider both energy efficiency and health impacts. Both methods aggregate the various performance criteria into a single criterion, but the first method monetizes the performance criteria, while the second method weights them in a more general way.

Unlike in the monetization approach, the generalized multi-objective optimization approach is found to be robust against scaling of the health impacts and energy savings that is independent of the ventilation rate. As a result it is less sensitive to assumptions made in the models regarding heating system efficiency, absolute health burden level, and dwelling occupancy. It is however sensitive to assumptions regarding pollutant production rates and balance-point temperatures, which affect health impacts and energy savings in a way correlated with ventilation rate.

A preliminary application of the methods to a typical UK flat and detached house finds that the optimal ventilation rate may vary with built form. Application of the generalized multi-objective optimization approach in which health impacts and energy savings are equally weighted, suggests an optimal annual average air change rate of 0.4/hr for the detached house, and 0.7/hr for the flat.

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Particulate concentrations within a reduced-scale room operated at various air exchange rates

April 18, 2013, 6:35 am

≫ Next: A Novel Model for Risk Assessment of Adjacent Buildings in Tunneling Environments

≪ Previous: multi-objective methods for determining optimal ventilation rates in dwellings

Publication date: Available online 17 April 2013
Source:Building and Environment
Author(s): W. Brock Faulkner , Farhad Memarzadeh , Gerald Riskowski , Keith Hamilton , Ching-Zu Chang , Jieh-Ren Chang

Precise prediction of particulate movement is needed to provide a better understanding of how airborne disease organisms move within ventilated facilities. Bacteria often adhere to larger airborne particulates, which will modify their movement behavior in ventilated rooms and may provide an environment to allow them to remain virulent longer. An empty chamber (206 H x 203 W x 386 cm L) with a circular air inlet and outlet on opposite ends was ventilated with air that had a known particulate density. The inlet and outlet openings were sized to maintain inlet and exit velocities at around 5.1 m/s at 5 different air exchange rates (around 2, 4, 5, 9, and 14 air changes per hour – ACH). Particulate concentrations were measured at the air outlet and at 12 locations within the chamber. In this study, the particulate concentration in the inlet air remained constant, so the amount of particulates injected into the chamber increased as the ACH increased. The measured particulate levels at the outlet also increased essentially linearly with an increase in ACH. However, the particulate concentrations in the occupied zone of the chamber did not increase linearly with an increase in actual ACH. Rather, it increased essentially linearly at the lower ACH levels (from around 2 to 5 ACH), but then leveled out at the higher ACH values. The advantages of increasing ACH in terms of providing better environments in the occupied zone of rooms may have limits, which warrant further investigation.

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A Novel Model for Risk Assessment of Adjacent Buildings in Tunneling Environments

April 18, 2013, 6:35 am

≫ Next: National survey of summertime temperatures and overheating risk in English homes

≪ Previous: Particulate concentrations within a reduced-scale room operated at various air exchange rates

Publication date: Available online 18 April 2013
Source:Building and Environment
Author(s): Limao Zhang , Xianguo Wu , Lieyun Ding , Miroslaw J. Skibniewski

This paper presents a novel model to assess the risk of adjacent buildings in tunneling environments based on Extended Cloud Model (ECM). ECM is an organic integration of Extension Theory (ET) and Cloud Model (CM), where ET is appropriately employed to flexibly expand the variable range from [0, 1] to (-∞, +∞), and CM is used to overcome the uncertainty of fuzziness and randomness during the gradation of evaluation factors. An integrated interval recognition approach to determine the boundary of risk related intervals is presented, with both actual practices and group decisions fully considered. The risk level of a specific adjacent building is assessed by the correlation to the cloud model of each risk level. A confidence indicator θ is proposed to illustrate the rationality and reliability of evaluating results. Ten buildings adjacent to Wuhan Metro Line Two (WMLT) are randomly chosen among hundreds of adjacent buildings for a case study, and the results have proved to be consistent with the actual situation. Compared with other traditional evaluation methods, ECM has been verified to be a more competitive solution with no demands on training data. The original data can be directly entered into ECM without a normalization procedure, avoiding the potential information loss. ECM can be offered as a decision support tool for the risk assessment in urban tunneling construction and worth popularizing in other similar projects.

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National survey of summertime temperatures and overheating risk in English homes

April 18, 2013, 6:35 am

≫ Next: Practical Correlation for Thermal Resistance of 45o Sloped Enclosed Airspaces with Downward Heat Flow for Building Applications

≪ Previous: A Novel Model for Risk Assessment of Adjacent Buildings in Tunneling Environments

Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): A. Beizaee , K.J. Lomas , S.K. Firth

This paper presents one of the first national scale studies of summertime temperatures in English dwellings. Living room and bedroom temperatures were recorded in 207 homes across the England during the cool summer of 2007. Data was also collected by face-to-face household interviews. Fourteen homes (7%) were observed to be heated for part or all of the analysis period (July to August). Based on the BSEN15251 adaptive thermal comfort model, the 193 free-running dwellings would, in general, to be considered as uncomfortably cool. Over 72% of living rooms and bedrooms had more than 5% of hours below the BSEN15251 Cat II lower threshold, with over 50% having more than 5% of hours below the Cat III threshold. Detached homes and those built before 1919 were significantly cooler (p < 0.05) than those of other type and age. Static criteria revealed that, despite the cool summer, 21% of the bedrooms had more than 5% of night time hours over 26 °C; which is a recommended upper limit for bedrooms. The bedrooms of modern homes, i.e. those built after 1990 or with cavity walls, were significantly warmer (p < 0.05). The bedrooms in homes built prior to 1919 were significantly cooler (p < 0.05). The living rooms of flats were significantly warmer than the living rooms in the other dwelling types (p < 0.05). The incidence of warm bedrooms in modern homes, even during a cool summer, is of concern, especially as there is a strong trend towards even better insulation standards in new homes and the energy-efficient retrofitting of existing homes.

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Practical Correlation for Thermal Resistance of 45o Sloped Enclosed Airspaces with Downward Heat Flow for Building Applications

April 19, 2013, 6:56 am

≫ Next: Mould resistance design (MRD) model for evaluation of risk for microbial growth under varying climate conditions

≪ Previous: National survey of summertime temperatures and overheating risk in English homes

Publication date: Available online 19 April 2013
Source:Building and Environment
Author(s): Hamed H. Saber

A table is provided in the 2009 ASHRAE Handbook of Fundamentals (Chapter 26) that contains the thermal resistances (R-values) of enclosed airspaces. The ASHRAE table provides the R-values for enclosed airspaces of different thicknesses, effective emittances, mean airspace temperatures, and temperature differences across the airspaces. This table is extensively used by modellers, architects and building designers in the design for the R-values of building enclosures. The effect of the airspace aspect ratio (length/thickness) on the R-value is not accounted for in the ASHRAE table. However, previous studies showed that the aspect ratio of the airspace can affect its R-value. In this paper, the previous studies that focused on determining the R-values for vertical enclosed airspaces and horizontal enclosed airspaces with upward and downward heat flow are extended to investigate the effect of the aspect ratio on the R-values of 45o sloped enclosed airspaces under downward heat flow for different airspace thicknesses and having a wide range of values for the effective emittance, mean temperature, and temperature differences across the airspaces. The predicted R-values are compared with those provided in the ASHRAE table. Considerations are also given to investigate the potential increase in the R-values of enclosed airspaces when a thin sheet is placed in the middle of the airspace and whose surfaces have different values of emissivity. Thereafter, practical correlation is developed for determining the R-values of 45o sloped enclosed airspaces for future use by modellers, architects and building designers. The simplicity of this correlation for the sloped enclosed airspaces along with those that were previously developed for vertical and horizontal airspaces suggests that these correlations could be included in the ASHRAE Handbook of Fundamentals.

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Mould resistance design (MRD) model for evaluation of risk for microbial growth under varying climate conditions

April 19, 2013, 6:56 am

≫ Next: The effect of cyclic moisture and temperature on mould growth on wood compared to steady state conditions

≪ Previous: Practical Correlation for Thermal Resistance of 45o Sloped Enclosed Airspaces with Downward Heat Flow for Building Applications

Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): Sven Thelandersson , Tord Isaksson

The risk for microbial growth depends on the microclimatic conditions at material surfaces. In the building envelope the microclimate will vary significantly with time. Whether microbial growth will occur or not, depends on humidity, temperature, duration of exposure and type of material (substrate). A limit state for onset of mould growth is here defined as a prescribed level observed by microscopy (40×) in laboratory tests. In this paper, a mould resistance design (MRD) model is proposed by which onset of growth can be predicted for an arbitrary climate history of combined relative humidity ϕ and temperature T. The model is calibrated and verified against a comprehensive set of new experimental data describing mould development on wood specimens (spruce and pine) as a function of exposure of relative humidity and temperature and material and surface characteristics. The exposure in the tests comprised both steady and time-variable conditions.

Application of the MRD-model is demonstrated by assessment of mould risk based on results from simulations of an external wall design with hygro-thermal computer software (WUFI). The results show that a generally applicable, quantitative model together with building physics software can be used as a powerful tool for moisture safety design in practice.

The model is designed to facilitate continuous improvement by further laboratory testing of various materials under specified climate conditions. The MRD-model is controlled by a basic parameter in the form of a critical dose D crit, which depends on the substrate or material surface on which growth may take place.

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The effect of cyclic moisture and temperature on mould growth on wood compared to steady state conditions

April 20, 2013, 7:17 am

≫ Next: Methods for Detailed Energy Data Collection of Miscellaneous and Electronic Loads in a Commercial Office Building

≪ Previous: Mould resistance design (MRD) model for evaluation of risk for microbial growth under varying climate conditions

Publication date: Available online 20 April 2013
Source:Building and Environment
Author(s): Pernilla Johansson , Gunilla Bok , Annika Ekstrand-Tobin

Moisture and temperature are the two key environmental parameters that determine the possibility of mould growth on building materials. The time that the material is exposed to these elements is also crucial. The natural environmental conditions of relative humidity and temperature are seldom constant over prolonged time periods in a building. Instead, they vary over time, with fungi encountering both favourable and unfavourable conditions; such variable conditions affect mould growth. This paper reports findings from a laboratory study in which mould growth at alternating RH (between 90 % and 60 %) or temperature conditions (between 22 °C and 5 °C) was studied and compared to steady state conditions. Fluctuating RH led to slower mould growth, and when the period of unfavourable/favourable conditions was longer (1 week), growth was affected more than if the duration of these conditions was short (12 h). When alternating the temperature weekly between 22 °C and 5 °C, with a mean of 13 °C, the mould growth rate was lower compared to when the temperature was held constant at 22 °C. The mould growth under fluctuating temperature conditions was comparable to when the temperature was kept constant at 10 °C.

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Methods for Detailed Energy Data Collection of Miscellaneous and Electronic Loads in a Commercial Office Building

April 24, 2013, 12:01 am

≫ Next: Natural ventilation of buildings due to buoyancy assisted by wind: investigating cross ventilation with computational and laboratory simulation

≪ Previous: The effect of cyclic moisture and temperature on mould growth on wood compared to steady state conditions

Publication date: Available online 23 April 2013
Source:Building and Environment
Author(s): Steven Lanzisera , Stephen Dawson-Haggerty , H.Y. Iris Cheung , Jay Taneja , David Culler , Richard Brown

Miscellaneous and electronic loads (MELs) consume about 20% of the primary energy used in U.S. buildings, and this share is projected to increase for the foreseeable future. Our understanding, however, of which devices are most responsible for this energy use is still rudimentary due to the difficulty and expense of performing detailed studies on MELs and their energy use. In order to better understand the energy use of MELs and the design of MELs field metering studies, we conducted a year-long study of MELs in an 89,500 sq. ft. (8310 m²) office building. We present insights obtained from this study using 455 wireless plug-load power meters including the study design process, the tools needed for success, and key other methodology issues. Our study allowed us to quantify, for the study buildings, how many devices we needed to inventory and meter as well as for how long we needed to collect meter data. We find that the study design of earlier work would not have yielded accurate results in our study building. This paper presents these findings along with a brief summary of the energy related results.

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Natural ventilation of buildings due to buoyancy assisted by wind: investigating cross ventilation with computational and laboratory simulation

April 24, 2013, 12:01 am

≫ Next: Potential of structural thermal mass for demand-side management in dwellings

≪ Previous: Methods for Detailed Energy Data Collection of Miscellaneous and Electronic Loads in a Commercial Office Building

Publication date: Available online 24 April 2013
Source:Building and Environment
Author(s): A. Stavridou , P. Prinos

In this paper cross natural ventilation due to buoyancy assisted by wind is investigated with computational and laboratory simulation. The impact of the outlet’s opening position is investigated, forming cross ventilation of variable distance h – namely, the vertical distance between midpoints of leeward and windward opening –, for three initial Froude numbers: (i) Fr0=1.15, (ii) Fr0=2.79, (iii) Fr0=4.85. For the computational simulation a fluid dynamic software is used and the problem is solved by solving the 3D unsteady Reynolds Averaged Navier Stokes (RANS) equations in conjunction with the energy equation and the turbulence model RNG k-ε. Τhe laboratory simulation took place in an open channel and the experimental model represents a building form of orthogonal shape. The interior of the experimental model is filled with solution of ethanol at conditions of normalized gravity, but also with salted water at conditions of inversed gravity. The time taken for the indoor space to empty is calculated numerically and experimentally. Based on Froude number dynamic similarity, the experimental and computational results are characterized by good agreement and the functional process of natural ventilation is being explicated. In addition, the suggestion of using ethanol solution for the density difference between interior and exterior fluid in laboratory simulation of natural ventilation is verified successfully, as the results with use of ethanol solution are in good agreement with those using salted water.

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Potential of structural thermal mass for demand-side management in dwellings

April 24, 2013, 12:01 am

≫ Next: Catalytic oxidization of indoor formaldehyde at room temperature – Effect of operation conditions

≪ Previous: Natural ventilation of buildings due to buoyancy assisted by wind: investigating cross ventilation with computational and laboratory simulation

Publication date: June 2013
Source:Building and Environment, Volume 64
Author(s): G. Reynders , T. Nuytten , D. Saelens

In order to avoid grid instability and decreasing production efficiencies of large power plants due to a widespread integration of renewable electricity production, demand-side management (DSM) is proposed as a solution to overcome the possible mismatch between demand and supply. This research evaluates the potential to improve the balance between the electricity use for heating and local electricity production of a nearly zero energy building (nZEB), by active use of structural thermal storage capacity of the building.

To quantify the DSM potential of structural thermal storage, the cover factors and peak electricity demand of a single family dwelling equipped with a photovoltaic (PV) system are chosen. Detailed representations of the PV system and the dwelling itself, heated by an air–water heat pump, are implemented in the modeling environment of Modelica and simulated for the heating-dominated climate of Belgium. The influence of the insulation level and the embedded thermal mass of the construction on the DSM potential is evaluated. The impact of the heat emission system is estimated by comparing a floor heating system with a radiator emission system.

Results show that although the influence on the cover factors is limited, the use of the structural storage capacity for demand-side management shows strong potential to shift the peak electricity use for heating to off-peak hours. Furthermore, it is shown that not only the availability of the thermal mass, but also the interaction between the heating system and the thermal mass is of significant importance.

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Catalytic oxidization of indoor formaldehyde at room temperature – Effect of operation conditions

April 24, 2013, 12:01 am

≫ Next: Measurement of ventilation and airborne infection risk in large naturally ventilated hospital wards

≪ Previous: Potential of structural thermal mass for demand-side management in dwellings

Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): Zhiqiang Wang , Jingjing Pei , Jianshun Zhang

Catalytic oxidization has been studied for elimination of formaldehyde, which is a common and toxic indoor pollutant. However, most of previous studies were conducted at temperature and concentration level much higher than typical room condition. The current paper is to determine the effectiveness of catalytic oxidization of formaldehyde at room condition. The performance of one noble metal catalyst (Pd/γ-Al2O3) and two transition metal oxide catalysts (Fe2O3–MnO2 and CuO–MnO2) were studied at room temperature (23–25 °C). The effect of concentration (0.5–5 ppm), relative humidity (20–80%) and air velocity (0.2–1.0 m/s) were studied with single-pass breakthrough method. The major conclusions are: (1) Under room temperature and much lower concentration levels than in previous studies, the noble metal catalyst also demonstrated significantly better removal performance than metal oxide, maintaining a constant efficiency with time; (2) For different concentration levels, the efficiency of Pd/γ-Al2O3 did not change significantly at concentrations below 5 ppm, while the efficiency increased as concentration decreased for Fe2O3–MnO2; (3) the effect of relative humidity on the catalysts performance was not consistent for different type of catalysts; (4) Regarding the mass transfer mechanism, the importance of external mass transfer process was revealed by tests at different velocity for surface coated catalyst and dimensionless analysis, while both internal diffusion and external mass transfer are influential for homogeneously formed catalyst pellet. (5) The effect of multi-pollutants existence was also investigated, and it was found that the presence of other VOCs slightly decrease the performance of Pd/γ-Al2O3, but not Fe2O3–MnO2.

Graphical abstract

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Measurement of ventilation and airborne infection risk in large naturally ventilated hospital wards

April 24, 2013, 12:01 am

≫ Next: A multi-criteria approach to compare urban renewal scenarios for an existing neighborhood. Case study in Lausanne (Switzerland)

≪ Previous: Catalytic oxidization of indoor formaldehyde at room temperature – Effect of operation conditions

Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): C.A. Gilkeson , M.A. Camargo-Valero , L.E. Pickin , C.J. Noakes

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.

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A multi-criteria approach to compare urban renewal scenarios for an existing neighborhood. Case study in Lausanne (Switzerland)

April 25, 2013, 8:17 am

≫ Next: The Activity of Acrylic-silicon/nano-TiO2 Films for the Visible-light Degradation of Formaldehyde and NO2

≪ Previous: Measurement of ventilation and airborne infection risk in large naturally ventilated hospital wards

Publication date: July 2013
Source:Building and Environment, Volume 65
Author(s): Maria Gracia Riera Pérez , Emmanuel Rey

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.

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The Activity of Acrylic-silicon/nano-TiO2 Films for the Visible-light Degradation of Formaldehyde and NO2

April 26, 2013, 8:19 am

≫ Next: Development of JOS-2 Human Thermoregulation Model with Detailed Vascular System

≪ Previous: A multi-criteria approach to compare urban renewal scenarios for an existing neighborhood. Case study in Lausanne (Switzerland)

Publication date: Available online 25 April 2013
Source:Building and Environment
Author(s): Gang Xiao , Anna Huang , Haijia Su , Tianwei Tan

Through a novel green and low-cost emulsion blend method, acrylic-silicon/nano-TiO2 films (ASTF) were prepared showing a broad absorption band in the visible light region and could be used for the photodegradation of indoor gaseous pollutants under visible light irradiation. Compared with acrylic-silicon films, the photodegradation rate of ASTF with TiO2 content of 1% (w/v) increased by almost twice for both gaseous formaldehyde (from 28% to 76.7% at the initial concentration of 0.8 mg/m³) and NO2 (from 20% to 68% at the initial concentration of 3.7 mg/m³) under visible light irradiation for 24 h and 50 h, respectively. The binary gas degradation confirmed the higher affinity of NO2 for ASTF. In addition, ASTF with Fe^Ⅲ ion doping (< 100 mg/L) showed even higher photocatalytic activity with maximum degradation rate of 83.4% for formaldehyde under visible light irradiation for 24 h. ASTF, as a kind of eco-friendly coating material, could be used easily in domestic buildings for our daily life.

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