Showing papers in "Building Simulation in 2011"

A novel approach for building occupancy simulation

Abstract: Building occupancy is an important basic factor in building energy simulation but it is hard to represent due to its temporal and spatial stochastic nature. This paper presents a novel approach for building occupancy simulation based on the Markov chain. In this study, occupancy is handled as the straightforward result of occupant movement processes which occur among the spaces inside and outside a building. By using the Markov chain method to simulate this stochastic movement process, the model can generate the location for each occupant and the zone-level occupancy for the whole building. There is no explicit or implicit constraint to the number of occupants and the number of zones in the model while maintaining a simple and clear set of input parameters. From the case study of an office building, it can be seen that the model can produce realistic occupancy variations in the office building for a typical workday with key statistical properties of occupancy such as the time of morning arrival and night departure, lunch time, periods of intermediate walking-around, etc. Due to simplicity, accuracy and unrestraint, this model is sufficient and practical to simulate occupancy for building energy simulations and stochastic analysis of building heating, ventilation, and air conditioning (HVAC) systems.

Understanding net zero energy buildings: Evaluation of load matching and grid interaction indicators

Abstract: Although several alternative definitions exist, a NetZero Energy Building (Net ZEB) can be succinctly described as a grid-connected building that generates as much energy as it uses over a year. The “net-zero” balance is attained by applying energy conservation and efficiency measures and by incorporating renewable energy systems. While based on annual balances, a complete description of a Net ZEB requires examining the system at smaller time-scales. This assessment should address: (a) the relationship between power generation and building loads and (b) the resulting interaction with the power grid. This paper presents and categorizes quantitative indicators suitable to describe both aspects of the building’s performance. These indicators, named LMGI - Load Matching and Grid Interaction indicators, are easily quantifiable and could complement the output variables of existing building simulation tools. The indicators and examples presented here deal only with electric generation and loads.

ThermalOpt: A methodology for automated BIM-based multidisciplinary thermal simulation for use in optimization environments

Abstract: This paper describes ThermalOpt—a methodology for automated BIM-based multidisciplinary thermal simulation intended for use in multidisciplinary design optimization (MDO) environments. ThermalOpt mitigates several technical barriers to BIM-based multidisciplinary thermal simulation found in practice today while integrating and automating commercially available technologies into a workflow from a parametric BIM model (Digital Project) to an energy simulation engine (EnergyPlus) and a daylighting simulation engine (Radiance) using a middleware based on the open data model Industry Foundation Classes (IFC). Details are discussed including methods for: automatically converting architectural models into multiple consistent thermal analytical models; integration/coordination of analysis inputs and outputs between multiple thermal analyses; reducing simulation times; and generating consistent annual metrics for energy and daylighting performance. We explain how ThermalOpt can improve design process speed, accuracy, and consistency, and can enable designers to explore orders of magnitude larger design spaces using MDO environments to better understand the complex tradeoffs required to achieve zero energy buildings.

An algorithm to represent occupant use of windows and fans including situation-specific motivations and constraints

Abstract: A theoretical model of the interaction between a building and its occupants is developed based on field survey data; the role of the model in building performance simulation is illustrated. If free to do so, people adjust their clothing or available building controls (windows, blinds, doors, fans, and thermostats) with the aim of achieving or restoring comfort and reducing discomfort. Initially responses to thermal conditions are considered. Trigger temperatures are established where responses to warm or cold thermal discomfort may occur. These trigger-temperatures depend on (among other things) clothing (which may depend on season and social conditions) and air movement (e.g., fan setting). Trigger-temperatures differ from person to person and from time to time. If several controls are available people will use those that are most user-friendly, effective and free from undesirable consequences, and this is represented in the model by a constraint assigned to each control option. The concept of constraints is then expanded to capture non-thermal stimuli for control use (e.g., fresh-air). Using datasets from surveys in Europe and Pakistan, estimates are made of the parameters used in the model: the comfort temperature in relation to the prevailing outdoor temperature, the extent of inter-personal variation of trigger temperature, the effect of a fan on the comfort temperature, and the values of constraints that affect the use of windows and fans in the surveyed buildings. The incorporation of the new model, including constraints, into building simulation code is illustrated. Some limitations or unknowns in the current model are identified and possible approaches for future research to fill these gaps suggested. The application of the model in building performance analysis and building design is discussed.

Impact of non-uniform urban surface temperature on pollution dispersion in urban areas

Abstract: Airflow pattern through street canyons has been widely studied to understand the nature of pollution dispersion in order to develop guidelines for urban planners. One of the major contributing parameters in pollution dispersion is thermal-induced flow caused by surface and air temperature difference. However, most of the previous studies assumed isothermal condition for street canyons. Those addressed the thermal-induced flow, have assumed a uniform wall surface temperature distribution. The external building wall surface temperature distribution is not uniform, and is influenced by many factors including the wall surface characteristics, and shading. The non-uniform temperature distribution significantly impacts on 3-dimensional airflow within street canyons. Moreover, effect of intersection is barely considered in the literature where L/H<3 (L and H are respectively length and height of street canyon). This Paper reports the development of a 3-dimensional model to study the effect of non-uniform wall surface temperature distribution on the pollution dispersion and flow pattern within the short street canyons (L/H<3). For this purpose, a computational fluid dynamics (CFD) model is developed to investigate these effects on pollution dispersion in various prevailing wind velocities and directions. Moreover, active and passive techniques to reduce the level of concentration are examined. The study clearly shows that thermal-induced flow dominates during fair-weather condition.

Case study of window opening behavior using field measurement results

Abstract: Window opening behavior has significant influences on indoor environment and energy consumption in residential buildings. As a response to indoor environment, the control mechanism (window and interior door open/closed) should be studied first by comprehensive understanding of the variation of indoor environmental conditions. For this reason, a field measurement of environmental conditions was carried out in five representative apartments in Beijing from April to May in 2010. By comparison analyses of the field measurement results, major findings are as follows: (1) the concentration of room CO2 can be the best predictor of occupant behavior, also window opening behavior, in residential buildings; (2) the variation in indoor air quality mainly results from large variation in window opening behavior; (3) apart from indoor and outdoor thermal environment, indoor air quality as well as occupants’ presence at room have also considerable effect on window opening behavior; (4) while defining window opening behavior for one room in residential building, it is necessary to take the window adjustment of its connecting room and the adjustment of the connecting door into consideration due to air diffusion between the two connecting rooms.

Determination of indoor humidity profile using a whole-building hygrothermal model

Abstract: During the design of a new building or retrofitting of an existing one, it is important to reliably assess the indoor humidity levels of the building as it can potentially affect the building envelope durability, occupants’ comfort and health risks associated with mould growth. Simplistic assumptions of indoor humidity profiles, which ignore the dynamic coupling of the indoor environment and building enclosure, may lead to inaccurate conclusions about the indoor environment and moisture performance of the building enclosure. In this paper, a whole-building hygrothermal model called HAMFitPlus, which takes into account the dynamic interactions between building envelope components, mechanical systems and indoor heat and moisture generation mechanisms, is used to assess the indoor humidity condition of an existing occupied house. HAMFitPlus is developed on SimuLink development platform and integrates COMSOL multiphysics with MatLab. The basic input parameters of the model are discussed in detail, and its simulation results are presented. In general, the HAMFitPlus simulation results are in good agreement with the measured data.

Comparison of Measured and Calculated Values for the Indoor Environment in One of the First Danish Passive Houses

Abstract: Energy savings in the residential area are essential in order to achieve the overall goal for energy savings outlined in the recast of the Energy Performance of Buildings Directive. This was adopted by the European Parliament in 2010. Unfortunately, the large focus on energy performance has reduced the focus on indoor environment. This has, among other problems, resulted in problems with overheated buildings. Therefore, a need for a simple and cheap method for evaluation of possible problems with overheating has arisen among the designers. A method which can be used early in the design process. The paper compares the measured indoor temperatures of a Danish passive house with results of both a simple prediction of the 24-hour average and maximum indoor temperature during summer and a dynamic simulation of the indoor conditions in the building in order to find a useable method for prediction of problems with overheating.

Improving energy modeling of large building stock through the development of archetype buildings

Abstract: In this paper a selection process, based on statistical techniques, of representative buildings is presented. Starting from a real estate stock it is possible to draw a sample and calculate the relevant sample statistics. As second step, their elaboration permits to pick out real buildings with geometrical and thermo-physical characteristics similar to the average of the building sample. In addition, the results of this method are compared to those obtained by segmentation (or cluster) analysis, that is a method to partition a set of houses into groups having similar profiles. Finally, using the Piedmont Regional Database of Energy Performance Certificates these approaches are applied in order to verify the reliability of the analyses proposed. Potentialities and limitations of the performed analyses are critically discussed, as well.

Model validation of a dynamic embedded water base surface heat emitting system for buildings

Abstract: A numerical model is developed to assess the static and dynamic operations of a new kind of floor heat emitter. Surface floor heating systems are widely used to achieve better comfort conditions in residential and tertiary building sector. Classical floor heating systems have a low thermal response while the emitting device studied in this paper is highly reactive. It allows comfort enhancement and energy savings. A finite element method based software COMSOL Multiphysics is applied to solve the heat equation. This work focuses on the thermal behaviour of the emitter itself, but does not include a building model. A test bench has been built for this application to verify the numerical model. Both computational and experimental results demonstrate the benefits of this new heating and cooling device.

Modeling and validation of the thermal performance of an affordable, energy efficient, healthy dwelling unit

Abstract: The thermal performance of an affordable energy-efficient single-story residential building designated as Tuskegee Healthy House (THH) was simulated by developing a computational model for the house using Visual DOE-4 commercial software. Visual DOE-4 package employs the same calculation engine of the proven DOE-2 building Energy Analysis program. The THH was built from conventional building materials and construction methods according to the southern building codes of the United States. Several energy efficiency and air quality control features were incorporated throughout the THH. The present model was validated by comparison of computed results with power consumption data available from a previous study of the same house. The experimental data were obtained for forced ventilation flow rates of 0, 28.3 L/s and 54.3 L/s. A favorable agreement between the model predictions and experimental data is observed which is indicative of the model’s accuracy. The simulations also show that the heating, ventilation, and air conditioning (HVAC) energy requirement for THH is reduced when forced ventilation is increased during the summer months. However, ventilation during the winter months leads to a rise in THH energy requirement.

Impact of lifestyle on the energy demand of a single family house

Abstract: The building sector is one of the highest energy consumers in Austria. The potential to save energy in existing buildings is very high. Current Austrian policy incentives encourage home owners to renovate buildings to meet the European requirements, reduce energy consumption, and reduce CO2 emissions. Nevertheless, there are often discrepancies between the measured and calculated energy consumption results despite efforts to take parameters into account such as the exact geometry and thermal properties of the building, energy demand for hot water, heating, cooling, ventilation systems, and lighting in the planning phase for selecting the best reconstruction option. To find the answer to this problem, many buildings are carefully investigated with the help of measurements, interviews, and simulations. This paper presents the analysis and results of the investigation of the impact of lifestyle on the energy demand of a single family house. The impact on energy performance of the most important parameters was observed by systematically changing parameters such as changing from a decentralized to a centralized heating system, considering various technologies and fuels for producing electricity and heat, use of renewable energy sources. Different occupant behaviours were changed systematically. The effects of these measures are analysed with respect to primary energy use, CO2 emissions and energy costs. The results of these investigations show that the lifestyle and occupants’ living standard is mainly responsible for the differences between the calculated and measured energy consumption.

Hospital ventilation simulation for the study of potential exposure to contaminants

Abstract: Airflow and ventilation are particularly important in healthcare rooms for controlling thermo-hygrometric conditions, providing anaesthetic gas removal, diluting airborne bacterial contamination and minimizing bacteria transfer airborne. An actual hospitalization room was the investigate case study. Transient simulations with computational fluid dynamics (CFD), based on the finite element method (FEM) were performed to investigate the efficiency of the existing heating, ventilation and air-conditioning (HVAC) plant with a variable air volume (VAV) primary air system. Solid modelling of the room, taking into account thermo-physical properties of building materials, architectural features (e.g., window and wall orientation) and furnishing (e.g., beds, tables and lamps) arrangement of the room, inlet turbulence high induction air diffuser, the return air diffusers and two patients lying on two parallel beds was carried out. Multiphysics modelling was used: a thermo-fluidynamic model (convection-conduction and incompressible Navier-Stokes) was combined with a convection-diffusion model. Three 3D models were elaborated considering different conditions/events of the patients (i.e., the first was considered coughing and/or the second breathing). A particle tracing and diffusion model, connected to cough events, was developed to simulate the dispersal of bacteria-carrying droplets in the isolation room equipped with the existing ventilation system. An analysis of the region of droplet fallout and the dilution time of bacteria diffusion of coughed gas in the isolation room was performed. The analysis of transient simulation results concerning particle path and distance, and then particle tracing combined with their concentration, provided evidence of the formation of zones that should be checked by microclimatic and contaminant control. The present study highlights the fact that the CFD-FEM application is useful for understanding the efficiency, adequacy and reliability of the ventilation system, but also provides important suggestions for controlling air quality, patients’ comfort and energy consumption in a hospital.

Optimal tree design for sunshine and ventilation in residential district using geometrical models and numerical simulation

Abstract: Vegetation has positive effects on the outdoor pedestrian comfort and thermal environment. Studied with He Qing Yuan district in Beijing, an investigation of the optimal landscape design of trees in residential buildings at northern China is carried out for good sunshine and comfortable wind environment. Firstly, in consideration of the legal planning requirement for basic sunshine hour control in winter for house, geometrical models for trees and buildings are built and analyzed by AutoCAD and Sketch-Up software to determine reasonable tree location between buildings, suitable heights and crown shapes. Secondly, aimed at comfortable wind environment inside the residential district, optimal arrangement of trees has been studied with numerical simulation by SPOTE (simulation platform for outdoor thermal environment), where the air velocity lower than 5 m/s is introduced as the aims of scheme optimization. With geometrical analysis and numerical simulation and comparison, the tree types and layout in green space between buildings were optimized.

Architecture data and energy efficiency simulation: BIM and interoperability standards

Abstract: Building Information Modelling (BIM) and energy simulation tools are increasingly used for the analysis of energy efficiency of buildings and comfort of their occupants. This paper starts with several definitions. Then, it presents a method to standardize the contents of 3D architectural models in existing and historical buildings aimed to obtaining an effective interoperable model to enable faster and reliable energy performance simulations during the building’s life-cycle and specifically its management stage. Given the significant variety of architectural modelling and energy simulation tools, it is crucial to understand limitations of the tools and the complexity of such simulations, considering at the same time their user-friendliness.

A net zero energy building in italy: design studies to reach the net zero energy target

Abstract: The aim of this work is to model the energy consumption and the on-site production of an existing building, the Leaf House (LH), that was designed in order to be a Net Zero CO2 emission home. For a more effective use of energy some of the most advanced available technologies in the field of renewable sources were used. In particular, the technological building plant includes several subsystems as a Geothermal Heat Pump (GHP), solar PV and thermal panels, integrated in a fully automatic heat distribution system. The building is only “nearly NZEB” and it is necessary to introduce some improvements in thermal plant and in energy production technological systems for reaching the NZEB goal.

Integrating neural network models with computational fluid dynamics (CFD) for site-specific wind condition

Abstract: Most building energy simulations tend to neglect microclimates in building and system design, concentrating instead on building and system efficiency. Energy simulations utilize various outdoor variables from weather data, typically from the average weather record of the nearest weather station that is located in an open field, near airports and parks. The weather data may not accurately represent the physical microclimate of the site, and may therefore reduce the accuracy of simulation results. For this reason, this paper investigates utilizing computational fluid dynamics (CFD) with neural network (NN) model to predict site-specific wind parameters for energy simulation. The CFD simulation is used to find selected samples of site-specific wind conditions. Findings from CFD simulation are used as training data for NN. A trained NN predicts site-specific hourly wind conditions for a typical year. The outcome of the site-specific wind condition from the neural network is used as wind condition input for the energy simulation. The results of energy simulation using typical weather station data and site-specific weather data are compared in this paper, in order to find the possibility of using site-specific weather condition by NN with CFD to yield more realistic and robust ES results.

Multiphysics modeling of building physical constructions

Abstract: The paper presents an overview of Multiphysics applications using a Multiphysics modeling package for building physical constructions simulation The overview includes three main basic transport phenomena for building physical constructions: (1) heat transfer, (2) heat and moisture transfer and (3) heat, air and moisture (HAM) transfer It is concluded that full 3D transient coupled HAM models for building physical constructions can be build using a Multiphysics modeling package Regarding the heat transport, neither difficulties nor limitations are expected Concerning the combined heat and moisture transport the main difficulties are related with the material properties but this seems to be no limitation Regarding the HAM modeling inside solid constructions, there is at least one limitation: the validation is almost impossible due to limitation of measuring ultra low air velocities of order μm/s

Development of an optimal design aid system based on building information modeling

Abstract: This study proposes an optimal building design aid system that integrates computer aided design (CAD), building environmental simulation tools and an optimization algorithm, based on the concept of building information modeling (BIM). BIM is a process of generating and managing data during a building’s life cycle. It can be used to demonstrate the entire building’s life cycle, including its construction and operation. Because the design of a build may vary from an abstract shape to precise details, the building’s database should vary accordingly. To store, manage and utilize the building’s data efficiently, we suggest an evolving database structure for our design aid system. A case study verifies that the system can acquire data from CAD, run a number of simulations and generate Pareto solutions automatically during several design stages.

Double skin facades in the hot summer and cold winter zone in China: Cavity open or closed?

Abstract: Double skin facades (DSFs) have gained increasing popularity worldwide for potential building energy savings. Such energy advantages are widely thought to be attributed to the ventilation feature of the DSF cavity. Keeping the cavity open to the outside, however, practically causes noise problems, dust pollution, and safety issues and thereby raising the maintenance cost of DSFs. This paper attempted to bring up this issue for more attention. We first numerically examined the thermal performance of DSF windows based on the climate of Hangzhou City featured by hot summer (>30°C) and cold winter (∼4°C). Then we discussed the potential energy benefits of DSFs and the ventilation design of the cavity. Results from our simulations showed that the DSF window was more energy efficient than a double glazing window in summer regardless of the cavity open or closed. Such energy advantages were more due to the additional pane of the DSF window to reduce the solar transmittance than due to ventilation of the cavity. Although ventilation is beneficial in summer, the annual energy gain may be limited. Our simulations showed that ventilation can save annual energy by no more than 8% under Hangzhou climatic conditions. Therefore, to justify the use of ventilation in a DSF, we recommend a comprehensive evaluation to be performed by balancing the annual energy gains and investment increase associated with the open cavity.

Categories of indoor environmental quality and building energy demand for heating and cooling

Abstract: Maintaining suitable indoor climate conditions is a need for the occupants’ well being, while requiring very strictly thermal comfort conditions and very high levels of indoor air quality in buildings represents also a high expense of energy, with its consequence in terms of environmental impact and cost. In fact, it is well known that the indoor environmental quality (IEQ), considering both thermal and indoor air quality aspects, has a primary impact not only on the perceived human comfort, but also on the building energy consumption. This issue is clearly expressed by the European Energy Performance of Buildings Directive 2002/92/EC, together with the most recent 2010/31/EU, which underlines that the expression of a judgment about the energy consumption of a building should be always joint with the corresponding indoor environmental quality level required by occupants. To this aim, the concept of indoor environment categories has been introduced in the EN 15251 standard. These categories range from I to III, where category I refers to the highest level of indoor climate requirement. In the challenge of reducing the environmental impact for air conditioning in buildings, it is essential that IEQ requirements are relaxed in order to widen the variations of the temperature ranges and ventilation air flow rates. In this paper, by means of building energy simulation, the heating and cooling energy demand are calculated for a mechanically controlled office building where different indoor environmental quality levels are required, ranging from category I to category III of EN 15251. The building is located in different European cities (Moscow, Torino and Athens), characterized by significantly different wheatear conditions. The mutual relation between heating and cooling energy demand and the required levels of IEQ is highlighted. The simulations are performed on a typical office room which is adopted as a reference in validation tests of the European Standard EN 15265 to validate calculation procedures of energy use for space heating and cooling.

Setpoint control for air heating in a church to minimize moisture related mechanical stress in wooden interior parts

Abstract: The paper presents the setpoint control for air heating in a church to minimize moisture related mechanical stress in wooden interior parts, with the focus on the preservation of a monumental organ. The setpoint operation of the heating, ventilation, and air conditioning (HVAC) system is evaluated by simulation using MatLab, COMSOL and Simulink models. The main model components are presented and combined in a single integrated Simulink model: (1) a HAMBase Simulink building model for simulating the indoor temperature and relative humidity, (2) a COMSOL partial differential equation model for simulating detailed dynamic moisture transport and related mechanical stresses in the monumental wood (organ) and (3) a Simulink controller model. The main advantage of the integrated model is that it directly simulates the impact of HVAC control setpoint strategies on the indoor climate and the related mechanical stresses in wooden objects, like a monumental organ. As control strategy the limited indoor air temperature changing rate is discussed. Recommendations from international literature suggest that a limitation of the relative humidity changing rate of 2 to 5RH%/h will preserve the interior of churches. This study shows that a limitation of indoor air relative humidity changing rate of 2RH%/h can reduce mechanical stresses by a factor of 2.5, compared to maximum capacity heating.

A comparison of luminous efficacy models based on data from Vienna, Austria

Abstract: To support building design in view of daylight quality, computational (simulation) tools can provide effective support. To perform detailed daylight analysis via simulation, appropriate sky models are needed. In the past, various sky luminance distribution models have been developed. Such models, however, require illuminance data for the relevant location. As measured external illuminance levels are not available for many locations, the more widely available irradiance measurements can be translated, using proper luminance efficacy functions, into illuminance values. The present paper compares five global luminous efficacy models based on a database of measured illuminance and irradiance data from Vienna, Austria. These models typically involve mathematical formulations with multiple coefficients, whose values are derived for a specific location. The results suggest that these models performed rather poorly, once tested against Vienna data. However, the models’ performance improved significantly, once the respective coefficients were modified (calibrated) using the Viennese database.

Predicting natural ventilation flows in whole buildings. Part 1: The Viipuri Library

Abstract: For energy efficient restoration of historical buildings, especially historic monuments of international importance such as the Viipuri Library by Alvar Aalto (1898–1976), new analytical tools are needed. Of interest to this research is the evaluation of air movement within this building due to spatial composition, which can also prove very useful in helping architects determine how best to renovate and restore historical buildings. The objective is to analyze how radiant heating and passive cooling are currently exploited in the Viipuri Library. The knowledge will be useful to restore this historical building to function efficiently while ensuring that the existing mechanical ventilation systems and natural convective flows work well together after restoration. Computational fluid dynamics will be used to model, simulate and predict multiple environmental conditions to examine spatial layout effects on the ability of natural ventilation to maintain a comfortable thermal environment and acceptable rates of ventilation. The preliminary results demonstrate that airflow and thermal effects can be predicted and validated for any set of conditions, such as specifying which windows or doors are open, and the ambient conditions exterior (e.g., wind and air temperature) and interior (e.g., radiant pipes) to the building.

Numerical studies on evaluation of smoke control system of underground metro rail transport system in India having jet injection system: A case study

Abstract: The rail based urban transport system is being developed for national capital of India, New Delhi. The smoke control using ventilation in case of fire inside the tunnel, similar to Delhi Metro corridor has been investigated using computational fluid dynamics technique. A section of tunnel having dimensions 400 m long, 5.5 m wide and 6 m high is considered for simulation. The analysis has been carried out by assuming a variable fire source with a peak heat release rate (HRR) of 16 MW, located at the center of the tunnel. Ventilation ducts are located in the ceiling near the tunnel portals and are inclined at 10 degrees to the plane of the ceiling through which fans discharge air. The influence of the fire HRR curve slope on the smoke flow dynamics in a realistic tunnel model fitted with jet injection type longitudinal ventilation system has been investigated. In case of fire two cases are studied: (1) fans activated immediately after detection, (2) fans activated at delayed times to take into account the response time for the fans to achieve its maximum speed. The velocity of supply and exhaust fans necessary to remove smoke in 30 s from the upstream direction is determined. The velocities of fan required to produce desired critical velocity in the longitudinal direction for different HRR of fire is predicted.

Analysis of thermal comfort in a residential room with insect proof screen: A case study by numerical simulation methods

Abstract: The present paper aims to investigate the characteristics of airflow inside the room with insect proof screens by employing computation fluid dynamics (CFD) technique. Insect proof screens attached to the window openings were simulated by porous media approach. The simulated pressure drop across the insect proof screen was compared with the experimental result and is having a good agreement with a maximum error of 8.77% for the air velocity of 0.15 m/s. The insect proof screen significantly reduces the airflow rate and increases the indoor air temperature by 3°C. The effect of different window sizes and porosity of the insect proof screen is included for the study of thermal comfort index, predicted mean vote (PMV). From the PMV contours, center portion of the room and portions nearer to the windows are identified as comfort zones.

A multi-physical simulation on the IAQ in a movie theatre equipped by different ventilating systems

Abstract: The paper deals with a numerical multi-physical investigation on performance assured by different ventilating systems in supplying air quality and comfort conditions in a movie theatre hall. Mixing air distribution, under floor displacement and personalized air distribution systems are outlined in a given geometry. Momentum, energy and mass conservation equations are solved in order to highlight velocity fields, temperature distributions and carbon dioxide levels in each condition. Effectiveness of ventilation and mean age of air supplied to spectators are also computed giving further evaluation parameters in order to strike a balance between strong and weak points characterizing the studied systems.

A system for the comparison of tools for the simulation of water-based radiant heating and cooling systems

Abstract: Low temperature heating and high temperature cooling systems such as thermally activated building systems (TABS) offer the chance to use low exergy sources, which can be very beneficial financially as well as ecologically when using renewable energy sources. The above has led to a considerable increase of water based radiant systems in modern buildings and a need for reliable simulation tools to predict the indoor environment and energy performance. This paper describes the comparison of the building simulation tools IDA ICE, IES , EnergyPlus and TRNSYS. The simulation tools are compared to each other using the same room and boundary conditions. The results show significant differences in predicted room temperatures, heating and cooling degree hours as well as thermal comfort in winter and summer.

Comparison of building load performance between first principle based and implementable shading control algorithms

Abstract: This paper presents the findings on the impact of two window shading control strategies on office building thermal and lighting loads over a year’s period through energy simulation in four different climatic contexts in the United States. While it is well known that window shades affect heat gain and loss through windows and thus building energy loads, there is limited information on the actual magnitude and specific behavior of their effects on the building thermal and lighting loads. The objective of the described study is to generalize the magnitude of the impact from window shading control strategies on building thermal and lighting loads over a year by modeling a representative office building construction in indicative geographical locations as well as internal window shades representative of those that are commonly used. Two control algorithms are developed and evaluated which are the ideal algorithm and implementable. The basic principle of both algorithms is to maximize heat gain and minimize heat loss when the building is in heating condition, and performs the opposite when the building is in cooling condition, subject to glare control. Some of the information that is used in the ideal algorithm is not available for a “real world” controller. Therefore, an implementable shading control algorithm is also described, which will take sensor measurable conditions as input. EnergyPlus is used to conduct the thermal and lighting loads computation. The control algorithm is implemented through the BCVTB (Building Control Virtual Test Bed). BCVTB is a software environment that allows expert users to couple different simulation programs for distributed simulation.