Building Simulation Applications (BSA) 2019 was the fourth
IBPSA-Italy conference on building performance simulation to take place
at the Free University of Bozen-Bolzano, from 19th to 21st June 2019.
The main topics dealt with were urban simulation, building energy
performance assessment, hygrothermal analyses, detailed modelling of
physical phenomena and building system components, advanced HVAC
controls, integrated performance analysis, and visual, thermal and
acoustic comfort assessment.
The principal mission of the
International Building Performance Simulation Association (IBPSA) is to
promote and advance the practice of building performance simulation in
order to improve the design, construction, operation and maintenance of
new and existing buildings.
IBPSA-Italy, the Italian
affiliate, is a non-profit association, which includes researchers,
developers and practitioners acting on the topic of building performance
simulation. IBPSA-Italy was founded in January 2011 and has now more
than 170 members including university professors, researchers,
professionals, software developers and students.
In building performance simulation, fixed input assumptions lead to fixed computed values for building performance indicators. This has been suggested to be misleading, as it does not express the uncertainty of simulation-based performance predictions. A counterargument to this position suggests that the empirical basis for the determination of the statistical uncertainty distribution of occupancy-related input assumptions is rather scant. Arbitrary assignment of uncertainty functions (distribution ranges and shapes) to input variables can indeed generate corresponding performance result distributions. However, this could be even more misleading than fixed values, as the resulting uncertainty impression is empirically ungrounded. To address this objection, it has been suggested that the computed uncertainty ranges for performance indicators may be, to a certain extent, resistant to the ranges and shapes of associated input data distributions and hence still useful. In the present contribution, we examine the above suggestion, namely the resilience of performance simulation output distribution to the assumed model input uncertainties. To this end, parametric simulations were conducted and processed to explore the implications of different input data assumptions for the values of computed performance indicator values for a sample building model.
New Tools for the Hygrothermal Assessment of Building Components: A Comparison of Different Methodologies
Carlotta Dolzani, Martina Demattio, Marco Larcher, Ulrich Klammsteiner, Ulrich Santa
This paper presents new tools for the hygrothermal assessment of building components. The first assessment method based on the Glaser approach is implemented on the existing software ProCasaClima, whereas the second method constitutes a new tool for the dynamic simulation of combined transport of heat and moisture in building components: ProCasaClima Hygrothermal. This latter tool is more advanced since it takes into account capillary liquid transport and moisture storage properties of materials. At the same time, ProCasaClima Hygrothermal aims to be user-friendly to maximize its diffusion among technicians. The two assessment methods will be presented and compared in the results through a case study represented by an external wall internally insulated and located in the climate of Bolzano/Bozen. A second analysis is carried out specifically on the Hygrothermal tool to compare the results obtained with two different climate files. The first uses the reference year data provided by the CTI while the second is based on climate data obtained from the software Meteonorm, once again on the city of Bolzano/Bozen, but also including data referring to the rain. Finally, it will be possible to evaluate the influence of this phenomenon on the risk of interstitial condensation for the specific case analysed. The studies presented in this paper are supported by the ERDF European project BuildDOP.
Evaluation of Energy Flexibility From Residential District Cooling
Space cooling represents one of the fastest growing energy demands in buildings. Without any action to increase energy efficiency, this trend will be confirmed in the next decades, contributing significantly to the peak electricity demand growth. The need to increase both the energy efficiency and flexibility of the air conditioning (AC) sector is so urgent because of the strong penetration of renewable energy sources (RES) in the electricity generation mix. District cooling (DC) systems are recognised as one of the best solutions to reach this goal. As the DC energy efficiency benefits are not questioned, the objective of this paper is to provide a qualitative evaluation of the potential of DC networks in terms of energy flexibility. By modelling a small residential neighbourhood to be satisfied with a given cooling power availability, the effect of the different DC thermal inertia levels (e.g. the pipelines network, the buildings envelope and a dedicated thermal energy storage device) is investigated by means of two qualitative flexibility indicators (the wasted cold energy and the overheating time). The analysis shows that a great potential of energy flexibility is contained in DC systems. In particular, a great thermal demand management potential can be obtained when the buildings envelope thermal inertia is activated properly.
Dynamic Characterization of Thermal Bridges in Historic Balconies in Palermo
The improvement of the energy performance of a historic building entails a process of intervention that should take into account the historical, aesthetic, technical and material features. The first step of the retrofit process is an accurate knowledge of the thermal behaviour of historic building in order to preserve this heritage and reduce their impact on the environment. In terms of the thermal characterization of the construction elements of the traditional building in the Mediterranean region, the balconies constitute a disruptive element of the heat transfer by the envelope. Although there are many catalogues that collect typical actual constructive solutions with the corresponding thermal bridge values, the use of catalogues induces an error of 35% compared to physical reality. In this paper, we present a numerical method for the evaluation that takes into account the effects of thermal mass of thermal bridges in different historic balconies in the city of Palermo. We select typical construction details of balconies based on relevant literature on traditional architecture in Palermo. We present internal heat flow results and we compare them with the results of homogeneous envelope. Finally, we relate the results performed in dynamic and steady conditions.
Multi-Stage Multi-Level Calibration of a School Building Energy Model
Ilaria Pittana, Alessandro Prada, Francesca Cappelletti, Andrea Gasparella
The calibration of the building input parameters is the process aimed at minimizing the difference between actual and simulated performance. It is of paramount importance to implement a reliable model of an existing building, as this enables the study of its behaviour and the evaluation of improvement actions. However, when the number of unknown or uncertain parameters (such as thermophysical properties of components and materials, infiltration and ventilation rates, internal thermal capacitances, system characteristics, etc.) is large, manual calibration methods require unacceptably long trial-and-error cycles and do not always ensure a significant improvement, as the complexity of the simulation increases. This paper explores the potential of calibrating an entire building simulation model by means of a stepwise approach and automated calibration of the model (optimization-based calibration). The approach is multi-stage since it considers different reference periods in order to calibrate different parameters, and multi-level as it starts from a room level, in order to apply the calibrated parameters to the entire building, and perform calibration to refine the estimation of the missing parameters. The described approach is shown to be effective in reducing the number of initial unknown inputs at each step as well as in validating the previous calibration results when moving to the multizone level. The application of the proposed calibration method to a case study aims at demonstrating the details of its implementation and its efficacy, using the available limited number of measurement sensors and short observation periods.
Dynamic Modelling and Control System Optimization of a Reversible Air-to-Water Heat Pump with Heat Recovery for Domestic Hot Water Production
Matteo Dongellini, Luigi Belmonte, Gian Luca Morini
Even if the energy demand for space heating/cooling of near zero energy buildings (nZEBs) is continuously decreasing due to the improvement of the insulation level of building envelope components, the energy requirement for domestic hot water (DHW) production cannot be similarly reduced: for this reason, the weight of DHW energy consumptions on the overall building energy performance is becoming more and more significant for nZEBs. A reversible heat pump with recovery of the condensation heat (HPHR) is one way to obtain significant energy savings and respond to this increasing influence of DHW production with respect to the energy demand in residential buildings, since this kind of device is able to simultaneously satisfy the energy needs for DHW production and space cooling during the summer season. In order to improve the energy efficiency of a HPHR, the heat recovery operating mode should be maximized during the cooling season: for this reason, a detailed analysis of the heat pump control system is needed. Heat pump performance strongly depends on the values of control parameters, which are influenced by the system working conditions, such as DHW draw-off profile, building heating/cooling load and thermal storage size. In this paper, a detailed analysis of the annual energy performance of a HPHR system is obtained by means of TRNSYS 17: several simulations are carried out by varying the control algorithm, in order to achieve the best seasonal performance factor of the system. The results reported present a series of rules for the best setting of the heat pump control system parameters to HVAC designers and heat pump manufacturers and highlight how significant energy savings can be achieved with the adoption of a HPHR with respect to traditional systems based on a gas boiler or a conventional heat pump without heat recovery.
Numerical Evaluation of Moisture Buffering Capacity of Different Inner Casing
How does the moisture buffering capacity of the inner casing vary, according to the degree of the relative humidity of the room? Can a "rule of thumb" be obtained from a numerical simulation of a case study? A numerical evaluation of a heavyweight building was run in order to estimate the different moisture buffering capacity of two different kinds of plasters. In this study, the environmental data of a room, calculated using a dynamic simulation, was integrated with the hygroscopic properties of the materials obtained from the archives of the software WUFI, in order to simulate the variation of the relative humidity of a room inside a nearly Zero Energy Building with a mechanical ventilation with heat recovery.
A CitySim Urban Energy Simulation for the Development of Retrofit Scenarios for a Neighborhood in Bolzano, Italy
Fahad Haneef, Federico Battini, Giovanni Pernigotto, Andrea Gasparella
The urban territory is responsible for a high percentage of natural resources depletion and waste generation. Population increases and cities expand, and thus energy demand climbs. Consequently, an efficient use of energy is becoming more and more crucial in order to promote both local and global sustainability. To achieve such a goal, the reduction of energy demand, the optimization of energy supply sources, and the increase of renewable energy share can facilitate the transition of urban areas into highly efficient and sustainable districts. In this framework, this study assesses to what extent typical building retrofit interventions can reduce energy consumption, enabling a transition towards a nearly Zero Energy District (nZED). A state-of-the-art urban simulation was developed with CitySim for part of the city of Bolzano, Italy, to evaluate the annual district energy uses and define possible efficiency measures (e.g., façade and roof insulation and substitution of windows). Achievable energy savings are analyzed and the most significant factors affecting the overall performance identified.
Wind and Urban Spaces. Evaluation of a CFD Parametric Framework for Early‐Stage Design
Outdoor comfort and microclimate have recently garnered growing interest as important factors determining the success of urban open spaces. Increasing urban density, amongst the consequences of global urbanisation, is considered environmentally positive, but can also have a negative impact on outdoor comfort and on the Urban Heat Island (UHI). Wind plays an important role in alleviating UHI and ensuring comfortable outdoor conditions. However, accelerated winds around tall buildings can cause down-draughts, negatively affecting pedestrian comfort and safety. Monitoring airflow behaviours from the earliest design stages is crucial to adjusting the design accordingly. Expensive physical wind tunnels and sophisticated Computational Fluid Dynamics (CFD) are mainly the domain of wind engineers, while there is an overall lack of fast, intuitive, and yet accurate tools for non-specialists, such as urban designers and architects, particularly involved in the first design phases, to test several design options. Recently, CFD has been fully integrated within the user-friendly and fast-responsive Parametric Design platform, where several environmental simulations can be combined. The aim of this work is to evaluate CFD parametric tools from an accuracy and speed point of view, as a possible solution for non-specialist designers to simulate wind. A CFD parametric framework describing the systematic process to correctly perform airflow simulations with these tools was set-up and included best practice guidelines, a CFD parametric model construction and verification tests. Time was recorded across all simulations. Coupling CFD and parametric design proved positive, in terms of high accuracy and modelling time reduction, thanks to the automatization of some steps. However, the simulations required a long time and some CFD specialist knowledge, limiting the use by non-specialists. Improvements to this technology, computing time reduction strategies and future research were proposed.
Analysis of Two Shading Systems in a Glazed-Wall Physiotherapy Center in Bolzano, Italy
Luca Zaniboni, Giovanni Pernigotto, Andrea Gasparella
This work presents a study of a physiotherapy center located in the southern area of Bolzano, discussing its indoor visual comfort conditions, energy consumption for artificial lighting and daylight exploitation. Specifically, three South-West oriented physiotherapy cabins with large glazed façades were analyzed, using both measurements, in-situ subjective surveys, and simulations. First, illuminance measurements and visual comfort questionnaire responses were analyzed to detect possible issues related to the lighting system and the visual environment in the therapy cabins. Daysim models were then developed, compared with empirical data and deployed to assess advantages and drawbacks of the internal double layer roller shades. Finally, an alternative external venetian blinds system was proposed and studied.
Assessing Solar Radiation in the Urban Area of Bolzano, Italy, by Means of SEBE Simulations
Gianluca Pappaccogli, Giovanni Pernigotto, Alessandro Prada, Andrea Gasparella
Downward shortwave incoming irradiance plays a key role in urban areas, especially in those located in complex terrains. Accurate modelling of this weather variable is crucial for the characterization of physical processes, and in particular heat exchanges, occurring between buildings and the urban atmosphere. In this framework, the present research evaluated the capabilities of the Solar Energy on Building Envelopes (SEBE) model, which can be used to describe the urban geometry through 2D high-resolution DSMs and simulate total irradiation on buildings’ façades. Specifically, this work focused on the urban area of Bolzano, a city located in the north-eastern Italian Alps in a basin where three valleys join, and assessed the SEBE output by comparison with the total daily irradiation on a vertical building façade for a six-month period (i.e. July-December 2018). Meteorological forcing for simulations was provided by the observed hourly data of shortwave radiation (i.e. global GHI and diffuse DHI horizontal, and direct normal DNI irradiance), collected at rooftop level in the urban area of Bolzano. The overall performance of the model was found to be accurate, both for different analysed periods and for daily climatic classification.
Numerical and Experimental Study on the Impact of Humidity on the Thermal Behavior of Insulated Timber Walls
Maja Danovska, Michele Libralato, Giovanni Pernigotto, Alessandra De Angelis, Onorio Saro, Paolo Baggio, Andrea Gasparella
The push towards a lower environmental impact of the building sector has led to the widespread adoption of renewable organic materials such as wood and other biobased insulation materials. These materials are characterised by a solid matrix with voids that can be filled with moist air and water and in which complex heat and mass transfer occurs, influencing the global thermal properties. Indeed, due to different heat transfer mechanisms involved, the apparent thermal conductivity varies both with temperature and moisture content because of water thermal conductivity is higher than air. However, many Building Simulation programs (e.g., EnergyPlus and TRNSYS) still adopt constant thermal properties for simulating the heat transfer in buildings, causing inaccuracies in calculations of heat flux and thus, in the prediction of the energy consumption of a building. The aim of this work is therefore to analyse experimentally and numerically the impact of both moisture and temperature on the thermal behaviour of an insulated timber wall. An experimental activity was conducted at the Building Physics Laboratory at the Free University of Bozen-Bolzano on Cross-lam (XLAM) and wooden insulation specimens to measure thermal conductivity at different temperatures and moisture contents by means of a heat flux meter (i.e., HFM) and a climatic chamber. A 1D model for coupled heat and mass transfer across the studied wall was then developed and calibrated against the experimental data. Finally, by simulating with both nominal (10 °C and 23 °C reference temperature) and actual thermal conductivity, hourly heat fluxes and energies were compared, taking into consideration climatic files relating to the Italian peninsula.
Sensitivity Analysis of SEBE Model Using Different Meteorological Input: A Case Study in Bolzano, Italy
Gianluca Pappaccogli, Giovanni Pernigotto, Alessandro Prada, Andrea Gasparella
In the present study, a sensitivity analysis was carried out in order to evaluate the performance of the Solar Energy on Building Envelopes (SEBE) model to different meteorological input data. The model was applied on a sixmonths period from July to December 2018. Geostationary satellite data provided by Meteosat MSG was first validated against measurements from permanent weather stations located both in the urban area of Bolzano and in the surrounding countryside. Subsequently, several SEBE simulations were performed in order to compare the outcomes obtained from satellite data against simulations fed by meteo-radiometric measurements. The validation of satellite data shows that global shortwave irradiance data provided by the Meteosat are representative of the solar radiation fluxes, even in a complex terrain. SEBE simulations fed by different meteorological input performed well at different comparison locations although showing slightly broad errors using satellite data as input.
Numerical and Experimental Characterization of the Thermal Behavior of Complex Fenestrations Systems Under Dynamic Conditions
Ingrid Demanega, Giuseppe De Michele, Martin Hauer, Stefano Avesani, Giovanni Pernigotto, Andrea Gasparella
Complex Fenestration Systems (CFS) with different types of shading devices are widely used to enhance the building envelope’s energy efficiency and the occupants’ visual and thermal comfort. These technologies are characterized, among other features, by advanced shading systems, with for example complex geometries and highly reflective surfaces, which introduce a performance dependence on the angle of incidence of solar radiation. This peculiarity has to be covered by adequate thermal and optical models. However, the current most widespread thermal models, based on the standard ISO 15099 and implemented in the main building energy simulation tools, have shown some restrictions in their applicability for CFS. In addition to this, professionals of the façade construction industry are interested in assessing the components’ critical temperatures and the performance of the fenestration system under real dynamic operating conditions and in representative extreme conditions. In this framework, this study has investigated a new modelling approach for the thermal characterization of CFS under dynamic conditions by comparing simulation results with in-situ measurements of a triple-glazed window with integrated commercial blinds installed at the Free University of Bozen-Bolzano, Italy. The numerical assessment of the thermal behaviour of CFS was based on CFD simulations with the separately computed effect of solar radiation. The experimental characterization was performed with several instruments, such as conventional heat flux plates and a temperature- controlled in-situ measurement device to determine the undisturbed, transient heat flux through transparent components. From the comparison, a good correspondence between numerical and experimental results emerged and both approaches appraised the inertial effect of the fenestration system on the solar heat gain. Finally, it was observed that accurate optical modelling, together with CFD simulation, made it possible to compute the solar absorption and its significant impact on the fluid flow in the cavity, the components’ temperatures and the solar gains.
Modelling the Sound Insulation of Mass Timber Floors Using the Finite Transfer Matrix Method
Federica Morandi, Marco Caniato, Olivier Robin, Luca Barbaresi, Andrea Gasparella, Patrice Masson, Noureddine Atalla
Cross Laminated Timber (CLT) technology has revolutionized the use of timber in construction in just 20 years. However, the development of mid- and high-rise CLT buildings has raised concerns about the sound insulation provided by these structural elements and about the reliability of simulation tools and models which are currently used. The mechanical characteristics of mass timber elements do not allow simplifications such as infinite out-of-plane stiffness, diffuseness of the vibrational field and perfectly elastic behavior upon impact, to mention a few, which are commonly assumed for traditional structures. The availability of modelling/ simulation tools (and the relative input data) that provide accurate predictions of airborne and structureborne sound insulation is therefore a current and relevant topic. This work presents an investigation into the input parameters to use for modelling CLT elements using the Finite Transfer Matrix Method (FTMM). The results of laboratory measurements on two CLT floors are compared to results obtained using two FTMM-based software packages in a three-step procedure. First, measurements were performed on two timber floor solutions. Following this, two operators working with different FTMM-based software packages performed blind simulations, based upon the information shared on the materials’ characteristics. Finally, the input data were modified in order to return the best fit to the experimental data. The aim of the work is twofold: (1) to verify the degree of accuracy of the software and (2) following a reverse-engineering process, to retrieve the properties of the materials that need to be modelled through equivalent physical dimensions. The results for the bare CLT floor show that using dynamic E value for the plate modelling returns slightly more accurate results. Conversely, the question of modelling of a complete floor, including a floating floor, deserves greater attention, as modelling the resilient underlay using static values of dynamic stiffness can alter the results to a great extent.
Safety at Chimney-Roof Penetration: A Numerical Investigation
Manuela Neri, Leppänen Perttu, Mika Alanen, Davide Luscietti, Mariagrazia Pilotelli
Chimneys convey exhaust gas produced in heat generators to the external ambient. To do this, they cross building elements such as floors and roofs, which can be made of flammable materials such as wood, wood fiber, cellulose, etc. This represents a dangerous condition that can lead to the overheating of the structure and, consequently, to possible fires. In recent years, numerous roof fires have occurred in Europe due to the presence of a chimney, and some of these have also involved certified chimneys. The aim of the certification procedure is the determination of the distance between chimney and flammable structures to avoid fires. This paper describes an investigation performed to understand the causes of the high number of fires and to propose solutions to the roof fires problem. The study was carried out numerically and experimentally, and consisted of three steps. Firstly, the chimney certification procedure was investigated to highlight possible weaknesses. Then, by means of a 2D and a 3D numerical models, the variables affecting heat transfer at chimney– roof penetration were identified. Finally, solutions and prescriptions to prevent roof fires are proposed. The solutions consist of a set of tables for checking chimney installations, and a universal device to be installed between chimney and roof to prevent the overheating of the latter, also in very critical conditions represented by soot fires, and installations in very thick and insulating roofs.
Building Energy Models with Morphological Urban-Scale Parameters: A Case Study in Turin
With a growing awareness around the importance of the optimization of building efficiency, being able to make accurate predictions of building energy demand is an invaluable asset for practitioners and designers. For this reason, it is important to continually improve existing models as well as introduce new methods that can help reduce the so-called energy performance gap, which separates predicted from actual consumption values. This is particularly true for urban scale simulations, where even small scenes can be very complex and carry the necessity of finding a reasonable balance between precision and computational efforts. The scope of this work is to present two different models that make use of morphological urban-scale parameters to improve their performances, taking into account the interactions between buildings and their surroundings. In order to do this, two neighbourhoods in the city of Turin (IT) were taken as case studies. The buildings studied present similar characteristics but are inserted in a different urban context. Several urban parameters were extracted using a GIS tool and used as input, alongside the building-scale features, for two different models: i) a bottom-up engineering approach that evaluates the energy balance of residential buildings and introduces some variables at block-ofbuildings scale, ii) a machine learning approach based on the bootstrap aggregating (bagging) algorithm, which takes the same parameters used by the previous model as inputs and makes an estimation of the hourly energy consumption of each building. The main results obtained confirm that the urban context strongly influences the energy performance of buildings located in high built-up areas, and that introducing simple morphological urbanscale parameters in the models to take these effects into account can improve their performance while having a very low impact on the computational efforts.
Use of the ISO 12354 Standard for the Prediction of the Sound Insulation of Timber Buildings: Application to Three Case Studies
Francesca Di Nocco, Federica Morandi, Luca Barbaresi, Antonino Di Bella
The ISO 12354 standards provide a method for modelling the sound insulation of building elements using the performance of the single elements as a starting point. The revision of the ISO 12354 Part 1 and 2 standard makes it possible to model timber buildings. In particular, the standards provide prediction formulas for estimating the vibration reduction index (Kij) of heavy and light weight junctions and CLT junctions. The aim of this research is to study the dependence of the ISO 12354 output values on the input data fed to the model, in the specific case of timber buildings. The prediction tools were applied to three different timber buildings on which sound insulation and flanking transmission measurements were carried out on site. Different input data were used: laboratory and in situ measured values of airborne sound insulation, impact sound insulation and flanking transmission. The calculated values are compared with in situ acoustic tests of airborne sound insulation and impact sound insulation. The results show that the blind application of the ISO 12354 model can provide results that differ significantly from the measured on-site values; considerations are drawn concerning the availability of input data and the resonant transmission.
Testing the BIM-Ladybug Tools Interoperability: A Daylighting Simulation Workflow
Laura Pompei, Giulia Spiridigliozzi, Livio De Santoli, Cristina Cornaro, Fabio Bisegna
While a considerable number of studies on Building Information Modelling (BIM) have been conducted in recent years, this area of research has long been considered important in the building sector, with particular concerns about Energy Design. In this regard, the work proposes an automated early design workflow to evaluate the building daylighting performance during the first design stages. Thanks to the potential use of interchange files and visual coding tools, such as Grasshopper, it is possible to implement the parametric design concepts, thus automating complex tasks. Specifically, in the analysed workflow, environmental algorithms and simulations are integrated to achieve reliable results with the minimum error percentage in data loss. The main finding concerns the BIM applications to perform daylighting design by the use of Ladybug tools from the Autodesk Revit export.
An Attempt to Rank Italian Historical Opera Houses Based on Numerical Simulation
Due to the complexity of the acoustic field in articulated closed spaces, architectural acoustics is often approached as a reverse-engineering problem: criteria, reference values and analysis methods are extrapolated by comparing results from measurements in a set of case studies. Considering the methods and the results of previous works on Italian historical theatres, the present study shows the results of geometrical acoustic (GA) numerical simulations with the aim to attempt a ranking based on the subjective preference theory. The models were calibrated using several room criteria that had been previously measured in the framework of a measurement campaign performed in Italian theatres. The cluster chosen is intended to represent an adequate sample of case studies relative to different capacities and different design approaches, which were first developed in the seventeenth century.
Energy and Exergy Analysis of a HVAC System Having a Ground Source Heat Pump as Generation System
This study reports on a dynamic simulation of the annual performance of a HVAC system consisting of a ground coupled heat pump (GCHP), which has which has a ground heat exchanger with horizontal pipes for winter and summer seasons. The simulations are performed by employing the software Trnsys. The HVAC system is connected to a thermal storage tank containing warm water in winter and cold water in summer, which serves a singlefamily dwelling located in the city of Rome, Italy. A firstand second-law analysis of the yearly performance of the entire system and of the single components was carried out, highlighting the components with the lowest exergy efficiency.
Double-Layer Gypsum Panels: Prediction of the Sound Reduction Index Using the Transfer Matrix Method
Gypsum board walls are widely used in buildings today. A possible way to considerably increase the sound insulation performances of such light-weight walls is to apply a double or triple layer of screwed boards separated from each other. The separation between the boards prevents the decrease of the critical frequency towards lower values, while retaining the improvement of the sound insulation performances provided by the double layer. In this paper the loss of acoustic insulation performances due to the thin air layer between the coupled boards is studied and a modelling technique based on the transfer matrix method is used to simulate the acoustic behaviour of the resulting structure. The simulations are compared with laboratory measurements carried out according to the ISO 10140 series standards, and the transfer matrix approach is found to be suitable to describe the problem, provided that a modified model for the air gap between the boards is used.
Static vs Dynamic Hygrothermal Simulation for Cellulose-Based Insulation in Existing Walls: A Case Study Comparison
Matteo Bilardo, Fabrizio Giorgio, Enrico Fabrizio, Francesco Prizzon
When dealing with energy-saving topics, it is increasingly common to focus on the efficiency of existing systems, rather than adopting new ones. In the specific case of the building envelope this practice is supported by the difficulty in completely replacing opaque components of the envelope, such as external walls or roofs. This work involves the renovation of a cavity wall, with the aim of improving its energy performance. A traditional cavity wall has been modified by blowing a bio-based insulating material obtained from cellulose flakes inside the air cavity gap. Although an operation of this type leads to a significant increase in thermal performance of the wall, it is not equally obvious that it is effective in terms of humidity and vapor condensation. The purpose of this work is to evaluate the effect of the blowing process on the hygrometric performance of the opaque component to ensure correct compliance with the performance parameters established by Italian legislation in terms of vapor transmission and condensation phenomena. In order to study the hygrometric behaviour, a numerical model of the construction was developed and simulated. The simulation involved two different regulatory approaches, which were compared: a first calculation was carried out in steady-state conditions, according to the UNI EN ISO 13788 standard (ISO, 2012). Afterwards, a dynamic simulation following the UNI EN 15026 standard was performed (CEN, 2007). The results obtained by both the methods were analysed and compared. The results demonstrate that by adopting the calculation procedure in steadystate conditions, the phenomenon of interstitial condensation occurs. A different result is obtained by applying the calculation method in dynamic regime, according to which the vapor would not condense inside the structure.
Design and Evaluation of Extreme Moisture Reference Years for Moisture-Related Risk Assessments
Michele Libralato, Giovanni Pernigotto, Alessandro Prada, Alessandra De Angelis, Onorio Saro, Andrea Gasparella
The risk analysis of moisture-related damages can potentially be carried out with the use of heat and moisture transfer simulations. These models require weather files as boundary conditions but, for most locations, the only weather files available are Typical Reference Years, for instance the TRYEN defined in accordance with EN ISO 15927-4:2005. These reference years do not provide the critical conditions that should be used in risk assessments. In this work, two procedures to define Extreme Moisture Reference Years (ERYm1 and ERYm2) are presented. ERYm1 and ERYm2 are designed to generate critical weather files to be used in simulations for the assessment of moisture related risks. The presented procedures are structure-independent and suitable for risk assessments that involve high air moisture content and low air temperature values. In order to assess the capabilities of ERYm, five types of walls with different materials are simulated, considering three Italian climates (those of Gemona del Friuli, of Legnaro and of Trento) and four wall orientations (North, East, South, West). The results of simulations with ERYm1 and ERYm2 as weather files showed higher wall moisture contents and interstitial moisture accumulation risks than those with TRYEN. This suggests that ERYm could be used as a valid alternative to the TRYEN in decision making frameworks and legislations that cannot include the ad hoc definition of a weather file for each structure, exposure and location.
Building Integrated Photovoltaic Thermal Collectors: Modelling and Experimental Investigation of Two Novel Cost-Effective Prototypes
Giovanni Barone, Annamaria Buonomano, Cesare Forzano, Adolfo Palombo
This paper presents a comprehensive analysis of three different building-integrated solar systems. Specifically, two building-integrated photovoltaic thermal collector prototypes (alternatively water and air cooled) are investigated along with a building-integrated photovoltaic panel; these prototypes were fabricated and experimentally tested at University of Patras (Greece). Note that the active performance of such devices has already been investigated in other works. This chapter presents the analysis of the passive effects on a building’s thermal behaviour caused by the integration of the devices. A suitable dynamic simulation tool, capable of assessing the whole device-building performance analysis, is outlined. A case study aimed at proving the potential of such code and showing the effects of the adoption of building integrated solar systems on a building’s thermal behaviour is presented. The case study considers a simple dwelling unit in a multi-storey residential building, located in different weather zones and subject to diverse boundary conditions. The investigated collectors on the south facades of the building are integrated, and the associated passive effects are analysed. The analysis provides interesting outcomes from the point of view of energy and comfort.
A Psycho-Acoustical Experiment Using a Stereo Dipole for Spatial Impression of Music Signals
Acoustic performance of concert halls and opera houses is usually assessed by measuring the BIRs (Binaural Impulse Responses). Anechoic music convoluted with BIRs constitutes the virtual sound in the way it is played in the sound field, i.e. the room. From BIRs, the IACC (Inter- Aural Cross Correlation) can be computed. This parameter makes it possible to evaluate the spaciousness of the hall. However, the calculation of the IACC value is affected by the convolution technique used as well as the kind of musical motif. For example, in the same concert hall, the BIR provides three different IACC values in the case of three different motifs played in it. This study has conducted a psycho-acoustic experiment by using a virtual sound field representation produced by the stereo dipole technique in a listening room. In the experimental set-up there were two or four loudspeakers, corresponding to the single stereo-dipole or the dual stereo-dipole, respectively. By cancelling the cross-talk pathways (i.e. from left loudspeaker to right ear), the parallel sound presentation creates a 3D sound field for listeners sitting in the target point. The invert Kirkeby method was adopted to determine the inverse filters. Finally, the auralization technique with measured BIRs in theatres was utilized and the virtual sound field was generated in the Arlecchino listening room (Bologna, Italy), a low reverberation room equipped with an Ambisonic system. In the virtual sound field, the BIR was recorded again by the same dummy head used during the measurement in the theatres. The similarity between real and virtual sound fields was evaluated by comparing some acoustic parameters. The stereo-dipole technique demonstrates a good degree of accuracy of the sound field appearance. Moreover, the accuracy of the sound field appearance was analysed using two musical motifs and three musical instruments, comparing the values of the IACC calculated by echoic music with the virtual echoic music.
On the Use of 3D Auralisation to Evaluate Room Acoustic Enhancement in Auditorium Restoration
The acoustic quality in auditorium and concert halls is normally evaluated by the measurements of Impulse responses (monaural, binaural or even MIMO). The subjective evaluation is often obtained by convolving anechoic music with the measured IRs. The psychoacoustical experiment is achieved using a virtual sound field representation. At the University of Bologna, the listening room Arlecchino includes Ambisonics and stereo dipole techniques for playback. In this paper, two different Italian opera houses and two Japanese concert halls were analysed. They were the Teatro Nuovo in Spoleto (Italy), the Teatro Alighieri in Ravenna (Italy), the Kirishima International Musical Hall in Kagoshima (Japan), and the Tsuyama Musical Cultural Hall in Okayama (Japan). The similarity between real and virtual sound fields, obtained with stereo dipole technique, was evaluated by comparing different acoustic parameters calculated by real and virtual sound fields, in the four halls in different designed configurations. Finally, the stereo dipole technique was added to the ambisonic methodology to reproduce the sound fields for the psycho-acoustical experiment. The dual stereo-dipole technique using two kinds of cross-talk cancelling filters can be one of the solutions for improving the acoustical quality of home theatre.
Acoustic Comfort for Spaces Used by People with Cognitive Impairment: A Starting Point for the Application of Acoustic Event Detection and Sound Source Recognition Systems
Federica Bettarello, Marco Caniato, Giuseppina Scavuzzo, Andrea Gasparella
The AED (Acoustic Event Detection) and SSR (Sound Source Recognition) systems are increasingly used in projects involving home automation, security, help for the visually impaired or for the elderly who want to pursue projects of independent living. The application of such technologies can also become a valid reference in the case of subjects suffering from cognitive, not just physical, deficits (Down syndrome, autism, etc.). In these cases remote assistance systems can represent a strong support both for the people who take care of them (parents, specialized personnel), and also for people with cognitive disabilities to pursue projects of independent living. Based on the study of the peculiarities that the internal spaces hosting activities for people with various cognitive deficits must have, criteria for acoustic comfort and internal design have been optimized for certain types of living, working and resting spaces. The aim of this work is to understand how the indoor sound field of dedicated rooms may affect boundary conditions for the installation of AED and SSR and how the specific interior design for special spaces may influence the speech intelligibility and clarity of these rooms.
Acoustics and Spatial Sound Distribution in the Theatre Comunale in Bologna, Italy
The acoustic quality of concert halls is extremely relevant for the modeling and simulation of the global music experience and for improving the acoustic design of music spaces. Furthermore, the acoustic characteristics of historical opera houses are considered to be one of the most important intangible elements of the cultural heritage of Italian history. An important Italian opera house is the theatre “Comunale” in Bologna (designed in the 18th Century by Galli Bibiena), and has a particular characteristic: the shape of the balconies and the materials with which they were constructed are different from those of a classical Italian opera house. This special feature of the balconies affects the listening conditions related to the position of sound sources on the stage and in the orchestra pit. This study investigates the acoustic properties of this important theatre in order to reproduce the sound properties by means of a 3D auralization. For describing the spatial sound characteristics of the hall, an experimental campaign was carried out. An omnidirectional, pre-equalized sound source was installed in the orchestra pit and on stage, and a dummy head was put in several listening positions on the balconies and in the stalls, accomplished with a B-format (soundfield) microphone. Moreover, the special features of the ACF (autocorrelation function) and the IACC (InterAural Cross Correlation) and other acoustic parameters were measured experimentally in order to reproduce them in the listening room “Arlecchino” at the laboratory of University of Bologna, by means of the Stereo Dipole and Ambisonics technique. The main results from the experiments are reported in this paper.
The Acoustic Simulation of Performing Area in the Auditorium: Some Examples in Italy
The design of auditoria and opera houses requires particular care for the stage area, where several different requirements should be achieved for the performers. Among these, the acoustic quality represents a fundamental aspect, and it differs from the listeners’ perspective. Moreover, the performing area in concert halls is often an important area for non-acoustic reasons, since lighting, thermal plants, etc. are often placed in this special zone, and should be properly designed in order to guarantee a high level of global comfort. This paper presents some examples of how to design exhibition zones in opera houses and auditoriums that show both acoustic and technical improvements, both in theory and in architecture.
Acoustic Refurbishment on a Temporary Auditorium: BIM Design and Interventions Influences
Marco Caniato, Federica Bettarello, Matteo Bellè, Andrea Gasparella
Building Information Modelling (BIM) is playing an increasingly greater role in the world of construction. BIM should combine as many stakeholders as possible during the design workflow and make it possible to manage the created object before its realization, as well as follow it during its entire lifetime. Holding together such a large number of functions is not an easy task; managing each of them in the best possible way is even more complex, especially if, as is happening today, the sectors involved in the construction of a building are becoming increasingly specialized. In order to verify (i) what the limits are that a BIM software can reach, (ii) what the most common difficulties are and (iii) in which sectors they usually appear, it is necessary to study a real project carried out in its entirety with the BIM method. For this reason, a complex case study has been chosen which would be useful in formulating a response to the previous key points. The critical aspects linked to the possible choices that should be made between the various software have been highlighted as well as the pros and cons of the possible paths that can be followed. Finally, the future scenarios of integrated software development are identified and the way in which they may be adopted to address the difficulties and weaknesses that BIM still presents, is discussed.
Control Strategies to Increase the Photovoltaic Self-Consumption for Air-Source Heat Pump Systems
Decreasing the use of fossil fuels for heating and cooling applications in buildings is one of the main concerns in reaching the energy reduction targets defined by the European Union countries. For this purpose, high efficiency heating and cooling systems are required, together with appropriate control strategies. The use of heat pumps (HP) in residential buildings is spreading, and the combination of these systems with the on-site production of photovoltaic (PV) energy can lead to high levels of renewable energy self-consumption. However, a poor design and a lack of control in the system can lead to a large amount of PV energy surplus, which has to be sold to the grid, or wasted. For this purpose, the use of energy storage and demandside management strategies are crucial. This paper describes a control strategy for an air-source HP system combined with a PV plant for a residential building. The control strategy aims to maximize the self-consumption of PV power, varying the system behavior depending on the instantaneous PV production. When an overproduction of PV energy occurs, the HP operates to store the surplus of solar energy by exploiting the storage capacity and the building thermal capacitance. In this study, the heat pump was controlled by acting on the compressor rotational speed (i.e. the frequency of the supplied power). The compressor was controlled in order to operate at the maximum capacity level compatible with the power supplied by PV. The effectiveness of the control strategy was assessed over a whole year, considering both the heating and cooling season and domestic hot water (DHW) preparation. The simulations were performed using the TRNSYS simulation software, considering a double-story residential building in northern Italy. The results obtained with the proposed demand side management (DSM) strategy show a reduction of around 33% of the energy taken from the grid with respect to a similar system with a standard control strategy.
Sound Reduction Index of Clay Hollow Brick Walls
Nicola Granzotto, Edoardo A. Piana, Antonino Di Bella
This paper investigates the sound insulation properties of clay hollow brick walls with low void fraction, horizontal/ vertical mortar joint and plaster finishing. Methods based on homogeneous walls (Sharp theory and ISO 12354 procedure) are evaluated. A reference curve obtained as the mean of normalised sound reduction index curves measured in laboratory on real brick walls is proposed and its suitability for sound insulation estimations is discussed.
Prediction of the Acoustic and Thermal Performance of a Multilayer Partition
Manuela Neri, Mariagrazia Pilotelli, Edoardo A. Piana, Adriano M. Lezzi
Multilayer partitions are often designed so that, because of their peculiar composition or structure, they exhibit characteristics that are not normally found in single layer panels. “Multifunctional” partitions are engineered to optimize different features at the same time. In this paper the authors try to deal with the problem of optimizing thermal and acoustic behavior by designing a thermo-acoustic insulation structure. From the thermal point of view, the material should combine good insulation properties, given by low thermal conductivity, and high delay of the thermal wave due to external conditions, given by low thermal diffusivity. From the acoustic point of view, the material should have good absorption characteristics, whenever possible, and primarily high transmission loss in order to respect the relevant law prescriptions. In this way the composite panel, used as a façade element, can improve the comfort conditions in buildings and reduce energy consumption for winter heating and summer cooling. The coupled thermo-acoustic element is made of different wooden and recycled material layers, chosen for their specific properties and sustainable characteristics. Thermal properties were estimated by means of a self-developed code based on the ISO 13786 standard. The acoustic properties of the individual layers, according to the ASTM E2611-09 standard procedure, were measured in a fourmicrophone impedance tube, and the transfer matrix method was used to estimate the overall acoustic behavior of the material. Particular attention was paid to the layer sequence, because of great importance for both thermal and acoustic performances. The preliminary combined study showed encouraging results.
Implementing the Sustainable Energy (and Climate) Action Plans: Quasi-Steady State or Dynamic Modeling Approach
Actions contemplated in Sustainable Energy (and Climate) Action Plans (SEAPs), which municipalities adhering to the EU initiative called “The Covenant of Mayors” are required to prepare, regard many sectors, among which are buildings. To implement such plans, it is necessary to make use of methods for predicting energy use in buildings. Technicians involved in this tend to adopt easy-touse simulation models because of the common mid-level expertise of the offices involved. However, such simplified methods could result in a less accurate evaluation of the energy demand of buildings. In this paper the suitability of the quasi-steady state and the dynamic approach, in the frame of these new urban energy planning tools, is assessed. Specifically, a comparison between the two methods reported in the EN ISO 52016-1 Standard (namely the quasi-steady state monthly method and the dynamic hourly method), used here as representative of the two cited classes of models, is drawn. Despite some limitations of the quasi-steady state model found in the analysis, the possibility to still use both modelling approaches to implement SEAPs is argued in the paper. Moreover, a tentative procedural scheme is proposed, which technicians working on SEAPs can usefully follow in order to choose the most appropriate modelling approach that can be used depending on the specific situation to address.
Comparison Between the EN ISO 52016-1 Hourly Calculation Method and a Fully Detailed Dynamic Simulation
Giovanna De Luca, Mamak P.Tootkaboni, Ilaria Ballarini, Vincenzo Corrado
The present research proposes a preliminary investigation of the new hourly method for the assessment of building energy needs for heating and cooling introduced by the EN ISO 52016-1 standard. It was applied to a case study and compared with a fully detailed dynamic model (EnergyPlus). The comparison was performed considering two building operation modes: in a free-floating condition, the hourly differences between the indoor operative temperatures were analysed considering the different contributions to the heat balance; in an ideal heating and cooling system operation, the heating and cooling energy needs were compared on a monthly basis. The discrepancies between the calculation methods, both in the indoor operative temperature and in the thermal energy needs, were investigated and the causes of the deviations were identified.
On the Thermophysical Performance Optimization of Italian Schools of the 60s: A Case Study in Ostia (RM)
Francesco Asdrubali, Luca Evangelisti, Lucia Fontana, Claudia Guattari, Ilaria Montella, Pietro Prestininzi, Ginevra Salerno, Chiara Tonelli, Valeria Vitale
In recent years, energy efficiency and energy saving issues have dominated the field of buildings research. Since new constructions are characterized by an efficient design, the real challenge is to define accurate and effective retrofit interventions for existing buildings. In order to understand the energy behavior of buildings and identify the best viable retrofit solutions, accurate analyses, carried out by means of dynamic simulations and in-situ measurement campaigns, are needed. Furthermore, in Italy compliance of the effects of the proposed interventions with standards is necessary. In this paper, a school built in the 1960s was considered as a case study and its energy performance was investigated. An in-situ measurement campaign was conducted with a thermal imaging camera, a heat flow meter and air temperature probes. Following this, a dynamic model of the school was implemented by means of TRNSYS dynamic code and different retrofit scenarios were evaluated and compared. The aim of this analysis was to quantify the effectiveness of the chosen refurbishment strategies on the energy demands of the investigated school.
On the Parasitic Heat Transfer Between Dwellings in the Case of Individual Heating: First Results by Simulation Across the EU
In residential applications with individual thermostat controls, a major problem arises as a consequence of heat transfer between conterminous dwellings when at least one is unconditioned or under-conditioned. Any absence of people, or under-heating by any tenant, can significantly falsify the accounting of heat flows, particularly in the case of highly performing building envelopes. In this paper, the effects of this kind of “parasitic” heat transfer across the apartments of a residential building is simulated, using, as a preliminary approach, a simplified proprietary calculation code, which considers different setpoints of thermostats assumed by different tenants, and internal gains as occupancy-related. Results show that there is a real need for thermal insulation of interior partitions and, especially for existing buildings, diseconomies as much high as the climate is mild. These results reveal the intrinsic heat accounting iniquity as a result of parasitic heat transfer through conterminous dwellings.
Analysis of the Surroundings Impact on the Building Energy Performance by Means of a BIM Analytical Model Coupled with Dynamic Simulation
Alessia Maiolatesi, Alessandro Prada, Fabio Luce, Giovanna Massari, Paolo Baggio
Building design often does not result in an actual limitation of energy consumption during the building occupation phase since a performance gap emerges. This gap is often related to occupant behaviour, but other factors, such as uncertainties and errors occurring during the design, construction and management phases, may also have an impact. Because of this, the correct evaluation of the interactions between the building and the context is an important consideration, but is often not correctly incorporated into energy analyses. The correct modelling of neighbouring buildings can be an expensive activity due to the difficulty in gathering data. The research reported here describes a methodology to develop a simulation model of an existing building and its surroundings by using a drone survey. With reference to a point cloud created from a drone survey, a geometric description of an existing building is developed in the BIM environment (Building Information Modelling). Following this, the BIM model is converted into a dynamic simulation model and the impact of neglecting the building’s surroundings is quantified. The aim of this complete and complex approach is to propose a working methodology and a process that integrates geometricarchitectural and energy disciplines. The results suggest that it is possible to develop an innovative operating methodology for intervention in existing built heritage.
Calibration of a UMI Simulation Model for a Neighborhood in Bolzano, Italy
Federico Battini, Giovanni Pernigotto, Andrea Gasparella
In recent decades, public authorities have focused their attention on the building sector, since it is responsible for a large share of the total energy consumption and, thus, should be involved in the development of sustainable energy policies. In this context, Urban Building Energy Models UBEM can play a significant role as they make it possible to study the behaviour of whole cities, as well as the potential of different building retrofitting strategies. In this contribution, the UBEM tool umi is used to study a neighbourhood in Bolzano, Italy, to contrast its capabilities and test the potential of a k-fold approach as preliminary calibration of the model, based on energy certificates and annual energy consumption data.