Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

Please note that all times are shown in the time zone of the conference. The current conference time is: 5th July 2022, 15:44:35 CEST

Session Overview
Session W3.2: Ensuring high quality building simulations
Wednesday, 01/Sept/2021:
14:40 - 16:10

Session Chair: Steffen Petersen, Aarhus University
Session Chair: Kristof Vlieghe, Viessmann
Location: Concert Hall - Artiestenfoyer
't Zand 34, Bruges

External Resource: Click here to join the livestream. Only registered participants have received the access code for the livestream.
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14:40 - 14:58

Characterised sun path patches as a way to design better shading

Andrew Corney1, Vladimir Bajic2

1Trimble SketchUp, United Kingdom; 2Trimble SketchUp, USA

Aim and Approach

(max 200 words)

Interviews and surveys identified that a large proportion of architects use shadow analysis as the primary (and often only) way of designing shading systems.

The aim of this project was to find ways to enhance this natural workflow by providing low friction ways to get a better understanding about sun quality. The aim is to improve shading outcomes by providing better information in established workflows.

The concepts were developed and studied as part of a beta program with 190 participants, mostly archtiects. The beta program started with a range of surveys and interviews asking participants about if and how they design shading systems.

A beta application with the proposed workflow was then developed, firstly as a web-app, and then as a SketchUp extension.

Scientific Innovation and Relevance

(max 200 words)

Understanding sun path diagrams and shadows are incredibly important and included in most architectural design courses.

However in most climates the time of day and time of year, the cloudiness of the sky, intensity of the sun and outside temperature as well as the nature of the building affect whether or not shading is really useful or not. Annual simulations with analysis tools are outside the capabilities of most architects and even where they are available, the use is sporadic because it does not fit neatly in the architect's design workflow.

A key reason identified in our research (over years) is that any friction in the architectural design process drastically reduces the effectiveness of building simulation. The work here sought to provide a defensible and useful improvement to the information used, while minimising the level of friction added to the design process and we feel this is very relevant.

Preliminary Results and Conclusions

(max 200 words)

So far in the beta program research has shown that a very large proportion of participants (mostly architects, all SketchUp users) use the shadow functionality in SketchUp to design shading systems without using any other hourly simulation input.

Although many participants reported not remembering how to use sun path diagrams, most were able to pass straightforward tests on what the information presented is. This meant that the division of the sun path into 3 types of characterised "patches" (overheating, warming or passive) could also be interpreted and applied to inform design.

We used reverse shadow projections for shading strategies onto sun path diagrams to create visual explanations as to the effectiveness of different shading approaches. These could be generated quickly and easily while using SketchUp and provided a way to dynamically see how important and effective shading devices are, without the need to take the model into dedicated simulation.

We hope results from prototypes being made available for design use will also be presentable at the conference.

Main References

(max 200 words)

Interviews and Discussions with architects and specialists participating in our beta program from the United States and Europe.

Sun, Wind and Light: Architectural Design Strategies, M, DeKay, GZ Brown

14:58 - 15:16

Modelling solar shadings with metallic slats for optimal daylighting. What parameters should we focus on?

Bertrand Deroisy1, Marshal Maskarenj2, Sergio Altomonte2

1Belgian Building Research Institute, Brussels, Belgium; 2Université Catholique de Louvain, Louvain-la-Neuve, Belgium

Aim and Approach

(max 200 words)

Designing high performance buildings requires a proper consideration of solar exposures and indoor climate conditions. In the current context of the climate change it must be possible to guarantee adequate thermal and visual comfort even with future climate conditions. Overheating is obviously an increasing risk factor for the occupants, especially in urban settings due to heat island effect. Meanwhile daylight, other than providing suitable conditions for vision, affects our physiological and psychological health. Solar shading systems with tilting metallic slats are commonly used to control daylight provision and energy transfer to the interior space. However, a precise characterization of their performance has to include many parameters, which are not always available. Very often, component level metrics are used to compare solutions, but these are neither consistently related to a specific context nor they are reliable for more complex building envelope assemblies. This study identifies the factors that most relevantly impact on the robustness of performance outcomes of daylighting simulations. It focuses specifically on the scattering properties of metallic surfaces and the shape of the slat profile on simulation results.

Scientific Innovation and Relevance

(max 200 words)

The main solar shading systems used in Europe include roller blinds and venetian blinds, consisting of stacked and guided metallic slats. Standardized methods for characterizing solar-optical properties of regular transparent materials are well established, but robust methods do not exist yet for light scattering, shading and daylighting systems, such as venetian blinds, which have specific angle-dependent properties. Simulations of daylight provision and thermal radiative transfer through complex building envelopes needs to integrate the spatial distribution aspects from the materials and surfaces finishes used in the models. A comparison of standard methods, up-to date building level simulation techniques and advanced optical simulation tools was done in this study. Exact geometrical models of the slats and the possibility to integrate measured BSDF data to describe the scattering properties of the slat surface were used in advanced optical simulations techniques. A detailed analysis of the sensitivity of a set of input parameters (sky model, optical properties, slat design, glazing type) on the global performance of the solar shading systems was done. The results of this study allow to identify the simulation and modelling parameters that should be primarily considered when evaluating the daylighting performance of a building envelope with solar shading systems.

Preliminary Results and Conclusions

(max 200 words)

Out of the four simulation parameters considered, the factor that has the largest effect on the consistency of simulation outcomes is represented by the tilt angle of the slats. An adequate and accurate setting of the tilt angle, based on solar altitudes and internal requirements, is essential to guarantee comfortable conditions for the building occupants at any time. The light scattering properties of the slat surfaces have a non-negligeable impact on daylight provision. Real slats are often relatively specular. Modelling them as diffuse surfaces generally underestimate transmittance ratios when the system is in a relatively open position. The shape of the slats can also have a significant influence when special profiles are used. However the difference between a flat slat and a typical curved slat is not detectable with advanced optical simulation techniques. The current building simulation applications do not allow to accurately estimate the impact of special slat profile shapes on daylighting performance. Large differences were observed between the two simulation based methods for medium sun angles. In general, more precise models are required whenever relatively specular surfaces, or special slat profiles, are used in shading systems.

Main References

(max 200 words)

Capperucci, Loonen R., Hensen J.L.M, Rosemann A.L.P. (2018). Angle-dependent optical properties of advanced fenestration systems - Finding a right balance between model complexity and prediction error. Building simulation 12, 113–127.

Inanici M., Hashemloo A. (2017). An investigation of the daylighting simulation techniques and sky modeling practices for occupant centric evaluations. Building and Environment 113, 220-231.

Konis T., Lee E.S. (2015). Measured daylighting potential of a static optical louver system underreal sun and sky conditions. Building and Environment 92, 347-359.

Kuhn T., (2017). State of the art of advanced solar control devices for buildings. Solar Energy 154, 112-133.

Nilsson A., Jonsson J. (2010). Light-scattering properties of a Venetian blind slat used for daylighting applications. Solar Energy 84, 2103-2111.

Tzempelikos A., Chan Y-C. (2016) Estimating detailed optical properties of window shades from basic available data and modeling implications on daylighting and visual comfort, Energy and Buildings 126, 396-407.

Uribe D., Vera S., Bustamante W., McNeil A., Flamant G. (2019). Impact of different control strategies of perforated curved louvers on the visual comfort and energy consumption of office buildings in different climates, Solar Energy 2019, 495-510.

15:16 - 15:34

A spectral model for longwave radiant heat transfer: influence of new generation polymers in BES

Edouard Walther, Antoine Hubert

AREP L'hypercube, France

Aim and Approach

(max 200 words)

In Building Energy Simulation (BES), the modeling of radiation relies on a dual-band model: longwave, infra-red radiant heat transfer is linearised and computed separately from shortwave, solar radiation. This robust technique originates from the optical properties of glass, the latter being opaque to longwave radiation.

In the recent year, the use of polymer materials such as ETFE or LDPE has become popular in stations, greenhouses or leisure halls (Giuliano et al. 2010). In comparison with glass, they exhibit attractive features such as a reduced weight or higher visible transmittance.

The dual-band model is consistent for standard glass but appears to be unadapted to the aforementioned materials. Indeed, they are partially transparent to longwave radiation, with transmissivities ranging from 20 to 80% depending on the wavelength, which particularly affects the “greenhouse effect”.

The present work aims at creating a spectral model for radiation transfer in multiple bandwidths and evaluating the influence of the new generation polymer materials on the greenhouse effect. Determining the ability of classical BES models for the simulation of radiant heat transfer through polymers depending on their cutoff wavelength in the infra-red domain is also an objective of this work.

Scientific Innovation and Relevance

(max 200 words)

A few references mention applications using ETFE (Cremers & Marx 2016), (Hu et al. 2016), (Cremers & Marx 2017), however, to the best of the authors’ knowledge, the effect of longwave transmissivity on indoor/outdoor radiation seems to be ignored. In the consulted literature, only (Poirazis et al. 2009) point out the lack of information about transmissivity in the longwave domain for polymers like ETFE and highlight the need for an extensive radiative model with experimental validation.

It hence appears interesting to explore the actual influence of such optical properties on heat transfer within buildings, which a spectral model reliably takes into account. Indeed, depending on the value of transmissivity in the infra-red range, this phenomenon may possibly be negligible as suggested in (Poirazis et al. 2009).

Preliminary Results and Conclusions

(max 200 words)

A single-room, “shoebox” house serves as a test case. The window transmittance model follows (Curcija et al. 2018) and the wall model is built after a 4R3C scheme (Fraisse et al. 2002). In order to confirm the accuracy of the building model, a cross-validation is led using the EnergyPlus software with mere glass on transparent the southern walls. The results obtained show that the spectral model compares well with the dual-band model of EnergyPlus.

Preliminary results have demonstrated that ETFE does not filter the infrared radiations as efficiently as glass does, which is beneficial for longwave radiant cooling, however, given the higher transmittance in the solar spectrum, the temperature in buildings with ETFE may exceed the glazed building's temperature.

A comparison of the ETFE with LDPE, which transmissivity is even higher in the longwave range is currently explored. The differences obtained are in favour of a spectral model for BES of buildings with longwave transparent polymers.

Main References

(max 200 words)

Vox, Giuliano & Teitel, M. & Pardossi, Alberto & Minuto, A. & Tinivella, F. & Schettini, Evelia. (2010). Sustainable greenhouse systems. Sustainable Agriculture: Technology, Planning and Management. 1-80.

Poirazis, H., Kragh, M., & Hogg, C. (2009, July). Energy modelling of ETFE membranes in building applications. In 11th International IBPSA Conference, Glasgow, Scotland (Vol. 144).

Curcija, C., Vidanovic, S., Hart, R., Jonsson, J., & Mitchell, R. (2018). WINDOW Technical Documentation. Lawrence Berkeley National Laboratory.

Cremers, J., & Marx, H. (2016). Comparative study of a new IR-absorbing film to improve solar shading and thermal comfort for ETFE structures. Procedia Engineering

Cremers J, Marx H. A new printed and spatially transformed ETFE foil provides shading and improves natural light and thermal comfort for membrane structures'. PLEA 2017.

Poirazis H, Kragh M, Hogg C. Energy modelling of ETFE membranes in building applications. In11th International IBPSA Conference, Glasgow, Scotland 2009

Hu J, Chen W, Qiu Z, Zhao B, Zhou J, Qu Y. Thermal performances of ETFE cushion roof integrated amorphous silicon photovoltaic. Energy Conversion and Management. 2015

Fraisse G, Viardot C, Lafabrie O, Achard G. Development of a simplified and accurate building model based on electrical analogy. Energy and buildings. 2002

15:34 - 15:52

Modelling naturally ventilated double skin facade in Modelica

Alessandro Dama1, Jaime Varas del Ser1, Ettore Zanetti1, Francesco Casella1, Olena Kalyanova Larsen2

1Politecnico di Milano, Italy; 2Aalborg University, Denmark

Aim and Approach

(max 200 words)

In recent decades, Double Skin Facades (DSF) and their thermal performance have been subject of numerous studies in literature. Despite this, the availability of rapid, robust and accurate tools for evaluating the performance of naturally ventilated double skin facades is still very limited, since only few published models have been accompanied by a complete experimental validation under variable boundary conditions, i.e. temperatures, solar irradiance and wind. Furthermore, the integration and/or coupling of such models within building energy simulation tools remains a complex task due to the multiple functionalities of the transparent and ventilated façade interacting with the building environment.

To this purpose this paper presents the implementation and validation of a model for naturally ventilated DSF in Modelica. The aim is to provide an open and robust tool easily integrable in the recent development of Modelica building libraries. Modelica, in fact, is an object oriented and open source programming language that has gained attention in the last decade, thanks to its ability to standardize and simplify modelling and thanks to its high potential when working with multi-domain systems.

Scientific Innovation and Relevance

(max 200 words)

An ongoing international cooperation, under IBPSA Project 1, aim at creating a freely accessible, editable, documented and validated Modelica simulation library to support the design and operation of buildings and districts [1]. This work would contribute to the building library developments.

Validations of the selected model for naturally ventilated DSF was already presented in [2] and [3]. The further advantage of its implementation in Modelica is, thanks to its modularity, the possibility to perform again the model validation under different choices of the boundary conditions, isolating different model domains. Moreover, in this study the validation was extended to the simulation of a building module with the south facing DSF, giving a proof o the integration of the DSF model with the zone thermal model in Modelica. The experimental database used was provided by a field study on a full scale DSF "The Cube" carried out in Aalborg, Denmark [4].

Finally, a sensitivity analysis was performed on the convection in the ventilated channel, on the glazing solar absorptions and on the thermal capacities. It gave insight on the most relevant choices for the model parameters.

Preliminary Results and Conclusions

(max 200 words)

Preliminary results of the DSF model implementation in Modelica had confirmed its capability to predict the variability of the mass flow rate, mainly due to the variable wind conditions, and improved its accuracy in predicting the outlet temperature and the inward heat flux. Such improvements are likely due to a better coupling in Modelica of the thermal and fluid-dynamic problems. The sensitivity analysis shows the importance of an accurate and detailed optical characterization of the window system and the role of the correlation adopted for the convection inside the ventilated channel. Otherwise, thermal capacity of glazing does not influence significantly the prediction even using a simulation timestep of fifteen minutes.

Main References

(max 200 words)


[2] A. Dama, D. Angeli, O. K. Larsen, Naturally ventilated double-skin facade in modeling and experiments, Energy and Buildings 144 (2017) 17–29

[3] A. Dama, M. Dopudi, O. K. Larsen, Experimental Validation of a Model for Naturally Ventilated Double-Skin Facades in proceedings of 7th International Building Physic Conference, IBPC 2018, Syracuse, NY, USA

[4] O. Kalyanova, Empirical Validation of Building Simulation Software: Modelling of Double Facades Final Report Technical Report IEA ECBCS Annex43/SHC Task 34 Validation of Building Energy Simulation Tools Subtask E

15:52 - 16:10

Open-source photovoltaic model for early building planning processes: Modeling, application and validation

Laura Maier1, Michael Kratz1,2, Christian Vering1, Philipp Mehrfeld1, Dirk Müller1

1RWTH Aachen University, E.ON Energy Research Center, Institute for Energy Efficient Buildings and Indoor Climate, Aachen, Germany; 2currently studying at ETH, Zurich, Switzerland

Aim and Approach

(max 200 words)

Within buildings, a great potential to reduce CO2 emissions exists. One common solution is to integrate renewable energy sources (RES) into BESs which are called interconnected systems. In this regard, PV systems are a promising technology as they enable sector coupling on the one hand and support local electricity generation on the other hand.

In order to exploit the full potential of PV systems, they have to be systematically integrated into the local control system. In this context, the proper sizing of PV modules plays an important role. This decision is made at an early planning stage. However, the optimum sizing of PV systems is challenging due to dynamic boundary conditions such as weather and its interdependencies with the whole BES, i.e. mounting’s influence. In this context, simulation models facilitate the process of estimating future operation of PV modules.

We contribute to a more simplified planning process by applying the following steps:

1. We develop an open-source Modelica PV model for wafer-based cells, which is based on manufacturer data only and is suitable for early stage design.

2. We validate the model with measured data to prove mounting’s influence.

Scientific Innovation and Relevance

(max 200 words)

None of the researched Modelica PV models cover all of the following aspects:

• Open-source access

• Parameters based on manufacturer data only

• Integration of the mounting´s influence

• Validation based on measurement data

In addition, we quantify the influence of ohmic losses on the DC power output.

Preliminary Results and Conclusions

(max 200 words)

In order to evaluate the model accuracy, we compare the simulated electrical energy of selected days with the measured one. The simulation mostly overestimates the electricity generation. This is caused by effects such as ageing, ohmic losses (OL) or staining, which are neglected within the model. Apart from that, the highest relative error is observed for the roof system at around 16 %.

To understand higher model errors for some days, we analyze the DC power output of the roof system in more detail. Here, we compare the simulated and the measured power on the day with the highest model error. The absolute difference between the data sets increases with raising power output. When also taking into account the OL, the model error is decreased to 7 %. Here, we estimate the OL using the simulated cell temperature and measured current.

For a simulative OLs estimation, the detailed interconnection of the implemented PV modules has to be known. This information is not necessarily given at an early planning stage and complicates the parameterization tremendously. As this contradicts the model’s aim to be simple and used at an early stage of planning, OLs are neglected.

Main References

(max 200 words)

Batzelis, E., Papathanassiou, S.. A Method for the Analytical Extraction of the Single-Diode PV Model Parameters (2016). IEEE Transactions on Sustainable Energy 7, 504-512.

Boyd, M. (2015). High-Speed Monitoring of Multiple Grid-Connected Photovoltaic Array Configurations.

Boyd, M. (2017). Performance Data from the NIST Photovoltaic Arrays and Weather Station. Journal of Research of the NIST 122.

Duffie, J.A., Beckman, W.A. (edited by). (2013). Solar engineering of thermal processes. Fourth edition. Wiley. Hoboken, NJ (USA).

King, D.L., Boyson, W.E., Kratochvill, J.A. (edited by). (2005). SANDIA REPORT SAND 2004-3535 Unlimited Release Printed December 2004 Photovoltaic Array Performance Model.” (2005).

Müller, D., Lauster, M., Constantin, A., Fuchs, M., Remmen, P. (2016) AIXLIB- An open-source Modelica library within the IEA-EBC Annex 60 Framework. Proceedings from BauSIM2016. Dresden (Germany), 14-16 September.

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