External coupling of building energy simulation and building element heat, air and moisture simulation

The present challenge for the building industry is to provide buildings that are safe, comfortable, energy efficient and sustainable; creating a healthy and productive environment for users. Computational building performance simulation (CBPS) can play an important role to deal with this challenge, particularly for performance indicators related to the heat, air and moisture (HAM) at the whole-building scale. These indicators are currently assessed by a large number of programs with considerable uncertainty in their results, such as building energy simulation (BES) programs and building element heat, air and moisture (BEHAM) programs. This thesis poses the hypothesis that the lack of integration between these programs represents an important source of uncertainty in whole-building HAM simulation, which can compromise, in some circumstances, the accuracy of their results. In order to test this hypothesis, this thesis proposes, implements, verifies and validates protocols to integrate BES and BEHAM programs using external coupling. These protocols, which are based on literature review and theoretical analysis of the governing equations, are implemented in prototype computer programs using numerical simulation and inter-process communication routines. The prototypes are verified by a number of techniques developed in this thesis, such as the use of emulators, one-way coupling and self-coupling. Validation is carried out using analytical solutions, inter-model comparison and experimental results reported in the literature. Coupled BES-BEHAM simulations showed improvements in the accuracy when compared to stand-alone BES or BEHAM simulations. In order to identify cases where coupled BES-BEHAM simulations provide significant improvement in the results, the coupling necessity decision procedure (CNDP) is formulated. Capabilities of coupled BES-BEHAM simulations in combination with the CNDP are demonstrated by case studies, where some capabilities and deficiencies of stand-alone programs are also evaluated. This research concludes that coupled BES-BEHAM simulation provides a viable and reliable way to perform whole-building HAM simulation. A number of additional results are also provided in this thesis, such as the solution for several coupling features addressed in the coupling protocols, the verification techniques developed and the use of TCP/IP sockets for the communication between the programs

Uncertainties due to the use of surface averaged wind pressure coefficients

A common practice, adopted by several building energy simulation (BES) tools, is the use of surface averaged wind pressure coefficients (Cp) instead of local Cp values with high resolution in space. The aim of this paper is to assess the uncertainty related to the use of surface averaged data, for the case of a cubic building with two openings. The focus is on wind-driven ventilation and infiltration, while buoyancy is not taken into account. The study is performed using published empirical data on pressure coefficients obtained from wind tunnel tests. The method developed to calculate the uncertainty is based on comparison of: the flow rate calculated using the averaged values (fAV), and the one calculated using local values (fLOC). The study considers a large number of combinations for the opening positions in the facade. For each pair of openings (i), the values of fLOC_i and fAV_i are calculated. Based on the ratio between fLOC_i and fAV_i the relative error (ri) is calculated. The relative error is presented statistically, providing probability density graphs and upper and lower bounds for the confidence interval (CI) of 95%. For this CI, the conclusion is that 0.24 fAV <fLOC <4.87 fAV

External coupling between BES and HAM programs for whole building simulation

This paper discusses a procedure for the two-way runtime external coupling between Building EnergySimulation (BES) and building envelope Heat, Air and Moisture (HAM) programs for enhanced wholebuilding simulation. The coupling procedure presented here involves a description of the relevant physical phenomena at the interface between the programs, domain overlaps, coupling variables, coupling strategy and types of boundary condition. The procedure is applied using the programs ESP-r and HAMFEM, where the implementation and verification issues are discussed. This work concludes that the coupling between BES and HAM programs is feasible, and it can potentially enhance the accuracy in whole-building simulation

Capability and deficiency of the simplified model for energy calculation of commercial buildings in the Brazilian regulation

This paper provides a preliminary assessment on the accuracy of the Brazilian regulation simplified model for commercial buildings. The first step was to compare its results with BESTEST. The study presents a straightforward approach to apply the BESTEST in other climates than the original one (Denver, Colorado, USA). The second step consisted on applying the simplified model for common buildings, and compare the results with those obtained using a state of the art building energy simulation (BES) program. Significant errors were found when comparing the simplified model with BESTEST and the common buildings analyzed

Performance simulation of climate adaptive building shells - Smart Energy Glass as a case study

As opposed to traditional building shells, climate adaptive building shells (CABS) do have the ability to change their properties and behavior over time. Provided they are designed and operated effectively, CABS offer the potential for energy savings without the need for compromising comfort levels. This paper explores the role that building performance simulation (BPS) can play in designing CABS. After analyzing the distinguishing characteristics of CABS, the need for BPS is introduced. The potential role of BPS is then illustrated via the case study of Smart Energy Glass. Based on a description of underlying physics, the model abstraction process is discussed first. This results in an integrated model for performance simulations that couples TRNSYS and DAYSIM. This model is empirically validated and subsequently used to evaluate the potential of Smart Energy Glass in a renovation case under various operational scenario’s. The paper concludes with some suggestions for future research and development of Smart Energy Glass

Towards the application of distributed simulation in HAM engineering

This paper presents ongoing research about an integrated approach to perform high resolution heat, air and moisture (HAM) simulation of whole buildings. There are several HAM modelling tools, with different space and time resolution. The integrated approach establishes run-time external coupling of existing tools (building envelope HAM, BES, CFD) and utilizes the capabilities of one tool in an attempt to compensate the deficiencies of the other. The paper presents the literature review of approaches for domain integration, the physical processes as dealt with by existing tools, coupling requirements and it addresses the importance of validation and coupling necessity decision procedures

Uncertainty in airflow rate calculations due to the use of surface-averaged pressure coefficients

Mean wind pressure coefficients (Cp) are key input parameters for air infiltration and ventilation studies. However, building energy simulation and stand-alone airflow network programs usually only provide and/or use a limited amount of Cp data, which are based on several assumptions. An important assumption consists of using surface-averaged Cp values instead of local Cp values with a high resolution in space. This paper provides information on the uncertainty in the calculated airflow rate due to the use of surface-averaged Cp data. The study is performed using published empirical data on pressure coefficients obtained from extensive wind tunnel experiments. The uncertainty is assessed based on the comparison of the airflow rate () calculated using the surface-averaged Cp values (AV) and the airflow rate calculated using local Cp values (LOC). The results indicate that the uncertainty with a confidence interval of 95% is high: 0.23 AV <LOC <5.07 AV. In cases with the largest surface-averaged ¿Cp, the underestimation or overestimation is smaller but not negligible: 0.52 AV <LOC <1.42 AV. These results provide boundaries for future improvements in Cp data quality, and new developments can be evaluated by comparison with the uncertainty of the current methods

Validação de simulações combinadas usando programas de simulação de energia do edifício e programas de transferência de calor, ar e umidade em componentes construtivos

Desempenho higrotérmico dos edifícios tem sido estudado usando uma variedade de programas de computador, os quais consideram determinados domínios geométricos (exterior, envelope e interior) e físicos (calor, ar e umidade). Estes programas podem ser classificados em três principais grupos: programas de simulação de energia do edifício (BES), transferência de calor, ar e umidade em componentes construtivos (BEHAM) e dinâmica de fluidos computacional (CFD). A falta de integração entre esses programas constitui uma importante fonte de incerteza em simulações do desempenho higrotérmico do edifício. Trabalhos recentes apresentaram mecanismos para a simulação combinada de programas BES e BEHAM. Na simulação combinada, os programas são executados em paralelo, trocando informações durante o curso da simulação, de forma a aprimorar a qualidade de ambas as simulações. O presente artigo apresenta a validação inicial de simulações combinadas usando BES e BEHAM, utilizando os programas ESP-r e HAMFEM. A validação é realizada através da comparação com soluções analíticas, comparação com resultados de outros modelos e com resultados experimentais. Simulações combinadas usando BES e BEHAM demonstram grande melhoria na qualidade dos resultados, em particular com relação ao cálculo da umidade relativa no interior do edifício.ABSTRACTHeat, air and moisture (HAM) performance of buildings has been studied in the past using a variety of computer models, which are focused on specific geometrical and physical domains. These programs can be classified in three main types: building energy simulation (BES), building element heat, air and moisture simulation (BEHAM) and computational fluid dynamics (CFD). The lack of integration between these programs constitutes a major source of uncertainty in whole-building HAM simulations. This paper presents the initial validation of a generic framework for two-way coupling of two of these program types: BES and BEHAM. The BES program ESP-r and the BEHAM program HAMFEM are used to demonstrate the implementation of this generic framework. Validation is carried out through comparison with analytical solutions, inter-model comparison and experimental results, where the BES-BEHAM coupled simulations demonstrate major improvements in the accuracy of results when compared to stand-alone simulations, particularly concerning the prediction of moisture content in the indoor air

Computersimulatie van geotabs-systemen

Geotabs is een recent afgerond Europees onderzoeksproject gericht op de verbetering van installatieontwerp en -regeling van kantoorgebouwen voorzien van geothermische warmtepompen en betonkernactivering. Het uiteindelijke doel is een betere energieprestatie en een eenvoudigere commissioning-procedure terwijl het thermisch comfort gewaarborgd blijft. Gebouwsimulatie was één van de onderzoeksmethoden. De belangrijkste conclusies worden in dit artikel beschreven

Prestatiesimulatie van adaptieve gevels - Smart Energy Glass als case-study

In tegenstelling tot traditionele gevels bieden adaptieve gevels de mogelijkheid om slim in te spelen op veranderende binnen- en buitenomstandigheden. Het succesvol ontwerpen van adaptieve gevels blijkt echter een complexe opgave waardoor toepassing van dit beloftevolle concept in de praktijk vooralsnog beperkt is. Dit artikel gaat in op de rol die gebouwsimulatie kan spelen in het ontwerpproces van adaptieve façades en illustreert dit aan de hand van Smart Energy Glass. De modelvorming en simulatiestrategie worden beschreven, waarna de prestaties van het concept zijn beoordeeld op basis van integrale simulaties voor verwarming, koeling, daglicht en elektriciteit. Het artikel concludeert dat adaptieve gevels kunnen bijdragen aan het bereiken van de steeds scherpere energiedoelstellingen zonder daarbij te hoeven tornen aan comfortbeleving. Gebouwsimulatie vormt een belangrijke schakel voor het bereiken van dit doel