Characteristics that matter in a climate façade: A sensitivity analysis with building energy simulation tools

Double skin façades (DSFs) are considered façade technologies that can reduce energy use and improve occupant comfort due to their advanced features. Their design requires reliable simulations due to their complex thermophysical behaviour, which are often carried out by practitioners using building energy software (BES) tools. Using an exhaust-air façade (also called climate façade) case study, the paper analyses the sensitivity of in-built DSF models in two popular BES tools (EnergyPlus and IDA ICE) for different orientations and climates. Small variations in input variables were considered to identify the parameters that the designer should pay most attention to during the design of the DSF according to different performance indicators. The results show that, regardless of the climate or orientation, the optical properties of the system (glazing and shading) were the most important in determining its performance, followed by the thermal properties of the glazing, while the geometrical, airflow and frame characteristics were less relevant. The model validation process also showed how differences in the in-built models (i.e. the use of a capacitance node for the glazed layers) lead to a difference in the reliability of the two BES tools. This is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Reliability and Performance Gap of Whole-Building Energy Software Tools in Modelling Double Skin Façades

The careful design of the façade is one of the most influential strategies to lower the energy use in a building. A double skin façade (DSF) is one type of façade that allows the interaction between the outdoor and the indoor environment to be managed in a more advanced way, by increasing the control over the energy transfer between the two environments, while providing high architectural flexibility and transparency. The design of the thermophysical performance of a DSF is a complicated process that has to take into account several aspects, such as geometric parameters, thermal properties, ventilation strategy, shading devices, and the integration between the façade and the building energy concept. There exist different whole building energy software tools (BEST) that practitioners can use to predict the energy and indoor environmental performance of a building and to support an informed choice to select the most appropriate building components during the design phase. However, when it comes to the simulation of DSF in BEST, complexity and inaccuracies in prediction usually rise, as these envelope systems are characterised by a thermophysical behaviour that requires a more advanced modelling than the possibilities conventionally embedded in BEST. This paper reviews the scientific literature to show evidence on how BEST are used to predict the thermophysical behaviour of DSF, together with reporting the existing modelling capabilities for some selected BEST. The purpose is to highlight the challenges associated with the modelling of DSFs and to identify the major gaps between measured performance and prediction though BEST. The findings indicate that gaps are mostly connected to the dynamic behaviour of the DSFs and in particular the airflow within the façade cavity. The challenges associated with the modelling and simulation for each software tool, and the skills necessary to recognise and implement the best-suited model among the different options available are also discussed

Modelling of double skin facades in whole-building energy simulation tools. A review of current practices and possibilities for future developments.

Advanced building envelope systems can contribute to the reduction of greenhouse gas emissions and improve the energy flexibility of buildings while maintaining high levels of indoor environmental quality. Among different transparent envelope technologies, the so-called double skin facades (DSFs) have been since long time proposed as an effective, responsive building system. The implementation of DSF systems in a real building is highly dependent on the capabilities of the prediction of their performance, which is not a trivial task. The possibility to use whole-building energy simulation (BES) tools to replicate the behaviour of these systems when integrated into a building is, therefore, a crucial step in the effective and conscious spread of these systems. However, the simulation of DSFs with BES tools can be far more complex than that of more conventional facade systems and represents a current barrier. This article is based on evidence from the scientific literature on the use of BES tools to simulate DSF, and provides: (i) an overview of the implementation of DSFs systems in BES tools, with the current capabilities of some selected BES tools; (ii) a comprehensive review of recent, relevant simulation studies, where different approaches to modelling and simulating DSFs are reported; and (iii) the identification of current gaps and limitations in simulation tools which should be overcome to increase the possibilities to correctly predict the performance of DSFs when integrated into a building

Characteristics that matter in a climate façade: A sensitivity analysis with building energy simulation tools

Double skin façades (DSFs) are considered façade technologies that can reduce energy use and improve occupant comfort due to their advanced features. Their design requires reliable simulations due to their complex thermophysical behaviour, which are often carried out by practitioners using building energy software (BES) tools. Using an exhaust-air façade (also called climate façade) case study, the paper analyses the sensitivity of in-built DSF models in two popular BES tools (EnergyPlus and IDA ICE) for different orientations and climates. Small variations in input variables were considered to identify the parameters that the designer should pay most attention to during the design of the DSF according to different performance indicators. The results show that, regardless of the climate or orientation, the optical properties of the system (glazing and shading) were the most important in determining its performance, followed by the thermal properties of the glazing, while the geometrical, airflow and frame characteristics were less relevant. The model validation process also showed how differences in the in-built models (i.e. the use of a capacitance node for the glazed layers) lead to a difference in the reliability of the two BES tools

The effect of spatial and temporal randomness of stochastically generated occupancy schedules on the energy performance of a multiresidential building

Building performance simulation is frequently used to support building design, renovation, and operation. However, modelers are traditionally concerned with accurately describing technical input data, and have only limited interest in investigating the influence of occupant behavior on buildings’ energy performance. To fill this gap, this article examines the effects of stochastically generated occupancy schedules on the energy performance of a multiresidential high-rise building located in Shanghai, China. The building’s energy performance is analyzed under two design proposals: a law-compliant proposal developed by the designers, and a second proposal conceived through an automatized optimization process. A statistical analysis quantifies the energy implications of adopting different degrees of randomness when creating occupancy and occupancy-dependent schedules. Simulation outcomes show that temporal and spatial randomness of occupancy and occupancy-dependent schedules have a statistically significant influence on the building’s energy performance, with an estimated uncertainty of up to 10%. At least in Shanghai, occupant behavior affects cooling more than heating, and its influence on the energy performance is stronger in high-performance buildings than in poorly insulated ones. Finally, accurate modeling of high-performance buildings would require a detailed and precise description of occupancy and occupant-dependent input variables even if this increases the modeling effort and costs

Modelling double skin façades (DSFs) in whole-building energy simulation tools: Validation and inter-software comparison of a mechanically ventilated single-story DSF

Double skin façades (DSFs) have been proposed as responsive building systems to improve the building envelope’s performance. Reliable simulation of DSF performance is a prerequisite to support the design and implementation of these systems in real buildings. Building energy simulation (BES) tools are commonly used by practitioners to predict the whole building energy performance, but the simulation of the thermophysical behaviour of DSFs may be challenging when carried out through BES tools. Using an exhaust-air façade case study, we analyse and assess the reliability of four popular BES tools when these are used to simulate a DSF, either through available in-built models or through custom-built representations based on zonal models. We carry out this study by comparing numerical simulations and experimental data for a series of significant thermophysical quantities, and we reflect on the performance and limitations of the different tools. The results show that no tool is outstandingly better performing over the others, but some tools offer better predictions when the focus is placed on certain thermophysical quantities, while others should be chosen if the focus is on different ones. After comparing the different models’ limitations and challenges, we conclude that BES tools can simulate the performance of DSF systems over long periods. However, their use alone is not recommended when the simulation’s scope is to replicate and study short-term phenomena and dynamic aspects, such as sizing the building’s HVAC system