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

A Study on the Impact of Green Infrastructure on Microclimate and Thermal Comfort

This study focuses on exploring the impact of urban forms and vegetation combination patterns on the microclimate in a complex urban environment. Results shown that the closed urban form has higher air temperature resulting in pedestrians are easier to feel heat stress; instead, the open urban form usually has higher wind speed. Vegetation can effectively reduce wind speed while reducing the change rate of the mean radiant temperature. However, the effect on air temperature and humidity are most distinct in the morning. Trees and shrubs could improve the surrounding thermal comfort conditions by reducing heat stress, but this effect depends on the density of the leaf area. More importantly, study has not found that the ground cover plants contribute to the improvement of thermal comfort

Interdisciplinary survey to investigate energy-related occupant behavior in offices – the Hungarian case

In recent years, both legislative instruments and market demand drive the construction industry towards high-performing, low-energy consuming buildings. However, without considering the human dimension, technologies alone do not necessarily guarantee high performance in buildings. Occupant behavior is a leading factor influencing energy use in buildings. To investigate and quantify the human dimension in a building’s energy use, an international research study has been launched as part of project ANNEX66, organized by the International Energy Agency using an interdisciplinary framework. The framework is a synthesis of theories from building physics and social psychology including social cognitive theory, the theory of planned behavior, and the drivers-needs-actions-systems ontology for energy-related behaviors. As a research tool, an online survey was designed to collect cross-country responses from office occupants among 14 universities within 6 countries from 4 continents. This paper introduces results and findings of the Hungarian data collection campaign conducted among 207 occupants in 6 universities across the country

Current performance and future development paths of transparent PV glazing in a multi-domain perspective

Transparent PV (TPV) layers allow solar energy exploitation across the thermal, daylighting, and energy conversion domains. However, the current power conversion efficiency (PCE) and visible transmittance (VT) features of such systems may hinder the effectiveness of such solutions when the global performance of the building envelope is considered. In this study we assessed, from a multi-domain perspective, if the performance of façade configurations based on commercially available TPV layers can compete with the performance of façade configurations based on more conventional (opaque) PV solutions. The outcome of this research is thus, on the one hand, a better, evidence-based understanding of the current performance levels of this technology – whether it is mature enough for successful uptake, and which applications are the most relevant – and on the other hand, evidence-based recommendations for product development paths to make TPV systems more competitive for a wider range of applications. In this simulation study we employed a simple room with standardised user patterns and requirements, and repeated the analysis in multiple European climates, to make our results as generic as possible. We carried out the analysis by computing and comparing the performance across the three different domains (total energy use, daylighting, and energy conversion), thanks to a co-simulation environment, of south-facing façade configurations with different TPV or opaque BIPV solutions, which were parametrically changed in terms of window-to-wall ratio, glazing type, and BIPV system. The results showed that TPV systems provided global performance levels that were, in a large range of cases, worse than those of other façade configurations integrating only opaque PV layers and conventional glazing. The trade-off between solar/visual transmittance and absorptance, necessary to ensure a certain PV conversion output in TPV layers, led to a worse global (multi-domain) performance in all the investigated climates. When a fully glazed façade is an absolute design requirement, TPV-based façades can give a better total energy performance than solutions without any PV conversion feature, while providing acceptable daylighting exploitation. However, these envelope solutions showed a worse performance compared to other configurations with a better, more balanced window-to-wall ratio, with BIPV only on opaque surfaces. Accordingly, these findings have implications for both recommended applications of today’s TPV systems and technology development directions. Current TPV systems may be suitable for large, glazed surfaces (such as atria or roofs above circulation spaces) where visual performance requirements are less tight than in office or dwelling settings. TPV solutions can become more competitive for broader façade applications if a PCE of at least 3 times the current value is achieved without reducing the VT. Increasing the VT while keeping the current PCE could also be a suitable research trajectory to enable TPV systems that provide a better balance in solar energy exploitation. Combining a TPV with more advanced glazing solutions (e.g., vacuum insulation or thin-glass glazing) can, however, only marginally expand the range of usability of these systems

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

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