The present paper is the first comprehensive review of the integration of phase change materials in building walls. Many considerations are discussed in this paper including physical considerations ...about building envelope and phase change material, phase change material integration and thermophysical property measurements and various experimental and numerical studies concerning the integration. Even if the integrated phase change material have a good potential for reducing energy demand, further investigations are needed to really assess their use.
A significant portion of the total primary energy is consumed by today's buildings in developed countries. In many of these buildings, the energy consumption can be significantly reduced by adopting ...energy efficiency strategies. Due to environmental concerns and the high cost of energy in recent years there has been a renewed interest in building energy efficiency. This article strives to make an exhaustive technical review of the building envelope components and respective improvements from an energy efficiency perspective. Different types of energy efficient walls such as Trombe walls, ventilated walls, and glazed walls are discussed. Performance of different fenestration technologies including aerogel, vacuum glazing and frames are presented. Advances in energy efficient roofs including the contemporary green roofs, photovoltaic roofs, radiant-transmittive barrier and evaporative roof cooling systems are discussed. Various types of thermal insulation materials are enumerated along with selection criteria of these materials. The effects of thermal mass and phase change material on building cooling/heating loads and peak loads are discussed. Application of thermal mass as an energy saving method is more effective in places where the outside ambient air temperature differences between the days and nights are high. Air tightness and infiltration of building envelopes are discussed as they play a crucial role in the energy consumption of a building. Energy efficiency approaches sometimes might not require additional capital investment. For example, a holistic energy efficient building design approach can reduce the size of mechanical systems compensating the additional cost of energy efficiency features.
This paper reviews and analyzes technological design options, which have become available to date for BIPV systems on roofs and facades, independently of specific products or building projects. This ...means that this survey does not analyze existing products or realized buildings, but provides an overview of the technologies for BIPV. The starting point is an analysis of the relevance of BIPV technologies for the decarbonization of energy systems, providing energy for direct use of electricity and sector coupling together with an analysis of the German BIPV market. The paper presents the wide range of technical design options for BIPV systems and categorizes and analyzes them to provide a structured overview. This comprises a detailed analysis of the design options for BIPV modules, in which not only the design options for the PV cell layer were comprehensively investigated, but also the different variants of embedding materials, front and rear cover materials, additional interlayers and electrical module layout. Two fundamental module-level design options were investigated in particular detail: The use of PV cells as basic elements of patterns and the use of color to conceal the PV cells. Subsequently, options for the design of complete electrical systems are reviewed, ranging from sub-module level design parameters to building energy systems. Design options for the constructional integration of BIPV modules in the building envelope complete the review of technological design possibilities.
Airflow in wall-to-wall junctions is known to have a major hygrothermal impact on building performance. However, current and validated modeling options to simulate such phenomena are limited. This ...paper develops and compares two numerical models to study the heat and moisture transfer due to air infiltrations through a prefabricated wall-to-wall junction. The first model explicitly accounts for the airflow with a pipe flow approach. The second model is a modification to a typical approach to simulate ventilated cavities in building envelope simulation tools and mimics the effect of the airflow through source terms. Both approaches were introduced in a heat and moisture transfer 2D finite element model. Additionally, laboratory measurements were conducted in a climatic chamber to validate the simulation results. Six scenarios were tested experimentally under steady-state conditions. These datasets were used to calibrate different parameters of the models, such as material properties, the junction air gap thickness, and the magnitude of the heat and moisture source terms. Both sets of numerical results provided reasonable agreement with the measurements. The first approach outputs more accurate temperature and relative humidity values than the second one. However, considering uncertainties, no method predicted a perfect fit with the relative humidity profiles. Close to the junction, the first method estimates better the relative humidity than the second one. This work provides guidelines to better model and account for wall junctions in building envelope simulators.
•Airflow in wall junctions impacts hygrothermal performance, but is hard to model.•Temperature and humidity results from 2 models are compared to experimental results.•Pipe flow model better predicts temperature measurements than source term model.•Both models exhibited differences in relative humidity compared to measurements.
The paper proposes a multi-objective optimization approach to address the energy design of the building envelope. A genetic algorithm (GA) is implemented by means of the coupling between MATLAB® and ...EnergyPlus to minimize primary energy consumption (PEC), energy-related global cost (GC) and discomfort hours (DH). The design variables concern the set point temperatures, the radiative properties of plasters, the thermo-physical properties of envelope components, the window type, the building orientation. The GA performs a Pareto optimization and finally two optimal solutions are recommended: the nZEB (nearly zero energy building) optimal solution, which minimizes PEC, and the cost-optimal solution, which minimizes GC. These solutions provide the optimal design strategies for the public and private stakeholders, respectively, which represent the main actors involved in building design. The approach is applied for the design of a new typical Italian residential building. Four locations are considered to investigate the typical Italian climates. The outcomes can give precious indications to rebuild the Italian residential stock with a view to energy-efficiency and cost-optimality, given that the optimal solutions provide low values of PEC – between 62.0 and 91.9 kWhp/m2a – and of GC – between 456 and 665 €/m2 – depending on the location.
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•The methodology optimizes envelope energy design by using a genetic algorithm.•Primary energy consumption, global cost and discomfort hours are minimized.•The optimal most sustainable (nZEB) and the cost-optimal designs are achieved.•The methodology is applied to four different Italian climatic zones.•Original indications to rebuild the Italian residential stock are provided.
The building sector accounts for approximately 40% of total global energy usage. Energy consumption for space heating and cooling makes up 60% of the total consumed energy in buildings. This paper ...presents a comprehensive technical review of passive wall systems in building envelopes while discussing their respective capabilities in optimizing energy efficiency. Different types of energy efficient walls such as Trombe Walls, Autoclaved Aerated Concrete Walls, Double Skin Walls, and Green Walls are explored. Furthermore, novel concepts for optimizing energy efficiency in building envelopes are also introduced. Finally the utilization of passive wall systems to save energy while improving the building environmental impacts is discussed.
With the global target to promote energy saving in buildings, various studies draw attention to the role of environmentally benign building envelopes. In this regard, double-skin façades (DSFs) have ...been proposed as a promising passive building technology to enhance the energy efficiency and improve the indoor thermal comfort at the same time. A comprehensive analysis of the current design of DSFs, and their technical aspects is presented in this paper. Construction characteristics of DSFs are also reported. The impacts of DSFs on the energy efficiency and thermal performance are discussed by looking at measured and simulated performances. Findings confirm that significant benefits result from using DSFs. Finally, research opportunities are outlined for further investigation.
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•Developments, challenges, and improvements of radiative sky cooling in buildings are reviewed.•The actual effects of radiative sky cooling on the indoor environment are ...emphasized.•Five main challenges with the current application of radiative sky cooling in buildings are presented.•Switchable building envelopes are reviewed and attempted to be optimally combined with radiative sky cooling.
Radiative sky cooling (RSC), acting as a passive cooling method, reduces the heat gain by dissipating the excessive heat via reflective and radiative approaches. The heat sink of RSC is mainly the deep space with temperatures close to absolute zero. Recent research shows that RSC offers high cooling potential in many fields because of its wide and low-temperature heat sink. Most studies on RSC focus on equipment performance and material development, and only a few addresses its actual applications in cooling buildings. Considering the potential of RSC in building energy saving, this paper reviews the developments, challenges, and improvements of RSC in buildings which is one of the main application scenarios for RSC. The paper reviews five main challenges with the current applications of RSC in buildings, based on the discussion of the cooling effect of RSC in the indoor built environment. The application of RSC in buildings is more related to its passive integration with the building envelope, which limits its overall effectiveness. Therefore, the combinations of RSC with active building cooling systems are further reviewed and analyzed in order to improve RSC dynamic performance. For future use, some advanced building envelopes, such as switchable building envelopes, are discussed, along with RSC. Using the optimal combination of the two, an optimal solution for the application of RSC in buildings is sought, providing a reference and basis for the application of RSC in buildings.
•Literatures on simulation-based building envelope optimization were reviewed.•Optimization algorithms, objectives and popular tools were compared and discussed.•Single-objective optimization was the ...major measure while energy was the top concern.•Limitation in comfort evaluation and occupant behavior requires further attention.•Comprehensive building envelope design involves energy efficiency and comfort issue.
Green building design is presently among the hottest research topics in the world. Maintaining a comfortable indoor environment with minimum energy consumption is a challenging task that attracts the attention of experts around the world. With the recent advances in building performance simulation tools, it is now possible to predict and assess building performance at the design stage. Simulation-based optimization of building design is a potential application that connects building performance simulation with optimization algorithms. In this paper, numerous studies on the optimization of building envelope design were assembled and reviewed. Popular optimization algorithms were compared and discussed. Targeted objectives were collected and summarized. Based on the statistical results, the limitations in this research area were identified, and some potential breakthroughs were suggested.
•The energy performance of radiative cooling and low-E coatings is investigated.•Radiative cooling coatings yield energy saving in most climates.•Low-E coatings provide better energy savings for ...poorly insulated buildings.•Heating penalties are countered in most climate zones.•A strong linear correlation between outdoor temperature and energy saving is noted.
Radiative cooling and low-emissivity coatings are promising strategies for building energy savings. Despite their potential, comprehensive assessments across diverse climate zones remain limited. This study addresses this gap by investigating the potential energy performance associated with these coatings in buildings at 250 locations worldwide, spanning all ASHRAE climate zones. To quantitatively assess the energy efficiency benefits, this study employs EnergyPlus simulations to analyse annual thermal energy needs in two-floor, single-family detached apartments with varying levels of thermal transmittance. Results indicate that radiative cooling coatings provide considerable energy-saving effects for most locations, including those with higher heating demands than cooling demands. For buildings with poor insulation, low-emissivity coatings provide substantial annual energy savings in over 74% of the case locations. Moreover, the study also assesses heating penalties due to overcooling effects, revealing that these are generally less critical than the cooling energy savings in most climate zones. Furthermore, a strong linear correlation was found between yearly energy savings and the annual average outdoor temperature for each coating type in zones 0 to 6. The insights from this study have broad implications for the applicability of radiative cooling and low-emissivity coatings in new constructions and existing building retrofits across various climate zones.
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