Envelope Solutions Research Articles

An interval iterative method for response bounds analysis of structures with spatially uncertain parameters

Parameters with spatial uncertainties are very common in practical engineering, which could have a significant effect on structural performances. Different from the framework of probability theory, the interval field model describes the spatial uncertainty with upper and lower bounds rather than the probability distribution function or other statistical characteristics. By introducing the interval field model into finite element analysis and solving the resulting interval finite element equilibrium equation, the upper and lower bounds of structural responses can then be obtained. This paper proposes an interval iterative method for static displacement response analysis of structures with spatial uncertainties, effectively improving the overestimation existing in traditional interval analysis due to dependency problems and obtaining a compact interval envelope of the exact response bounds. Firstly, the spatially uncertain parameters described by the interval field are represented by the interval Karhunen–Loève (K-L) expansion, based on which the interval finite element equilibrium equation is formulated. Secondly, the interval finite element problem is decomposed into several subproblems, and an interval iterative method is developed for an envelope solution of the structural response bounds. Finally, the accuracy and efficiency of the proposed method are verified by several numerical examples.

Comparing the thermal performance of Living Lab monitoring and simulation with different level of input detail

Dynamic envelope solutions are critical to achieve comfort conditions minimizing the need of active air conditioning systems, emphasizing the potential of thermal adaption of the building occupants. Dynamic systems are, however, difficult to be implemented in European building energy certification schemes, based on semi-stationary calculation method, standard uses and reference boundary conditions. In the attempt to develop a flexible and dynamic method able to reduce the performance gap between real and expected performance, this paper presents the comparison between measurements and simulations of a Living Lab office operated in thermal free floating, with different strategies for the solar protection and the night ventilative cooling. Simulations were performed using the dynamic platform PREDYCE, which allows for manipulating monitored and simulated data. The first phase was dedicated to the model calibration using the indoor air temperature as relevant indicator against monitored data. The coefficient of variation of the root mean squared error is in the 8-9% range. Building simulations of the calibrated model demonstrated a large variation of the results as a function of the input data, with increase of discomfort hour up to a factor 20 and a reduction of discomfort hours up to 95%.

Wall and roof solutions for a retail building considering cost investment and life cycle approach: A case study in Portugal

This study explored which envelope solutions in retail buildings led to cost-optimal levels considering the Energy Performance of Building Directive and Portuguese regulation. For such, energy simulations were run in BIM software based on the analysis of a case study in Portugal. Typical alternative solutions were tested against the original case study, and solutions with considerably lower U-value considering the code for commercial buildings (0,7 W/m2°K for walls and 0,5 W/m2.°K for roofs). To assess the cost-effectiveness of alternative envelope solutions, the Payback Period, the Net Present Value and the Internal Rate of Return at 15 years and 50 years were assessed. Results indicate that solutions with lower U-values are related to 2–5% savings in energy consumption and can be cost-effective at 15 and 50 years, namely vacuum insulation panels of 2.5 cm and sandwich panels of 8–12 cm. This leads to the conclusion that lowering present code U-values can be cost-effective, but it will result in additional initial costs.

Thermal performance assessment of a retrofitted building using an integrated energy and computational fluid dynamics (IE - CFD) approach

The comfort of the occupant in the indoor thermal environment can be efficiently analysed using the principle of computational fluid dynamics (CFD) technique. This can be modelled as a difference of measure of a region equivalent to air circulation and diffusion in/out of the area. Other parameters influence the room operating condition and energy consumption by the building systems directly and indirectly over a period of time. This paper represents how to use comfort theory and CFD concepts to do a computational study of building comfort and improve the energy performance of the building during the summer and winter seasons in the subtropical climate. The occupants’ overall comfort evaluation results in the chosen building are recorded, taking into account the suitable climate-responsive heating, ventilation and air conditioning approach and envelope systems. The thermal CFD simulation model used in this study incorporates the most current turbulence simulation methodology appropriate for airflow modelling in buildings. The numerical comfort analysis methodology is used to analyse the indoor thermal condition, considering the Cooled Beam cooling system and BioPCM as an envelope solution for possible retrofitting. The simulation findings show that the uniform temperature distributions observed during working hours are adequate and demonstrate improved energy performance by the building systems. Moreover, the results suggest that the use of advanced computational fluid dynamics techniques is a valuable method for the analysis of human comfort in indoor spaces.

The incidence of smart windows in building energy saving and future climate projections

The ongoing climate crisis leads to develop smart communities with zero net emissions, and the Responsive Building Envelopes (RBEs) have a crucial role for the goal to be achieved. In this frame the smart windows are promising building envelope solution. With respect to conventional static windows, on one hand they could reduce the building thermal loads and therefore lead to an energy saving and to an improvement of the thermal comfort, on the other hand they could reduce the possible glare, improving the also the visual comfort. There are some smart windows based on widespread technologies and deepen investigated in the scientific literature, such as the electrochromic solution, but there are some others, such as liquid crystal devices, not really investigate, or characterized only by means of simulative analysis, often without calibrated models with experimental data. Thus, the present study aims to investigate, under experimental and numerical point of view, an electric-driven window with liquid crystal technology installed in a full-scale facility located in a Mediterranean climate. A calibrated numerical model is carried out and different windows control logics and future climate projections (to 2050s and 2080s) are analyzed. Among different control logics, the one depending on daylight illuminance level on the work plane shows the best performance, with a total energy saving (lighting and cooling) of -3% with respect a static window in clear state.

Ecological performance of reusable load-bearing constructions

This study provides an overview of sustainable reusable load-bearing constructions as a contribution to the debate over whether building construction provides the building industry with the best and most environmentally friendly qualities. By contrasting their building-specific features, it demonstrates the benefits and drawbacks of particular structural elements and envelope solutions and ecological aspects using various system boundaries of life-cycle assessment (LCA). Following a careful consideration of ecological factors and sustainable circular economy criteria, a structural component that is sustainably optimized is defined. This component should be chosen based on external conditions. By selecting environmentally friendly building materials and proper connecting procedures that enable separability, resource-efficient and sustainable buildings can be achieved. Both the selection of load-bearing elements and the necessary insulating material have a significant impact on the ecological performance and reusability options of the components. The elements of homogeneity, separability, and pollutant-freeness play a significant influence in the reuse process, namely in terms of details and construction type in general, as well as the ways of reusing and recycling them. Sustainable solutions for load-bearing building components can be created by simultaneously investigating environmentally friendly building materials and the structure of the components. This paper illustrates how the natural resources can be used both optimally and sustainably. It presents a conceptual framework for scenario development of the LCA of load-bearing structures, their effect on the design and decision-making process. There is a potential of increasing total resource efficiency at the building level with a suitable combination of the material components employed at the component level. Because of this, the overall energy efficiency and its consequent ecological impacts are the main topics of this study.

Energy saving through building automation systems: Experimental and numerical study of a smart glass with liquid crystal and its control logics in summertime

Smart glass technology is promising building envelope solution for Responsive Building Envelopes (RBEs) if smart communities with zero net emissions must be achieved. This solution could lead to energy saving and a thermal comfort improvement, but also a reduction of possible glare, improving the visual comfort. On the basis of an extended literature analysis there are some smart window technologies, such Electrochromic ones, most mature at research level, showing a large impact in the reduction in cooling demand. On the other hand, these solutions have some issues, like the long switching period or the alteration of indoor perceived colours. An example of promising alternative to Electrochromic technology could be the liquid crystal device, which performances have not been enough investigated in the current literature. In this context the purpose of the present study is to develop a deep investigation, thus numerical and experimental, of a full-scale electric-driven window (liquid crystal technology) installed in an outdoor test-room, in order to evaluate the effect of its usage on energy consumption and daylight control. Based on continuous monitoring, a numerical model of HVAC-building system with smart window was developed and calibrated. It allowed to carry out a sensitivity analysis on the energy demand by considering all window exposures, the window control logic (based on illuminance level or indoor air temperature), different climate zones (Benevento, Athens, London and Cairo) and the window to wall ratio (18% or 100%) also. Comparing the results with a static window, for all exposures and all climates, the dynamic window could reach an energy saving, up to −17%.

Chirped self-similar pulses and envelope solutions for a nonlinear Schrödinger's in optical fibers using Lie group method

In this work, we present an application of Lie group analysis to study the generalized derivative nonlinear Schrödinger equation, which governs the evolution of a nonlinear wave and plays an important role in the propagation of short pulses in optical fiber systems. To construct Lie group reductions, we study the symmetry properties and introduce various infinitesimal operators. Further, we obtain self-similar solutions and periodic soliton solutions of the generalized derivative nonlinear Schrödinger equation. This type of solution plays a vital role in the study of the blow-up and asymptotic behavior of non-global solutions. And at the end, we present graphs for each solution by considering the physical meaning of the solutions.

Giant planet formation in Palatini gravity

Some parts of the accretion model of the jovian planets' formation are studied in the context of Palatini gravity. We mainly focus on the critical core mass, that is, a mass for which there is no hydrostatic equilibrium solution for the planet's envelope, which is a starting point of the runaway accretion. We also discuss the conditions needed to be satisfied by a planet such that it can posses a massive gaseous envelope around a solid core.

Enviro-economic assessment of buildings decarbonization scenarios in hot climates: Mindset toward energy-efficiency

As buildings consume a considerable portion of the global energy output and have a key role in greenhouse gas emissions, several steps have been taken to lower the energy and emissions from buildings especially through the adoption of renewable energy sources. The emerging building integrated photovoltaic (BIPV) technologies act as replacements for conventional building envelopes as well as energy generation sources. The purpose is examining, through parametric analysis, the potentials of energy-efficient building solutions in different hot climatic regions. Through an enviro-economic assessment, a building envelope solution is proposed that enhances the building energy performance in terms of reducing the building energy use, generating green energy, and reducing indoor thermal discomfort. Results showed that CO2 emission reductions ranged from 9% to 31% and the discomfort hours reductions ranged from 10% to 25% based on the model specifications. Moreover, several financial elements were considered such as IRR, ROI, NPV and the Payback period were calculated for each model. Promising numbers were obtained in terms of the economic analysis of the models. The models demonstrate an IRR index of 26.45%, 21.6%, and 16.85% for Aswan, Cairo, and Alexandria, respectively, an ROI index of 18.32%, 15.68%, and 13.23% for Aswan, Cairo, and Alexandria, respectively, with nearly half the PBP in all locations. According to the techno-economic outcomes, the Reflective paint model integrated with the Glazing Integrated PV tends to be the most cost-effective implementation in the three different locations.

Retrofitting Old Silk Factory in Valmadrera, Italy with Insulated Envelope Solutions.

Building industry is responsible for almost 50% of the world’s total energy demand. It takes more energy to operate buildings than it takes to run the manufacturing or transportation industry. In the drive for climate change, a lot of work is being done by policy makers for making new projects better aligned with environmental and energy conservation goals. It is not enough to only focus on improving the climate response of new construction. Work also needs to be done on improving the energy performance of existing building projects which will in turn, further reduce the CO2 footprint of the building operations industry. One way to reduce the energy consumption of existing buildings, is to add insulation to façade elements during building retrofitting projects. The purpose of this research is to shed light on probable options and benefits for adding insulation to traditional envelopes. This will enhance the operating capacity of buildings without the need for demolition or re-construction. This project demonstrates the energy efficient retrofitting of an old silk factory in the historic city of Valmadrera, Italy to act as a prototype project testing suitable options for adding insulation to existing structural systems. One of the biggest challenges for this type of upgrade is the porous nature of the existing building material and how it conflicts with the hygroscopy of synthetic insulation materials. The research suggests the use of organic insulating materials for the envelope elements. At the same time it also offers valuable suggestions for future explorations. This research has a high impact value globally, due to the vast treasure of historical architecture buildings which need to be preserved, but also need improvement in terms of their technological performance. Furthermore, it holds strong relevance for the Saudi Vision 2030 because preserving local architectural practices, materials and techniques is a significant part of the national motivation to preserve Saudi cultural identity.

Integration and Verification of PLUG-N-HARVEST ICT Platform for Intelligent Management of Buildings

THe energy-efficient operation of microgrids—a localized grouping of consuming loads (domestic appliances, EVs, etc.) with distributed energy sources such as solar photovoltaic panels—suggests the deployment of Energy Management Systems (EMSs) that enable the actuation of controllable microgrid loads coupled with Artificial Intelligence (AI) tools. Such tools are capable of optimizing the aggregated performance of the microgrid in an automated manner, based on an extensive network of Advanced Metering Infrastructure (AMI). Modular adaptable/dynamic building envelope (ADBE) solutions have been proven an effective solution—exploiting free façade areas instead of roof areas—for extending the thermal inertia and energy harvesting capacity in existing buildings of different nature (residential, commercial, industrial, etc.). This study presents the PLUG-N-HARVEST holistic workflow towards the delivery of an automatically controllable microgrid integrating active ADBE technologies (e.g., PVs, HVACs). The digital platform comprises cloud AI services and functionalities for energy-efficient management, data healing/cleansing, flexibility forecasting, and the security-by-design IoT to efficiently optimize the overall performance in near-zero energy buildings and microgrids. The current study presents the effective design and necessary digital integration steps towards the PLUG-N-HARVEST ICT platform alongside real-life verification test results, validating the performance of the platform.

Multilayer assembly of phase change material and bio-based concrete: A passive envelope to improve the energy and hygrothermal performance of buildings

Phase change materials (PCMs) can improve indoor thermal comfort and reduce energy consumption, while bio-based concrete is an environment-friendly material that enables indoor humidity regulation and heat insulation. However, only a few studies have explored the integrated application of the two materials and comprehensively analyzed the energy and hygrothermal performance. In this study, a passive envelope solution that integrates PCM and hemp concrete is proposed to improve buildings’ energy, thermal, and hygric performances simultaneously. Four integrated scenarios were considered and compared with a baseline scenario (hemp concrete only). The performance of the integrated envelope was studied numerically based on the impact of the PCM’s properties and its location in the envelope. The results highlight the indispensable role moisture transfer plays in determining the indoor hygric environment and heat load, as well as the valuable effect of the integrated envelope on improving both energy and hygrothermal performance. Scenario 4/5 (with PCM closest to the interior) in the summer showed the greatest performance improvement compared to the baseline scenario, with reductions of 8.2%, 46.3%, and 43.7% for heat load, temperature fluctuation, and partial water vapor pressure fluctuation, respectively. The impact of the PCM properties in scenario 4/5 illustrate that the optimization of the integrated envelope can be achieved by increasing the thickness and latent heat of the PCM and identifying its appropriate phase transition range. From a year-round perspective, scenario 4/5 is also notable, as it shows great potential for saving energy and adapting to climate humidity variation while guaranteeing moisture equilibrium within the hemp concrete. The three-year assessment confirmed a lack of condensation and no risk of mold growth for such an integrated envelope, as the relative humidity in key locations remains below 75%.

Integrated life cycle assessment of a southern European house addressing different design, construction solutions, operational patterns, and heating systems

The construction industry is responsible for a substantial fraction of materials and energy consumption, waste generation, CO2 and other pollutant emissions. Life cycle assessment (LCA) can be used to study and compare the environmental impacts of buildings under different scenarios. This study comparatively assesses the impact of several design options, envelope solutions and operational conditions on the energy life cycle (LC) of a single-family house in southern Europe (Portugal) taken as case-study. The following parameters are evaluated: location, orientation, building shape, windows placement and sizing, insulation level, exterior wall construction, operational pattern, ventilation level, heating system, and end-of-life (EoL) scenarios. The non-renewable primary energy (NRPE) results are presented for the total LC of the house. Afterward, the overall embodied energy is analyzed and the results are presented per component and LC process of the house, in order to assess the contribution of each component. Finally, different circular economy EoL scenarios are analyzed to assess their potential benefits. As buildings are typically unique, complex, and difficult to compare with each other, the results of this paper will contribute for future comparison purposes, in order to foster LCA studies devoted to Mediterranean houses.

Design and Thermal Characterization of Two Construction Solutions with and without Incorporation of Macroencapsulated PCM

Improving the energy efficiency of new and existing building stock while fostering the use of renewable energy is one of the major goals of the Renovation Wave initiative promoted by the European Union. In this framework, the present research focuses on the design of an innovative and efficient construction solution for an external envelope and internal partitions that can improve energy efficiency and thermal comfort in lightweight construction technology for buildings. The use of phase change materials (PCMs), particularly in the macroencapsulated form, in building construction solutions or components enhances the buildings’ thermal mass without significantly increasing the solutions’ weight. Therefore, the solution herein developed is essentially targeted at lightweight building technology since the incorporation of a macroencapsulated PCM core will allow to store and release large amounts of energy per volume unit, in order to attenuate high indoor temperature fluctuations. In the scope of this study, the use of a thermally active core in a lightweight construction solution was designed and thermally characterized. Thus, an experimental campaign on the thermal properties of the solution containing macroencapsulated PCMs was performed, intended for applications in two twin full-scale cold-formed steel lightweight tiny houses. Regarding the hot box heat flux meter approach, the results revealed the following: good correlation between thermal conductivity and mean specimen temperatures for both construction assemblies tested, and significant thermal amplitude reduction with the use solution containing the macroencapsulated PCM core.

Thermoeconomic Analysis in Advanced Cogeneration Systems in Buildings

In this work thermoeconomics is applied to a central thermal system covering three buildings that consists of a cogeneration engine, an aerothermal heat pump and a natural gas condensing boiler. Cogeneration systems integrated with renewable energy technologies are very attractive solutions in the building sector. Nevertheless, the use of cogeneration systems together with active envelope solutions, such as the one encountered in this work, are scarce and the efforts to enhance the synergies between both systems are even scarcer. A heat pump is connected to a so-called solar wall to provide hot air and a renewable photovoltaic system supplies the electricity consumed by the heat pump. Thermoeconomics is applied to evaluate the cost of flows based on its energy-quality. Hence, this innovative and complex system can be analysed and diagnosed by this methodology. As a result, thermoeconomics is presented as an effective tool for the detailed study of the energy cost distribution and the key to enhancing energy efficiency.

Techno-economic evaluation of building envelope solutions in hot arid climate: A case study of educational building

Building energy use is becoming increasingly important worldwide, with the increasing necessity to attain indoor thermal conditions. The high temperatures in hot climates cause human dissatisfaction resulting in higher use of air conditioning systems. As a result, energy in those buildings rises regularly driven by the increase in the air conditioning systems operation. In the non-residential building sector, the air conditioning system consumes the majority of the building’s energy to satisfy the thermal comfort requirements. With this aim, simulations have nowadays become an important tool to fulfill various high-performance buildings. Dynamic simulations have often been used by designers to evaluate buildings’ energy performance to accomplish specific goals, as minimizing energy usage and environmental impacts. This study analyzes the energy savings obtained by the execution of retrofitting measures in an educational building located in Egypt through dynamic simulations of the building performance. The main objective is the creation of a decision matrix to select an optimal solution for the building envelope based on the effectiveness of thermal insulation, cost, and environmental factors. Based on the precise physical characteristics of the building’s vacancy schedule, geographical location, weather conditions, and the nature of construction, overall energy consumption would be determined. A sensitivity analysis is undertaken to assess the key factors that influence building energy consumption through the validated baseline model. The envelope is chosen as it is vital for the building’s energy efficiency and could account for up to 50% of the total heat gain in a building. Thermal insulation is one of the most effective implementations to provide desirable thermal comfort and minimize heat transfer into buildings, resulting in an energy consumption reduction. Two insulation materials are assessed through the building simulation model, the cost of each measure is estimated, and the emissions mitigation produced is obtained. With this information, a decision matrix is created that allows highlighting the best option based on the effectiveness of the measure in Egyptian hot arid climates. Among different insulations surveyed in Egypt, the study highlighted the effectiveness of using Extruded polystyrene insulation (XPS) with a thickness of 25 mm, resulting in reductions of about 16% in Heating, Ventilation, and Air-Conditioning (HVAC) energy consumption and 8% of the overall energy consumption with a payback period of about 25 months and a 29% Return on investment (ROI).

Mechanical characterization of a concrete masonry block enhanced with micro-encapsulated phase changing materials

Global energy demand has been increasing exponentially in the last three decades, which has been exacerbated by climate change. To alleviate the energy load, researchers have been exploring innovative passive techniques to enhance the thermal performance of building envelopes. This research evaluates a novel building envelope solution, which includes the development of a Concrete Masonry Unit that is integrated with bio-based micro-encapsulated Phase Changing Materials. The mechanical behaviour of the enhanced CMU is investigated to study the applicability of PCMs into the no-slump concrete mix. Compatibility with the applicable standards opens a broader prospect for thermal characterization and building performance simulations of PCM enhanced CMU building envelopes.

Mass Timber Envelopes in Passivhaus Buildings: Designing for Moisture Safety in Hot and Humid Australian Climates

The uptake of buildings employing cross-laminated timber (CLT) assemblies and designed to Passivhaus standard has accelerated internationally over the past two decades due to several factors including responses to the climate crisis by decarbonising the building stock. Structural CLT technology and the Passivhaus certification both show measurable benefits in reducing energy consumption, while contributing to durability and indoor comfort. However, there is a general lack of evidence to support a fast uptake of these technologies in Australia. This paper responds to the compelling need of providing quantitative data and adoption strategies; it explores their combined application as a potential pathway for climate-appropriate design of energy-efficient and durable mass timber envelope solutions for subtropical and tropical Australian climates. Hygrothermal risk assessments of interstitial condensation and mould growth of CLT wall assemblies inform best-practice design of mass timber buildings in hot and humid climates. This research found that the durability of mass timber buildings located in hot and humid climates may benefit from implementing the Passivhaus standard to manage interior conditions. The findings also suggested that climate-specific design of the wall assembly is critical for mass timber buildings, in conjunction with excellent stormwater management practices during construction and corrosion protection for metallic fasteners.

New building simulation method to measure the impact of window-integrated organic photovoltaic cells on energy demand

Building integrated photovoltaics is an envelope solution that combines energy generation, net energy demand reduction, and aesthetics. Lighter and semi-transparent technologies made the integration of photovoltaic cells in windows possible, which could not be achieved with traditional silicon technologies. This article aims to propose a new method to measure building energy performance using parametric models, simulation, and the use of genetic algorithms, resulting in a more precise and time-saving process compared to regular methods. Three different geometries and six façade configurations were designed, window-to-wall ratio and orientation were set as variables to optimize energy demand reduction. The software used is Rhinoceros, alongside the plugins Grasshopper, Ladybug, Honeybee, and Galapagos, running all simulations and optimizations in a single platform. Galapagos performs the optimizations, an automatic process that required on average 600 simulations to find the optimal solution, while regular methods take up to 9,720 possibilities. Although the benefits from building integrated photovoltaics vary depending on building geometry and envelope configuration, a net energy demand reduction was achieved in all cases. Such values ranged from 6.76%, reached by low-rise buildings with one photovoltaic façade, to 24.04%, accomplished by mid-rises where all façades had window-integrated photovoltaics.