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Built environments contribute significantly to mitigating climate change. However, existing buildings, which form most urban infrastructures, do not typically meet contemporary ...stringent energy efficiency standards. They are naturally continuously deteriorating, making them a continuous negative contributor to their surrounding environments, which keeps getting worse. Therefore, there is a need to develop performance diagnosis frameworks and approaches for accurate Building Energy Model (BEM) simulations to develop impactful retrofitting design solutions that could make existing buildings perform closer to current efficiency measures. This paper reports on research that focuses explicitly on calibrating envelopes of existing BEMs using drones equipped with thermography sensors. The study specifically focuses on the automation of on-the-fly envelope U-value estimations and verification of calibrated envelope BEMs. The paper examines a renovated campus building in Boston, MA., representing material degradation, thermal bridging, and insulation failures using thermal imaging. A BEM is then calibrated, and post-renovation metered and modeled wintertime heating energy are compared. Goodness of fit measures showcase BEM performance improvement from 21.8%to 0.9%, which demonstrates the utility of the proposed framework. Further research is recommended to expand the focus on anomalies in the envelope and increase the scope from the building scale to the neighborhood scale.
Decarbonistation goals for building stock calls for innovative solutions on both supply and demand side. Thermal envelopes with in-build energy storage could gather on-site solar energy and reduce ...cooling or heating loads of the buildings. Results of on-site testing of dynamic facade system with the solar energy storage are presented in the paper. Proposed solar façade consists of phase change material to rise the heat capacity of the building envelope, aerogel for insulation, Fresnel lens for solar energy concentration accompanied by moving reflective blades for heat transfer enhancement. Comparative study was conducted in PASLINK type test booths– the performance of proposed solar façade was compared to the reference element – the highest performance triple glazed window suitable for low energy buildings. The detailed measuring setup provide information on the thermal performance of phase-change material enhanced building envelope under different outdoor conditions (summer, autumn, winter) in Northern European climate. The gained results indicate that proposed solar façade module provides lower energy demand during the cooling season compared to the window, in mid-season it performs similarly, however in heating season proposed solar façade in its current composition is outperformed by high performance triple glased window.
•Facade module combines adaptive tech with phase change material for energy storage.•Real-world testing in cold climate to assess impact on heating and cooling demand.•Results show potential for temperature and cooling peak savings in summer.•In midseason energy consumption is similar and higher in winter.•Facade system's performance vs. highest-performing triple-glazed window compared.
•A novel prototype of dynamic insulation systems is described.•Potential benefits of the dynamic insulation system are outlined.•Testing results of the dynamic insulation system performance are ...summarized.•A CFD analysis of the dynamic insulation system is presented.
This paper evaluates a prototype of dynamic insulation systems (DIS) suitable for switchable building envelope to minimize heating and cooling thermal loads while maintaining indoor thermal comfort. The thermal performance of the novel DIS prototype has been evaluated through both experimental and numerical analyses when applied to an opaque wall section. The DIS prototype is able to vary continuously the R-value of the building envelope using rotating insulation layers controlled through an actuator to a specific angle depending on the desired thermal resistance level. The experimental testing showed that the prototype DIS provides a significant reduction of over 50% of the wall R-value when the insulation layers no longer overlap due to the increased convection inside the wall cavity. The CFD analysis predictions, matching the experimental results, demonstrate that the DIS prototype offers a simple design option that can be easily controlled and modulated to adjust the R-value of the building envelop based on the angle of the insulation layers. The CFD analysis also showed that the DIS performance depends on several design features including the depth of the wall cavity as well as the width and the thickness of the insulation layers.
Recent developments in metamaterials made daytime radiative cooling possible, by engineering material surfaces to achieve high emissivity in the 8–13 μm atmospheric window and high reflectivity ...elsewhere. In this study, we demonstrated a daytime radiative cooling application using a scalable polymer-based spectrally selective metamaterial (named Radiative Cooling film (RC-film)) to passively cool a full-scale model house. When exposed under direct solar irradiation peaking 720 W/m2, the RC-film model house achieved a roof surface temperature of consistently 2–9 °C below the ambient during a continuous 72-h experiment period. Further, setting a new milestone, the indoor air temperature of the RC-film house was also consistently 2–14 °C below the ambient during the daytime. This implies that the RC-film envelope had achieved a de facto cooling effect on the indoor space without active energy consumption. Compared to a metal sheet house, the RC-film house achieved a 25–30 °C cooler roof temperature and a 4–12 °C cooler indoor temperature during the daytime. For the South wall where the most solar radiation was received, the RC-film envelope demonstrated a 60–70% heat influx reduction. The entire exposed envelope as a whole achieved an aggregated radiative cooling power ranges from 5 to 55 W/m2 during the testing days.
•A scalable metamaterial (RC-film) was used for daytime radiative cooling of a house.•All-time sub-ambient roof temperature was achieved for the RC-film covered house.•Nearly all-time sub-ambient indoor air temperature was achieved in the RC-film house.•The RC-film envelop as a whole achieved a positive net radiative cooling power.•A North-facing low-angle RC-film roof yields the best radiative cooling performance.
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•Reaction kinetics of as-synthesised thermochemical sorbents are established.•Composite's dehydration activation energy drops by 13%.•Novel building envelope achieves space heating ...and air purification.•Clean air delivery rate of 41.8 m3/h is achieved for the proposed model.•Total efficiency including heating and air purification of 81% is obtained.
In this paper, the dehydration (heat charge) and hydration (discharge) reaction kinetics of thermochemical sorbents synthesised in previous work by the author is established by using the isothermal method, with the aim of understanding their thermochemical conversion behaviour and developing reaction models for numerical simulations. The effects of temperature, reaction advancement, and vapour pressure are fully considered and employed in a thermochemical energy storage model. The derived dehydration reaction activation energies of the LiOH/LiCl@ expanded graphite (LiO2C1@EG and LiO3C1@EG) sorbents are 54.7 and 52.2 kJ/mol, respectively, which are lower than that of pure LiOH·H2O. To achieve the dual-function of space heating and air purification in an efficient manner, a novel solar building envelope combining thermochemical energy storage and photocatalysis is proposed and studied numerically based on the established reaction kinetics. Fresh air can be produced during solar harvesting. The porous wall, which is made of a composite sorbent, absorbs thermal energy to heat air near the wall and thus creates a chimney effect in the channel for continuous space heating. During discharge, the desorbed heat storage wall adsorbs the moist air and the hydration reaction enthalpy can be used again for air heating. The total efficiency including the equivalent formaldehyde degradation efficiency and the thermal efficiency is around 81% when the solar radiation is 600 W/m2. Results indicate that this passive building envelope can achieve a higher heat harvesting and utilisation efficiency in a more compact space compared to previous studies. Moreover, the influence of radiation intensity on air purification and thermal performance is investigated. The present work provides new insights and promotes the integration of passive solar building envelopes and thermochemical energy storage.
•Ultra-lightweight concrete (ULWC) combines insulating and structural properties.•This paper assesses the energy and comfort performance of ULWC constructions.•ISO 13786 characterization methods are ...not well suited for such innovative materials.•A dynamic simulation strategy in EnergyPlus was developed and validated.•ULWC is a suitable construction type in cases with intermittent building operation.
Ultra-lightweight concrete (ULWC) was recently introduced as a novel building material that combines moderate thermal insulation properties with load-bearing capacity. Its intended use as monolithic building envelope brings new opportunities in building physics, by merging characteristics of both heavyweight and lightweight construction types. This paper investigates the potential of ULWC building envelopes in terms of energy efficiency and thermal comfort. The dynamic thermal characteristics of a monolithic structure of ULWC were first compared to more conventional constructions using EN-ISO-13786 calculation methods. The main contribution of this article lies in the subsequent development and application of a simulation strategy for predicting the energy and comfort performance of ULWC on the whole-building level. The quality of the simulations in EnergyPlus was first ensured in an analytical validation study, and then applied to assess the performance of ULWC for commercial and residential case studies in the Netherlands. Results show that ULWC constructions are comparable to heavyweight buildings in long-term behaviour, whereas they resemble the performance of lightweight building envelopes for short-term heating periods. ULWC can therefore be a suitable construction type in buildings with intermittent operation, but in other cases it can get outperformed by conventional constructions with low or high thermal mass.
Building envelope parameters and geometric configurations can considerably influence the building energy performance. However, determining the best trade-offs of different building shape and envelope ...configurations to yield near-optimal design alternatives with respect to their energy performance is not a straight-forward task. Consequently, different methods have been utilized to optimize building envelope parameters and geometric configurations to achieve better energy performance. The objective of this paper is to provide an extensive review of the optimization methods and their application in energy-efficient architectural building design to better identify the potentials and applicability of different optimization methods. This paper reviews the optimization research, where building envelope parameters and geometric configurations are considered remarkably as the optimization independent variable(s) and building energy consumption/demand is included as an objective in the optimization process. The associated derivative-free and derivative-based optimization methods and their application in energy-efficient building design are included in this review. In addition, decision-making approaches are discussed for multi-objective optimizations. Current optimization tools are demonstrated. Finally, crucial considerations, including limitations and suggestions for the related future studies are concluded.
•Building envelope and geometric configurations impact building energy performance.•Derivative-free/derivative-based optimizations are widely used in building design.•Both problem and optimization method features yield the appropriate optimization.•Automation/interoperability of the tools are indispensable parts of the platform.
Building envelope is a key element in providing adequate energy and thermal comfort performance to buildings. In this regard, improvement solutions are implemented in recent studies that focus on new ...techniques and methods. The main techniques adopted in this context are discussed to identify modern and effective methods with a particular focus on phase change materials (PCMs). Incorporating PCMs with building construction materials is a booming technology, owing to their enhancement potential of storing and releasing heat during phase transition. This work highlights the importance of PCMs in building envelope, focusing on roof and external wall applications. PCM types, general and desired properties and application area are presented and discussed. Influential parameters, incorporation techniques and methods, main numerical tools, and modelling equations are used to describe the thermal behaviour of PCM. A comprehensive assessment on the basis of recent studies has been conducted to point out the potential of PCM with the most appropriate techniques under different locations. The main findings of PCM thermal performance have been described, considering the cooling/heating load reduction, energy-saving and thermal comfort gained along with several research hiatuses for future studies.
•PCMs incorporated building envelope related research in recent years are reviewed.•The advantages of PCM in buildings based on energy-saving and thermal comfort are discussed.•PCM types, properties, influential parameters, incorporation techniques and modelling are presented and analysed.•A comprehensive assessment of PCM incorporated construction materials is highlighted.•Main findings in the literature and research gaps are identified.
•Building integration of solar thermal is defined by its building-related functions.•BIST has been 40% less expensive than conventional solar thermal installations.•Suitable measurements to ...characterize BIST products are presented.•Methods for better integration into the building process are described.
Solar building envelopes are attracting increasing interest. Building-integrated solar thermal (BIST) systems are one of the subgroups of solar building envelopes. This paper summarizes the most important contributions of recent years and extends them. First, BIST elements are defined and available BIST elements are presented. Then, the general functions which BIST systems can provide are presented and the conflict between the constant U and g values of simple planning software and the variable g and U values of BIST elements is discussed. Measurements to characterize BIST elements are presented as well as a design parameter space in which the current BIST elements are located and which can be used when developing innovative new components. Methods to evaluate and compare BIST technologies are presented. The substantial cost savings which were achieved in three building projects between 2002 and 2009 are discussed. Roles within the building process are presented, as well as the general methods and challenges for economic BIST calculations and one economic calculation as an example. Based on existing building processes, a vision for future BIST building process integration is presented. Simple BIST models, which need no programming, are provided with easy-to-use equations. The challenges of standards and regulations are outlined and future research topics are presented. This paper summarizes important recent contributions to BIST research as a basis for future progress in building-integrated solar thermal systems. Instead of aiming to cover all recent BIST developments, the focus is on BIST research findings which are relevant for cost reduction of BIST components and therefore necessary for the economic success of BIST technology. These are discussed, together with proposals for future research.
•Quantitative ITT methodology to obtain the thermal bridge heat flow rate in buildings presented.•Methodology suitable for determining Ψ-values of any existing building envelope.•Excellent agreement ...found while testing the methodology in the hot box device.•Relative deviation in Ψ-values from ITT and from hot box measurements varied from −5% to −36%.
A key aspect in assessing the thermal standard of building envelopes is the quantification of the heat loss though thermal bridging, which can be expressed in terms of the linear thermal transmittance Ψ. Values of Ψ may be obtained from tabulated values for standard building details, from numerical modelling or from measurement. Where the internal structure of the building envelope is unknown, which is very often the case, measurement is the only option. This study shows how the infrared thermography technique (ITT) can be used as a non-invasive and easy-to-use method to provide quantitative measures of the actual thermal bridging performance. The novelty of this approach includes evaluation of the actual heat flow rate caused by thermal bridge qTB and Ψ-value by means of the ITT solely, without any supporting methods. Another important aspect of the methodology is that it accounts for the correlation between the surface temperature and the convective and radiative heat transfer coefficients. Values for these coefficients are assessed for the whole range of the surface temperatures recorded on the thermogram resulting in improve accuracy. The qTB and Ψ-value calculated using the presented methodology fully mirrors the real thermal performance of the thermal bridge. The methodology has been tested under laboratory conditions in a steady state in a hot box with excellent agreement.
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