Low Energy Buildings Research Articles

Summer thermal and energy performances assessment of a modular hydronic thermal barrier wall for ultra-low energy buildings - A field experimental study

Hydronic thermal barriers with ultra-low carbon emission attributes are progressively gaining prominence in the competition of thermal insulation solutions for opaque envelopes of low-energy buildings due to their excellent thermal performance and low-grade energy utilization potential. This paper introduces a novel approach involving a modular hydronic thermal barrier wall (MHTB) that incorporates preset pipe cavities and replaceable filling material. This proposition seeks to address the challenges confronted by conventional hydronic thermal barrier walls (CHTBs), specifically in terms of internal heat transfer enhancement and rapid assembly/dismantling. On-site thermal performance tests and energy-saving evaluations were conducted in summer conditions based on three scaled-down rooms with MHTB, CHTB and a conventional external insulation wall as the south walls. The results showed that the MHTB could significantly reduce heat passing through the south wall in summer, resulting in a decreased cooling load attributed to the wall and subsequently lowering indoor temperatures. At a charging temperature of 17.0 °C, the MHTB exhibited a reduction of 11.3 °C in interior surface temperature compared to the conventional external insulation wall, accompanied by a corresponding increase of 2.76 kWh·m−2 in cumulative heat flux. In addition, the MHTB could effectively mitigate inhomogeneous heat transfer within the wall, enhancing the overall heat transfer effect. Across the four investigated conditions, the MHTB with a steel grit-sand mixture as the filling material demonstrated an approximate 4.7% increase in cumulative heat flux and a 12.2% enhancement in cumulative cooling quantity compared to the CHTB. Overall, the findings substantiated the efficacy of the MHTB system and offered a crucial point of reference for advancing research in optimizing the performance and modular construction of hydronic thermal barrier walls.

Comparison of the embodied and operating energy in agricultural greenhouses and in residential buildings

The increase of the energy efficiency in buildings and greenhouses is important for reducing the use of fossil fuels and the emissions of greenhouse gases. Energy efficiency evaluation requires the consideration of both the embodied and the operational energy. Many estimations regarding the embodied and the operational energy in various types of buildings have been reported so far. However, studies regarding the embodied energy in agricultural greenhouses are rare while there are many estimations regarding their operational energy. The goal of our study is the comparison of the embodied and the operational energy in residential buildings and in agricultural greenhouses. The embodied and operational energies are compared in greenhouses as well as in low-energy and in conventional residential buildings. Our results indicate that the ratio of embodied energy to life-cycle energy in low-energy residential buildings and in nearly-zero energy buildings varies in the range at 36% to 83% that is significantly higher than the ratio in conventional residential buildings which is in the range of 6% to 20%. The ratio of embodied energy to life-cycle energy in agricultural greenhouses, at 0.86% - 70.41%, varies significantly depending on many parameters. The importance of carbon emissions related to embodied energy in low-energy buildings, in net-zero energy buildings and in agricultural greenhouses is highlighted. Our work could be useful to policy makers who are willing to accelerate the green transition to a low carbon economy in the coming decades.

A coupled analysis on human thermal comfort and the indoor non-uniform thermal environment through human exergy and CFD model

The importance of human thermal comfort evaluation lies of the development of healthy buildings as well as low-carbon buildings. In recent years, the applications of the second law of thermodynamics to thermal comfort offered a new perspective and this study, for the first time, an integrated human exergy model and the indoor CFD model for a coupled analysis is put forward, which supplements a critical link between human and building environment. In this paper, a predefined office model is investigated to improve the efficiency and thermal comfort of occupants. Based on the human exergy model, the parameters of metabolism, respiration, evaporation, convection, radiation, skin, and core heat storage terms are optimized. Additionally, the effects of gender, age, and clothing thermal resistance on the exergy model values are also separately explored. Finally, the optimized human exergy model is combined with computational fluid dynamics (CFD) to calculate, under different air supply conditions, the distribution of exergy consumption values in the predefined room model. The results show that the factors of gender, age, and thermal resistance of clothing have some influences on human exergy consumption, while the above factors do not have a significant enough influence on the model in the thermal comfort interval. Moreover, the combination of the human exergy model and CFD can offer some suitable air supply conditions for the development of indoor thermal comfort and work efficiency. This study presented a new tool that bridges human thermal sensation and indoor thermal environment.

Cost-optimal analysis of energy efficient hvac solution-sets for low-energy apartment buildings

Cost-optimal analysis of energy efficient hvac solution-sets for low-energy apartment buildings

Multiscale ab-initio modeling and experiment of nano-CaCO3 and fiber synergy on toughening low-carbon geopolymer composites

Although the geopolymer is generally regarded as a solution to low-carbon building materials, the intrinsic high brittleness greatly limits its further engineering practices. Here, we performed multi-scale ab-initio modeling and experiment on synergistic effect of nano- calcium carbonate (NCC) and polyethylene fiber (PEF) on toughening mechanisms of geopolymer composites for the first time. Results showed that NCC significantly improved micro-scale geopolymer gels aggregation on the surface of PEF through the nano-scale calcium (Ca)-triggered electrostatic attractions and high bonding between N/CASH-polyethylene. Due to micro-scale gel aggregation, meso fiber dispersion, geopolymers with 12 mm + 6 mm PE fiber + 1% NCC showed the best synergistic effect on macro- scale bending toughness and multiple cracking characteristics. The relationship of fiber reinforcing index-toughness, toughness-crack amount and toughness-crack fractal dimension tracked good linear, natural log and exponential function, respectively. The crack number and crack fractal dimension are applicable visible indicators of the bending toughness of PEF reinforced GCs.

Spectrally selective nanoparticle-enhanced phase change materials: A study on data-driven optical/thermal properties and application of energy-saving glazing under different climatic conditions

The optical and thermal performances of energy-saving glazing require improvement to reduce peak thermal load and increase solar energy conversion and management efficiency. Herein, it is indispensable to develop novel composite materials that designate the ability to achieve multifunction by thermal load migration as well as radiation transmittance modulation. This study developed a nanoparticle-enhanced phase change material (NEPCM) with spectrally selective and phase change functions. A data-driven algorithm is first developed to evaluate the solar-weighted absorption fraction, integrated irradiance, and spectral irradiance for the considered nanoparticles. The base fluids, nanoparticle diameter, concentrations, and proportions are taken into account in the program, and adjustments to the properties of NEPCM can be easily made. The NEPCM properties exhibit a high blocking performance of near-infrared solar radiation by 30.9%, while keeping visible transmittance at 51.8% using ATO-Al2O3 NEPCM. Furthermore, the photothermal conversion performance of a NEPCM-filled energy-saving prototype window is explored, which yields a heat absorption rate of up to 0.27 °C/min when the solar irradiance is 800 W/m2. In addition, the energy consumption of transparent envelopes with NEPCM filler in a full-scale building is investigated. The results show that NEPCM regulated glazing potentially provides annual heating energy-saving from 5.1 to 41.7 kWh·m−2·year−1 in three representative climatic conditions in different global locations. Outcomes on the spectrally selective capabilities of the energy-saving window provide ideas for advancing the development of low-carbon transparent building envelopes.

Thermo-mechanical behavior of cementitious material with partial replacement of Class-II biochar with Accelerated Carbonation Curing (ACC)

Using carbon-neutral materials is a promising way to mitigate the CO2 emissions of the construction industry. Biochar prepared from agricultural waste has a great potential to sequester CO2. This study demonstrates a new sustainable method for preparing biochar from rice husk having class II category as it has less than 60% carbon content and is derived at a temperature of 500 ℃. The prepared biochar was partially replaced in cement paste and cured under a CO2 environment for 7 and 28 d. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) showed that the replacement of biochar promoted cement hydration and mechanical properties. Addition of 3 wt% and 5 wt% biochar increased the compressive strength of the composite by 34.7% and 35.6%, respectively. However, a further addition to 10 wt% biochar reduced the compressive strength by 16.7%. Replacement of up to 5 wt% biochar successfully promoted the carbonation with 10.2% CO2 uptake after 28 d of accelerated CO2 curing. Carbonation of biochar-cement composite substantially improves thermal conductivity, specific heat, and thermal diffusivity compared to control samples at 7 and 28 d. Field Emission Scanning Electron Microscope (FESEM) analysis revealed the numerous cement hydrates which enhance the bond strength after carbonation, and the carbonate densifies the microstructure, considerably enhancing mechanical strength and carbon binding capability. Biochar-cement composites with CO2 could be innovative low-carbon building materials for sustainable engineering applications.

Performance Evaluation of High-Rise Buildings Integrated with Colored Radiative Cooling Walls in a Hot and Humid Region

Radiative sky cooling is an appealing form of heat exchange between terrestrial objects and outer space through thermal radiation, which is attracting worldwide interest due to its nature as passive cooling, that is, cooling without consuming energy. Due to a recent breakthrough in material science, sub-ambient daytime radiative sky cooling has been effectively achieved, which has significantly stimulated research interest in this field. In view of the numerous radiative coolers being reported as having excellent spectral properties and cooling ability under sunlight, integrating these superb cooling materials into building skins is a promising route to implementing radiative sky cooling technology. To this end, this study deploys state-of-the-art colored radiative cooling coatings as a new retrofitting strategy for building walls, and then conducts a comprehensive performance evaluation by considering a high-rise building situated in the hot-humid city of Hong Kong. Potential benefits of implementing differently colored cooling wall strategies, including their performance regarding thermal insulation, energy savings, economic viability, and environmental sustainability, were thoroughly investigated. The obtained results elucidate that for the utilization of the porous P(VdF-HFP)-based bilayer wall, relative to the monolayer, the frequency of the wall temperature exceeding the surrounding environment on an annual basis can be further reduced by up to 4.8%, and the yearly savings in cooling electricity vary from 855.6 to 3105.6 kWh (0.4–1.5%) with an average of 1692.4 kWh. Besides this, the yearly savings in net electricity cost vary from 1412.5 to 5127.3 HKD and the reduction in carbon emissions ranges from 1544.4 to 5606.1 kg with an average of 3055.0 kg. In addition, discussions of the combination of the super-cool roof strategy with blue porous polymer-based cooling walls reveal that the achievable savings in terms of energy costs and reductions in carbon emissions are 1.6 and 2.2 times more than either the application of the super-cool roof or porous polymer bilayer walls alone, respectively. This research offers new understandings of the deployment of colored cooling coatings on vertical building façades in hot and humid regions, which can considerably facilitate the realization of low-energy buildings in a passive approach for stakeholders.

Effects of Building Materials on Building Thermal Load in Malaysian Institutional Library

Green building, net-zero energy building, low energy building, and sustainable building are the common terms being used in the building industry nowadays, with the primary aim to produce buildings with low energy and low carbon dioxide (CO2) emissions. Different types of building materials can have significant implications for energy efficiency, especially in the warming climate. The energy crisis, future global warming, and climate change can be mitigated by choosing the right building materials, which will also lower the building's energy consumption and carbon dioxide emissions. This paper presents the effects of different building materials on the cooling capacity and cooling energy consumption of a building for four (4) different climate change weather data, namely, the present time scenario, the 2020s, 2050s, and 2080s time scenario using TRNSYS simulation software. The main library of a university in Petaling Jaya, Malaysia, was chosen as the case study. Three (3) types of building materials were studied, namely, Type 1 (brick walls with single-glazed windows), Type 2 (foam insulation cavity walls with double-glazed windows), and Type 3 (air gap cavity walls with double-glazed windows). The simulation results showed that the Type 2 building materials could reduce the yearly cooling energy consumption by 14.5%, compared with the current building materials (brick walls with single-glazed windows). The Type 3 building materials (air gap cavity walls with double-glazed windows) with the lower installation were wound to reduce the yearly cooling energy consumption by 9% compared with the Type 1 building materials. For architects, designers, politicians, and library administrators, the research's conclusions have immediate practical implications that will help them make decisions and implement energy-saving plans. In the end, this research helps libraries in Malaysia remain sustainable and resilient in the face of global warming and the energy crisis.

AI and Big Data-Empowered Low-Carbon Buildings: Challenges and Prospects

Reducing carbon emissions from buildings is crucial to achieving global carbon neutrality targets. However, the building sector faces various challenges, such as low accuracy in forecasting, lacking effective methods of measurements and accounting in terms of energy consumption and emission reduction. Fortunately, relevant studies demonstrate that artificial intelligence (AI) and big data technologies could significantly increase the accuracy of building energy consumption prediction. The results can be used for building operation management to achieve emission reduction goals. For this, in this article, we overview the existing state-of-the-art methods on AI and big data for building energy conservation and low carbon. The capacity of machine learning technologies in the fields of energy conservation and environmental protection is also highlighted. In addition, we summarize the existing challenges and prospects for reference, e.g., in the future, accurate prediction of building energy consumption and reasonable planning of human behavior in buildings will become promising research directions.

Experimental investigation on thermal performance of an actively cooled light shelf

Although the energy efficiency of light shelves has been studied, the thermal effects due to reflected solar radiation from light shelves have yet to be adequately investigated in previous research. The key research questions are whether this radiation results in additional heat load in buildings in tropical climates and how this can be reduced. In this work, the performance of an exterior aluminium light shelf is studied experimentally using a scaled prototype. The total amount of heat transmitted by the light shelf is about 40 W/ m2, which is close to the average thermal transmission of the envelope of a low-energy building. Experimental data analysis has revealed two components of the radiant heat transmitted by a light shelf: a) a direct instantaneous reflection of infrared radiations and b) secondary long-wave radiation resulting from the heating up of the light shelf material. The secondary radiation is a significant part of the overall heat transmitted by the light shelf. The light shelf was actively cooled by circulating water through hydronic radiant capillary mat tubes to reduce this component, and the radiant heat transmitted was measured. These experiments showed that an actively cooled light shelf could considerably reduce the secondary radiant heat transmitted through a clerestory window. A significant decrease in secondary heat transmission within a range of 3.8–5.9 W/m2 was observed when compared to an identical light shelf that was not cooled. This reduction is about 10% of the total heat transmitted by the light shelf.

Research on the Design of Carbon-Neutralized Building in Rural China: A Case Study of “Impression of Yucun”

Energy conservation and emission reduction in rural buildings is essential to China’s response to climate change. Within the context of China’s ‘dual carbon’ initiative and the overarching goal of a ‘zero carbon countryside’, the first rural carbon-neutral building in China—‘Impression of Yucun’ was established in Anji County, Zhejiang Province. Accordingly, this study investigates building carbon-neutral design, calculating and analyzing the carbon emissions and offsets facilitated by carbon neutrality technology throughout the buildings’ life cycle. In addition, the comprehensive benefits of the buildings are evaluated from both technical and economic perspectives. The implementation pathway for rural carbon-neutral buildings is also explored. The results demonstrate that through the judicious application of carbon neutrality technology design, the inherent carbon emissions of the buildings amount to 120.91 t and the energy consumption during the operational phase of the building is 64,284.4 kWh/a, correlating to carbon emissions of 33.72 t. The case can theoretically reduce carbon emissions by 65.64 tCO2 annually by implementing carbon offset measures. Considering photovoltaic cell decay, the building can achieve a carbon-neutral state for the first time in the fifth year of operation, with a net carbon emission of −5.58 tCO2. Simultaneously, the investment in photovoltaic systems can be recouped between the seventh and ninth years of operation. This study can offer methodological reference and data support for designing and evaluating carbon-neutral buildings.

Net-Zero Energy Consumption Building in China: An Overview of Building-Integrated Photovoltaic Case and Initiative toward Sustainable Future Development

Carbon-neutral strategies have become the focus of international attention, and many countries around the world have adopted building-integrated photovoltaic (BIPV) technologies to achieve low-carbon building operation by utilizing power-generating building materials to generate energy in buildings. The purpose of this study is to review the basic status of the development of building-integrated photovoltaic (BIPV) technologies in China, to identify and analyze the existing problems and challenges, and to propose optimization strategies and methods so as to better promote the overall development of green buildings and net-zero energy consumption buildings in China and the world. Primarily, the research area of BIPV is focused on the Chinese region through a case study approach. Subsequently, it elaborates on the theoretical basis of zero-net energy buildings and BIPV as well as the current status of the construction of the world’s low-carbon building standard system, and it summarizes the annual electricity generation of zero carbon buildings adopting BIPV in some European countries. Then, the article further quantitatively and comprehensively analyzes six successful BIPV application cases in China, and it graphically and visually evaluates and demonstrates the average annual net-zero energy performance percentage of the application cases by using the EPI evaluation and measurement tool. At the same time, based on the results of the above assessment, the challenges facing the development of BIPV in China are summarized, and specific incentives for new BIPVs are proposed to address the challenges as well as strategic approaches to optimize BIPVs that are applicable to China as well as Europe and the US. Ultimately, it is concluded that several classic BIPV building cases have achieved essentially 100% net-zero energy operation and maintenance with significant reductions in CO2 emissions and savings of tens of thousands of tonnes of coal consumption. This shows that BIPV technology is gradually developing and maturing in China, and there are great advantages and incremental development space for promoting BIPV in China in the future. The application and promotion strategy of its results in China is also applicable to other countries in the world. It is hoped that based on this experience, countries around the world will implement the “carbon neutral” strategy and zero-net energy consumption development more efficiently and with higher quality so as to realize a greener and cleaner future.

Wood sawdust waste-derived nano-cellulose as a versatile reinforcing agent for nano silica cement composites: a systematic study on its characterization and performance

The development of sustainable construction materials is a pressing concern for researchers worldwide, as the cement industry is a major contributor to environmental degradation. The incorporation of nano-materials with cement composites has emerged as a promising solution to sustainable materials production. In this study, the effect of the addition of nano cellulose produced from wood sawdust waste on the performance of cement-based nano-silica composite was investigated. The nano-materials were incorporated at low concentrations and in gel form to eliminate the need for any advanced dispersion techniques. The results indicated that the addition of even low concentrations of nano cellulose significantly enhanced the compactness and mechanical properties of the cement matrix. The crack propagation was observed to be arrested with better adherence to the cement hydration product, which resulted from the presence of nano-silica. The nano cellulose fibers were found to bridge the calcium silicate hydrate products, arresting the propagation of cracks at their initial condition. The high pozzolanic reactivity of nano-silica ensured a minimal amount of calcium hydroxide, which is a significant contributor to the carbon footprint of cement production. Overall, the findings of this study suggest that the incorporation of nano cellulose from wood sawdust waste with cement-based nano-silica composite can lead to the development of sustainable and high-performance building materials with improved mechanical properties and reduced environmental impact.

Thermodynamic performance analysis of air-to-air hybrid heat recovery unit driven by pump combined with booster

The air conditioning energy consumption for fresh air handling in buildings increases yearly, especially in low energy buildings. This energy consumption can be greatly reduced when exhaust air is recovered for preheating or precooling fresh air. Then, significant savings in the total energy consumption in buildings will be achieved, which in turn helps achieve the carbon peak in the building field. In this paper, a booster/pump coupled energy recovery ventilator is proposed for energy recovery in buildings. The system performance, which depends on the loop number and combination strategies were analyzed and compared through model simulations. Results indicate that the heat transfer rate of different coupling systems increases with the temperature difference. In summer, the pump/booster driven dual-loop system has the highest average temperature effectiveness of 47.3% and average heat transfer rate of 4.97 kW. The booster/booster-driven dual-loop system has the highest average heat transfer rate of 5.07 kW and average temperature effectiveness of 47.1%. The average temperature effectiveness of the pump/booster/booster driven triple-loop system reaches up to 45% and average heat transfer rate of 4.73 kW. The booster/booster/booster-driven triple-loop system has the highest average heat transfer rate of 4.82 kW and average temperature effectiveness of 44.7%. In winter, the maximum average heat transfer rate and temperature effectiveness of the pump/booster driven dual-loop system are 8.54 kW and 44.44%, respectively. The maximum average heat transfer rate and temperature effectiveness of the pump/booster/booster driven triple-loop system are 7.90 kW and 41.5%, respectively. Throughout the year, the best coupling scheme of the dual-loop system is the pump/booster driven dual-loop system, and its average heat transfer rate and temperature effectiveness are 6.755 kW and 45.85%, respectively. The best coupling scheme of the triple-loop system is the pump/booster/booster-driven triple-loop system, and its average heat transfer rate and temperature effectiveness are 6.315 kW and 43.25%, respectively.

On the effectiveness of passive controls for summer thermal comfort in highly insulated dwellings

ABSTRACT Among environmental controls, solar shading and ventilative cooling are widely considered as key passive strategies for limiting the overheating risks in buildings. While their application is encouraged through Energy Performance of Buildings Directive regulations, several studies have shown that summer thermal comfort in heating-dominate temperate climates still requires deeper investigation, particularly in low-energy residential buildings. Based on qualitative and quantitative data collected through surveys and monitoring in 147 highly insulated houses in Wallonia (Belgium), this paper gives an overview of the implemented passive strategies and discusses their effectiveness. Statistical tests are conducted to evaluate their impact on both perceived and measured indoor conditions. In general, the results highlight a limited impact of the implemented strategies, questioning their proper operation. Operational modes for environmental controls thus appear crucial, and should better respond to occupants’ needs, preferences and control opportunities. At a more general level, the study calls for a better understanding of the barriers inhibiting successful integration and operation of environmental controls, in order to effectively reduce overheating risks in residential buildings and limit future diffusion of active cooling systems with their induced environmental impacts.

Energy savings and thermal comfort in a zero energy office building with fans in Singapore

Elevated air movement produced by fans can offset air-conditioning energy requirements by allowing temperature setpoints to be raised without compromising thermal comfort. These advantages are even greater in hot and humid climates that inherently have large and sustained indoor cooling requirements. Few studies have assessed the in-situ benefits of fans in actual buildings. We installed ceiling and desk fans into a Zero Energy office building (675 m2) in Singapore. Across an 11-week period, 35 occupants alternated between two conditions (no fan vs. fan): 24 °C setpoint with fans off, and 26.5 °C setpoint with fans on. When the temperature setpoint was raised and elevated air movement was provided, a 32% energy reduction was obtained. The energy savings accrued without any negative impacts occurring on thermal satisfaction. Overcooling caused by thermal preference to slightly warmer and warmer conditions was substantially reduced from 33 to 9%. No changes in perceived air-staleness or self-reported alertness and ability to concentrate occurred either, indicating parity across the no fan and fan conditions. Although occupants primarily relied on ceiling fans at the 26.5 °C setpoint, they were by default on at the beginning of each day, giving less incentive to use the desk fans. Our study took place in a high-performance Zero Energy building, whereby thermal dissatisfaction was already low (7%). Therefore, notable changes did not occur, but significant improvements to thermal comfort could still occur in buildings that are unable to maintain high levels of thermal satisfaction.

Study of the possibility of using vacuum insulation panels in building construction in comparison with conventional insulators

The use of super insulating materials in the construction industry, including vacuum insulation, closely corresponds to the ever-increasing requirements for the construction of low-energy and passive buildings. Their indisputable advantage is their excellent thermal insulation properties at low thickness compared to conventional thermal insulation materials. However, there are also many risks associated with the experience and practice of the personnel involved in the application of these materials to structures. The paper focuses on the overall comparison of the possible use of vacuum insulation panels in modern building structures in terms of possible design solutions and achieved properties. The paper presents the results of selected case studies of the optimal use of vacuum insulation panels (VIP) in the construction industry, which are focused on different areas of building structures, specifically on the detail of the transition of the terrace and the adjacent floor, as well as on the solution of the filling of openings - doors. Based on the results of the studies carried out, it can be concluded that, provided that all procedures for maintaining the VIP properties are followed in the implementation of these materials in structures, vacuum insulations represent a more suitable solution for structural details in selected details (less thickness and comparable thermal insulation properties compared to conventional insulations).

Electromagnetic–Thermal Analyses of Distributed Antennas Embedded Into a Load-Bearing Wall

The importance of indoor mobile connectivity has increased during the last years, especially during the Covid-19 pandemic. In contrast, new energy-efficient buildings contain structures like low-emissive windows and multi-layered thermal insulations which all block radio signals effectively. To solve this problem with indoor connectivity, we study passive antenna systems embedded in walls of low-energy buildings. We provide analytical models of a load bearing wall along with numerical and empirical evaluations of wideband back-to-back spiral antenna system in terms of electromagnetic- and thermal insulation. The antenna systems are optimized to operate well when embedded into load bearing walls. Unit cell models of the antenna embedded load bearing wall, which are called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">signal-transmissive walls</i> in this paper, are developed to analyze their electromagnetic and thermal insulation properties. We show that our signal-transmissive wall improves the electromagnetic transmission compared to a raw load bearing wall over a wide bandwidth of 2.6-8 GHz, covering most of the cellular new radio frequency range 1, without compromising the thermal insulation capability of the wall demanded by the building regulation. Optimized antenna deployment is shown with 22 dB improvement in electromagnetic transmission through the load bearing wall.

Techno-economic and environmental evaluation on radiative sky cooling-based novel passive envelope strategies to achieve building sustainability and carbon neutrality

As the pursuit of carbon neutrality gains momentum, retrofitting high-performance buildings with novel, energy-efficient passive envelope systems has emerged as a promising pathway towards building sustainability. To this end, this study aims to propose, evaluate, and optimize such envelope systems considering varying climate patterns in China by incorporating state-of-the-art passive cooling strategies into buildings. Comprehensive techno-economic and environmental evaluations were conducted on a standard-compliant three-story typical commercial building, considering newly proposed passive approaches. The energy performance evaluation reveals that the super-cool white roof corresponds to annual cooling electricity savings of 2.5–6.1% for the entire building and 7.0–17.1% for the top floor in response to varying climate patterns. By contrast, the radiative cooling red and yellow walls exhibit cooling energy saving rates of 1.4–1.9% and 1.9–2.6%, respectively. The insulated grey clear double-glazing window can garner even greater cooling energy savings of 2.6–13.5%. It is highlighted that for the cities located in cold regions, the thermal improvement in windows offers a significantly greater opportunity for cost savings and carbon reduction compared to retrofitting roof and wall surfaces. To maximize net savings, the optimization scheme can achieve cost savings in hot-summer cities ranging from 859.1 to 1835.1 $/year, with an average of 1151.2 $/year, and from 784.4 to 1076.5 $/year, with an average of 658.8 $/year for cold cities. To minimize carbon emissions, the optimal design approach can reduce carbon emissions by 18,093.6–37,526.6 kg/year, with an average of 22,745.0 kg/year, in response to varying climate patterns. Overall, this study sheds light on the state-of-the-art passive envelope strategies that can achieve energy-efficient carbon-neutral buildings for a variety of climates in China. The optimization scheme proposed in this study provides a useful framework for designing passive envelope systems that are tailored to specific climate patterns.