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Energy Efficiency and Energy Performance in Buildings—2nd Edition
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Energy Efficiency and Energy Performance in Buildings—2nd Edition

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "G: Energy and Buildings".

Deadline for manuscript submissions: 30 June 2026 | Viewed by 5563

Special Issue Editor

Prof. Dr. Moncef Krarti

E-Mail Website
Guest Editor
Building Systems Program, Civil, Environmental and Architectural Engineering Department, University of Colorado Boulder, Boulder, CO 80309, USA
Interests: building energy efficiency; building-integrated renewable energy systems; optimal design and control strategies; smart building energy systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In order to achieve carbon-neutral economies, it is crucial to improve the energy efficiency performance of the built environment, as well as integrated on-site power generation from renewable energy sources. The deployment of innovative materials and technologies is crucial in order to make buildings more energy-efficient, resilient, and adaptable to our ever-changing climate. In addition, optimal design and control strategies, as well as advanced modeling approaches, are needed in order to maximize the energy performance of both new and existing buildings, especially under extreme weather conditions.

This Special Issue aims to present and disseminate the most recent advances related to the design, retrofitting, modeling, control, and energy assessment of building systems.

Topics of interest for publication include, but are not limited to, the following:

  • Optimal design and retrofitting strategies for carbon-neutral buildings;
  • Innovative materials suitable for energy-efficient buildings;
  • Highly efficient systems for heating and cooling buildings;
  • Smart and dynamic systems to enhance energy-efficient buildings;
  • Modular construction and retrofitting techniques of energy-efficient buildings;
  • Building systems that integrate on-site power generation from renewable energy sources;
  • Advanced modeling and analysis approaches for building energy systems;
  • Measurement and monitoring techniques for the energy assessment of buildings;
  • Cost–benefit analysis techniques for designing and retrofitting building energy systems.

Prof. Dr. Moncef Krarti
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • energy efficiency
  • optimal designs
  • optimal control strategies
  • new and existing buildings
  • retrofitting technologies

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Related Special Issue

Published Papers (4 papers)

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Research

28 pages, 2918 KB  
Article
Investigation of Different Feature Selection Methods for Virtual Sensors of District Heating Systems
by Haohan Sha, Zheng Xu, Junjie Gao, Hongrui Yu, Zhigang Shi, Jin Tu and Hang Qiu
Energies 2026, 19(9), 2062; https://doi.org/10.3390/en19092062 - 24 Apr 2026
Viewed by 310
Abstract
District heating systems play a critical role in urban energy supply; however, secondary networks suffer from frequent sensor failures that undermine thermal balance control. The development of virtual sensors to estimate return-water temperatures offers a promising solution to this challenge. This study investigates [...] Read more.
District heating systems play a critical role in urban energy supply; however, secondary networks suffer from frequent sensor failures that undermine thermal balance control. The development of virtual sensors to estimate return-water temperatures offers a promising solution to this challenge. This study investigates the performance of different feature selection methods for developing virtual sensors. The investigated feature selection methods include two engineering experience-based methods, one embedded method, one wrapped-based method, and two filter methods. Using operational data from a real secondary district heating network over an entire heating season, the embedded method’s performance is investigated, and an appropriate machine learning algorithm, paired with the wrapped and filter methods, is selected. For the filter methods, the paper additionally examines the differences between the rank-based and threshold-based filter implementations. The performance of the wrapped and filter methods on accuracy, computational cost, and sensitivity to data volume was compared. The results indicate that the embedded method exhibits relatively unstable performance under the engineering experience-based baselines, but the gradient tree boosting (GTB) method demonstrates better performance in both accuracy and stability. Further tests combining GTB with wrapped and filter methods revealed that both the filter and wrapped methods show an acceptable performance in terms of accuracy. The mean RMSE of both filter and wrapped methods consistently ranges from 0.75 °C to 0.8 °C when the selected feature is more than 6. However, the wrapped method exhibits a higher computational cost and is more sensitive to data volume. The training time of the wrapped method is approximately 136 times that of the fastest filter method. Considering overall performance, the combination of GTB with an HSIC indicator, employing either the rank-based selection of the top 9 features or the threshold-based feature selection, is recommended. These findings provide methodological guidance for the development of virtual sensors in district heating systems. Full article
(This article belongs to the Special Issue Energy Efficiency and Energy Performance in Buildings—2nd Edition)
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40 pages, 4463 KB  
Article
Driver–Pathway Analysis of EUI in Historic Buildings: Rank Fusion and Rolling Validation
by Chen Liu, Fuying Liu and Qi Zhao
Energies 2026, 19(7), 1795; https://doi.org/10.3390/en19071795 - 7 Apr 2026
Viewed by 491
Abstract
Historic buildings often exhibit high energy use intensity (EUI), while conservation constraints limit envelope retrofits, making it difficult to identify robust and actionable operational predictors. Using four in-use historic buildings in Shenyang, China, this study presents a pilot methodological demonstration with a controlled-comparability [...] Read more.
Historic buildings often exhibit high energy use intensity (EUI), while conservation constraints limit envelope retrofits, making it difficult to identify robust and actionable operational predictors. Using four in-use historic buildings in Shenyang, China, this study presents a pilot methodological demonstration with a controlled-comparability workflow consisting of two linked layers: (i) a Driver layer of intervenable operational variables and (ii) a Pathway layer of calibrated EnergyPlus heat-balance terms for physics-informed interpretation. Three importance approaches (Spearman, wrapper RFE with XGBoost, and Random Forest) are compared; rankings are fused via reciprocal rank fusion, and stability is tested using cross-period rolling validation across Top-K feature sets. After similarity screening, EUI variation is better explained by operational predictors and the corresponding simulated loss channels than by macro-scale structural heterogeneity. Infiltration-related indicators and envelope/infiltration loss components remain consistently prominent, while Spearman importance is less stable in the Pathway layer under seasonal switching and nonlinear coupling. A Top-10 subset provides a favorable accuracy–stability trade-off. The proposed Driver–Pathway mapping supports conservation-compatible prioritization hypotheses within a simulation-consistent interpretive framework; findings are associational and context dependent and should be validated through field measurements and experimental or quasi-experimental studies before prescriptive claims are made. Full article
(This article belongs to the Special Issue Energy Efficiency and Energy Performance in Buildings—2nd Edition)
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20 pages, 3781 KB  
Article
Thermal Impacts of Air Cavities Associated with Insulated Panels Deployed for Exterior Building Envelope Assemblies
by Utsav Dahal and Moncef Krarti
Energies 2025, 18(13), 3573; https://doi.org/10.3390/en18133573 - 7 Jul 2025
Cited by 2 | Viewed by 1635
Abstract
This paper presents a comprehensive investigation to evaluate the impacts of air cavities between existing walls and insulated panels on the overall R-values of the retrofitted building envelope systems, addressing a key challenge in exterior envelope retrofitting. The effects of several factors are [...] Read more.
This paper presents a comprehensive investigation to evaluate the impacts of air cavities between existing walls and insulated panels on the overall R-values of the retrofitted building envelope systems, addressing a key challenge in exterior envelope retrofitting. The effects of several factors are considered including the air cavity thickness (ranging from 0.1 cm to 5 cm), airflow velocity (varying between 0.1 m/s and 1 m/s), and surface emissivity (set between 0.1 and 0.9), in addition to the thickness of the insulated panels (ranging from 1 cm to 7 cm). It is found that any increase in the air cavity thickness increases the overall R-values of the building envelope assemblies when air is trapped within the sealed cavity. However, when air convection is prevalent, the overall R-value of the retrofitted walls decreases with any increase in air velocity and air cavity thickness. For sealed air cavities, the analysis results show a 9% improvement in R-value of the retrofitted walls. However, the R-value of retrofitted walls with unsealed air cavities can degrade by 76% and 81% for natural and forced air flows, respectively. Emissivity adjustment is found to be the most effective in improving the thermal performance of building envelopes with sealed air cavities, increasing the R-value of retrofitted walls by 13.6% when reduced from 0.9 to 0.1. Full article
(This article belongs to the Special Issue Energy Efficiency and Energy Performance in Buildings—2nd Edition)
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21 pages, 3571 KB  
Article
An Experimental Study of Wind-Driven Ventilation with Double Skin Facade During Transition Seasons
by Guoqing He, Zhewen Fan, Yuan Meng, Linfeng Yao and Changqing Ye
Energies 2025, 18(13), 3249; https://doi.org/10.3390/en18133249 - 21 Jun 2025
Cited by 1 | Viewed by 2575
Abstract
Double skin facade (DSF) is an energy-efficient solution for glazing facades. However, previous studies have reported inconsistent findings regarding thermal comfort in naturally ventilated DSF buildings. To examine this issue, this study evaluated airflow velocities in naturally ventilated DSF buildings during transition seasons [...] Read more.
Double skin facade (DSF) is an energy-efficient solution for glazing facades. However, previous studies have reported inconsistent findings regarding thermal comfort in naturally ventilated DSF buildings. To examine this issue, this study evaluated airflow velocities in naturally ventilated DSF buildings during transition seasons through a comparative study approach. A full-scale box-type DSF room and a traditional window-wall room were simultaneously monitored in a laboratory building under real climatic conditions, with indoor environmental parameters recorded for 10 days. Airflow sensation surveys complemented the physical measurements to evaluate perceived comfort. The results showed that the DSF room consistently exhibited lower air velocities (≤0.2 m/s) compared to the traditional room, demonstrating minimal response to wind conditions related to its small openings (opening ratio of 4.7%) and increased flow resistance from the dual-layer structure of the DSF. Under unfavorable wind conditions, the DSF room demonstrated higher ventilation rates due to the enhanced stack effect. However, this advantage had a negligible effect on the thermal comfort vote for the indoor temperature range (26 °C to 28 °C). These findings highlight the climate-dependent performance of DSFs: while advantageous for thermal comfort in cooler climates, they may lead to reduced thermal comfort in warm and hot climates due to low indoor airflow velocities. Future work could include the optimization of DSF opening configurations to enhance wind-driven ventilation while maintaining stack ventilation benefits. Full article
(This article belongs to the Special Issue Energy Efficiency and Energy Performance in Buildings—2nd Edition)
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