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Roof Retrofitting for Enhanced Sustainability and Energy Efficiency

A recent article published in Sustainability provided a catalog of optimized and sustainable solutions based on standardization and prefabrication principles for highly energy-efficient buildings. The proposed methods apply to the prevalent roof types that are considered as the national residential building heritage.

Optimizing Roof Retrofit for Energy Efficiency
Study: Optimizing Roof Retrofit for Energy Efficiency. Image Credit: Dirk Ott/


Energy efficiency has become a crucial strategy for reducing carbon emissions, lowering energy use, and improving building performance, aligning with sustainable construction principles. This approach is vital for achieving the Sustainable Development Goals set by the United Nations, particularly through the renovation of building stocks to enhance their energy efficiency.

Various interventions have been suggested to transform existing structures into high-performance energy buildings. These include upgrading the building envelope—such as roofs, walls, and windows—along with enhancements to lighting systems and thermal energy production and distribution.

Although innovative simulation tools for energy modeling in both new and existing buildings have been developed, these tools and interventions often overlook the use of standardized, prefabricated insulation solutions and do not provide cost estimates. Additionally, current research on building renovations rarely evaluates the environmental sustainability of these energy efficiency measures.

Therefore, this study focuses on elevating the energy efficiency of residential buildings nationwide. It emphasizes the construction and renovation of buildings in compliance with energy transition regulations, aiming to integrate both economic and environmental sustainability into building practices.


This study was carried out as part of a national program at the University of Rome and identified common construction types and those most likely to benefit from energy retrofit interventions, specifically those predating existing energy efficiency regulations. Accordingly, the researchers developed an abacus containing the most representative stratification and construction era classes. This tool included all elements related to building envelope closures, such as flat and sloped roofs.

The researchers then created a standardized catalog of optimized buildings and retrofit systems for roofs. They assessed various insulation materials available on the market, comparing them based on energy performance, environmental impact, cost, and insulation effectiveness in both winter and summer conditions. From this comprehensive analysis, 21 top-performing insulation solutions with minimal environmental impact were selected.

To determine the appropriate insulation thickness for each solution, simulations were conducted using certified Building Information Modeling (BIM) energy software, which allowed for the evaluation of different insulation scenarios. These selected insulation solutions were then matched to the types of roofing described in the Abacus of Existing Upper Horizontal Closures (UHCs), which typify the residential building heritage.

The applicability of the proposed insulation solutions was determined by verifying compliance with common criteria for all building components. These criteria included the proportion of disassembly and the content of recovered/recycled materials, aiming to minimize raw material use and enhance waste valorization from the design phase through to demolition.

Results and Discussion

The research concluded with the creation of an optimized technological solutions diagram tailored to specific climatic, geometric, and performance criteria. Primarily selected for their prefabrication capabilities, these solutions offer a practical guide for stakeholders in the residential real estate sector looking to implement energy efficiency interventions. Additionally, these solutions include a significant proportion of recycled content, thereby aligning with prevailing environmental standards. This approach not only enhances energy efficiency but also promotes sustainability by minimizing waste and encouraging material reuse.

After identifying suitable insulation solutions, performance data for each option across all UHCs in the national residential building stock were compiled through simulations. This data contributed to the creation of an abacus featuring the most efficient standardized retrofit solutions. This tool enabled the development and definition of performance sheets, which outline a wide array of solutions for renovating existing roof structures, including estimates of construction costs.

The performance sheets allow for the immediate identification of the most appropriate system for different climatic zones. These efforts led to the creation of a matrix detailing the most common opaque closure configurations in the national residential building stock. Additionally, this matrix includes a link that provides access to a summary of the simulation results detailed in the respective performance sheet.

The research demonstrated the effectiveness of the proposed methodology in enhancing energy efficiency, with targeted interventions improving the steady-state thermal transmittance of UHCs by over 66 % on average. This outcome provides guidance for designers to adopt more efficient, prefabricated, and sustainable standardized solutions for the national residential building stock.

However, the study has limitations, primarily the lack of evaluation of maintenance costs for the proposed thermal insulation solutions. Additionally, it focused on the most commonly found roofing types, potentially overlooking other variations. Moving forward, the researchers plan to expand their scope to include all building envelope closures, such as vertical perimeter walls, to ensure a comprehensive evaluation of energy efficiency.


Overall, this study can guide the stakeholders in selecting suitable solutions for energy efficiency interventions. Performance data compiled into accessible sheets can assist them in identifying the appropriate options based on climatic zones, construction era, and building type, ultimately contributing to enhanced energy efficiency outcomes.

Additionally, the matrix developed during the study serves as an essential tool for identifying the most suitable retrofit solutions for specific types of UHCs. This matrix can form the basis of future advanced tools designed to facilitate energy efficiency in residential buildings during renovation processes.

Journal Reference

Pennacchia, E., Romeo, C., & Zylka, C. (2024). Towards High-Efficiency Buildings for Sustainable Energy Transition: Standardized Prefabricated Solutions for Roof Retrofitting. Sustainability16(9), 3850–3850.

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Article Revisions

  • May 17 2024 - Title changed from "Optimizing Roof Retrofit for Energy Efficiency" to "Roof Retrofitting for Enhanced Sustainability and Energy Efficiency"
Nidhi Dhull

Written by

Nidhi Dhull

Nidhi Dhull is a freelance scientific writer, editor, and reviewer with a PhD in Physics. Nidhi has an extensive research experience in material sciences. Her research has been mainly focused on biosensing applications of thin films. During her Ph.D., she developed a noninvasive immunosensor for cortisol hormone and a paper-based biosensor for E. coli bacteria. Her works have been published in reputed journals of publishers like Elsevier and Taylor & Francis. She has also made a significant contribution to some pending patents.  


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