A new study published investigates how low-cost, easy-to-install window retrofit solutions can improve energy efficiency and cut emissions in aging residential buildings.
Study: Development and Analysis of Easy-to-Implement Green Retrofit Technologies for Windows to Reduce Heating Energy Use in Older Residential Buildings. Image Credit: Andrew Angelov/Shutterstock.com
The study, published in Sustainability, highlights how straightforward green retrofits—like secondary glazing and windproofing materials—can significantly reduce heating energy use and greenhouse gas emissions. The research also used simulations to evaluate the effectiveness of these upgrades under various building conditions.
Background
Green remodeling and retrofitting have become essential strategies for improving the sustainability of existing buildings. Retrofitting, in particular, focuses on enhancing energy efficiency and minimizing environmental impact by upgrading specific structural components.
While many retrofit strategies have been developed to help older buildings meet carbon neutrality goals, there's still a gap when it comes to affordable, high-efficiency options—especially for aging residential properties. Even with global efforts to promote retrofitting through financial incentives and public awareness campaigns, key policy gaps continue to limit widespread adoption.
This study aims to bridge that gap by focusing on practical, low-cost retrofit solutions for homes over 30 years old—particularly those occupied by low-income residents. It evaluates how simple window upgrades can make a measurable difference in energy savings and emissions reduction.
Methods
The research team developed and tested several easy-to-implement green retrofit solutions for windows in older buildings. For the secondary glazing system, they fabricated a transparent 2 mm polycarbonate panel paired with a glazing pad. For windproofing, they created a custom window sealing liner made of transparent, flexible PVC for a snug fit.
To further enhance sealing performance, they also designed a U-shaped end cap made from a combination of rigid ABS and flexible PVC, targeting the vulnerable edges of window frames.
These components were tested in a controlled lab environment using a full-sized window model (2000 mm × 2000 mm × 271 mm) simulating a standard double-pane window with a 12 mm air gap.
The team also conducted a simulation study focused on a mid-floor unit in a 68 m2 apartment within an older, government-subsidized complex. To validate the results, they analyzed utility bills from six households in a public housing community in southwestern Seoul, South Korea.
Results and Discussion
Lab tests revealed a notable improvement in performance. The overall heat-transfer coefficient dropped by 21.1 %, while airtightness improved by 45.9 %. These gains not only boost energy efficiency but also help with condensation control, noise reduction, and protection from dust, insects, and vibrations—largely due to the improved sealing features.
Simulation results using Korea’s ECO2 program showed heating energy savings ranging from 5.4 % to 16.3 %, depending on the building's age.
Real-world data echoed these findings. Utility bill analysis showed natural gas savings between 0.6 % and 31.3 % during the winter months of January to March 2024. Given the low cost of materials and installation, these upgrades offer a budget-friendly alternative to full window replacements.
A satisfaction survey of 100 tenants in public rental housing added further weight to the study. An impressive 91 % reported being satisfied overall. Residents highlighted benefits such as improved noise insulation (77 %), better airtightness (84 %), increased protection from dust and insects (79 %), and easier window and door operation (85 %). These results point to the day-to-day value of the retrofits, especially in aging public housing.
Conclusion and Future Prospects
This study offers a compelling case for low-cost, accessible window retrofit technologies as a means to enhance energy efficiency in older homes. By combining lab tests, simulations, and real-world data, the research makes a strong argument for secondary glazing and windproofing as practical, effective solutions.
Future research should look at how these upgrades perform over time and across a wider range of climates and building types. Broadening adoption of these solutions could be a key step toward improving comfort in older housing stock while advancing carbon reduction goals.
Journal Reference
Oh, S., Ahn, H., Bae, M., & Kang, J. (2025). Development and Analysis of Easy-to-Implement Green Retrofit Technologies for Windows to Reduce Heating Energy Use in Older Residential Buildings. Sustainability, 17(8), 3307. DOI: 10.3390/su17083307, https://www.mdpi.com/2071-1050/17/8/3307
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