Building retrofit for energy efficiency in existing buildings: A case study on sustainable renovation
Across Europe, the building sector accounts for nearly 40% of total energy consumption and over a third of CO2 emissions. Decarbonizing the built environment is thus a critical pillar of the continent’s clean energy transition. While new construction can integrate the latest energy-efficient designs and renewable technologies, the vast majority of existing buildings were built before modern efficiency standards. Retrofitting these aging structures offers a massive opportunity to unlock substantial energy savings and emissions reductions.
The European Union’s Renovation Wave strategy aims to at least double the annual energy renovation rate of buildings by 2030. This will require deploying a diverse toolkit of retrofit solutions tailored to local building typologies and climates. A comprehensive, multifaceted approach is essential—from optimizing building thermal envelopes to integrating rooftop solar, upgrading HVAC systems, and empowering occupants through smart building technologies.
To showcase the potential of sustainable building renovation, let’s examine a case study from Qingdao, China. The historic Liyuan courtyard buildings, dating back over a century, demonstrate how thoughtful retrofits can breathe new life into existing structures while dramatically improving energy performance.
Sustainable Building Renovation Strategies
The Liyuan buildings were originally constructed in the early 1900s, blending European and Chinese architectural styles. Today, these century-old structures face a range of preservation and efficiency challenges. Field assessments have revealed issues like inadequate insulation, outdated fenestration, and aging mechanical systems—all contributing to high heating and cooling demands.
To address these deficiencies, the municipal government of Qingdao has embarked on a multifaceted renovation program. Key strategies include:
Enhancing the Building Envelope: Upgrading wall, roof, and window assemblies to boost thermal resistance and reduce heat transfer. This can involve adding exterior insulation layers, replacing single-glazed windows with double-glazed units, and optimizing air sealing.
Modernizing Building Systems: Swapping out inefficient HVAC equipment for high-efficiency alternatives, incorporating smart thermostats and controls, and exploring renewable energy integration like rooftop solar PV.
Preserving Historic Character: Carefully balancing energy efficiency improvements with the need to maintain the Liyuan buildings’ distinctive architectural features and cultural significance. This requires considerate selection of materials and techniques.
Engaging Occupants: Educating residents on energy-saving behaviors and empowering them with building management tools to optimize comfort and minimize consumption.
Building Energy Performance Assessment
To quantify the energy savings potential of these retrofit strategies, the Qingdao project team conducted detailed building performance simulations. Using Autodesk Ecotect software, they modeled three scenarios:
- Baseline: The original, unimproved Liyuan building.
- Standard Retrofit: Upgrades to the building envelope per local green building standards.
- Advanced Retrofit: Further envelope enhancements incorporating recycled construction materials.
The results showed that the standard retrofit approach could reduce annual heating demand by 11.8%, while the advanced model achieved a 12.3% reduction compared to the baseline. Cooling loads, though a smaller overall share, also saw modest improvements.
Drilling down, the simulations revealed that enhancing the thermal properties of the building envelope was the most impactful measure. By reducing heat transfer through walls, roofs, and windows, the retrofit scenarios significantly curbed heating requirements during Qingdao’s long, cold winters. Meanwhile, the slightly higher cooling needs stemmed from the buildings’ better insulation retaining more heat gain.
Passive Design Approaches
Beyond active efficiency upgrades, the Liyuan buildings’ inherent design features also lend themselves to passive strategies. The courtyard layout, for instance, promotes natural ventilation by enabling cross-flow air circulation. Thoughtful window placement and overhang design can further harness daylighting to reduce electric lighting needs.
Recognizing these inherent assets, the renovation plan aims to revive and optimize the Liyuan buildings’ passive performance capabilities. For example, restoring original window systems and strategically adding operable vents can enhance natural ventilation. Selective pruning of landscape elements can also improve daylight penetration without compromising the buildings’ historic character.
Active Building Systems
To complement the passive approaches, the Qingdao retrofit also incorporates active efficiency upgrades. Key measures include:
- HVAC System Overhaul: Replacing aging furnaces, chillers, and air handlers with high-efficiency, variable-capacity equipment.
- LED Lighting Retrofit: Swapping out traditional lamps for LED fixtures, offering superior efficacy and controllability.
- Building Automation: Integrating smart thermostats, occupancy sensors, and other digital controls to fine-tune energy use.
These active system enhancements, when combined with the passive design features, can drive substantial reductions in the Liyuan buildings’ total energy consumption and carbon footprint.
Challenges and Opportunities
Executing a comprehensive retrofit on century-old buildings like the Liyuan courtyards presents unique technical and logistical challenges. Carefully navigating historic preservation requirements, managing tenant disruptions, and coordinating complex construction logistics are just a few of the obstacles the project team must overcome.
However, the Qingdao case study also highlights the immense potential of sustainable building renovation. By thoughtfully blending energy efficiency upgrades with preservation of cultural heritage, these historic structures can be transformed into shining examples of how the built environment can contribute to a clean energy future.
The lessons from Qingdao offer valuable insights for other cities across Europe grappling with aging building stocks. Innovative financing mechanisms, strengthened policy frameworks, and public-private collaboration will be essential to scaling up deep energy retrofits at the pace required to meet ambitious climate goals. But with the right strategies and stakeholder engagement, the energy optimization of existing buildings can become a powerful lever for decarbonization.
To learn more about sustainable building renovation and other clean energy solutions, visit the European Future Energy Forum.