In our collective pursuit of sustainability, a focal point emerges: optimizing energy efficiency in existing buildings. Globally, existing buildings represent three quarters of the 21% of carbon emissions of the built environment. These structures, with their historical significance and ingrained presence in our communities, wield immense potential to curtail energy consumption and reduce environmental impact without resorting to demolition and reconstruction.
However, for a variety of reasons, such as the non-homogeneity of the existing stock and therefore of the solutions to be provided, and the multiplication of stakeholders between landowners and users, it is above all the new-build sector that has been targeted by the most ambitious energy performance constraints. This has its limits, as the annual renewal of the housing stock is estimated at only around 1%. As a result, more and more initiatives are being taken on the existing stock. One example is the adoption in April 2024 of a reinforced directive on the energy performance of buildings (EPBD) in the European Union, with quantified targets for reducing energy consumption in both the residential sector (16% average primary energy consumption by 2030) and the tertiary sector (renovation of the 16% least efficient buildings by 2030).
As we embark on the journey to transform existing structures into beacons of energy efficiency, this step-by-step checklist provides a comprehensive guide for industry professionals committed to weaving sustainability into the very fabric of our built environment.
Step 1: Start with a Comprehensive Energy Audit
The quest for energy efficiency commences with illumination—understanding the current landscape. Very often, the existing housing stock is little known, which is an obstacle to its renovation. The information obtained is limited, and in formats such as 2D scanned plans, making it difficult to identify solutions quickly. A comprehensive energy audit serves as the initial stride on this transformative journey. It’s precisely in this area that new technologies can make a major contribution in many ways. Firstly, in the collection of information on the building, its characteristics and geometry with advanced tools such as thermal imaging, 3D scan potentially leading to the creation of a digital twin. Then in the processing of its information and decision-making with energy simulation, helping professionals meticulously analyse energy usage patterns, pinpoint inefficiencies, and evaluate system effectiveness. This audit not only identifies areas ripe for improvement but also serves as the compass guiding the deployment of tailored energy-saving solutions tailored to the unique needs of each structure.
Step 2: Improve Efficiency Through Insulation and Air Sealing
Energy loss through inadequate insulation and air leaks is a formidable adversary. Strengthening the building envelope becomes paramount in addressing this challenge. By augmenting insulation in walls, roofs, and floors, and sealing air leaks around windows, doors, and ducts, structures can significantly diminish heat loss. This not only enhances occupant comfort in the winter but also lightens the load on heating and cooling systems, paving the way for substantial, long-term energy savings. These optimizations must be carried out in a well-considered way, and efforts must be made in the most optimal places. For example, above a certain level of insulation, the marginal benefit of increasing insulation thickness is low. It is necessary to find the optimum balance between performance and cost/quantity of materials used. But that’s not all: insulating a building has consequences not only in winter. This step needs to be tackled simultaneously with thermal comfort simulations to avoid overheating in the summer. BIM and simulation software can greatly help in doing so by carrying out multi-criteria studies over the whole year, integrating current meteorological scenarios and even anticipating climate change. With all this information, the best compromise can be found for a realistic and complete solution that best meets all these challenges.
Step 3: Upgrade Lighting and HVAC Systems
Outdated lighting and inefficient HVAC systems cast shadows on energy efficiency. Uplift comes through the introduction of energy-efficient lighting solutions, such as LED bulbs and fixtures, providing immediate energy savings. Simultaneously, replacing or retrofitting HVAC systems with newer, high-efficiency models ensures optimal performance, reduced energy consumption, and enhanced indoor air quality. Here too, several options are available to us, ranging from simply replacing the existing system with a similar but newer one to choosing a completely new system. While the first option may seem easier to implement and provide immediate benefits through improved efficiency, the second can sometimes offer other advantages. For example, switching from a gas boiler to an electric heat pump, in addition to being more efficient in terms of energy consumption by recovering heat from the air, also allows for a transition to a less carbon-intensive energy source (electricity versus gas) and, due to its reversibility, provides active cooling in the summer. Of course, each system has its constraints in terms of implementation (smoke evacuation, ducts, presence of an outdoor unit) and its costs, so the choice must be made based on the resources available. The decision will be different depending on whether it is a major renovation or just a simple reinforcement of insulation. Yet it is important to keep in mind that while an upfront HVAC investment might seem significant, the long-term dividends translate not only into lower monthly costs.
Step 4: Embed Smart Technologies
The dawn of enhanced energy efficiency arrives with the integration of smart technologies. Programmable thermostats, occupancy sensors, and smart building management systems offer precise control and optimization of energy usage. These innovations empower facility managers to adapt energy use to seasonal variations and changes in building occupancy, minimizing waste. Automated adjustments based on occupancy, natural light availability, and temperature maximize efficiency while minimizing energy waste. We’re not talking about taking control of their systems away from the occupants or even compromising on comfort. We’re simply talking about free gains that may have no impact on occupant comfort (e.g., turning off lights, reducing temperatures or managing solar protection when absent). This first step is already being taken, and today it’s rare for a system replacement or renovation project not to include the tools needed for this kind of management. The “free” non-occupancy gains mentioned above are just the first step. Our habits don’t always meet a real need. It’s only with this first step, and the proven gains in terms of energy bills, that occupants will be able to realize the significant differences this can make. This in turn will raise their awareness of the need for even greater energy savings.
Step 5: Educate on Maintenance Practices
True energy efficiency encompasses not only infrastructure but also behavioural change and updated maintenance practices. Educating building occupants on energy-saving habits fosters a culture of conservation. Implementing routine maintenance schedules for equipment ensures optimal functionality, preventing energy inefficiencies due to outdated systems.
Step 6: Monitor continuously
After implementing energy-saving measures, the journey doesn’t conclude but transforms into a continuous evolution. Regular assessments of energy consumption data and building performance ensure that structures remain adaptive and efficient. This is even more important given the need for all companies with real estate holdings to know their environmental performance, as part of their CSR policy. In addition to the importance for their image, directives (such as the CSRD) on this point are already binding on very large companies and will progressively concern more and more of them. Collecting precise data on the company’s real estate holdings is a crucial factor in ensuring compliance. That’s why the tools needed for this kind of monitoring must now be an integral part of every renovation project. A range of technologies, from sensors installed inside the building to a cloud-based platform collecting data and potentially creating a digital twin, are now available and integrated into many businesses This process, bolstered by BIM technology, empowers facilities managers to harness increased data for heightened efficiency, ensuring structures maintain their energy prowess and adapt to changing needs over time.
