Guaranteeing energy performance: a challenge throughout a project’s life cycle

Creating very high-efficiency buildings and supporting the goal of reaching higher volumes of energy renovation in the construction industry are top priorities in the fight against climate change and fuel poverty. Success is not possible without the commitment of every stakeholder. But, according to the Climate Plan, “the lack of confidence in the reality of the energy savings that will be generated by construction projects, like their cost, remains one of the main obstacles to taking action.” How can individual and joint owners be persuaded to undertake construction projects?

“Providing security and developing trust are crucial, given the scope of the investments and the life cycle of buildings. It requires the development of reliable, competitive solutions to make promises and demonstrate that they are going to be kept. A trusted third party, the CSTB is mobilized alongside the stakeholders, at each stage of their projects, to guarantee the energy performance of buildings,” explains Julien Hans, Deputy Director for Research, Energy & Environment Division of the CSTB. Here is a close-up of two avenues of action: promoting Energy Performance Contracts (CPEs) before projects begin, and measuring the actual energy performance upon commissioning and during use of the building.

“The CPE (Energy Performance Contract) is possible and works well for small apartment buildings and large building stocks,” stated the CPE Observatory in 2017. The observatory is run by ADEME (the French Environment and Energy Management Agency), the CEREMA (Center for the Study and Expertise of Risks, the Environment, Mobility and Development) and the CSTB. Project owners are increasingly turning to Energy Performance Contracts as a tool for ensuring the energy performance outcomes of buildings in construction contracts. To date, CPEs are mainly used for the renovation of public real estate assets, apartment buildings and schools. The gains observed range from 25% to 40% of energy savings, depending on the work performed (buildings and/or systems).

Within the context of the Observatory, the role of the CSTB is to measure the effectiveness of the CPE through the collected data, to share good practices with the project owners and help simplify CPEs as a matter of public policy, in order to facilitate their full-scale deployment. “To achieve this goal,” explains Julien Hans, “the CSTB considers both the need to industrialize solutions and the need to customize their applications to fit different contexts.” That is why it supports project owners through fact-finding missions, to implement CPEs adapted to their needs. For stakeholders who offer commitments regarding outcomes, a major challenge lies in determining the targeted energy performance levels. Before reaching the stage of signing the CPE, the CSTB guides them by analyzing the energy consumption of the buildings, taking a probabilistic approach. The goal is to offer a prediction that precisely identifies the level of uncertainty, in order to facilitate the decision-making process.

“A result-oriented approach,” says Julien Hans, “also requires an objective, reliable verification of the outcomes after completion of the work. Involved in the measurement of actual energy performance, the CSTB has developed two original methods, REPERE and ISABELE.” In 2017, the CSTB’s ISABELE measurement method was transformed from an R&D protocol into a fully operational system, known as MERLiN, made available to the professional sector. It was developed by the CSTB, the CEREMA and COSTIC (Scientific and Technical Committee of Climatic Industries) as part of the PACTE program. REPERE is deployed in the field for the renovation of housing units managed by local authorities or social housing operators, aiming for exemplary long-term performance of construction projects and the improvement of occupants’ comfort. This is the case of Groupe 3F for example, and Polygone SA and Montluçon Habitat since 2017. The CSTB guides stakeholders in identifying any possible discrepancies between the predicted results, those upon commissioning and during use. The advantage of this approach is to offer reliable, comparable outcomes at each stage of a project, even though there may be variations in the weather and conditions of use. The methods of the CSTB also offer the advantage of being easy to use, as they are based on an optimized on-site system of instruments, supplemented with innovative calculation solutions.

“In 2018, the CSTB is continuing its experimentation on tools dedicated to energy performance and its research conducted with stakeholders in science and industry, including a new partnership with the Nobatek/INEF4 Applied Research Center, on energy, environmental and digital challenges,” says Julien Hans. In connection with the Energy Performance Guarantee, this work aims to increase control over the energy performance of projects, through their entire life cycle. This involves paying closer attention to the future uses of buildings during energy simulations (design phase), and developing innovative methods of commissioning (construction phase) and of installations’ management (operation phase).

Thierry Repentin
president of the Higher Council of Construction and Energy Efficiency
“Helping guide stakeholders and convince them to participate”

“One of the major challenges in meeting the 2050 goals, concerns the renovation of the existing building stock. We must help owners, co-owners and managers to get involved in a program for several years, or even decades, by supporting them throughout the project. The Energy Performance Contract (CPE) is one of the technical and financial tools that helps guide stakeholders and convince them to participate. The aim is to develop the use of CPEs. To this end, the CPE Observatory will play an essential role, supported by the French Environment and Energy Management Agency (ADEME), the CSTB and the Center for the Study and Expertise of Risks, the Environment, Mobility and Development (CEREMA). The CSCEE also believes it is important to support the quality of renovations. It supports the development and democratization of tools for measuring the actual energy performance of buildings. The members of the Council observed the promising work by the CSTB in this field, in the MERLiN project, and are convinced of the need to continue supporting these tools and performing tests under full-scale conditions.”