Energy performance of windows and doors: UFME calls for consistent application of regulatory requirements in technical specifications

Indeed, for the past few months, some design offices have been adopting a "simplistic" or "ultra-secure" approach, imposing a single thermal performance for all windows, bays and doors of a building, regardless of their dimensions and purpose.

These practices lead to requiring identical Uw values ​​for a large bay window and a small bathroom window, for example. The UFME warns of the risk of prescribing unsuitable solutions that may prove to be more carbon-intensive and more expensive, thus jeopardizing the technical and economic viability of the project.

The French door and window industry is therefore urging all stakeholders to prioritize an approach based on sound judgment, in-depth technical analysis of the overall building structure, and dialogue between design offices and manufacturers. These are essential conditions for reconciling energy efficiency goals, reducing carbon footprint, and industrial feasibility!

Discernment of design offices

The UFME encourages design offices and clients to adopt a more nuanced approach when drafting their technical specifications. The thermal performance requirements should be specifically tailored to each window/door unit (RE2020) or refer to an average value corresponding to the standard product in the range and its reference dimensions (CE marking standard). A building's energy performance results from an overall balance. Demanding the highest level for all windows/door units, regardless of their individual contribution to the building envelope, does not necessarily lead to better overall building performance and often creates situations incompatible with standard solutions.

The educational role of UFME members

The UFME reminds its members of their duty of vigilance and their advisory role. Companies must pay close attention to the terms of the technical specifications and clearly explain the limits of these technical overbiddings by referring to regulatory requirements. This educational approach is essential to anticipate misunderstandings, ensure the security of tenders, and avoid subsequent disputes. Its ultimate goal is to strengthen collaboration between manufacturers and engineering firms.

Reminder of the regulatory context

The RE2020 regulation mandates the achievement of energy consumption targets, comfort levels during periods of high heat, and a reduction in the carbon footprint of new buildings. The calculation method for regulatory energy indicators (Cep, Bbio, and DH of discomfort) requires as input data the thermal insulation performance (Uw), the components of the solar factor (Sw), and the light transmission (Tlw) of each window/door unit, with achievement of the targets being assessed at the building level.

Thermal regulations for existing buildings also set minimum performance requirements for windows and doors in the case of renovation projects. The Uw value of ≤ 1,9 W/m².K is given in reference to the performance declared under the CE marking (compliant with the harmonized standard EN 14351-1 and conventional dimensions), as are the eligibility criteria for renovation grants.

Future developments in CE marking are moving towards a declaration of thermal performance (Uw) limited to that of the standard product with reference dimensions, supplemented by the performance of the window and door components. A study conducted by Tribu Energie, at the request of UFME, at the end of 2025, established that calculating the Uw, Sw, and Tlw coefficients, using average performance values ​​of the reference product components (Uf, Up) and the actual window dimensions, leads in most cases to the same values ​​as the actual detailed calculation. It also highlights that the building's regulatory energy indicators are not affected by this approximation.