Energy performance in heritage buildings

Avoid systematic work

The search for energy savings must avoid leading to work of a systematic nature resulting in irremediable modification of the facades by installation of insulation from the outside, the replacement of all the windows and old carpentry and the dispersion of solar panels on the roof, without taking into account the heritage and landscape interest of the built heritage.

Aware of the risk of trivialization and disappearance of a large part of the built heritage, Architects and specialist companies are now offering interventions that seek to optimally reconcile the objectives of energy performance and the preservation of heritage and the built environment.

Focus on sustainable interventions

This specific and sustainable approach is reflected in the desire to preserve what makes the building essential, to highlight the intrinsic qualities of the building and to fill or recycle a maximum of materials. This approach combines a thorough preliminary study of the building (inertia, ventilation), detection of thermal bridges, search for innovative solutions from a technical point of view, use of sustainable and risk-free materials and products for the long-term preservation of structures, of the second work and architectural decoration.

Through appropriate studies, we must find pragmatic solutions adapted to each building of heritage interest.

A European methodology standard to assist in evaluation

Action has been taken in this direction in the context of the production of specific European standards adapted to the conservation of cultural heritage.

Thus, in June 2017 was published the NF EN 16 883 - Energy performance of heritage buildings.

This European standard, designed by heritage practitioners and professionals, provides guidelines for sustainably improving the energy performance of buildings of historical, architectural or cultural value, while respecting their heritage interest. It recommends a working procedure for the choice of measures, based on the investigation, analysis and documentation of the building and on the evaluation of the impact of these measures in relation to the preservation of the characteristic elements of the building.

Each building of heritage interest must be considered as a special case. The heritage value of the building must be carefully assessed against its regional, national and even international cultural context. Understanding the building’s authenticity, integrity and heritage value helps define the characteristic elements that must be preserved.

The measures recommended must comply with the principles of building conservation defined in international charters and regulations.

Maintain above all

The standard also reminds us that proper maintenance of the heritage building is the best conservation measure. Any improvement measures therefore facilitate the continuous maintenance of the building and of any added element and material.

Respect features

Any intervention carried out on a building of heritage interest must respect its characteristic elements, which can take the form of spatial configurations, appearance, construction structure and technical systems of the building. Any measure leading to alteration of these elements should be avoided. Interventions must be additive and, as far as possible, non-invasive and reversible in order to minimize their impact on the asset value.

It is particularly recommended that the selection of stakeholders (architects, design offices, diagnosers, auditors, companies) take into account their training, qualification and experience to intervene on buildings of heritage interest.

Regulations that take into account technical, architectural or heritage constraints

In 2022, under the Climate and Resilience Act, the regulation on regulatory energy audits provided for in Article L. 126-28-1 of the Building and Housing Code takes into account “technical, architectural or heritage constraints” and the proposed works “must be compatible with the easements provided by the heritage code”.

• Decree no. 2022-780 of 4 May 2022 on energy audit mentioned in Article L. 126-28-1 of the Building and Housing Code
  This order, made pursuant to theArticle 158 of the law Climate and resilience, which provides for the obligation of an energy audit for the sale of the least efficient single-property dwellings, specifies the qualifications and skills of the professionals who carry out these energy audits.
  Article 2 of the Decree provides in particular that "where the technical, architectural or heritage constraints or the cost of the work impede the attainment of Class B within the meaning of Article L. 173-1-1 of the Building and Housing Code, the auditor justifies this in his report”.
• Decree of 4 May 2022 defining for metropolitan France the content of the regulatory energy audit provided by article L. 126-28-1 of the Building and Housing Code
  In particular, thearticle 2 of this order recalls that the work proposals made as part of the energy audit must be compatible with easements under the Heritage Code ».
  TheArticle 3 specifies, by way of derogation, the energy performance class to be achieved in the case of technical, architectural or heritage features and provides that “the six work stations are considered to be treated once the auditor certifies that they have been raised to a high level of performance using the best available techniques compatible with the characteristics of the building concerned”.
  TheArticle 4 provides that the summary report drawn up during the audit includes in particular the justification of the technical, architectural or heritage characteristics.