The increase of the energy performance of buildings may have an impact on fire safety. The current trend is to increase buildings insulation in order to reduce energy waste. The new products that singly or together may have an impact on fire safety. The renovation market for building insulation is also growing and technical solutions for external facades must provide the highest fire safety. The recent dramatic events, in particular in London, remind us of the importance of addressing these fire issues.
In France, the constructive methods evolve thanks to the current thermal regulation (RT 2012). In this context, external thermal insulation (ETI) has many advantages and has developed strongly. This potentially translates into an increase in the fuel mass on the façades.
The risk of ignition and propagation of a fire to the facade takes place mainly according to several scenarios, by the external surface, by a flame exit of a generalized fire in a room or within the insulating system, in particular for the case of ventilated cladding, for which an air layer between the cladding and the insulation material exists. For most of the fire scenario, one of the weaknesses of the facade reaction is the windows, or more generally the singularities on the insolation panels.
There are no theory and simple model that can reliably explain or predict from first principles how a facade will behave in case of fire. It must be considered a complex process and is due to the effect of several chemical, thermal and physical phenomena. Some theoretical approaches exist, to predict for example the time to ignition as a function of the heat flux on the material, or a critical temperature. However, there are based on some assumptions and outside their range of applicability, they fail to predict correctly the material ignition or flame propagation. It is then important to better characterize and study the ignition and propagation processes on the ETI systems and their singularities.
Fire Safety Engineering designs weakly take this hazard into account. The necessary tools for the Fire Safety Engineering are not enough developed, although feasibility of numerical approach has been shown. Another important point is the constructive dispositions, laid down in the technical instruction 249 (IT 249)17 of the French safety regulations, must help limiting the risks of fire spread. However, when the facade does not comply with the requirements of the IT 249, the only way to justify its compliance involves the completion of a specific real scale test called LEPIR 2. This test has advantages in the regulatory sense but its limits are not well known. It is important to analyze and better understand the representability of LEPIR2, in particular with a view to extending it to other geometric configurations.
The purpose of the project is to acquire the scientific and technical knowledges necessary to the control of the fire safety of façades and to reinforce the research for new materials having a low flammability. Using both experimental methods and CFD simulations, the studies will be carried out at small (matter), intermediate (panel ) and large (system) scales. The objective is to characterize the thermal decomposition, to evaluate the reaction of fire, to validate models of fire propagation with an upscaling approach, to characterize the flame-facade interactions, and finally to study the fire reaction of realistic facade configurations.
ETI systems are now widely used and they may represent important construction costs, especially for high-rise buildings. The development of modern facades is an important issue in the construction. High performance systems must be designed with advanced engineering and perform much better performances than traditional facades. This will reduce vulnerabilities and increase the resilience of buildings.
Monsieur Alexis Coppalle (COMPLEXE DE RECHERCHE INTERPROFESSIONNEL EN AEROTHERMOCHIMIE)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Pprime Institut P' : Recherche et Ingénierie en Matériaux, Mécanique et Energétique
CORIA COMPLEXE DE RECHERCHE INTERPROFESSIONNEL EN AEROTHERMOCHIMIE
UMET Unité Matériaux et Transformations
EFECTIS France EFECTIS France
Help of the ANR 532,908 euros
Beginning and duration of the scientific project: December 2019 - 42 Months