14 players in wood construction are coming together within the “Groupe Feu” to develop a new wood facade solution

Led by Bois HD, the engineering center of the ESB - Wood & biobased materials engineering school, the collective was formed with the objective of developing solutions complementary to those of the guide "Wood Construction and Fire Propagation par les façades ”edited since 2016. About fifteen working meetings and experiments carried out by the Efectis laboratory - approved in resistance & reaction to fire - resulted in a LEPIR 2 test (Experimental Room For Real Fire at 2 levels) qualifying, in December 2020.

Regulations that encourage companies to come together to develop new solutions

The regulations require obtaining a laboratory assessment attesting to the non-propagation of fire by the facades. This assessment is linked to the performance of a LEPIR 2 test, the cost of which is estimated at € 40. A budget that is difficult to meet for companies in the wood industry.

For 3 years, the “Groupe Feu” brought together the association Ingénierie Bois Construction (wood design offices), the professional organization UICB (Union des Industriels et Constructeurs Bois) and the companies Bouygues Construction (78), CMB ( 79), Construction Bois EMG (22), FP Bois (40), Groupe ISB (35), Lignalpes (74), Maître Cube (75), PIVETEAUBOIS (85), Protac (22), Siniat (84) Sivalbp (74) ) and Techniwood (75).

The objective of this pooling of expertise and resources was to develop an optimized solution for a “complex”: the entire wall, made up of the structure, the exterior / interior facing and the insulation, in structure and wood cladding. . The latter was supposed to make it possible to obtain a laboratory assessment relating to the fire behavior of a facade element according to §5.3 of IT249: 2010 and in accordance with the decree of August 7, 2019 of the Ministry of the Interior and the housing.

After a search for influencing factors by small-scale tests, numerical modeling and a first LEPIR 2 orientation test carried out in February 2020, the “Groupe Feu” obtained, last December, a LEPIR 2 test qualifying on the design. facade.

The advantages of the solution developed by the “Groupe Feu”:

• Limitation of the overhang of the deflectors to a maximum of 50 mm
• Use of wood cladding with a minimum reaction to fire classification D-s2-d0
• Postage of the air gap closure device
• Implementation of bio-sourced insulation with a minimum Euroclass D facing
• Use of several types of cladding, including openwork aspect if horizontal installation

This laboratory assessment is personal and therefore reserved exclusively for members of the group. The solution constitutes an alternative to the proposals listed in the guide "Timber Construction and Propagation of fire by facades" and which meet the objective of limiting the spread of fire from one level of a building to another or in such a way. lateral.

Yves-Marie Ligot, director of a technical design office specializing in timber construction and representative of the IBC association within the “Groupe Feu” is at the origin of the grouping. He comes back to the reasons which led to this collaborative approach: “The solutions referenced in the guide are technically efficient but difficult to implement from an operational point of view. They generate additional costs and complicate prescribing. For example, the installation of deflectors to keep the flame away from the facade increases the external dimension of a building and marks it from an aesthetic point of view. The “Fire Group” brought together industrialists, designers and manufacturers in order to find a “universal” solution. The latter makes it possible to highlight the wood material in the cladding and must now be applied in the context of concrete projects. The feedback from the various participants will allow adjustments to be made, if necessary. All the players who took part in this process confirmed their satisfaction. Depending on regulatory changes, the group could thus be reactivated with a view to new collective projects.

The solution developed now enables the group's companies to enrich their offer dedicated to high-rise buildings, certain establishments open to the public and third-family residential buildings. These represent an important part of the market for construction companies in the timber industry.

Bois HD: a role of structuring and management

Created in 2012 by the ESB - Bois & Biosourcés Materials Engineering School (Nantes), the Bois HD engineering center supports 120 companies each year in their research, development and innovation projects. Its activities are divided between testing, innovation, engineering, modeling and continuing education. The objective: to stimulate the wood industry by contributing to the improvement of products and processes. A professional approach rewarded by an increase in the scope and flexibility of the accreditation issued by the French Accreditation Committee (Cofrac).

Bois HD was involved from the start of the project in order to ensure its assembly and coordination.

Amélie Roux, R&D engineer in charge of the project, details: “We first intervened to structure the project: establish the budget, mobilize participants, set up a partnership contract, organize discussions and determine the different phases. Carrying out a LEPIR 2 test in an approved laboratory requires the creation of a complete two-level facade - 7,10 m high by 5 m wide - at a cost of approximately € 60. Thanks to the pooling of resources, we were able to have an overall budget of 40 € which made it possible to initiate studies, the development of prototypes, the orientation test and, finally, the qualifying test. This “Fire Group” is a very good example of collaboration within a growing timber industry, particularly with a view to the 000 Olympic Games. ”

The different stages of the project:

• September 2017: launch of the working group
• February 2018 - September 2018: search for solutions, determination of acceptable constraints (additional costs, aesthetic appearance, durability of solutions, etc.)
• October 2018 - May 2019 : determination and analysis of influencing criteria (via numerical simulation by Efectis and performance of a medium-scale SBI-type test at Efectis - Belfast, in April 2019),
• June 2019 - January 2020 : design of the facade prototype
• February 2020 : completion of the LEPIR 2 orientation trial at Efectis
• April 2020 - November 2020 : revision of the facade design based on the results of the orientation test
• December 2020 : Realization of the LEPIR 2 qualifying test at Efectis