Thermal Breaker: Reducing Losses by 70%
Thermal bridges occur in particular in buildings with concrete façades, where the slabs, the walls and the perimeter wall meet. Heat passes through the floor into the façade and is diffused towards the outside.
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To find a solution to this problem, in 2007 Lafarge set up a working group with, among others, Bouygues Bâtiment Ile de France, Fehr-Technologies, Pouget Consultants and the Centre Scientifique et Technique du Bâtiment. The outcome of this project, which benefited from the support of ADEME, was an innovative component: the Ductal® thermal breaker.
"A thermal breaker can reduce thermal bridges by 70%," explains Alain Birault, Head of the Ductal® thermal break project for Lafarge, "and thereby achieve a Psi-value of 0.3, in line with the specifications for a low-energy house. This performance was made possible by integrating Ductal® concrete at a mechanical level so as to achieve a continuous bond between the slab and the perimeter wall using the thinnest possible ribs, surrounding the structural tendons. This creates a continuous concrete bond. We use 1.20 m long, precast elements with ribs every 60 cm which make them very easy to fit in place. In addition, this continuity is combined with insulation and thermal and acoustic lining systems to ensure compliance with acoustic regulations.
Mechanical trials and fire resistance
The Ductal® thermal break has undergone several rounds of mechanical testing at the Centre Technique et Scientifique du Bâtiment: it can support a load greater than 8 t. In practical terms, it can take the strain of floors with spans of up to 6.5 m, which means that it is able to meet the requirements for the majority of layouts encountered in the residential sector.
Furthermore, a fire test in CSTB's large furnace showed a resistance of more than 2 hours 20 minutes, which is exceptional for this type of component. The thermal break can therefore be used in buildings up to 50 m high. |
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