Thermally insulated roofing device

A thermally insulated deck-roofing or pitched-roofing device with compact structure, comprising:

• an area support made up of panels based on agglomerated woodchip and/or wood particles, on which there are laid, in succession and according to a layered approach, at least a first layer that forms a barrier regulating the passage of water vapor, at least an insulating second layer made up at least in part of a material based on wood fiber, and at least a third layer that is substantially impervious to liquid water,
• the insulating second layer being a composite layer formed by the superposition of two distinct homogeneous elementary layers, namely a lower elementary layer made from a material based on wood fiber, resting on the first layer, and an upper elementary layer on which the third layer rests,
• said device being one wherein:
• the third layer that forms the upper and outer layer of the device has a sealing membrane, made either of bituminous or synthetic material,
• the upper elementary layer is formed of an at least partially bio-sourced material having hygroscopic, antifungal and thermal-insulation properties, offering low resistance to the diffusion of water vapor and selected from the group formed from expanded cork, expanded perlite and wood wool,
• the ratio upper layer/lower layer, in terms of the ratio of their respective thicknesses or of their respective thermal resistances, is comprised between 0.25 to 1 and 0.6 to 1, and
• the first layer has a membrane forming a hygrovariable vapor barrier.