A façade wool with one of the best lambda thermal conductivity coefficients for external walls, ceilings and ceilings over garages and car parks. It has excellent insulating properties and, unlike polystyrene, it is vapour-permeable and does not impede the diffusion of water vapour through the envelope, accelerating the drying of walls from process dampness and preventing long-term dampness of walls, which is conducive to the occurrence of moulds and fungi. PETRAFAS 34 is a façade wool that significantly reduces the heat flow between internal and external spaces. External wall insulation is one of the most effective ways of reducing heating bills.