Abstract: A composite system having insulation properties is disclosed. The system includes a multi-wall profile and a thermal insulation element. The profile, made of a thermoplastic material includes a transparent upper plate and a radiation-absorbing lower plate that are joined together by webs; the webs extending in the longitudinal direction in such a manner that flow channels parallel one to the others are formed. The outer surface of the lower plate is joined to the thermal insulation element. The system is particularly suitable for use as solar collector.