Modular insulating upholstery for a closed chamber (7) consistin of panels (1, 2) and prefabricated elements, specially suited to chambers for the transport of goods such as containers. The panels and prefabricated elements form part of an assembly set or kit adaptable to the dimensions of the chamber interior (7) to be insulated and comprise all the necessary upholstering elements. The panels (1) covering the chamber peripheral walls and ceiling consist of a self-supporting sheet insulator in one piece. The prefabricated elements essentially comprise spacing units (6) in the form of small blocks, which are placed between the inner chamber surface and at least the outer panel surfaces, and are made of a material capable of breaking any thermal conduction between the two surfaces.