Abstract: A heating/cooling system includes a plurality of solid panels which form part of a wall or floor. The panels are in the form of heating/cooling modules and incorporate a heat exchange element within the panel and in thermal contact with the material, e.g. chipboard, fibreboard or plywood, forming the panel. The panels can be provided with, for example, tongue and groove formations so that they can engage with like panels or with "industry-standard" panels which do not incorporate heat exchange elements.