Abstract: A thermal control material which is flexible and highly conformable comprises a thin substrate of porous expanded polytetrafluoroethylene which has been metallized on one of its surfaces by vacuum deposition to provide a thin metal film (usually aluminum). A multi-layer construction is made up by joining together a plurality of metallized layers at intervals over the areal extent of the construction, e.g. by discontinuous stitching or by adhesive spots. The material is light, strong and has excellent drape characteristics, together with good thermal insulation properties.