Insulated air transfer duct

An air duct transporting air between an interior location within a building and an air management system exterior to the building, the duct comprising:

• a metal duct wall defining a hollow interior through which the air passes between the interior location and the air management system with at least an exterior part of the metal duct wall subject to an environment of extreme temperature difference and/or extreme humidity;
• a first sheet assembly surrounding at least the exterior part of the metal duct wall;
• the first sheet assembly comprising a layer of rigid insulating material and an exterior covering foil layer laminated thereto;
• the first sheet assembly being attached to the exterior part of the metal duct wall by pins which project through the exterior covering foil layer and the layer of rigid insulating material and attached to the metal duct wall to define exterior heads of the pins exterior to the foil layer;
• and a covering material surrounding the first sheet assembly;
• the covering material comprising a laminate of two layers of a plastics material including an intermediate layer of fibers;
• the covering material being free from a foil layer;
• the covering material being bonded to the exterior covering foil layer of the first sheet assembly by a self-adhesive material laminated to an inner surface of the covering layer so as to be carried thereby;
• the covering material covering the heads of the pins.