6.3.2.6A.Construction and Installation of Ducts and Plenums

(1) Rectangular panels in plenums and ducts more than 300 mm wide shall be shaped to provide sufficient stiffness. (2) Where the installation of heating supply ducts in walls and floors creates a space between the duct and construction material, the space shall be fire stopped with noncombustible material at each end. (3) Ducts shall be securely supported by metal hangers, straps, lugs or brackets, except that where zero clearance is permitted, wooden brackets may be used. (4) All round duct joints shall be tight-fitting and lapped not less than 25 mm. (5) Rectangular duct connections shall be made with S and drive cleats. (6) Trunk supply ducts shall not be nailed directly to wood members. (7) Branch ducts shall be supported at suitable spacings to maintain alignment and prevent sagging. (8) Ducts in or beneath concrete slabs-on-ground shall be watertight, corrosion-, decay- and mildew-resistant. (9) Where a supply or return duct is not protected by an insulated exterior wall or where the duct is exposed to an unheated space it shall be insulated to prevent condensation.