Use of breathable roof membranes with non-ventilated ‘cold’ pitched roofs Subject No: 3 Subject: Tyvek 2001B PRO underlay in Sealed Cold Pitched Roof Systems Introducing Officer: G E Jones (Weymouth & Portland BC) The Chief Building Control Officers asked this committee to look into the acceptability of the use of Tyvek 2001B PRO roof underlay in cold pitched roof situations without the provision of ventilation, as this is being advocated by the manufacturer to the building industry. Both Approved Document F and BS 5250 require the provision of ventilation to the roof void above insulated cold-pitched roof constructions. Tyvek’s Agreement Certificate 94/3054 only permits the use of 2001B PRS without ventilation in cold roof situations. At our committee on the 26 August 1998 the committee unanimously agreed that until such time as an independent approved body has successfully tested this produce within insulated cold pitched roof constructions, and published their recommendations and certificate of approval in use. The Dorset Building Control Technical Committee would advise that whilst no advocating its use in such circumstances, the product should be installed strictly in accordance with manufacturers requirements. POLICY STATEMENT The use of Tyvek 2001B PRO Underlay in Sealed Cold Pitched Roof Systems is deemed acceptable in use, provided that it is installed strictly in accordance with the requirements of Agreement Certificate 99/3635.

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