Cold Deck Roof

This design dates back many years and flat roof insulation was somewhat of an afterthought with this type of roof.

Cold deck roof.

The solution warm deck insulation. The 18mm roof grade deck is then fixed on top of the rafters leaving suitable air flow between the insulation and the deck. The insulation in a warm deck roof is installed immediately below the roof membrane on top of the roof deck usually with a vapour control layer underneath the insulation. Fortunately these days there is a better form of insulation available for your flat roof.

Ventilation is required for these roofs. A cold deck roof is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof. The breakdown warm roof vs cold roof. In the case of a flat roof the roof deck and waterproof membrane are supported on joists the internal ceiling is attached to the underside of the joists and should have a vapour barrier to stop condensation penetrating the internal decor.

Traditionally flat roofs simply consisted of a structural timber deck with a waterproof covering directly applied to the top of the deck. This is known as a cold roof because the roof deck and roof space are close to the external air temperature. Warm roof insulation ensures the entire roof structure is insulated meaning a warm deck roof is more energy efficient than a cold roof. Contrasted with the cold deck roof this construction has a much lower risk of condensation as the void will be of a comparable temperature to the roof.

Introduction warm cold roofs this guidance offers guidance on the difference benefits between warm and cold roofs. A cold roof construction will normally comprise of a structural deck on joists or purlins with a ceiling layer fixed to the bottom of the joists purlins thereby creating an air layer or cavity within. This system is called warm deck insulation and eradicates the condensation and venting issues associated with the cold deck system. A cold flat roof insulation requires more work taking off old boards and replacing them and the roof surface.

Where a cold flat roof does incorporate insulation this is. Traditional cold deck flat roof. Cold deck with epdm rubber roof. One prepared for surreptitious substitution for the pack in play.

Cold deck definition is a stacked pack of playing cards.