Cold Deck Flat Roof Design

What is a cold roof.

Cold deck flat roof design.

Well a cold roof is created by laying insulation between the rafters. In the case of a flat roof insulation is usually either a rigid board above the deck or a mineral glass wool quilt immediately above the underdrawn ceiling depending on the type of roof design and construction. Where a cold flat roof does incorporate insulation this is in the form of mineral wool. Can be slightly more difficult to install than a cold roof design.

Cold flat roof designs. In cold and very cold climates selecting a roof deck condensing surface temperature criteria of 45 f is very conservative. The sandwich warm deck roof is the most common type of flat roof. A cold roof has the insulation placed below the structural deck which thus remains cold.

Warm cold and inverted. The waterproof layer is above the insulation and a vapour control layer is placed below the insulation. Inverted warm deck roof. There are two basic categories of roof design.

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. Traditionally flat roofs simply consisted of a structural timber deck with a waterproof covering directly applied to the top of the deck. This temperature criteria can be reduced to 40 f which corresponds to interior average conditions of 70 f 35 rh where high interior moisture loads due to spas indoor swimming pools and excessive humidification are. In the case of a flat roof insulation is usually in the form of either a rigid board above the deck or a fibrous quilt immediately above the ceiling depending on the type of roof construction.

There are three recognised designs of flat roof construction. The recognised flat roof build ups for best design practices are. The insulation is placed below the waterproof covering and is either mechanically fixed or bitumen bonded on to the top of the deck. A warm roof has the insulation above the structural deck which is thus kept warm.

Which makes sense as this space is otherwise empty and so it s a simple low impact way to insulate a roof. Flat roof design guide. 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. The alternative roofing insulation design places the insulation layer between or under the timber rafters level with the ceiling joist.

A cold roof design usually leaves a 50mm gap between the top of the insulation and the roof deck above. This design dates back many years and flat roof insulation was somewhat of an afterthought with this type of roof. This therefore leaves the roof and timbers cold requiring a breathable membrane between the insulation and roof.