Cold Deck Flat Roof Design

Warm cold and inverted.

Cold deck flat roof design. There are three recognised designs of flat roof construction. 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. The insulation boards in an inverted warm deck are laid over the structural deck and the waterproof covering. Can be slightly more difficult to install than a cold roof design.

Where a cold flat roof does incorporate insulation this is in the form of mineral wool. 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. Flat roof design guide. 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.

So what exactly is a cold roof. The alternative roofing insulation design places the insulation layer between or under the timber rafters level with the ceiling joist. Traditionally flat roofs simply consisted of a structural timber deck with a waterproof covering directly applied to the top of the deck. There are two basic categories of roof design.

The insulation is placed below the waterproof covering and is either mechanically fixed or bitumen bonded on to the top of the deck. The recognised flat roof build ups for best design practices are. A cold roof design usually leaves a 50mm gap between the top of the insulation and the roof deck above. This therefore leaves the roof and timbers cold requiring a breathable membrane between the insulation and roof.

A warm roof has the insulation above the structural deck which is thus kept warm. Hopefully this video will help explain the difference between cold flat roof construction and warm flat roof construction this videos show detailed drawings. In cold and very cold climates selecting a roof deck condensing surface temperature criteria of 45 f is very conservative. What is a cold roof.

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. Which makes sense as this space is otherwise empty and so it s a simple low impact way to insulate a roof. The waterproof layer is above the insulation and a vapour control layer is placed below the insulation. The sandwich warm deck roof is the most common type of flat roof.

This design dates back many years and flat roof insulation was somewhat of an afterthought with this type of roof. A cold roof has the insulation placed below the structural deck which thus remains cold. Inverted warm deck roof.