Cold Deck Flat Roof Ventilation

Introduction warm cold roofs this guidance offers guidance on the difference benefits between warm and cold roofs.

Cold deck flat roof ventilation.

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. Ventilation is required for these roofs. What is flat roof ventilation. Flat roof ventilation allows for the circulation of air in the property particularly for warmer rooms in residential buildings.

Warm deck the type of insulation for this is usually of a rigid type and the thickness will vary depending on the manufacturer s specifications. Ventilation is not needed in a warm roof. A cold roof is where all of the insulation is placed either between and under or completely under the joists or deck. In this way the roof itself is kept cold.

Guidance advice on warm cold. Cold deck this is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof. Ventilation is required for these roofs. This cold deck construction is considered problematic in the humid temperate climate of the uk where the effective ventilation of restricted roof voids may be impractical particularly in sheltered built up areas.

When placed below the structural deck. Ventilation is required to the underside of the deck. The minimum requirements for cold roof ventilation are set out in bs 5250 control of condensation in buildings which takes into consideration span pitch and roof area. A cold roof is the most common type of roof construction often taking the form of an uninhabited storage space.

In a cold roof construction the sarnafil membrane is installed directly to the structural decking usually timber with firrings to fall. There must be an adequate void minimum 50mm between the deck and the insulation traditionally mineral wool to allow free movement of air and to prevent moisture vapour being transmitted from the building outwards where it could condensate in the roof. There are two types of flat roof systems warm and cold roofs which affect the positioning of the ventilation.