Warm Deck Flat Roof Ventilation

For a simple duo pitch roof bs 5250 specifies sufficient ventilation as being.

Warm deck flat roof ventilation.

This cold deck construction is considered problematic in the humid temperate climate of the uk where the effective. In a warm flat roof construction the insulation is positioned above the structural deck and no ventilation is required. For guidance on roof insulation please contact us on 44 01257 488 000. There are two types of flat roof systems warm and cold roofs which affect the positioning of the ventilation.

Ventilation is not needed in a warm roof. Flat roof u value 0 18 w m2k 2 warm deck flat roof 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 required to the underside of the deck. Adequate ventilation must be provided between the insulation and the underside of the roof deck to prevent the risk of interstitial condensation forming within the void area.

Throughout the course of the year the roof deck and all below it is kept at a temperature close to that of the inside of the building therefore the roof structure is protected from extremes of hot and cold lessening the. The roof itself is therefore kept warm. What is flat roof ventilation. Thickness varies according to the manufacturer s specifications.

When thermal insulation is placed below the deck the ventilation must. In flat roof construction thermal insulation can be placed above and below the structural roof deck or waterproofing layer. Warm roof ventilation specification. By majority the rule of thumb is that in a domestic house not flats approximately a third of the total thermal performance of insulation can be placed below the deck with two thirds above the deck sometimes this is called a hybrid warm roof.

This is placed over the roof joists and a board normally external ply is laid on top. If ridge or eaves ventilation is not possible ventilation tiles can be used at high or low level to achieve the required airflow. Ventilation is required for these roofs. 25mm at eaves on each slope and 5mm at ridge.

Flat roof ventilation allows for the circulation of air in the property particularly for warmer rooms in residential buildings. When placed below the structural deck. Hopefully this video will help explain the difference between cold flat roof construction and warm flat roof construction this videos show detailed drawings.