Warm Deck Flat Roof Ventilation

The insulation is applied above the roof deck with waterproofing on top which eliminates the need for ventilation and keeps the roof warm.

Warm deck flat roof ventilation.

A cold roof is where all of the insulation is placed either between and under or completely under the joists or deck. 25mm at eaves on each slope and 5mm at ridge. 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 potential for damage caused by thermal movement. Warm air rises and will naturally collect in your home beneath the roof.

No insulation is on top. When thermal insulation is placed below the deck the ventilation must also be on the underside. The roof itself is therefore kept warm. Warm roof ventilation specification for a simple duo pitch roof bs 5250 specifies sufficient ventilation as being.

A warm deck roof is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation. The insulation is placed below the waterproof covering and is either mechanically fixed or bitumen bonded on to the top of the deck. In the instances where a warm flat roof has been laid ventilation isn t usually required. Where the insulation is placed above the structural deck warm deck and either above or below the waterproofing.

If ridge or eaves ventilation is not possible ventilation tiles can be used at high or low level to achieve the required airflow. If you have a hot roof this warm air changes the temperature of your roof decking as it isn t protected by insulation. 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. In a warm flat roof construction the insulation is positioned above the structural deck and no ventilation is required.

Make sure your comply with flat roof building regulations. It is universally recommended that cold deck flat roof construction should be avoided. Ventilation is not needed in a warm roof. A little bit but ventilation is still key to prevent some serious problems that might develop in your building otherwise.

Warm roofs are recommended for homes. The sandwich warm deck roof is the most common type of flat roof.