Warm Flat Roof Insulation Thickness

A cold roof has the insulation placed below the structural deck which thus remains cold.

Warm flat roof insulation thickness.

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. The chosen insulation laid on top of this should be able to take the weight of anything put above it on the roof without compression or protected from compression by further sheeting. These are can be supplied with rebated edges which interlock reducing the risk of uplift. Inverted roofs are a type of warm flat roof where the insulation is above the waterproofing layer.

Achieving a u value of 0 20w m meaning your roof will be better insulated than your walls will need 120mm thickness of rigid foam or 200mm of mineral wool or natural insulation. Thickness varies according to the manufacturer s specifications. This means that the insulation should be highly resistant to water absorption for example an extruded polystyrene based product which will not be affected by water or repeated freeze thaw cycles. This is placed over the roof joists and a board normally external ply is laid on top.

Cold flat roofs are typically avoided as you d need to install ventilation which can prove problematic for many reasons relating to space labour costs etc. There are two basic categories of roof design. The typical u value of an existing uninsulated flat roof is 1 5w m2k. A warm roof has the insulation above the structural deck which is thus kept warm.

Insulation in a warm roof. There are two types of flat roof. The insulation for a warm roof will usually be boards of extruded polystyrene or rigid compressed boards of glass fibre or rock fibre. 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.

In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay. Cold roofs and warm roofs. 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. A flat roof where the insulation sits below the waterproof membrane and above the structural deck is a warm roof deck.

It should be of the maximum available thickness. The insulation material for a warm flat roof should. However if we do not include removal of old roofing you are looking at about 7 50 to 9 00 per foot of roofing plus about 2 50 to 3 00 per foot of 5 thick insulation say about 10 12 per square foot. With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.

Flat roof insulation thickness. Ventilation is required for these roofs.