A ventilation gap usually 50mm should be provided between the top of the insulation and underside of the roof covering to allow the air to flow across.
Cold flat roof insulation thickness.
Cold roofs and warm roofs.
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.
As for insulating below the joists an insulating laminate insulation bonded to plasterboard such as celotex pl4000 or a separate rigid pir insulation board finished with a separate sheet of plasterboard can be securely fixed to the joists to provide an internal finish to the roof.
Saint gobain insulation uk manufacture and supply glass mineral wool slabs and rolls along with rigid polyisocyanurate pir boards that can be considered suitable for a wide range of applications across flat roofs whether you re looking to insulate at joist level or above the roof deck in your flat roof construction.
The insulation material is placed between the supporting joists leaving a gap of 50 60mm between the roof and insulation.
The waterproof layer is above the insulation and a vapour control layer is placed below the insulation.
With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.
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.
There are two types of flat roof.
The insulation is below the deck but above the plasterboard.
A cold roof has the insulation placed below the structural deck which thus remains cold.
Cold deck flat roof the thickness of insulation required will vary depending on the material you decide to use and the manufacturer s specification.
A cold flat roof is one where the insulation is between or between and below the roof joists.
This may help with condensation but causes such a loss of heat that it has been banned in scotland.
Ventilation is required for these roofs.
Cold flat roof insulation.
This means there is a vapour control layer in the ceiling and cross ventilation at the eaves or the top of the walls.
A warm roof has the insulation above the structural deck which is thus kept warm.
Lots of traditional flat roofs are of the cold roof construction type.
Warm flat roof insulation.
Alternatively battens can be secured to the underside of the.
In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay.
Cold roofs have the waterproof layer placed directly onto the roof deck and the insulation inside the roof just above the ceiling.
There are two basic categories of roof design.
Many properties use this option as there are no additional costs for scaffolding or organising how to gain safe access to the roof exterior.
Ventilation openings either at.
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.
