In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay.
Insulation thickness for flat 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.
Cold roofs and warm roofs.
There are two types of flat roof.
Typical recommendations for exterior walls are r 13 to r 23 while r 30 r 38 and r 49 are common for ceilings and attic spaces.
Insulating a flat roof is a task that must be done during construction.
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.
The typical u value of an existing uninsulated flat roof is 1 5w m2k.
It should be of the maximum available thickness.
Use rigid foam insulation panels on your flat roof before applying the final roof covering or inside the house before adding sheetrock or paneling.
Retrofitting flat roof insulation is a difficult task and often a messy one that involves pulling up the waterproof layer that finishes off the deck so as to put flat roof insulation in underneath.
Flat roof insulation thickness.
Fm approved subject to the conditions of approval as a roof insulation when installed as shown in the current edition of the factory mutual research approvals guide.
See the department of energy s doe ranges for recommended levels of insulation below.
Benefits of energyguard polyiso roof insulation include.
Excellent lttr value compared to any other fm class 1 rated products of equivalent thickness.
Rockwool stone wool roof insulation combines the thermal performance dimensional stability impact resistance and acoustic control required to increase the performance of many flat roof assemblies.
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.
Rockwool products are available with a bitumen or mineral coated fiberglass face to be used in a number of roofing solutions.
With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.
