Insulation Thickness For 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.

Insulation thickness for flat roof.

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. Insulating a flat roof is a task that must be done during construction. See the department of energy s doe ranges for recommended levels of insulation below. It should be of the maximum available thickness.

With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same. 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. Cold roofs have the waterproof layer placed directly onto the roof deck and the insulation inside the roof just above the ceiling. 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.

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. 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. Use rigid foam insulation panels on your flat roof before applying the final roof covering or inside the house before adding sheetrock or paneling. Rockwool products are available with a bitumen or mineral coated fiberglass face to be used in a number of roofing solutions.

In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay. 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. Cold roofs and warm roofs. There are two types of flat roof.

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. The typical u value of an existing uninsulated flat roof is 1 5w m2k.