Flat Roof Insulation 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.

Flat roof insulation thickness.

The typical u value of an existing uninsulated flat roof is 1 5w m2k. Rockwool products are available with a bitumen or mineral coated fiberglass face to be used in a number of roofing solutions. A lower u value indicates better insulation properties hence u value requirements usually specify a maximum value. It should be of the maximum available thickness.

Flat roof insulation thickness 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. Recommended roof insulation r value is 38 r but ideal is to have 50 r or more. Since your attic is insulated i would advise at least 2 of polyiso insulation in the roof for good measure. 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 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. If you are upgrading the roof to meet current thermal requirements then the thickness of insulation will vary depending on its thermal conductivity. U value of a flat roof to comply with part l of the building regulations 2010 all roofs to rooms except those in unheated buildings should be thermally insulated to a maximum u value of of 0 18 w m k. 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.

As for insulation thickness it depends on how much you can afford. Better to have 3 or more.