Minimum Insulation Thickness For Flat Roof

Cold roofs have the waterproof layer placed directly onto the roof deck and the insulation inside the roof just above the ceiling.

Minimum insulation thickness for flat roof.

Figure 5 5 keep insulation away from a recessed light fixture by creating a barrier minimum 12 5 mm 1 2 in clearance 150 mm 6 in preferred centre the fixture if possible keep it a minimum of 12 5 mm 1 2 in from the sides and top. 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. The typical u value of an existing uninsulated flat roof is 1 5w m2k. When building a flat roof it is vital that a degree of falls is built into the construction to ensure rainwater run off.

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. 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. Minimum insulation r value requirements non residential above roof deck. With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.

State applicable energy ashrae zone minimum r value state local ms mississippi ashrae 90 1 2010 2 r 20 3 r 20 state local mo missouri 2012 iecc 4 r 25 5 r 25 state only mt montana 2012 iecc 6 r 30. There are two types of flat roof. Others would treat even steeper pitches as flat roofs. 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.

120mm of kingspan tr26 or similar will make the. If you are upgrading the roof to meet current thermal requirements then the thickness of insulation will vary depending on its thermal conductivity. In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay. It should be of the maximum available thickness.

Flat roof insulation thickness. 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. A lower u value indicates better insulation properties hence u value requirements usually specify a maximum value.