Minimum Insulation Thickness For Flat Roof

If you are upgrading the roof to meet current thermal requirements then the thickness of insulation will vary depending on its thermal conductivity.

Minimum 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. When building a flat roof it is vital that a degree of falls is built into the construction to ensure rainwater run off. 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. Minimum insulation r value requirements non residential above roof deck.

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. Cold roofs and warm roofs. The typical u value of an existing uninsulated flat roof is 1 5w m2k. 120mm of kingspan tr26 or similar will make the.

There are two types of flat roof. 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. Cold roofs have the waterproof layer placed directly onto the roof deck and the insulation inside the roof just above the ceiling. See the department of energy s doe ranges for recommended levels of insulation below.

Flat roof insulation thickness. It should be of the maximum available 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. With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.

In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay. 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. A lower u value indicates better insulation properties hence u value requirements usually specify a maximum value.