Minimum Insulation On A Flat Roof

Cold roofs and warm roofs.

Minimum insulation on a flat roof.

The typical u value of an existing uninsulated flat roof is 1 5w m2k. To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity. A lower u value indicates better insulation properties hence u value requirements usually specify a maximum value. In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay.

If you are upgrading the roof to meet current thermal requirements then the thickness of insulation will vary depending on its thermal conductivity. The target should be to achieve a u value of 0 25w m2k or better. We recommend having at least 20 r value worth of material for optimal energy efficiency. However some in the industry would consider up to 15 o as their definition of a flat roof.

With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same. 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. While expensive the best insulation is polyiso rigid foam. Flat roof hello there s a lot of good material in this post for comment.

Cold roofs have the waterproof layer placed directly onto the roof deck and the insulation inside the roof just above the ceiling. Gropius and le corbusier in the 20s sought to capture the machine age by using industrial style roofs. There are two types of flat roof. When building a flat roof it is vital that a degree of falls is built into the construction to ensure rainwater run off.

13 july 2017 kingspan insulation uk. Let me just mention that the flat roof as a motif certainly predates 1933. The definition of a flat roof according to bs 6229 is having a pitch less than 10 o to the horizontal. For a 1 inch board equivalent of 6 r value.

You can expect to pay about 55 100 sq ft. 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. 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.