Minimum Insulation On A Flat Roof

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

Minimum insulation on a flat roof.

Flat roof hello there s a lot of good material in this post for comment. With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same. When building a flat roof it is vital that a degree of falls is built into the construction to ensure rainwater run off. The definition of a flat roof according to bs 6229 is having a pitch less than 10 o to the horizontal.

You can expect to pay about 55 100 sq ft. Minimum insulation r value requirements non residential above roof deck. However some in the industry would consider up to 15 o as their definition of a flat roof. Let me just mention that the flat roof as a motif certainly predates 1933.

The target should be to achieve a u value of 0 25w m2k or better. Cold roofs and warm roofs. 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.

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. 120mm of kingspan tr26 or similar will make the. While expensive the best insulation is polyiso rigid foam. 13 july 2017 kingspan insulation uk.

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. For a 1 inch board equivalent of 6 r value. The typical u value of an existing uninsulated flat roof is 1 5w m2k.

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. We recommend having at least 20 r value worth of material for optimal energy efficiency. Gropius and le corbusier in the 20s sought to capture the machine age by using industrial style roofs.