Cold Flat Roof Insulation Thickness

The typical u value of an existing uninsulated flat roof is 1 5w m2k.

Cold flat roof insulation thickness.

120mm of kingspan tr26 or similar will make the. Refurbishing an existing timber joisted flat roof which has no insulation. Unless the joists are exceptionally deep there is also likely to be a requirement to install insulation to the underside of the joists as the upper 50mm of joist space is usually required to be left clear for ventilation purposes. It should be of the maximum available thickness.

It has only 1 r value per inch and is always installed in 0 5 inch 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. While insulation for a flat roof is expensive and can account for as much as 25 of the total installation. Fiberboard is not an 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. A cold deck flat roof will typically require insulation to be installed between the roof joists to comply with building regulation requirements. Therefore you get practically 0 r value out of it. Insulating a flat roof with recticel powerdeck u recticel s powerdeck u offers 0 024 u value for thicknesses 120mm or more so it s a great thermal insulator as well as a strong and stable board for structural integrity.

A cold flat roof is one where the insulation is between or between and below the roof joists. If you are upgrading the roof to meet current thermal requirements then the thickness of insulation will vary depending on its thermal conductivity. Between and under joists. This is used for refurbishment e g.

Additionally attic condensation and leaks will make fiberboard wet. Cold deck the thickness of insulation required will vary depending on the material you decide to use and the manufacturer s specification. The target should be to achieve a u value of 0 25w m2k or better. To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity.

A ventilation gap usually 50mm should be. The insulation is below the deck but above the plasterboard. It allows insulation to be added without having to replace the waterproofing on.