Cold Flat Roof Insulation Thickness

120mm of kingspan tr26 or similar will make the.

Cold flat roof insulation thickness.

It allows insulation to be added without having to replace the waterproofing on. If you are upgrading the roof to meet current thermal requirements then the thickness of insulation will vary depending on its thermal conductivity. Additionally attic condensation and leaks will make fiberboard wet. 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.

Therefore you get practically 0 r value out of it. 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. A cold flat roof is one where the insulation is between or between and below the roof joists. Between and under joists.

A ventilation gap usually 50mm should be provided between the top of the insulation and underside of the roof covering to allow the air to flow across. While insulation for a flat roof is expensive and can account for as much as 25 of the total installation. To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity. The insulation is below the deck but above the plasterboard.

A ventilation gap usually 50mm should be. This is used for refurbishment e g. It has only 1 r value per inch and is always installed in 0 5 inch thickness. It should be of the maximum available thickness.

Refurbishing an existing timber joisted flat roof which has no insulation. 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. Fiberboard is not an insulation. Cold deck flat roof 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. Kingspan and recticel are the two of the most well known flat roof insulation brands and they re firm favourites of insulation superstore customers. With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.