Cold Flat Roof Insulation Thickness

Cold deck flat roof the thickness of insulation required will vary depending on the material you decide to use and the manufacturer s specification.

Cold flat roof insulation thickness.

It should be of the maximum available thickness. 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. Therefore you get practically 0 r value out of it.

A cold deck flat roof will typically require insulation to be installed between the roof joists to comply with building regulation requirements. While insulation for a flat roof is expensive and can account for as much as 25 of the total installation. 120mm of kingspan tr26 or similar will make the. This is used for refurbishment e g.

With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same. Fiberboard is not an insulation. It has only 1 r value per inch and is always installed in 0 5 inch thickness. The insulation is below the deck but above the plasterboard.

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. The typical u value of an existing uninsulated flat roof is 1 5w m2k. Refurbishing an existing timber joisted flat roof which has no insulation. A ventilation gap usually 50mm should be.

It allows insulation to be added without having to replace the waterproofing on. Additionally attic condensation and leaks will make fiberboard wet. To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity. 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.

A cold flat roof is one where the insulation is between or between and below the roof joists. 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. Between and under joists.