A cold deck flat roof will typically require insulation to be installed between the roof joists to comply with building regulation requirements.
Cold flat roof insulation thickness.
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.
Fiberboard is not an insulation.
Cold deck the thickness of insulation required will vary depending on the material you decide to use and the manufacturer s specification.
120mm of kingspan tr26 or similar will make the.
It allows insulation to be added without having to replace the waterproofing on.
This is used for refurbishment e g.
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.
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 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.
While insulation for a flat roof is expensive and can account for as much as 25 of the total installation.
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.
It has only 1 r value per inch and is always installed in 0 5 inch thickness.
With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.
If you are upgrading the roof to meet current thermal requirements then the thickness of insulation will vary depending on its thermal conductivity.
Therefore you get practically 0 r value out of it.
The typical u value of an existing uninsulated flat roof is 1 5w m2k.
A cold flat roof is one where the insulation is between or between and below the roof joists.
A ventilation gap usually 50mm should be.
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 insulation is below the deck but above the plasterboard.
To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity.
Between and under joists.
