It should be of the maximum available thickness.
Warm roof insulation depth.
To eliminate all condensation risks and making it a true warm roof construction.
The chosen insulation laid on top of this should be able to take the weight of anything put above it on the roof without compression or protected from compression by further sheeting.
Flat roof insulation thickness.
Our roof conversions can be completed in just 2 3 days.
Flat roof insulation always requires professional insulation and damp roofs require professional assessment before work can be carried out.
The typical u value of an existing uninsulated flat roof is 1 5w m2k.
A flat roof where the insulation sits below the waterproof membrane and above the structural deck is a warm roof deck.
Insulation which prevents any risk of condensation and stops the build up of damp within the roof.
Warm flat roofs do not need to be ventilated as the insulation is.
Warm deck the type of insulation for this is usually of a rigid type and the thickness will vary depending on the manufacturer s specifications.
The below table shows the thickness of insulation required for a typical warm roof construction with insulation fitted above the rafters.
As only a few years ago the recommended depth of insulation was 200mm.
Warm roof solutions are generally more.
If 180mm is to be installed then 100mm board might be introduced between the rafters there has to be a minimum 25mm air gap between the insulation and the underside of the tiles or slates with an 80mm board running across the rafters.
Cold flat roofs are typically avoided as you d need to install ventilation which can prove problematic for many reasons relating to space labour costs etc.
With a warm roof the usual process is to split the insulation into two layers.
Insulating between the joists of your loft will keep your house warmer but make the roof space above colder.
The benefits of a warmer roof 2 3 day installation time.
Cold deck this is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof.
Pipes water tank and loft hatch.
A cold roof can be cheaper as ridged warm roof insulation tends to be more expensive a warm roof is sometimes the only option when it is difficult to get the required cross ventilation rigid warm roof insulation can allow for smaller timber depths as the 50mm air gap does not have to be maintained.
Ventilation is required for these roofs.
Our u value calculator is free and simple to use for calculating u values specific to your roof construction design.
There is a requirement when refurbishing a roof to have a minimum u value of 0 18 w m k in england and wales but for a complete re roof in wales the minimum u value required is 0 15 w m k.
