It s what s called the cold roof principle.
Residential flat roof insulation.
To achieve this add 100 to 160mm of insulation above the structural deck dependant upon insulant conductivity.
Pros and cons for flat roof materials all three types of flat roofing cost 250 to 350 per square 100 square feet but prices vary according to region and size of the roof.
These products provide a high r value inch excellent sound attenuation characteristics and outstanding fire performance.
Rockwool products are available with a bitumen or mineral coated fiberglass face to be used in a number of roofing solutions.
Insulating a roof from inside is technically feasible.
Flat roofs usually come with a 10 to 20 year warranty but can last 25 years if you build the roofs right and maintain them using commonsense rules.
Rockwool stone wool roof insulation combines the thermal performance dimensional stability impact resistance and acoustic control required to increase the performance of many flat roof assemblies.
The type that is right for your flat roof insulation job depends upon the state of the roof expert opinion on the best type and your budget.
Recommended roof insulation r value is 38 r but ideal is to have 50 r or more.
The typical u value of an existing uninsulated flat roof is 1 5w m2k.
From there the flat roof system you choose will determine the materials you apply.
This system was often used in the past but is not recommended nowadays.
Since your attic is insulated i would advise at least 2 of polyiso insulation in the roof for good measure.
The target should be to achieve a u value of 0 25w m2k or better.
Better to have 3 or more.
Underneath the basics flat roofs are usually constructed with a ceiling nailed to joists which support a deck usually wood in residential construction a vapor barrier insulation and a roof board.
That accounts for its materials membrane insulation and decking as well as snow and rainfall and even for equipment like an air conditioner.
As for insulation thickness it depends on how much you can afford.
Can a flat roof be insulated from inside from the ceiling of the area below.
Thermafiber residential mineral wool blankets are ideal for insulating walls floor ceilings and attic spaces in homes.
Products are also inorganic non combustible and mold resistant.