The thermal efficiency isn t as good as with warm roof insulation.
Warm and cold flat roof construction.
A ventilation gap usually.
A warm flat roof or a built up roof bur is one where all the insulation is above the joists deck making them part of the warm fabric of the building.
There are three recognised designs of flat roof construction.
Hopefully this video will help explain the difference between cold flat roof construction and warm flat roof construction this videos show detailed drawings.
It is usually the most acceptable type of construction for domestic possessions and belongings as it avoids the need for aeration of the roof construction.
The major difference between the warm flat roof and the cold flat roof has to do with the air flow between the roofing timbers known as joists that help to hold up the roof.
In creating the cold flat roof air is allowed to circulate freely between the joists and there is no insulation.
Cncd 053 v1 5 7 2019 0 cold deck flat roof the thickness of insulation required will vary depending on the material you decide to use and the manufacturer s specification.
A cold flat roof insulation requires more work taking off old boards and replacing them and the roof surface.
A warm roof is much more straightforward to install and provides a superior thermal performance and is therefore more costly.
Cold roof construction requires that a suitable ventilated air space exists above the insulation layer within which the air is constantly mobile being replenished by fresh incoming air whilst the air resident within the void space is being expelled via a natural vent action at another point.
In case of warm roofs they have an insulation above the roof deck in this way it keeps the deck warm.
In the warm flat roof construction there is insulation packed into every possible space where air can flow.
A warm deck roof is much easier to install offers great thermal performance but adds height to the flat roof.
The insulation is immediately below the waterproofing layer.
A cold roof is best when you re initially creating a flat roof and is cheaper than a warm roof but does provide an inferior thermal performance.
In a warm roof construction the principal thermal insulation layer is located above the structural decking resulting in the structural deck and support structure being at a temperature close to that of the interior of the building.
Guidance advice on warm cold roofs www cncbuildingcontrol gov uk continuous 5mm gap at ridge.
Warm flat roofs make it easier to eliminate cold bridging.
Allows heat to be conserved with no requirement for roof void ventilation.
The breakdown warm roof vs cold roof.
The membrane is then attached to the insulation.
On a flat roof this could be air in at one ventilated facia soffit and air out via an opposite ventilated facia soffit.
