No ventilation is required for these types of roofs.
Insulating hot cold flat roof.
There are three types of insulation solution if you have a flat roof.
A warm deck roof is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation.
Flat concrete roofs are generally not ventilated since the ceiling internally is generally a plaster and skim coat directly to the underside of the cold concrete.
This is then covered with a further weatherproofing layer.
With a warm roof the insulation is installed on top of the existing surface rather than in between the rafters.
On a warm flat roof the layer is installed underneath the insulation to stop moisture interacting with it through rising thermal pressure lower down in the building.
For a 1 inch board equivalent of 6 r value.
Installing a warm roof can be extremely straight forward and simple to do.
Basically the term cold roof refers to a traditional roof or vented roof while hot roof refers to a roof that is not ventilated and which has foam insulation attached directly to the roof sheathing.
Many properties use this option as there are no additional costs for scaffolding or organising how to gain safe access to the roof exterior.
This will enable the airflow to circulate freely.
The insulation material is placed between the supporting joists leaving a gap of 50 60mm between the roof and insulation.
To produce a hot roof rigid insulation is fitted outside above the weatherproofing.
Warm roofs offer a superior thermal performance and therefore come with a higher cost.
You can expect to pay about 55 100 sq ft.
This means there is a vapour control layer in the ceiling and cross ventilation at the eaves or the top of the walls.
Creating a void between the old ceiling and new is better but ideally you need to eventually consider insulating the top of the concrete roof with solid insulation and a better covering grp or epdm.
Warm flat roof insulation.
Cold roof a very bad idea.
This may help with condensation but causes such a loss of heat that it has been banned in scotland.
It is top quality and the most cost effective product for your flat roof.
Lots of traditional flat roofs are of the cold roof construction type.
Basically there are two options to choose from when insulating a flat roof.
Cold roof systems are highly inadvisable as insulation from the inside will inevitably lead to the formation of condensation.
For cold flat roofs the vapour layer needs to be positioned underneath the insulation layer on top of the room below to create an effective barrier.
While expensive the best insulation is polyiso rigid foam.
