Today there are more options.
Vent insulate flat roof.
All insulation materials require proper venting.
The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow.
Hot roofs have the roof deck then insulation then the roofing material.
For the same reason insulation shouldn t touch the roof s underside.
The answer depends on the type of roof you have.
How to insulate a flat roof.
Cold roofs have insulation beneath the.
The majority of domestic cold flat roofs use insulation between and under the joists.
Vent a foam insulated roof there used to be a time when the only insulation available was pink fiberglass.
Insulation is placed in between the joists underneath the roof surface above.
Insulation material is placed on top of the roof rather than in between the ceiling and the decking.
Vapor barriers a vapor barrier is a layer of protection between the insulation and the climate conditioned area.
How much ventilation does a flat roof need.
Cathedral roofs especially need a lot more insulation between the ceiling and the rafters because there usually isn t.
It is preferred to have the bulk of the insulation between the.
The rule of thumb for foil faced boards like thermapitch tp10 or kooltherm k7 in this scenario is that you can have no more insulation under the joists than you have between the joists.
Both these variants require different approaches to insulation which will be covered in this guide.
Cold roof systems are highly inadvisable as insulation from the inside will inevitably lead to the formation of condensation.
Roof vents on flat roofs need to be sufficiently sealed and positioned off the roof so water cannot seep in through them.
Through provision r806 4 the irc also allows you to build an unvented roof assembly.
Rigid foam and spray foam are two of them.
This is then covered with a further weatherproofing layer.
At pitched roofs with the insulation between joists we know a back vented roof is a great way to keep the roof functioning well as stated in a prior 475 blogpost.
It depends on where the insulation is installed.
Unvented assemblies work particularly well on complex roofs that would be difficult or impossible to vent properly or on roofs where it would be difficult to insulate properly if the roof were vented.
To produce a hot roof rigid insulation is fitted outside above the weatherproofing.
And while we can back vent a flat roof is it the most effective and safest approach.
Cold roof a very bad idea.
But what s true for a pitched roof is not necessarily true for a flat roof.
