The only approach that i can think of is to install a thick layer of semi rigid mineral wool insulation above the roof sheathing followed by another layer of roof sheathing.
Insulating flat roofs outside.
Materials used to make insulation in these three types include mineral wool fiberglass cellulose fiber vermiculite styrofoam polystyrene and polyurethane.
Like other roofs insulating a flat one requires ample ventilation a vapor barrier and sealed bypasses.
Unfortunately too many dwellings suffer from this problem.
One of the main benefits you will receive from installing a warm flat roof is condensation will not.
How to insulate a flat roof warm flat roof.
Improve energy efficiency a roof without good insulation is a great contributor to energy loss.
Warm deck flat roof insulation is now the standard way to insulate a flat roof click to enlarge.
Because most flat roofs don t have an attic crawl space or venting.
Many properties use this option as there are no additional costs for scaffolding or organising how to.
Why its important to insulate your flat roof 1.
They lose loads of heat and are prone to leaking causing the materials to deteriorate.
While it s fairly common to install semi rigid mineral wool insulation above roof sheathing the method is usually restricted to low slope flat roofs.
Homes with flat roofs require a different approach to insulation than the standard approach used for homes with pitched roofs.
Flat roofs for example on extensions bathrooms and dormer windows are not the best of ideas.
The mineral wool insulation would need to be thick enough to keep the lower layer of roof sheathing above the dew point during the winter.