Insulation for cold flat Roof without air ventilation

[lamywaby]

Hi, help please on protecting a newly built cold roof whilst trying to add insulation and under boarding.

We have a newly built extension utility area to the side of our house. It is constructed with a cold flat roof with small pitched ends that have flat back parapet style to the mid flat roof. The total length is about 10m (the mid section flat roof makes up about 8m). A spray foam has been applied to the deck underside (a roofing felt style barrier between deck & foam).

Due to the construction of the flat roof beams running side to side and with the way doors have been fitted each end it would be near on impossible to add any air ventilation.

I would like to finish off internally by boarding the underside but have concerns about the terrors of condensation and damp problems. Due to the lack of air ventilation my intention is to fit a tightly sealed damp proof membrane as a vapour barrier then simply plasterboard I would keep all the electrics and lighting below the p/board so not breaking the barrier).

Does anyone see a problem with my intentions (YouTube videos of rotting flat roof decks has worried me).

I am not being restricted or governed by building regulations but just the need of doing the best & right thing.

 

[lamywaby]

Hi, help please on protecting a newly built cold roof whilst trying to add insulation and under boarding.

We have a newly built extension utility area to the side of our house. It is constructed with a cold flat roof with small pitched ends that have flat back parapet style to the mid flat roof. The total length is about 10m (the mid section flat roof makes up about 8m). A spray foam has been applied to the deck underside (a roofing felt style barrier between deck & foam).

Due to the construction of the flat roof beams running side to side and with the way doors have been fitted each end it would be near on impossible to add any air ventilation.

I would like to finish off internally by boarding the underside but have concerns about the terrors of condensation and damp problems. Due to the lack of air ventilation my intention is to fit a tightly sealed damp proof membrane as a vapour barrier then simply plasterboard I would keep all the electrics and lighting below the p/board so not breaking the barrier).

Does anyone see a problem with my intentions (YouTube videos of rotting flat roof decks has worried me).
https://superfoamusa.com
I am not being restricted or governed by building regulations but just the need of doing the best & right thing.

thanks in advance for any help

 

[semipro]

Without some graphics to refer to, I really can't offer any advice on the build.
Whether you might have some condensation problems is dependent upon the thickness of your spayed insulation, the temps, humidity levels, etc. Given an outside temp, you basically want the temp gradient across the insulation to result in the condensation point occurring within the insulation, not at the insulation face within the structure.
I'd suggest you browse greenbuildingadvisor for some answers there.