Dry lining rooflight upstand - condensation risk ?

[bmj1]

Hi all,

 

We've got some rooflights built like this:

 

 

I'm not entirely sure on the insulation in the upstand (if any).

 

Is there any reason not to use a insulated plasterboard here (17mm PIR + 9.5mm plasterboard), in order to reduce the thermal bridging ?

 

(My concern is of creating interstitial condensation)

[Nickfromwales]

I always recommend Marmox boards and plaster directly to them.  

[Dave Jones]

upstands should have the same level of insulation as the roof. 99.9% of chippies totally ignorant of this fact including yours. 

[Wumpus]

We used compacfoam to form the upstand. Robust and insulated.

[nod]

99% are boarded withe 12.5 mil wallboard without any condensation issues Ideally there would be enough room for an insulation board But there rarely is 

[Dave Jones]

  On 15/06/2023 at 09:48, nod said:

99% are boarded withe 12.5 mil wallboard without any condensation issues Ideally there would be enough room for an insulation board But there rarely is 

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make the upstand wider externally. still takes the same size light and has full level of insulation.

[bmj1]

  On 15/06/2023 at 13:04, Dave Jones said:

make the upstand wider externally. still takes the same size light and has full level of insulation.

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I've got space for insulated plasterboard internally, just wondering if a risk of condensation?

[Dave Jones]

  On 15/06/2023 at 13:46, bmj1 said:

 

I've got space for insulated plasterboard internally, just wondering if a risk of condensation?

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as long as the U value and depth are the same as the roof. e.g lower U value (more ££££) can be slimmer as long as end result is same.

[Nickfromwales]

25mm Marmox + skim. Almost 100% of the thickness is then insulation.