VCL for a warm flat roof

[ToughButterCup]

The only job for the VCL in a warm flat roof is to prevent water vapour condensing inside the insulation layer isn't it?

Maybe it would be better to say .... condensing on any suitable surface above the VCL.

Should, therefore, the VCL extend up the sides of the PIR insulation (as well as underneath it) ?

 

[ADLIan]

In a warm roof condensation may (will?) occur on the underside of the waterproof layer and BS 6229 gives maximum allowable winter build-up when assessing the condensation risk.

The VCL should be taken up the sides of the insulation and onto the top of the insulation (or up any upstand) and sealed to the waterproof layer so that the insulation is encapsulated. See guidance from insulation or waterproofing manufacturers.

[ToughButterCup]

1 hour ago, ADLIan said:

(...) See guidance from insulation or waterproofing manufacturers.

I'm glad you replied. And glad I asked.... I haven't ever seen (edited to 'noticed') guidance from either source recommending that the vcl be sealed to the waterproof membrane. 

 

 

Another steep learning curve ahead of me then. 

But I have now. (10 minutes later) 

Thanks @ADLIan, very much. 

Edited November 13, 2018 by recoveringacademic
Stupidity on my part

[ADLIan]

You’re welcome.

[Jimbo37]

@ADLIan Just passed this to my architect, as I was concerned that my insulated upstands were not insulated at the top. She didnt understand the reasoning (this edge of the insulation is facing up/cold) - do you have any references or further comment you can give. TIA