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  1.  
    Hi,

    Hoping someone here can advise. I'm about to have the SIPs manufacturer finalise manufacturing drawings, but I would like to ensure that there are no issues with the opening sizes in the panels when the time comes to install the rooflights. The given size Velux roof windows are 550x980 and looking at typical velux installation instructions, they appear to indicate a tolerance of 40-60mm for the width (EDZ):

    http://www.professional.velux.co.uk/en-GB/Documents/Installation%20instructions%20pdf/GGL_GGU452953-2013-03.pdf

    So I presume the manufacturing drawings should be 600ish for the width? And I guess with this 40-60mm gap, it's intended to have their insulation kit fitted around the frame (BDX kit)?

    Obviously I don't want my installer thinking he can simply hack away at the SIP panels on the day, if the fit is a bit tight. Nor do I want a massive gap that needs to be filled with sealant etc.
    • CommentAuthortony
    • CommentTimeMar 2nd 2015
     
    The SIP panel is likely to have great chunks of wood round the hole (thermal bridges) so make the hole as big as you ever dare, for me 50mm all round and then cantilever battens for the fiing clip screws. This will allow you to mitigate the thermal bridge to the reveal very nicely, if you are a coward then even 40mm big all round will allow 48mm pir to the reveal.
  2.  
    Thanks Tony. I will allow for some more width then to get some sheet insulation in there.
  3.  
    Hi kentishgreen,

    Did this go ok in the end?

    Did you leave the 50mm gap, and was it straightforward to mount the Velux in the SIP panel?

    Just about to tell my Timber Frame company how big to make the hole for the Velux. There seems to be limited info out there on how to mount these in SIPS, all the Velux information shows battens, tiles, etc.

    Thanks

    Pete
  4.  
    Should have said, I'm fixing Tata Colorcoat Urban Steel roofing directly over the SIPS membrane, hence no Battens, etc.
    • CommentAuthorDarylP
    • CommentTimeMar 21st 2017
     
    @OracsRevenge,
    If no battens above, how are you going to mitigate/manage the condensation that forms under the steel?
    Or, is this the one with the anti-condensation fleece?
  5.  
    Hi,

    Tata recommend fitting directly through the membrane onto the OSB face of the Kingspan SIP.

    Thanks
  6.  
    Hi,

    I had no issues with the installation. Can't recollect exactly what tolerance I had though. Mine was counter battened so windows are elevated quite high from the OSB now. Still need to sort out the splays inside. Biggest issue I had was with the roofer who was throwing the velux vapour barrier from the roof - "I never bovva fittin' that sh1t. I don't see the point...":angry: So I ended up doing 90% of the windows myself and just relied on his muscle to give me a hand lifting the windows in.

    With your steel roofing, I'd still be inclined to have some battens between the OSB and steel to ensure ventilation. I'm no expert but would be extra cautious with the roof. I've seen pics where condensation (In US builds have caused the SIP panels to rot.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 10th 2017 edited
     
    Posted By: DarylPthe condensation that forms under the steel?
    Where wd that condensation come from? Assuming a SIP is non-breatheable (with VCL) so water vapour's nor coming to the steel from the interior (until the VCL goes faulty in due course). Until then, that leaves just atmospheric condensation, occuring on any skyward-facing material, prob both faces, on a clear night. How much of a threat is that? Is that why Tata say battens unnecessary? Anyway, battens wouldn't help unless there's deliberate, copious through-ventilation from eave to ridge outlet, of the batten space.
    • CommentAuthorDarylP
    • CommentTimeApr 10th 2017
     
    @fosertom,
    I have not read up on the physics, but I imagine it is the same principle / related to condensation on car roofs in the morning.....?
    It does exist as a phenomenon, I have seen it myself, and others have too. Hence the 'fleece' fitted to the underside of some roofing sheets?
    •  
      CommentAuthorfostertom
    • CommentTimeApr 10th 2017
     
    I ask because it makes a massive difference, whether the layers beneath are breatheable, or rely on a (hopefully) perfect long-term VCL. I wonder whether Tata's advice (to fix direct to the OSB, no battens, with or without through-ventilation) is strictly in case of non breathable, VCL'd layers beneath. If no such stipulation, then I'd strongly question that advice.
    •  
      CommentAuthordjh
    • CommentTimeApr 10th 2017
     
    Read the BBA
    •  
      CommentAuthorfostertom
    • CommentTimeApr 10th 2017 edited
     
    Don't need to - I can't imagine using metal sheeting that way - but I might alert someone else.
      P1000611 autocorrect med.jpg
    • CommentAuthorringi
    • CommentTimeApr 10th 2017
     
    But Tom, you do use glue OSB with EWI that way without being concerned about how much it can breath to the outside.....
    •  
      CommentAuthorfostertom
    • CommentTimeApr 10th 2017
     
    How do you mean? OSB is fair-to-good vapour-breatheable (but pretty airtight), along with everything else in my favourite build-up (as pictured) and when it goes seamlessly from wall to roof (minus the render) the batten/crossbatten-space above it, beneath the corrugated iron, is copiously cross-ventilated.
    •  
      CommentAuthordjh
    • CommentTimeApr 10th 2017
     
    Sorry, Tom, maybe I'm misunderstanding, but you ask questions and then refuse to read the document in which they're answered?
    •  
      CommentAuthorfostertom
    • CommentTimeApr 10th 2017
     
    We've got along fine on that basis - division of labour - for many years so far. I've learned a lot and am extreemely grateful for GBF.
    • CommentAuthorEd Davies
    • CommentTimeApr 11th 2017
     
    Posted By: djhRead the BBA
    Linky? I'm confused as to which Tata product is involved here so not even sure what to search for.
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