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Using Commercial Insulated Panels for Roofing on Passive House?

  • 28-04-2022 7:43pm
    Registered Users Posts: 1,423 ✭✭✭ blobert


    We've just started work on a new build passive house that has a very large roof area (it's a big bungalow)

    This is a low pitch roof which we'd planned to clad in metal (zinc too expensive so we were planning on aluminium/steel)

    It's one of the most expensive parts of the build, and a lot of the cost appears to be the labour involved.

    Our QS had mentioned that maybe we could look at using a more commercial roof to cut costs here, using insulated roof panels somthing like these:

    While they are uglier than a standing seam metal roof I suspect they could be hugely cheaper, the metal and insulation are already in place and I'd imagine they would be a lot quicker/cheaper to fit.

    Using 150mm PIR panels you can hit a U Value of 0.13 which would be fine from an insulation point of view.

    I'm not sure how they would fare in terms of airtightness, the average warehouse is not going to be looking to hit the same thermal performance as a house though our current plan involves an airtight membrane inside the roof so I'd imagine similar might be possible with these.

    I'd floated it with our architect and they said they were not familiar with it being done, though the QS said he'd seen it used in rural houses before.

    Just wondering if anyone had any thoughts on this, on whether it's doable or if there's any glaring reasons it would not work?

    The current roof with insulation/sheet metal is somthing like €300 per m2 fitted. I can get the panels to the same insulation level for about €60 per m2 so assuming the installation costs are not astronomical (and generally commercial stuff is cheaper) it would seem as though a substantial saving could be made.

    If anyone had any input on this that would be great.



  • Registered Users Posts: 290 ✭✭ Biker1

    No problem using industrial type roof panels, however if you are building to the Passive House standard then your consultant will need to provide thermal bridging and airtightness details for the entire build including the roof. If you don't have specific knowledge of what is involved in a Passive build then it is unlikely you will achieve the standard.

  • Subscribers Posts: 37,787 ✭✭✭✭ sydthebeat

    I wouldn't need bringing my air tightness layer anywhere near those panels.

    Can you now split the insulation away from the roof panels and use single skin cladding? You'll get better selection of design if you do

    Design the air tight layer as close to the internal as possible

    Post edited by sydthebeat on

  • Registered Users Posts: 3,873 ✭✭✭ 10-10-20

    Also you'll need to be completely confident in the quality and warranty of those panels and request certs from the manufacturer/supplier.

    The last thing you need is de-lamination, fading or warping due to excessive heat. Does the manufacturer test the panels when backed with additional insulation or do they expect them to have free-air immediately behind the panel...etc.

    Also do you already have the detail on how they are sealed at the edges? That of course will be worked into the air-tightness detail, but get that info up-front.

  • Subscribers Posts: 37,787 ✭✭✭✭ sydthebeat

    much nicer options in single skin profiles

  • Registered Users Posts: 1,423 ✭✭✭ blobert

    Thanks for the replies guys.

    Absolutely you can get much nicer results with single skin stuff, but as I say it's turning out to be way way more expensive.

    With the low profile of the roof it's really not going to be all that visible and the the side that is from the garden is going to be plastered in solar panels so I can probably live with it being uglier if it's 1/2 the price!

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  • Registered Users Posts: 949 ✭✭✭ monseiur

    Seeing that it's a bungalow are you sure that the actual roof cladding has to be an insulated panel ? I'm not familiar with the details of passive house insulation requirements, but would, say, 600mm in attic be sufficient with a single skin roof panel or tile/slate on breather membrane ? If you have to fit insulated panels check out Kingspan's products, they're based in Cavan and do a wide selection of profiles and thicknesses from 30mm to 250mm - quality is good but not cheap. My advice would be to go with natural slate if budget allows or else Thrutone Slate or similar, not just because it's more aesthetically appealing but it's life span is at least 4 times that of cladding. I live next door to a house that was built over 140 years ago, has a natural slate roof, it's still good as new and looks splendid. Cladding is for commercial, industrial, farm buildings don't let anyone convince you otherwise.

  • Registered Users Posts: 165 ✭✭ thewiseowl12

    Hi Blobert - just wondering if you pursued the insulated panel approach or did you go with different cladding?


  • Registered Users Posts: 1,146 ✭✭✭ kieran.

    There is no real benefit to going with the insulated panel in this instance. If its a bungalow go with mineral wool or similar at ceiling joist level and then use 0.7mm colour coat galvanised single skin sheeting with the KS1000RW profile, there is actually 1000s of different profiles if your willing to buy out of the UK.