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Using Commercial Insulated Panels for Roofing on Passive House?

  • 28-04-2022 7:43pm
    #1
    Registered Users Posts: 1,495 ✭✭✭


    Hello,

    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:

    https://www.panelsell.ie/insulated-panels-stock-articles#productelement-4

    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.

    Thanks!



Comments

  • Registered Users Posts: 367 ✭✭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: 40,953 ✭✭✭✭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: 6,622 ✭✭✭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: 40,953 ✭✭✭✭sydthebeat



    much nicer options in single skin profiles



  • Registered Users Posts: 1,495 ✭✭✭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: 1,207 ✭✭✭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: 169 ✭✭thewiseowl12


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

    Thanks



  • Registered Users Posts: 1,174 ✭✭✭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.



  • Registered Users Posts: 3 ajarsm86


    I know I'm probably resurrecting a dead thread but would love to hear from @blobert if you went ahead with the insulated panels in the end?

    Building with metal cladding has obviously become a lot more popular in the last few years and we might be starting a cottage renovation in the next year, (the wannabe Architect in me wants to try make something aesthetically pleasing but do it a bit differently on a super tight budget)....



  • Registered Users Posts: 40 somebodude


    same here. : https://www.boards.ie/discussion/comment/120631633


    Cladding is for commercial, industrial, farm buildings don't let anyone convince you otherwise.

    They do use it domestically in germany though. I'm very tempted .....



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  • Registered Users Posts: 4 Dooranged creations


    Hello has anyone used insulated metal panels for siding on wood frame construction?



  • Subscribers Posts: 40,953 ✭✭✭✭sydthebeat


    Tricky detail.

    If you've a vented cavity outside the wood frame then the insulated panel is useless for insulation

    If you don't have a vented cavity then you've a very risky construction from the point of view of condensation.

    What are you thinking regarding the make up of the wall?

    Post edited by sydthebeat on


  • Registered Users Posts: 4 Dooranged creations


    Well, you see I went ahead and did this and now I’m in trouble with the city I removed the exterior sheathing, put Tyvek on there rim joist and studs remove the insulation in the vapour barrier and mounted the panel directly to the studs planning on spray foam insulation on the inside of the wall to alleviate the different expansion and contraction rates of the interior and exterior skins. The city now wants me to clear this with a building envelope engineer, and a structural engineer, which I don’t feel is possible. Now I’m likely going to have to remove it and go to conventional siding, but I was hoping to possibly use it as a carrier panel. And put some sort of siding on a rain screen outside of it.




  • Subscribers Posts: 40,953 ✭✭✭✭sydthebeat


    ...and thats the trouble with trying to build your own DIY single skin timber frame.



  • Registered Users Posts: 45,813 ✭✭✭✭muffler


    Out of curiosity what country is this house in?



  • Registered Users Posts: 6,622 ✭✭✭10-10-20


    Tyvek and "City" had me wondering too, and I have never seen that style of scaff either. But the clouds are Irish though. ;)



  • Subscribers Posts: 40,953 ✭✭✭✭sydthebeat


    tyvek would be a pretty common manufacturer of felts and vapour barriers here in ireland, but the terminology around "rim joist" and "carrier panel" is certainly strange



  • Registered Users Posts: 367 ✭✭Biker1


    Typical American terminology and by the looks of the construction type it's either in America or a Yank building in Ireland.!!!



  • Registered Users Posts: 4 Dooranged creations


    Canada



  • Registered Users Posts: 4 Dooranged creations


    Hello, just to clarify by rim joist, I mean the joist or band board that wraps the perimeter of the house sitting on the foundation, that caps off the ends of the floor, Joists and by carrier panel I mean, adding a rain screen system to the outside of it, which would be carried by the insulated metal panel. A girt is installed between the panel laps and a second layer of cladding is then installed onto the Girts I was hoping to find somebody with some experience or information about mounting. Imps to wood framing I have been doing architectural sheet metal for 15 years and have vast experience in multiple different panel systems. These panels are leftovers from various jobs that I have done. However, I can’t find any information about mounting them to wood obviously it isn’t recommended due to the fasteners being fatigued from expansion and contraction. These panels have been on my house for over two years now and I haven’t seen any problems. Just need to satisfy the building officials which is proving to be very difficult without any examples or literature on the subject I have installed metal cladding on countless wood buildings and it’s never been an issue also, I have installed insulated metal panels on countless buildings directly to the steel stud. Framing everything set in non-skid and butyl caulking never heard of a problem with condensation. I should also note that there is no visible windows on the house because the siding opens to expose them so there is no condensation there either




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  • Subscribers Posts: 40,953 ✭✭✭✭sydthebeat


    this is an 'ireland based' website so we woudlnt have the relevant info for canadian regulations and policies.

    i woudl say however that insurance companies in canada have been severely burnt in the past by single skin timber frame construction, so city officials and codes may very well be extreme strict on whats acceptable or not.


    your biggest issue is proving that the dew point (interstitial condensation) does not occur within the structural timber plane. From what youve described already, if i had to put money on it, i would suggest that it does actually occur there.



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