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    • CommentAuthorGMorin
    • CommentTimeJun 22nd 2017 edited
     
    Hi all,

    I'm building an extension with a glazed gable end.

    We have ended up having to have two steel beams for the inner and outer leaves, the outer leaf beam will support folding doors and glazing panels on top, the inner leaf beam just has a central post supporting the ridge beam. This is not high original design idea, but is what we have ended up having to have.

    At the moment the steels are in place and the doors and glazing will go in soon. My question is how best do you insulate the steel beams?

    We are looking at encasing the beams with aluminium. After a chat with the glazing company I've came up with the attached design, is this okay how can it be improved?

    Just looking for suggestions and options.


    I look forward to hearing your comments

    Thanks

    Gary
      steel insulation.PNG
    • CommentAuthorCWatters
    • CommentTimeJun 22nd 2017
     
    Which country are you in? In England steel beams frequently have to be protected from fire by a layer or two of plasterboard.
    • CommentAuthorGMorin
    • CommentTimeJun 22nd 2017
     
    I'm in England, The building reg drawings showed nothing and was not questioned. I would rather not put plaster board around it.

    Gary
    •  
      CommentAuthordjh
    • CommentTimeJun 22nd 2017
     
    Regarding fire safety rules see https://www.planningportal.co.uk/info/200130/common_projects/17/extensions/9
    Particularly at present I suspect aluminium cladding over foam insulation will ring alarm bells.

    The inner beam is entirely within the thermal envelope and other than fire safety there aren't any big concerns, I think.

    The outer beam is a large thermal bridge from inside the thermal envelope to outside, and the thermal bridge is made considerably worse by aluminium also passing from outside to inside. In short it looks like a disaster to me.

    The outer beam needs thermal insulation wrapped all around it, not just filling the webs, then the fire protection and finally some cladding. The cladding could be aluminium, as long as separate pieces are used externally and internally.

    How airtight are the bifold doors and how long-lasting is the seal design?
    • CommentAuthorGMorin
    • CommentTimeJun 22nd 2017
     
    thanks for the replies,

    I think we should be ok with fire resistant paint on the beams, the outer one is not load bearing. ( i will check with building control)

    "In short it looks like a disaster to me." I thought it may be , hence the question to the forum.

    Below is version 2, there is now a break in the aluminium cloak, and some form of insulation foam/tape between the steel beam and the aluminium.

    Would this work?, If so can someone recommend a product I can use for the installation tape? It would be good if is double sided.

    For the doors, we have gone to a single manufacturer for survey and install with a 20 year guarantee, so at least I have one place to go if they do fail.

    Regards

    Gary
      steel insulation v2.PNG
    •  
      CommentAuthorfostertom
    • CommentTimeJun 22nd 2017 edited
     
    Posted By: GMorinthe outer one is not load bearing
    So couldn't it be re-shaped (or is it already in?) to allow insulation thickess between outside, and top, bottom and outer faces?
    • CommentAuthortony
    • CommentTimeJun 22nd 2017
     
    How about exoskeleton, put the structure outside the thermal envelope?
    • CommentAuthorGMorin
    • CommentTimeJun 22nd 2017
     
    The Steels are in and the windows have been surveyed and are being made.

    I wonder if something like this would help

    http://www.fixfast.com/system/storage/downloads/1442918995_datasheet_cold_bridging_tape.pdf

    Gary
    •  
      CommentAuthordjh
    • CommentTimeJun 22nd 2017
     
    Posted By: GMorinThe Steels are in and the windows have been surveyed and are being made.

    It sounds like it's too late to ask for advice then.

    Basically there is no substitute for thickness when it comes to insulation. Though it can be reduced a lot by the use of aerogel or VIP panels (VIP is aerogel in a vacuum). A PE tape is next to useless.

    For the doors, we have gone to a single manufacturer for survey and install with a 20 year guarantee

    But what performance do they guarantee?

    Ask to see the thermal model from whoever designed the structure. Both heat flow and isotherms will be illuminating.
    • CommentAuthorGMorin
    • CommentTimeJun 23rd 2017
     
    ok, let's step back, it is not a passive house, it's just an extension on my house.

    This is my first project, as the build evolved this is what we have ended up. The building reg drawings was done by an architect, but for this detail, he just had a single steel spanning inner and outer walls coming straight through, will a liitle insulation in web on the outer side, that was it.

    So I'm in the situation as I am now, so how can I optimise the design? if you like make the best out of a bad thing.

    thanks
    •  
      CommentAuthorfostertom
    • CommentTimeJun 23rd 2017
     
    Fundamentally, you can't put any thickness of insulation to cover the 2 edges (and top/bottom) of the highly conducting beam flanges so the whole beam is going to be completely stone cold, regardless of insulation infilling its webs. Similarly, no insulation thickness between that stone cold lump and the interior.

    You have to create significant thickness to a) separate the beam from outdoors, and b) separate it from indoors.

    Can you extend outward the 'spandril' (beam facing between upper and lower glazing), and can you extend it upward and downward, if necessary 'mastering' across the face of the window frames?
    • CommentAuthorGMorin
    • CommentTimeJun 23rd 2017
     
    That makes senses, so if I understand you correctly something like this world be better.

    My main concern, and I will need to get back to window manufacture, is the drip outlet is at the bottom of the frame section. I will need to go back to them and see what can be done.

    Thanks
      steel insulation v3.PNG
    • CommentAuthorgyrogear
    • CommentTimeJun 23rd 2017
     
    From a PLP (pure layman perspective) that looks a lot better to me !

    gg
    •  
      CommentAuthordjh
    • CommentTimeJun 23rd 2017 edited
     
    Apparently fire resistant paint for steel is intumescent and needs a gap around the steel in order to work.

    http://www.bdonline.co.uk/a-guide-to-fire-protection-for-architects/5026079.article

    I'm beginning to think about solicitors and suing the architect. I hope there's a better solution.
    • CommentAuthorcaliwag
    • CommentTimeJul 5th 2017
     
    Mmm...sounds like you employed a plan drawer rather than architect. surely building control would've picked up the cold bridge. really the outer leaf steel should have been totally inboard of the glazing and the glazing support bracketed out...surely not an uncommon problem. but as others have said...it's too late now. A salutary lesson in employing a qualified industry expert with experience.
    • CommentAuthorowlman
    • CommentTimeJul 5th 2017
     
    Would removing the outer steel and replacing with Glulam be an option, aluminium cloaked if necessary? How far down the line is the window manufacture?
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