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Housing - New Build: SIP house sole plate detail, help needed

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31 to 57 of 57

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    Posted By: ringiWhy can't something like the Marmox Thermoblock be used below the SIP?


    Looks like it has been done: http://housingspecification.com/hs/news-article/3644/super-low-energy-sips-house-amplsquoriding-on-marmox-thermoblock

    I will have my SIPs on a piled slab, so hopefully can minimise cold bridging using something like the Thermoblock approach.

    Posted By: Viking House
    Sole plates below the screed level on a cold slab aren't a good idea, there was a court case in Sweden as a result of Sole Plate rot that nearly took down a major house insurer. In Sweden its all warm slabs now with the insulation underneath.


    What caused the rot in Sweden? Condensation? Ingress of water?
  2.  
    Posted By: kentishgreenLooks like it has been done: http://housingspecification.com/hs/news-article/3644/super-low-energy-sips-house-amplsquoriding-on-marmox-thermoblock
    It mentions it but shows no detail, how can you fix a soleplate to a sheet of XPS?

    Posted By: kentishgreenWhat caused the rot in Sweden? Condensation? Ingress of water?
    Cold Slab = Damp Slab, moisture moved towards the sole plates by capillary action. The fixings through the sole plate to the concrete slab punctured the dpc.
  3.  
    It mentions it but shows no detail, how can you fix a soleplate to a sheet of XPS?


    Standard blockwork would sit on top of the Thermoblock into which the soleplate would be screwed/nailed into.

    My architect has come up with the attached detail for my SIPs on top of piled slab. I'm likely to use Cellcore HX (anti-heave with insulation) under the slab (http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13221&page=1).

    I'd appreciate any comments on this layout the experts on here may have. My immediate concerns are :

    1) remaining thermal bridge adjacent to sole plate (area in red). Use insulating upstand (see green)?
    2) remaining thermal bridge below sole plate (area in blue, I think this is a Thermalite block)
    3) Cavity wall means fixing the sole plate could be an issue (i.e. crack/split block) when nailing sole plate (see pink). Doing away with a cavity wall structure and use just a 215mm wide Thermoblock (H:100mm) with further Thermalite block(s) on top.

    NB: Screed above the insulation needs to be added to the schematic, seems to have been omitted. This will have a retrofitted UFH board system on top (due to this also being used in existing bungalow)
      SIP slab1.JPG
  4.  
    And the specs:
      SIP slab1 detail txt.JPG
    • CommentAuthortony
    • CommentTimeMar 27th 2015
     
    Basically you have a monster cold bridge at the bottom of the panel and sole plate, combined amount to 125mm of just wood with no insulation, seems a shame to insulate the floor so well and the the walls no so well, with none at the bottom, for sure risk of premature decay of plate and bottom member of the panel.

    Need to mitigate the bridge.
  6.  
    Celotex/Kingspan PU type insulation is not suitable for use in damp conditions, its 90% closed cell so 10% open cell so the water will get in and reduce the performance. You have to wrap it in polythene all around, try to ensure that moisture from the concrete pour doesn't reach it and protect it from the damp slab.
    Here's a better Twin-Stud/Passive-Slab detail that delivers better U-values and solves the Cold Bridging issues.
    The inner stud is load bearing and there's also a detail for piled foundations available.
      TwinStud Passive Slab.jpg
    •  
      CommentAuthordjh
    • CommentTimeMar 27th 2015
     
    VH's detail is good. I believe the difficulty with SIPs is then getting the manufacturer to design and warrant it when only supported on the inside edge.

    There's also AWI 03 - EFo 01, AWI 06 - EFo 01 and similar details in the Passivhaus Details book that might be worth a look. You'll definitely want some perimeter insulation, I suspect.

    Find an existing certified Passivhaus that uses SIPs with a cold slab and copy whatever detail they used!
  8.  
    Thanks for the comments. I'm still in dialogue with the architect on the revisions, but it's been confirmed that the marmox block is the one ABOVE the yellow block, so the thermal bridge is actually less. I will ensure that the floor insulation is 'bagged up' too.

    I will try and have a look at the PassivHaus book when I get back from Spain - not something you pick up off the library shelves here.

    Once I get an updated schematic, I will post it back up here.

    Posted By: Viking House
    Here's a better Twin-Stud/Passive-Slab detail that delivers better U-values and solves the Cold Bridging issues.
    The inner stud is load bearing and there's also a detail for piled foundations available.


    I'm awaiting on feedback from SIPs people to see what there comments are on having the sole plate sit across EPS and concrete. I'll contact you for the piled foundation option.
    • CommentAuthorSaint
    • CommentTimeApr 7th 2015 edited
     
    Cast a second RC slab to act as a complete raft "floating" on XPS insulation laid on top of the 225mm piled slab?
    With compressive strengths of XPS up to 700kPa loading not an issue
    •  
      CommentAuthordjh
    • CommentTimeApr 8th 2015
     
    Posted By: kentishgreenhaving the sole plate sit across EPS and concrete

    Because the compressibility of EPS is greater than that of concrete, all the load is taken by the concrete, so as I said the question is their willingness to design and warrant a SIP supported only by its inner edge.

    Posted By: SaintCast a second RC slab to act as a complete raft "floating" on XPS insulation laid on top of the 225mm piled slab?

    That will work but be quite expensive. My first thought would be to do away with the piled slab altogether if the ground has the very limited bearing capacity needed to float a raft.
  11.  
    oops..
  12.  
    oops..
  13.  
    Posted By: kentishgreen
    Posted By: SaintCast a second RC slab to act as a complete raft "floating" on XPS insulation laid on top of the 225mm piled slab?

    Posted By: kentishgreenhaving the sole plate sit across EPS and concrete

    Because the compressibility of EPS is greater than that of concrete, all the load is taken by the concrete, so as I said the question is their willingness to design and warrant a SIP supported only by its inner edge.


    That will work but be quite expensive. My first thought would be to do away with the piled slab altogether if the ground has the very limited bearing capacity needed to float a raft.


    Yes, waiting for feedback from the SIP people on the fact that sole plate will cross over onto the EPS marmox block and I;ll see what the warranty provider say.

    Yes, I'm spending approx 20k on (60m2)piled slab as it is, and having another slab on top of XPS would simply blow my budget. Having to go down piled route due to trees and clay soil.

    Architect has now amended the slab detail adding screed layer and perimeter insulation. Still not great, but an improvement.
      SIP slab22.JPG
  14.  
    Apologies about the previous ' ooops' quotes. I couldn't delete my edits.

    Here's the accompanying text for above detail:
      SIP slab2 detail txt.JPG
    • CommentAuthortony
    • CommentTimeApr 20th 2015
     
    It looks to me like far too much cold bridging through the sole plates and sub structure, this is made colder by the addition of perimeter insulation above and below floor level, making it more likely for dew to form on top of and under the dpc!
    •  
      CommentAuthordjh
    • CommentTimeApr 20th 2015
     
    Posted By: kentishgreenHaving to go down piled route due to trees and clay soil.

    We have trees and clay soil. The main questions are the bearing capacity and expansivity of the clay and the proximity, size and type of the trees. The design rules to follow are generally those in chapter 4 of the NHBC standards. In our case, we found it best to go for a raft foundation, which then allowed a passive slab design as the top of it that removed the thermal bridge. I think we had a similar problem supporting our bale walls to what you have with SIPs. So it all depends on your particular circumstances.
    • CommentAuthorringi
    • CommentTimeApr 21st 2015
     
    Maybe don't use SIP!!!

    Or put a basement in with external insulation.
  18.  
    <blockquote><cite>Posted By: tony</cite>It looks to me like far too much cold bridging through the sole plates and sub structure, this is made colder by the addition of perimeter insulation above and below floor level, making it more likely for dew to form on top of and under the dpc!</blockquote>

    Thanks Tony. The inner leaf block is a 'thermoblock' though, so the sole plate directly above that should not be such an issue surely? I did suggest to my architect that instead of a cavity wall to just have single skin with one wider Thermoblock block supporting the entire sole plate. That would mean less risk of condensation surely? Marmox have also confirmed that the sole plate can be fixed to the Thermoblock (as long as it's done centrally).


    <blockquote><cite>Posted By: djh</cite><blockquote><cite>Posted By: kentishgreen</cite>Having to go down piled route due to trees and clay soil.</blockquote>
    We have trees and clay soil. The main questions are the bearing capacity and expansivity of the clay and the proximity, size and type of the trees. The design rules to follow are generally those in chapter 4 of the NHBC standards. In our case, we found it best to go for a raft foundation, which then allowed a passive slab design as the top of it that removed the thermal bridge. I think we had a similar problem supporting our bale walls to what you have with SIPs. So it all depends on your particular circumstances.</blockquote>

    Yes, we went by the NHBC bible and my engineer was pretty adamant that piles was the only way to go. I'll have to look at the soil report again though.



    <blockquote><cite>Posted By: ringi</cite>Maybe don't use SIP!!!

    Or put a basement in with external insulation.</blockquote>

    A bit late in the day to change construction. Delay after delay with supplier and architect...would not want to start all over again at this stage. But certainly for a future build I would look at other options more closely.

    Basement and piles? Wouldn't want to over complicate things...we're also extending from an existing bungalow with fairly shallow founds...would need underpinning technique$.
    • CommentAuthortony
    • CommentTimeApr 25th 2015 edited
     
    The problem with condensation is that it single-mindedly finds the coldest places to do its thing on. In my view this is likely to be immediately under your sole-plate both above and below dpc

    insulating inside the sips make the area colder!! Marmox is cold in comparison the the insulation inside the sip likely less well insulating than wood and isolated somewhat from the heat of the house
  20.  
    Posted By: tonyThe problem with condensation is that it single-mindedly finds the coldest places to do its thin on. In my view this is likely to be immediately under your sole-plate both above and below dpc

    insulating inside the sips make the area colder!! Marmox is cold in comparison the the insulation inside the sip likely less well insulating than wood and isolated somewhat from the heat of the house


    Thanks Tony. So I think what you are saying is that my interior insulation is accentuating the possibility of condensation risk under the sole plate (albeit reducing heat loss from inside to out). Should I omit the interior insulation therefore?

    Should I add an external layer of insulation on the outer leaf - would that help a bit at least?

    I've attached my latest thought (yellow = insulation; red = marmox block).
      SIP slab3.JPG
    • CommentAuthortony
    • CommentTimeApr 26th 2015
     
    The yellow insulation would be a very good idea on the outside and likely sort the danger out.

    I would like to see say 50mm expanded polystyrene and a bigger void behind the cladding.

    I talked to sips technicalabout this and theysid that in principle they were happy about insulation on the outside of sips, preferring breathable, hence eps,
    •  
      CommentAuthordjh
    • CommentTimeApr 26th 2015
     
    The external insulation would need vertical air passages through it to ensure the back of the cladding is ventilated. And the membrane would want running carefully to deflect water to the outside of the insulation.
  23.  
    Posted By: tonyThe yellow insulation would be a very good idea on the outside and likely sort the danger out.

    I would like to see say 50mm expanded polystyrene and a bigger void behind the cladding.

    I talked to sips technicalabout this and theysid that in principle they were happy about insulation on the outside of sips, preferring breathable, hence eps,


    Great! I will therefore get my architect to scrap the cavity, use single skin (marmox at the top), then stick 50mm insulation* on the outside of SIPs with a void before finishing with brick slips (cladding would sit above the slips). My intention was to go 300mm below and 300mm the sole plate height-wise with the insulation.

    *I was thinking of using XPS instead of EPS since some of the stuff would end up being below ground. Seems there is some debate as to whether more expensive XPS is safer than cheaper EPS... But I understand the need for breathability through to the SIPs, so EPS would be better...and cheaper. In my case there would only be about 5m of wall where the EPS would go below ground. And it wouldn't be too difficult to reduce the ground level so that none of it is in contact with the ground.


    Posted By: djhThe external insulation would need vertical air passages through it to ensure the back of the cladding is ventilated. And the membrane would want running carefully to deflect water to the outside of the insulation.


    I was going to have a gap at the bottom and top of the cladding to assist with ventilation (looking at firestop options).
    •  
      CommentAuthordjh
    • CommentTimeApr 27th 2015
     
    Posted By: kentishgreenI was thinking of using XPS instead of EPS since some of the stuff would end up being below ground. Seems there is some debate as to whether more expensive XPS is safer than cheaper EPS

    There is some debate but very little evidence, I think. I did read one paper where they actually dug up some EPS & XPS that had been installed for decades. Both were OK as I remember with the EPS in better condition. Certainly EPS is used to build railway embankments and motorways, so it must be pretty reliable!

    Posted By: kentishgreenI was going to have a gap at the bottom and top of the cladding to assist with ventilation (looking at firestop options).

    Yes. But how do you get the gap at the bottom if there's EPS blocking the space?
  25.  
    Posted By: djh
    Posted By: kentishgreenI was thinking of using XPS instead of EPS since some of the stuff would end up being below ground. Seems there is some debate as to whether more expensive XPS is safer than cheaper EPS

    There is some debate but very little evidence, I think. I did read one paper where they actually dug up some EPS & XPS that had been installed for decades. Both were OK as I remember with the EPS in better condition. Certainly EPS is used to build railway embankments and motorways, so it must be pretty reliable!

    Yes, I read a piece on that here also (by Fostertom, I think).

    Posted By: kentishgreenI was going to have a gap at the bottom and top of the cladding to assist with ventilation (looking at firestop options).

    Yes. But how do you get the gap at the bottom if there's EPS blocking the space?


    EPS stuck to face of wall/slope plate/SIPs with a void between the brick slip. There's only a small section of walled insulation that would potentially be below ground level. What i will do here is reduce the ground level (ensure it drains away from slab). This would mean that the bottom end of the brick slips is well out of the ground to enable ventilation (fitting vermin/fire stops as required).

    I've goofed together an amended detail below.
      Floor-slab detail.jpg
    • CommentAuthortony
    • CommentTimeApr 29th 2015
     
    breather membrane over the insulation, void only needs to be say 30mm, take insulation down to concrete, or even bottom of concrete

    looks good thiough
    • CommentAuthortony
    • CommentTimeApr 30th 2015
     
    We are 172 wide sips, blocks will be drilled in the middle for the sole plate.

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