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Housing - New Build: External insulation for basement walls

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  1.  
    • CommentAuthorstephendv
    • CommentTimeJan 9th 2009
     
    What type of insulation is suitable for using for below ground basement walls? The walls themselves will be poured concrete and I'd prefer insulation externally since it means I won't need to build interior basement walls.
  2.  
    Extruded polystyrene is commonly used over here in Canada.

    Paul in Montreal.
    • CommentAuthorstephendv
    • CommentTimeJan 10th 2009
     
    Thanks
    • CommentAuthortony
    • CommentTimeJan 11th 2009
     
    The deeper you go the less you need
    • CommentAuthorstephendv
    • CommentTimeJan 11th 2009
     
    Yep, the plan is to insulate the first 1.5m and leave 70cm and the basement floor uninsulated - so that the basement can be used as cool storage in summer.
    • CommentAuthortony
    • CommentTimeJan 11th 2009
     
    I think that it may not work? The basement floor will pretty much assume the average temperature of the basement over the whole year.

    ie not cool -- hopefully
    • CommentAuthorstephendv
    • CommentTimeJan 12th 2009
     
    There will be 10cm of insulation in the basement ceiling, and no active heating of the basement itself. The ground floor will be a slab of concrete that will act as thermal mass and heat storage for winter sun (large south facing windows). This slab will also have UFH in it, and I don't plan to put a thin sheet of insulation under the UFH as is customary - rather going to rely on the large slab of 10cm insulation in the basement ceiling to separate the basement from the ground floor; so the whole ground floor slab will act as thermal mass.
    Heat conducted through the ground floor slab and insulation would be the only source of external heat to the basement in winter.
    • CommentAuthorGuy
    • CommentTimeJan 20th 2009
     
    You could have a look at durisol blocks witch are made from waist wood have an layer of insulation on the outer skin ,the iner skin yoy fill with concrete. They come in a range of sizes, the largest with a u value of 0.19 and can be used for foundations upwards.

    But don't know how much they cost
    • CommentAuthorchuckey
    • CommentTimeJan 20th 2009
     
    I think there is a product called "claystop". Can't remember its manufacturer but it is an external foam slab that interlocks with its neighbours.
    Frank
    • CommentAuthorshakey
    • CommentTimeJan 29th 2009
     
    I've just returned from a visit to Austria where I visited a couple of new self builds by friends and relatives. The Austrians have a long tradition of basements which are the norm rather than the exception as in the UK. Both builders kept a photo diary and I was able to check out the build sequence which currently appears to be slab, steel shuttering followed by poured concrete, a coating of bitumin then about 100mm of insulation which appeared denser than polystyrene before a strong plastic sheet damp proof cover with sealed seams.

    My visit was during a period of very cold -15c weather and both basements were warm enough and no signs of damp, they have a wide open access to the living areas so cold is obviously not a problem.

    A side issue of interest was that rather than rain water storage both builders had driven a 100mm-150mm hollow pipe into the ground down to the water table (over 8m) from which a pump costing about £70 fed the toilets and washing machines directly. A link to 'town' water was available if required but never used and one of the property owners filled his large swimming pool every year from ground water. I had considered rain water storage but our water table is very high so I'm going to excavate a 2m hole and line it with concrete rings for my WC and washing machine supply, I already have a hand pump which supplies garden water through out the year so I've just saved over £3000 on a commercial system.
    • CommentAuthorSwarm
    • CommentTimeFeb 9th 2013
     
    Sorry to drag up an old topic and also go slightly off topic but I thought rather than start a new similar one...

    In an existing below ground level room (earth facing one side, south facing window the opposite), is internal insulation recommended? It is just a standard height one storey room.

    Also, shakey's comment about utilising water from the water table is fascinating. If anyone has more thoughts on that I'd be very interested to hear them!
  12.  
    I would'nt use internal insulation where you have big south facing windows. Recipy for summer overheating
    • CommentAuthorowlman
    • CommentTimeFeb 9th 2013
     
    Posted By: shakey...............to be slab, steel shuttering followed by poured concrete, a coating of bitumin then about 100mm of insulation which appeared denser than polystyrene before a strong plastic sheet damp proof cover with sealed seams.


    Similar to my experience in Germany. The builds I watched started much the same, then on top of the bitumin tanking a continous roll of material was stuck to the walls it seemed very similar to "flashband" but in 1M wide rolls. The walls were then insulated with thick EPS type slabs and then a sort of geotextile membrane and backfilled. The EPS was not the standard white stuff but with the individual beads coated in, I'm guessing, bitumin before forming into slabs. I've never seen it in UK.
  14.  
    Posted By: Mike GeorgeI would'nt use internal insulation where you have big south facing windows. Recipy for summer overheating


    Talk about hitting the nail on the head. Just trying to decide whether to put underfloor insulation in my basement (with huge south french door), however, walls are solid stone uninsulated and the glass will have shutters that will be religiously closed as required. I was tending towards a half way house of 25mm XPS under the screed, I was hoping to mitigate that really cold feel the tiled floor would have during the winter whilst not completely disconnecting the floor from the mass. Am I being a little naive here?
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 9th 2013 edited
     
    Consider wide wing insulation e.g. bed of Leca, going out horizontally just below GL, instead of surrounding the basement walls. Then after a yr or two the subsoil below and around will adopt a rock-steady temp, winter and summer, just a bit below your maintained internal temp. In other words, after a bit the basement won't need heating but will feel slightly nice and cool, and there will be no downward heat loss from the interior.
  16.  
    Posted By: Gotanewlife
    Posted By: Mike GeorgeI would'nt use internal insulation where you have big south facing windows. Recipy for summer overheating


    Talk about hitting the nail on the head. Just trying to decide whether to put underfloor insulation in my basement (with huge south french door), however, walls are solid stone uninsulated and the glass will have shutters that will be religiously closed as required. I was tending towards a half way house of 25mm XPS under the screed, I was hoping to mitigate that really cold feel the tiled floor would have during the winter whilst not completely disconnecting the floor from the mass. Am I being a little naive here?


    Positioning and use of thermal mass is a tricky call. I like Tom's method but obviously Climatic conditions as well as the design will determine how effective such a strategy will be. Sorry to sit on the fence :)
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 9th 2013 edited
     
    Posted By: Gotanewlifein my basement ... I was tending towards a half way house of 25mm XPS under the screed, I was hoping to mitigate that really cold feel the tiled floor would have during the winter whilst not completely disconnecting the floor from the mass
    They do say that's gd idea, and I think I would play safe in that way - tho perhaps even less insulation than that. Or a 50mm layer of Leca - somehow more of a continuity with the slab/subsoil whilst still steepening the near-surface temp gradient a little, so surface temp is freer to follow room temp, rather than being absolutely locked to subsoil temp, which is always going to be a little cooler than year-round av room temp
  18.  
    Thanks you 2 for joining the fray. I hope I'm not nicking your thread stephendv! I should have mentioned that this basement will become my in-laws apartment - ie the maintained internal temp will vary between 20 and 27 over each year. I can only put wing insulation along one edge, the cold edge. So, inside, 50mm dry laid leca (what dia leca?) with water proof barrier on top and then screed made with leca too? Outside, could I use leca as infill for a drainage trench (ie with holy pipe in the middle) and then bed my soil pipes in it a little higher up and then fill to surface with it - of course that's not wing insulation (and it's not cheap!)? What depth and width would you suggest if I went with a wing? As you say MG "tricky call" and this is my forever house...
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 10th 2013
     
    Posted By: Gotanewlifemaintained internal temp will vary between 20 and 27 over each year
    Sounds like http://greenershelter.org/index.php?pg=2

    Posted By: Gotanewlife... and then screed made with leca too?
    "If just enough is just right, then too much is even better" - is supposed to be a joke!

    Posted By: Gotanewlifeleca as infill for a drainage trench - of course that's not wing insulation
    well, it is, or can be, depending on the resultant path-length of heat thro resistant material to the surface.
    Posted By: Gotanewlife(and it's not cheap!)
    Can be, if you shop around - supply seems to be a shifting thing in UK at the mo - bagged has dried up at gd price, but now dumpy bags from another source. Also, to be clarified, is whether building-grade coated Leca is really necessary, or cheap basic uncoated as used for civil engineering fill.
    • CommentAuthorTriassic
    • CommentTimeMar 9th 2013 edited
     
    The following construction cost information may be of interest -

    The Basement Information Centre has produced this study in conjunction with The Concrete Centre in order to show the current viability of basements in housing, taking into account construction and land costs.

    http://www.basements.org.uk/ul_pdf/pnpdf_1.pdf
  21.  
    <blockquote><cite>Posted By: Guy</cite>You could have a look at durisol blocks witch are made from waist wood have an layer of insulation on the outer skin ,the iner skin yoy fill with concrete. They come in a range of sizes, the largest with a u value of 0.19 and can be used for foundations upwards.

    But don't know how much they cost</blockquote>


    I know someone who used to use Durisol blocks who is now using timber formwork
  22.  
    Extruded polystyrene and foam glass are the only insulators that I understand maintain their efficiency below ground.

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