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Insulating Walls

  • 04-08-2013 8:14pm
    #1
    Registered Users Posts: 86 ✭✭


    Hi,

    We are looking at purchasing a house that is half built.
    It is done as far as the slates were put on.
    No windows in.

    The external walls are:

    215mm Hollow Block outer leaf.
    50mm clear cavity Ventilated.
    Breathable Membrane
    140mm Timber frame Inner leaf.

    The 140mm is made up of 10mm sheet and studs of 130mm attached to this.
    No drywall on yet.

    What insulation should be placed in between these studs.


Comments

  • Site Banned Posts: 10 Afgan


    hi Shadow, can I ask what you did in the end? I am in a similar situation.


  • Registered Users Posts: 1,918 ✭✭✭whizbang


    I would strip out all the timber, and airtight as much as possible, then 70-100mm of Insulated plasterboard direct to the wall.
    Golden opportunity to get it done right.


  • Registered Users Posts: 2,820 ✭✭✭MicktheMan


    whizbang wrote: »
    I would strip out all the timber, and airtight as much as possible, then 70-100mm of Insulated plasterboard direct to the wall.
    Golden opportunity to get it done right.

    :eek:
    Do not do this.


  • Registered Users Posts: 45 Metalrobe


    whizbang wrote: »
    I would strip out all the timber, and airtight as much as possible, then 70-100mm of Insulated plasterboard direct to the wall.
    Golden opportunity to get it done right.

    Cold bridge straight into the house. Would be disasterous.


  • Registered Users Posts: 12,141 ✭✭✭✭Calahonda52


    whizbang wrote: »
    I would strip out all the timber, and airtight as much as possible, then 70-100mm of Insulated plasterboard direct to the wall.
    Golden opportunity to get it done right.

    This is NOT a good idea on a number of fronts.

    Firstly, it flies against all the known problems with IWI on single leaf walls, compounded by the HB and not knowing the external wall finish and how exposed the site is.
    The attached gives some idea of what happens.

    “I can’t pay my staff or mortgage with instagram likes”.



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  • Registered Users Posts: 12,141 ✭✭✭✭Calahonda52


    Afgan wrote: »
    hi Shadow, can I ask what you did in the end? I am in a similar situation.
    Every house is different so please describe your set up

    “I can’t pay my staff or mortgage with instagram likes”.



  • Registered Users Posts: 3,027 ✭✭✭Lantus


    whizbang wrote: »
    I would strip out all the timber, and airtight as much as possible, then 70-100mm of Insulated plasterboard direct to the wall.
    Golden opportunity to get it done right.

    In a timber frame house you can't remove the timber!

    The insulation board is cut and put between the timber frame structure. Usually 100mm of the solid board type. Plasterboard is just screwed to wood joists. It's a nice job and warm.


  • Registered Users Posts: 31,001 ✭✭✭✭Lumen


    Lantus wrote: »
    In a timber frame house you can't remove the timber!

    The insulation board is cut and put between the timber frame structure. Usually 100mm of the solid board type. Plasterboard is just screwed to wood joists. It's a nice job and warm.

    But if you have super high insulating material filling the studs, aren't you going to have massive cold bridging through the studs, and therefore cold spots on the plasterboard?

    Is the idea of using 100mm insulation in a 150mm stud to leave a service void? If so, wouldn't you need to tape the perimeter of every single piece of insulation to the studs to maintain continuity of air tightness?


  • Registered Users Posts: 12,141 ✭✭✭✭Calahonda52


    THE SERVICE CAVITY IS BEST OUSIDE THE INTERNAL VAPOUR LAYer so best to full fill the 130mm space with insulation and then put on the membrane and then counter batten, batten for a service cavity.
    This will reduce the risk of the thermal bridges to which u correctly allude

    “I can’t pay my staff or mortgage with instagram likes”.



  • Site Banned Posts: 10 Afgan


    Every house is different so please describe your set up

    hi Calahonda, thanks for asking. Doing a little holiday cottage on some isolated land and forestry I have. Mainly a place to stay in lambing season, but I want it fairly right and warm. Wall makeup is 4 inch block plastered, 3 inch cavity, breather membrane, 12mm osb, 150mm studs. My plan is to put 150mm rockwool between studs, vapour barrier and 37.5mm insulated slab on the inside. Can you see an issue with this? Thanks again, Frank.


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  • Registered Users Posts: 3,027 ✭✭✭Lantus


    Afgan wrote: »
    hi Calahonda, thanks for asking. Doing a little holiday cottage on some isolated land and forestry I have. Mainly a place to stay in lambing season, but I want it fairly right and warm. Wall makeup is 4 inch block plastered, 3 inch cavity, breather membrane, 12mm osb, 150mm studs. My plan is to put 150mm rockwool between studs, vapour barrier and 37.5mm insulated slab on the inside. Can you see an issue with this? Thanks again, Frank.

    Risk of interstitial condensation in rockwool. I'd check that and maybe consider foil faced board and no insulated plasterboard. 150mm would be very warm for a summer house. 100mm should be sufficient.


  • Registered Users Posts: 1,593 ✭✭✭50HX


    I have old stone email wall house, walls are 20inches thick
    Insulating the floors and new ceilings

    Thinking of 60mm insulated slab pinned directly into the wall

    I have no rising damp

    What would people think, wife is afraid of mold growing


  • Registered Users Posts: 2,820 ✭✭✭MicktheMan


    50HX wrote: »
    I have old stone email wall house, walls are 20inches thick
    Insulating the floors and new ceilings

    Thinking of 60mm insulated slab pinned directly into the wall

    I have no rising damp

    What would people think, wife is afraid of mold growing

    Not really enough info to advise definitively but there is real risk of issues with this. Yes you will have some people saying they've done it with no issues but the physics say there is a high risk with this specification.

    I would be listening to her good self.:)


  • Registered Users Posts: 1,593 ✭✭✭50HX


    Thanks mickle, what other information would you need to make a definitive judement on it??


  • Registered Users Posts: 2,820 ✭✭✭MicktheMan


    Off the top of my head;
    Any cement based products used on the wall over the years (either internal or external)?
    What air tightness is house at?
    What ventilation is there?
    How is the space heated? Is it used on regular basis?
    Assuming normal occupancy, i.e. normal family?
    French drains outside?
    Ground level relative to floor level?

    There are a number of interdependencies at play here which will influence greatly the risk of damp / mould. And I've probably left off some stuff too from the list above!


  • Registered Users Posts: 1,593 ✭✭✭50HX


    Thanks mick

    Internal and external walls both plastered over the years
    Ventilation will be mhresponsible
    Ufh and aluminium rads supplying the heating
    Used on a regular basis, family of 4

    I've dug away the back of the house so ground and floor are level now

    3ft drain around the back and sides walls

    My builder is adamant that pinning the insulation to the stone wall direct is better than studding the wall and creating an air gap then


  • Closed Accounts Posts: 24 ElderWanderer


    Retrofitting (properly) a stone built house with insulation is a nightmare apparently.

    The best solution I've heard of is straw+cob wall. That's a specialised job, and therefore is likely to be expensive, and apparently cob isn't a great insulator anyway- but putting insulation backed plasterboard directly on a stone wall is asking for trouble I would imagine, and I would normally be very enthusiastic about piling on large quantities of insulation anywhere it'll fit. Non-standard situations require non-standard solutions.

    In fairness though, if your walls are 450mm odd then just the sheer thickness of them will provide a reasonable about of insulation and a bucket load of thermal mass. If you're fully insulating the attic/roof, making it airtight with modern windows etc, and have a full-on HRV system you may be better off (and get away with) not insulating the walls at all. Secondary glazing of the windows could mitigate cold bridging, and straw+cob could enhance air-tightness while leaving breathable & attractive traditional finish.


  • Registered Users Posts: 31,001 ✭✭✭✭Lumen


    Retrofitting (properly) a stone built house with insulation is a nightmare apparently.

    I'm not sure that's true. You just need to have a good look round your local builders providers and make a mental note to buy nothing that you see there.


  • Registered Users Posts: 1,679 ✭✭✭MAJJ


    Lumen wrote: »
    I'm not sure that's true. You just need to have a good look round your local builders providers and make a mental note to buy nothing that you see there.

    My wife was getting her old family home done a few years ago. I was wary of regular insulation boards straight on to stone wall and concerned on mould. I found calsiterm boards and a a suitable plaster but of course her builder and her had none of it and did the regular board/regular plaster. Looks fine, comfortable, cheaper but I imagine mould.will fester. I am sharing to see what suggestions on material people might give the OP. I am not professing to be an expert.


  • Closed Accounts Posts: 24 ElderWanderer


    Lumen wrote: »
    I'm not sure that's true. You just need to have a good look round your local builders providers and make a mental note to buy nothing that you see there.

    That's pretty much my definition of a nightmare:D:D


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  • Registered Users Posts: 963 ✭✭✭heffo500


    MAJJ wrote: »
    My wife was getting her old family home done a few years ago. I was wary of regular insulation boards straight on to stone wall and concerned on mould. I found calsiterm boards and a a suitable plaster but of course her builder and her had none of it and did the regular board/regular plaster. Looks fine, comfortable, cheaper but I imagine mould.will fester. I am sharing to see what suggestions on material people might give the OP. I am not professing to be an expert.

    That calsiterm looks very good. I have an old house with 600mm thick walls so this could be ideal.


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