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New Build Insulation Conundrum

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Comments

  • Registered Users Posts: 26,960 ✭✭✭✭GreeBo


    If I was getting a house built I'd have my FLIR on me at all times and would be checking these details, but obviously 90% of people either wouldnt know or care.


  • Closed Accounts Posts: 3,292 ✭✭✭TheBoyConor


    GreeBo wrote: »
    If I was getting a house built I'd have my FLIR on me at all times and would be checking these details, but obviously 90% of people either wouldnt know or care.

    Well that is just it. And the contractors know that most clients are blissfully unaware of the details or don't care, so why would they be bothered with the time and expense of doing it right!

    Which is why, as you rightly do, have it be known that you do know what you are looking at, you do know how it is supposed to be, and you give a chit and you will be doing regular detailed checks and instructing for rectification of any deficiencies a the contractor's own cost.


  • Moderators, Home & Garden Moderators Posts: 10,135 Mod ✭✭✭✭BryanF


    Hi all, we are doing a new build and our engineer has speced partial fill insulation in the cavity (110 xtrowall plus no internal dry lining). We hear so many opinions about all the diff types of insulation and were looking for experience from people who have this spec and are now living in the house, and wondering how they find it? Any regrets etc Thanks in advance for any help

    If you are doing a self build, I’d recommend going on a passive house course. It will help you to understand the items being discussed here. Also read around the forum this topic has been covered so many times before.


  • Registered Users Posts: 23,201 ✭✭✭✭mickdw


    100%.

    All of the above not to mention the fact that a wall cavity is out of sight and therefore out of mind. You'll be going well if half of the insulation makes it into the wall cavity at all once no-body in authority is watching, not to mind there being no gaps or pressed tight against the inner leaf.

    I have seen walls insulated with badly cut, or cut wrong pieces of insulation, insulation fúcked in any old way sure who cares if there's gaps or broken sheets - no-one's gonna see it anyway. or in one case they just decided to stop installing insulation half way up a gable wall because they ran out, but carried on with the blocks anyway and slipped one row of sheets in along from the top of the gable so it looked right at a glance.

    I've also seen insulation omitted and all the plastic wrapping, block bale straps and other site rubbish stuffed down into the cavity in lieu of insulation because the contractor was too tight to pay for a skip and had already been told off for burning stuff. Again, topped of with a row of sheets to hide it, expecting that a check would be no more than a quick passing glance at it.

    Add in to the equation the dreaded apprentice (once it is in the wall it's ok right? Tight again the block? the outer blocks right? sure that's where the cold is, no?

    And the above wasn't from random cowboy man-in-van outfits either. This was contractors who, on the face of it, looked like a reputable quality above board business, ISO quality and safety certifications, fancy website, slick social media videos of their projects, 100 or more staff on different projects.

    Unless you stand over most of these fellas you'd end up with a build any celtic tiger suckler farmer turned property tycoon would be proud of. Especially for elements that are not outwardly visible on the finished house.

    Ive not great faith in cavity wall insulation either as installation standard is critical. You could very easily have air circulating around all sides of the insulation board if poorly fitted and that would make it useless.
    That said, i dont find trades as bad as being made out here. Sure you will get gaps around cavity trays etc at times but dumping waste into the cavity doesnt happen in any kind of reasonably managed site.
    Ive recently had a couple of blocklayers say that sheets without tongue and grove work much better in cavity. Let likely to climb and therefore a better prospect. I must look at that and see if those are approved for cavity use and whether the its a case of it being easier for blocklayer or genuinely a better product.


  • Closed Accounts Posts: 3,292 ✭✭✭TheBoyConor


    It happens on unreasonably managed sites where the job was underpriced and every conceivable trick is being used to get out of spending time or money on it. If they put half the effort into doing the actual work properly as they put into making spurious claims for fictitious additional costs it might have been a job that wasn't an absolute misery to be involved with.


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  • Registered Users Posts: 398 ✭✭Panjandrums


    Planning a build for myself at the moment. I'd love to built-

    100mm outer leaf
    50mm cavity
    120mm PIR
    215mm inner leaf.
    18mm sand cement render
    Plenty of thermal mass and airtight.

    I would built the 215mm inner leaf first without wall ties. - Using ancon insulation restraints fix 2.4*1.2m PIR insulation sheets to the block.- tape the joints - using Ancon 25/14 Restraint channels,fix through the insulation into the block, then it's ready for the blocklayers to build up the outer leaf.

    I would go to the extent of marking every single wall tie on the restraint channel for them.


  • Subscribers Posts: 40,722 ✭✭✭✭sydthebeat


    Planning a build for myself at the moment. I'd love to built-

    100mm outer leaf
    50mm cavity
    120mm PIR
    215mm inner leaf.
    18mm sand cement render
    Plenty of thermal mass and airtight.

    I would built the 215mm inner leaf first without wall ties. - Using ancon insulation restraints fix 2.4*1.2m PIR insulation sheets to the block.- tape the joints - using Ancon 25/14 Restraint channels,fix through the insulation into the block, then it's ready for the blocklayers to build up the outer leaf.

    I would go to the extent of marking every single wall tie on the restraint channel for them.

    have you priced EWI against that specification??

    because what you are basically doing is building an EWI house, but replacing the acrylis render with a cavity and block outerleaf


  • Registered Users Posts: 26,960 ✭✭✭✭GreeBo


    sydthebeat wrote: »
    have you priced EWI against that specification??

    because what you are basically doing is building an EWI house, but replacing the acrylis render with a cavity and block outerleaf

    Or SIP or ICF?


  • Registered Users Posts: 398 ✭✭Panjandrums


    sydthebeat wrote: »
    have you priced EWI against that specification??

    because what you are basically doing is building an EWI house, but replacing the acrylis render with a cavity and block outerleaf

    No I haven't, but you could say the same for any masonry house with a cavity and insulation.


  • Registered Users Posts: 398 ✭✭Panjandrums


    GreeBo wrote: »
    Or SIP or ICF?

    ICF would interest me, I know there's an Irish company manufacturing it. I've not come across an ICF house yet.
    I can imagine it being a niche area for contractors, any idea of cost comparisons?


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  • Registered Users Posts: 1,182 ✭✭✭housetypeb


    Planning a build for myself at the moment. I'd love to built-

    100mm outer leaf
    50mm cavity
    120mm PIR
    215mm inner leaf.
    18mm sand cement render
    Plenty of thermal mass and airtight.

    I would built the 215mm inner leaf first without wall ties. - Using ancon insulation restraints fix 2.4*1.2m PIR insulation sheets to the block.- tape the joints - using Ancon 25/14 Restraint channels,fix through the insulation into the block, then it's ready for the blocklayers to build up the outer leaf.

    I would go to the extent of marking every single wall tie on the restraint channel for them.

    503 mm wall thickness for an a2 rating seems the hard way of doing it when you could just use the 215 block on flat with 250 mm ewi for a passive result.


  • Subscribers Posts: 40,722 ✭✭✭✭sydthebeat


    No I haven't, but you could say the same for any masonry house with a cavity and insulation.

    No you couldn't.

    Most masonry houses aren't built with a 215 solid block on flat leaf completely finished before building the outer leaf.

    What you propose to do is essentially ewi construction with a traditional weather layer.


  • Registered Users Posts: 398 ✭✭Panjandrums


    sydthebeat wrote: »
    No you couldn't.

    Most masonry houses aren't built with a 215 solid block on flat leaf completely finished before building the outer leaf.

    What you propose to do is essentially ewi construction with a traditional weather layer.

    What's the lifespan of EWI and render? - Is there any case studies on the long term result of EWI in Ireland?

    It's the same principle. I'd ballpark it and say the cost increase of using a 215mm inner leaf v 100mm inner leaf is in the region of 10-15k on a 200sqm house.

    Hard to see it being recouped over the lifespan of the building.


  • Moderators, Society & Culture Moderators Posts: 38,158 Mod ✭✭✭✭Gumbo


    What's the lifespan of EWI and render? - Is there any case studies on the long term result of EWI in Ireland?

    It's the same principle. I'd ballpark it and say the cost increase of using a 215mm inner leaf v 100mm inner leaf is in the region of 10-15k on a 200sqm house.

    Hard to see it being recouped over the lifespan of the building.

    All that and your still only meeting minimum building regulations?
    The block of 3 bed semis being built by Johnny Developer have the same performance as your hybrid build up.


  • Registered Users Posts: 398 ✭✭Panjandrums


    Gumbo wrote: »
    All that and your still only meeting minimum building regulations?
    The block of 3 bed semis being built by Johnny Developer have the same performance as your hybrid build up.

    A tried and tested method of construction with the necessary skills available in the labour market. The 215mm inner leaf would allow it to be fully built and then the insulation is installed and in open view prior to the outer leaf going up.

    Kingspan is showing a 100mm outerleaf, 50mm cavity, 120mm PIR and 100mm inner leaf has a U-value of 0.13W/m2·K.

    An internal sand cement airtightness render provides excellent results and has a reduced likelihood of failure unlike some methods which relies on tape.

    The end result is a solid, airtight and well insulated structure. That would stand the test of time. I really don't see what else you could ask for.


  • Registered Users Posts: 363 ✭✭Biker1


    A tried and tested method of construction with the necessary skills available in the labour market. The 215mm inner leaf would allow it to be fully built and then the insulation is installed and in open view prior to the outer leaf going up.

    Kingspan is showing a 100mm outerleaf, 50mm cavity, 120mm PIR and 100mm inner leaf has a U-value of 0.13W/m2·K.

    An internal sand cement airtightness render provides excellent results and has a reduced likelihood of failure unlike some methods which relies on tape.

    The end result is a solid, airtight and well insulated structure. That would stand the test of time. I really don't see what else you could ask for.

    I think you will find that build-up will give you a U-value of 0.17w/m2k.


  • Registered Users Posts: 26,960 ✭✭✭✭GreeBo


    sydthebeat wrote: »
    have you priced EWI against that specification??

    because what you are basically doing is building an EWI house, but replacing the acrylis render with a cavity and block outerleaf

    It feels a lot like the american timber frame style of sticking an outer layer of siding over the whole house to shelter the insulation/wall from the rain.


  • Registered Users Posts: 26,960 ✭✭✭✭GreeBo


    An internal sand cement airtightness render provides excellent results and has a reduced likelihood of failure unlike some methods which relies on tape.
    I wouldnt knock tape, its used on millions of houses all over the world for this purpose. You are also relying on render *that you cant see* never cracking or failing.


  • Moderators, Home & Garden Moderators Posts: 10,135 Mod ✭✭✭✭BryanF


    GreeBo wrote: »
    I wouldnt knock tape, its used on millions of houses all over the world for this purpose. You are also relying on render *that you cant see* never cracking or failing.

    Ah now, ‘never cracking or failing’? Depends on the type of tape installed and/or plasterer. Neither should fail if the right materials are used. Btw with internal plastering they’ll still need tape at most junctions.


  • Registered Users Posts: 398 ✭✭Panjandrums


    BryanF wrote: »
    Ah now, ‘never cracking or failing’? Depends on the type of tape installed and/or plasterer. Neither should fail if the right materials are used. Btw with internal plastering they’ll still need tape at most junctions.

    I've seen tape used in multiple place's
    Taping the membrane to the wall
    Around windows

    I've even seen it used it on the floor to wall junction which I thought was pointless.

    The liquid airtightness products are something I would like to see more on, on like to like materials I would use it but on unlike materials I would be a bit worried about the joint failing with heating and cooling.


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  • Subscribers Posts: 40,722 ✭✭✭✭sydthebeat


    Biker1 wrote: »
    I think you will find that build-up will give you a U-value of 0.17w/m2k.

    Agreed

    I'm going to assume the poster meant phenolic and not PIR..... As there is no PIR product that will give a U value of 0.13 at 120mm

    Even the new Kingspan K8plus phenolic needs 130mm to give a 0.13 u value


  • Registered Users Posts: 26,960 ✭✭✭✭GreeBo


    BryanF wrote: »
    Ah now, ‘never cracking or failing’? Depends on the type of tape installed and/or plasterer. Neither should fail if the right materials are used. Btw with internal plastering they’ll still need tape at most junctions.

    That was exactly my point, the OP seems to believe that plaster will be better than tape, but both highly depend on the installer, one isnt "better" than the other.


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