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Cold Bridging and Insulation : the issues and solutions

  • 09-10-2007 03:35PM
    #1
    ircoha
    Closed Accounts Posts: 2,290 ✭✭✭


    There has been some commentary in a recent thread [http://www.boards.ie/vbulletin/showthread.php?t=2055158990 ] on CB and I think it worthwhile to assemble some succinct points on the topic in a standalone thread.
    What follows is not presented as being definitive, but a starting point.

    This link will serve to introduce the topic:http://www.bsria.co.uk/press/?press=232

    we will focus on the problem in a domestic situation: eg a wall.

    There are 3 basic methods of insulating:
    A: internal dry lining
    B: insulation fitted in cavity in cavity wall.
    C: Externally Applied Insulation

    They can be combined like in some of the ICF stuff. [A + C]

    AFAIK, C is not that common here yet.

    The 3 main areas where CB is a problem is
    1: the wall itself
    2: around doors and windows
    3: from the foundation.

    Internal Dry Lining

    From what has been posted earlier, it seems that internal drylining can cause damp issues if not ventilated, and VH has posted that if the detailing provides for an air gap, the insulation in the cavity is rendered useless.
    from Viking House in the post above: The Cold Bridge areas in 4 inch block partial filled cavity walls are where the inside block sits on the foundations and around the windows and doors and where the walls meet the roof. These are the areas where condensation/fungus/mould occur when you dryline. The correct way to dryline is to leave a ventilated air gap between the drylining and the wall which eliminates the effect of the insulation between the blocks.

    The best place for insulation is on the outside of your walls or foundations.
    2 inches on the outside has the same effect as four inches on the inside.

    This poses the question as to what is the point of insulating the cavity.

    The detailing for this around windows and doors can be tricky as generally the opes are the same dimensions on outside and inside so the insulation on the reveals will be much less because of the frames.

    In an ideal world with a cavity wall the inner ope should be say 4 " bigger all round.

    In addition it will be necessary to dryline all walls touching an external wall because of CB

    Insulation fitted in cavity in cavity wall.

    This is usually done with sheets of rigid polyXX and can be difficult to do properly with wall ties etc so quality of workmanship difficult to establish.

    Is getting the cavity filled with some 'blown' insulation a better option, particularly in relation to airtightness?


    Externally Applied Insulation

    This is not that common here in Ireland and there seem to be issues with suitable renders.

    However the concept seems good: the ope size issues are reversed.

    However I am interested in what VH had to say
    The best place for insulation is on the outside of your walls or foundations.
    2 inches on the outside has the same effect as four inches on the inside.

    as I dont see how external insulation solves the CB from foundations.


    In terms of addressing the sources of CB as listed above

    1: the wall itself
    2: around doors and windows
    3: from the foundation

    it seems to me that Drylining is the only one that addresses the CB in all cases, including from the foundations, and to address the damp issue will need to be ventilated as per VH in .


    I would welcome any observations/input.


«13

Comments

  • #2
    Mellor
    Registered Users, Registered Users 2 Posts: 40,378 ✭✭✭✭Mellor


    I commented on this in another thread and I had the same train of thought as you here. http://www.boards.ie/vbulletin/showpost.php?p=54156105&postcount=12

    Each method of insulation has its downside, and each downside can be eliminated through good detailing.

    Regarding the foundation coldbridging, It is true that the inner leaf sites on a cold rising wall and it is a source of heat loss. In an externally insulated wall, the contact area of the wall sitting on the cold rising wall is greater, therefore, imo, not only is external insulation exposed to the same flaw, it is greater here.
    This flaw can be solved in both methods, by the same detailing.


    The reveal problem also puzzles me, in drylining it is sovlable, granted you end up intruding on the frame, but it solves the cold bridge.

    What is done externally? how is the external reveal formed? I'd like to see details as I am concerned about its strength.


  • #3
    kadman
    Moderators, Home & Garden Moderators Posts: 5,134 Mod ✭✭✭✭kadman


    Perfect answer to cold bridging, what do you think



    kadman


  • #4
    ardara1
    Closed Accounts Posts: 495 ✭✭ardara1


    Thermal bridging at junctions becomes more of a problem in better insulated/sealed/performance building fabrics. The better the performance the more vunerable the junction. Our Part L recognizes the fact but doesn't quite tell you how to avoid problems.
    We're supposed to build to basic guideline laid down in a Homebond Document 18 - 'Right on site' - we're then referred to Robust Detail for Construction printed in the UK - a document by DEFRA.

    Bottom line is all junctions are measured as to their thermal performance AND the threat of condensation and moisture build up (Mould develops before moisture) by a single methodology - IP1/06.

    If a junction is suspected to be prone to moisture/mould - bloody measure it - if there's a risk - fix it.

    the amount of scare mongering that goes on from certain posters would scare you - lets get a realistic handle on things, most methods of measurement for moisture transfer/heat transfer or what ever has an agreed CEN methodology.


  • #5
    Mellor
    Registered Users, Registered Users 2 Posts: 40,378 ✭✭✭✭Mellor


    kadman wrote:
    Perfect answer to cold bridging, what do you think



    kadman
    Still a small cold bridge through the internal spray on structural concrete.
    Not to mention the 3mm galvanised steel bridging the insulation, 84 per metre squared I believe.
    There are still ways to improve all systems.

    The foundation detail cold bridge in a cavity wall can be eliminated by using a foam glass block as the first course,


  • #6
    sas
    Registered Users, Registered Users 2 Posts: 1,282 ✭✭✭sas


    Mellor wrote:
    What is done externally? how is the external reveal formed? I'd like to see details as I am concerned about its strength.

    In the case of the mosart passive house they built with 4 inch blocks on the flat with external insulation.

    The windows are fitted prior to the external insulation and they are positioned so that the front of the windows are flush with the outer face of the wall i.e. no visible reveal.

    Then the external insulation is fitted and they simply run the insulation across the frame of each window, thereby creating the reveal.

    The IAB cert for the weber therm system (06/0260) has diagrams of this detailing which will explain it better than I probably did.


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  • #7
    sas
    Registered Users, Registered Users 2 Posts: 1,282 ✭✭✭sas


    Mellor wrote:
    The foundation detail cold bridge in a cavity wall can be eliminated by using a foam glass block as the first course,

    The latest issue of construct ireland has an article on a development in Kildare where they used Perinsul foam glass blocks to break the bridge.

    They built a standard cavity wall (albeit with a 200mm cavity) and fully filled with ecobead platinum. They used 100mm perinsul blocks at the same level as the floor insulation on the inner leaf to break the bridge.

    As a related aside, www.atil.ie supply these blocks in ireland if anyone is interested.


  • #8
    Mellor
    Registered Users, Registered Users 2 Posts: 40,378 ✭✭✭✭Mellor


    sas wrote:
    The latest issue of construct ireland has an article on a development in Kildare where they used Perinsul foam glass blocks to break the bridge.

    They built a standard cavity wall (albeit with a 200mm cavity) and fully filled with ecobead platinum. They used 100mm perinsul blocks at the same level as the floor insulation on the inner leaf to break the bridge.

    As a related aside, www.atil.ie supply these blocks in ireland if anyone is interested.
    Thats similar to a detail I developed to great a domestic structure that had no significant cold bridges, all insulation was 100% continous. The only bridge was wall ties and these could be change to a less conductyive material than steel.


    I get what you mean with the external insulation, I've never seen one in practice and often wonder on the strength of the revel corner, could it take a knock


  • #9
    sas
    Registered Users, Registered Users 2 Posts: 1,282 ✭✭✭sas


    Mellor wrote:
    The only bridge was wall ties and these could be change to a less conductyive material than steel.

    The engineer in the article said that if he was going again he would consider using basalt wall ties. I looked these up out of interest and didn't find anything on them!


  • #10
    Mellor
    Registered Users, Registered Users 2 Posts: 40,378 ✭✭✭✭Mellor


    Basalt is a rock similar to granite, its the rock found in the giants causeway,
    it can be made into fibres that are similar to fibreglass or carbon fibre, it is used in fibre reinforced concrete
    try looking for basalt fibre ties


  • #11
    Viking House
    Registered Users, Registered Users 2 Posts: 551 ✭✭✭Viking House


    sas wrote:
    The latest issue of construct ireland has an article on a development in Kildare where they used Perinsul foam glass blocks to break the bridge.
    They built a standard cavity wall (albeit with a 200mm cavity) and fully filled with ecobead platinum. They used 100mm perinsul blocks at the same level as the floor insulation on the inner leaf to break the bridge.
    As a related aside, www.atil.ie supply these blocks in ireland if anyone is interested.
    The glass foam block has a lambda value of 0.3 so a 4 inch glass foam block has the same insulation effect as 10mm of Polysterene which is not so much.
    Trying to modify a partial cavity wall to build an energy efficient house is like putting a new engine into a Ford Escort.

    This is the system we are presently using giving a Swedish U-value of 0.11.
    (1.1 U-value Swedish windows are 0.8 here.)

    supergrundab.jpg

    The house sits on a 300mm bed of structural Polysterene with no part of the house or foundations touching the soil. The external walls sit on the insulated ring beam designed to take the loads.
    It completly eliminates all cold bridging between the floor and the wall when used with Poroton + external insulation or timber frame. The external wall insulation connects with the insulation around the ring beam and stops all cold bridging.
    It offers the highest U-value in the world for a similar amount of insulation because all the thermographic lines are concentrated to the Polysterene upstand between the ring beam and the floor slab as you can see in the two images below.


    Lelefarg1.JPG

    This is the Thermograph (above) for the older L-element with 300mm Polysterene under slab.

    Uminfarg1.JPG

    This is the Thermograph (above) for the latest Swedish U-min foundation system with 300mm Polysterene under slab.

    The U-value improves by 0.08 with no increase in material.
    Scan Homes are keen to use this foundation system on all their new houses as they see the value.
    The ring beam can take loads of up to 35 tonnes/linear metre.


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  • #12
    Viking House
    Registered Users, Registered Users 2 Posts: 551 ✭✭✭Viking House


    kadman wrote:
    Perfect answer to cold bridging, what do you think
    kadman

    A colleague of mine worked as an Architect in London and one of his jobs was to oversee the fitting of Combi boilers in an apartment block. In the first apartment they were coring the wall to install the flew. The walls were mass concrete with Polysterene in the middle. When the core contents fell on the ground my colleague picked up the Polysterene. He squeezed it and it was like squeezing a wet sponge.

    Poured vibrated concrete is quite dense and not very breathable and Condensation moisture was trapped between the two layers of dense concrete.

    Your image shows similar detail Kadman, with insulation trapped between two materials with similar breathability. Better to put 300mm of Polysterene on 150mm compacted Hardcord (18mm-35mm) and pour the concrete only once, on top of the insulation and in the ring beam at the same time.


  • #13
    Viking House
    Registered Users, Registered Users 2 Posts: 551 ✭✭✭Viking House


    sas wrote:
    In the case of the mosart passive house they built with 4 inch blocks on the flat with external insulation.

    It looks like the only Certified Passive House in Ireland has a 9 inch "Cold Bridge" all around the house, where the walls sit on the strip foundations.


  • #14
    [Deleted User]
    Posts: 31,118 ✭✭✭✭ [Deleted User]


    I built using ICF in the rising wall as well as the main external walls, with a minimum of 50mm EPS between the internal floor concrete & the concrete in the wall, completely eliminating the CB at that junction.
    The concrete within the ICF is still in direct contact with the strip foundation, therefore worst case U value is 0.25 (approx) at the junction between the floor & the strip foundation.


  • #15
    Viking House
    Registered Users, Registered Users 2 Posts: 551 ✭✭✭Viking House


    Deleted User wrote:
    I built using ICF in the rising wall as well as the main external walls, with a minimum of 50mm EPS between the internal floor concrete & the concrete in the wall, completely eliminating the CB at that junction.
    The concrete within the ICF is still in direct contact with the strip foundation, therefore worst case U value is 0.25 (approx) at the junction between the floor & the strip foundation.

    Hi DB

    100mm EPS gives a U-value of 0.32 so 50mm would give a U-value of 0.45 at a guess.
    You still have the issue of EPS between two layers of concrete though, creating a moisture trap.

    VH


  • #16
    Mellor
    Registered Users, Registered Users 2 Posts: 40,378 ✭✭✭✭Mellor


    Viking House wrote:
    The glass foam block has a lambda value of 0.3 so a 4 inch glass foam block has the same insulation effect as 10mm of Polysterene which is not so much.


    This is the system we are presently using giving a Swedish U-value of 0.11.
    (1.1 U-value Swedish windows are 0.8 here.)


    The house sits on a 300mm bed of structural Polysterene with no part of the house or foundations touching the soil.
    It completly eliminates all cold bridging between the floor and the wall when used with Poroton + external insulation or timber frame. The outside insulation connects with the insulation around the ring beam and stops all cold bridging.


    Scan Homes are keen to use this foundation system on all their new houses.
    The ring beam can take loads of up to 35 tonnes/linear metre.

    I have seen this insulated ring beam (or a similar one) when I met you at the RDS. It looks good, but I don't agree with the way you portray it when talking about other insulation methods.


    Firstly, Foamed glass can have a conductivity in the range of .07-.10, so its alot better than you suggest. Some of the stuff I seen was at the low end of the scale. Also, if a concrete block was replaced with this material, the effective distance isn't 100 (4") you suggested, its 215 as the heat is travelling vertically towards the foundations at this area. That looks to be more than the thickness of the insulation under the ring beam, as the insulation in the ring beam is made to take higher loads I imagine it has a less effective conductivity. The more dense polystyrene is the less effective it is as an insulator.


    The windows are also suitable for use with all other construction types, so thats universal too. They have a great U-Value, I'd be interested to get more info on them if possilble, maybe not this thread as its a little off topic.


    You said the ring beam insulation is suitable for use with external insulation and timber frame, why not cavity block walls? I would imagine thats its perfectly acceptable to use it in conjunction with all construction, your comments are a little misleading



    As for the strength per liner meter, 35 tonnes is very high. I'm impresssed, I would of thought it could handle domestic loads but not much more. The glass block can take 4 stories. Is the ring beam only supported by insulation, its not held at any point by piles is it?


  • #17
    [Deleted User]
    Posts: 31,118 ✭✭✭✭ [Deleted User]


    Viking House wrote:
    Hi DB

    100mm EPS gives a U-value of 0.32 so 50mm would give a U-value of 0.45 at a guess.
    You still have the issue of EPS between two layers of concrete though, creating a moisture trap.

    VH

    I was taking into account 600mm of concrete section of rising wall as well. The EPS is not trapped as such, only a small section the thickness of the floor (100mm) is between two layers of concrete, below that the EPS is between concrete & hardcore (vented for radon) above that Internal fermacell.


  • #18
    Viking House
    Registered Users, Registered Users 2 Posts: 551 ✭✭✭Viking House


    Mellor wrote:
    Foamed glass can have a conductivity in the range of .07-.10, so its alot better than you suggest. Some of the stuff I seen was at the low end of the scale. Also, if a concrete block was replaced with this material, the effective distance isn't 100 (4") you suggested, its 215 as the heat is travelling vertically towards the foundations at this area. That looks to be more than the thickness of the insulation under the ring beam, as the insulation in the ring beam is made to take higher loads I imagine it has a less effective conductivity. The more dense polystyrene is the less effective it is as an insulator.
    Aerobord told me that EPS 300 (The dense one) has a 17% better U-value than EPS 100. Something to do with more trapped air bubbles per m3.
    I take your points on the Foam Glass block that it should be measured vertically but the heat is also travelling vertically on the EPS upstand to a depth of 400mm. Sorry for ranting on!
    Mellor wrote:
    You said the ring beam insulation is suitable for use with external insulation and timber frame, why not cavity block walls? I would imagine thats its perfectly acceptable to use it in conjunction with all construction, your comments are a little misleading.

    You are right it is also suitable for cavity block walls. I am a bit biased on my comments on cavity block walls, I think it is a terrible system so my comments are not always fair on this point.
    Mellor wrote:
    As for the strength per liner meter, 35 tonnes is very high. I'm impresssed, I would of thought it could handle domestic loads but not much more. The glass block can take 4 stories. Is the ring beam only supported by insulation, its not held at any point by piles is it?

    If you used piles you can increase the loads even further. When you use the system for high loads you need a Ringbeam shaped like an upside-down T.
    I've seen 20 storey apartment blocks built on Polysterene-Waffle foundations in Sweden.

    There's a Railway line in Ballisadare Co Sligo that sank into the Bog 10 years ago, they dug away all the aggregate and put 2 metres of EPS 300 under the tracks. A 500 tonne train has been passing over this line @100kph twice a day for the last 10 years with no problems or restrictions.


  • #19
    Viking House
    Registered Users, Registered Users 2 Posts: 551 ✭✭✭Viking House


    Deleted User wrote:
    I was taking into account 600mm of concrete section of rising wall as well. The EPS is not trapped as such, only a small section the thickness of the floor (100mm) is between two layers of concrete, below that the EPS is between concrete & hardcore (vented for radon) above that Internal fermacell.

    I would have put down 300mm EPS on the compacted Hardcore and poured the concrete only once on top of the Polysterene.

    In your case the heat in the screed will leak quickly through the 100mm EPS and into the slab below which probably has a direct Cold Bridge contact with the rising wall in the foundations. Forgive me if I am wrong!!

    Keep it simple "Pour once" and wrap your rising wall/ring beam with EPS


  • #20
    [Deleted User]
    Posts: 31,118 ✭✭✭✭ [Deleted User]


    Oops forgot to mention the 200mm EPS under the concrete floor. :o


  • #21
    Viking House
    Registered Users, Registered Users 2 Posts: 551 ✭✭✭Viking House


    Mellor wrote:
    Regarding the foundation coldbridging, It is true that the inner leaf sits on a cold rising wall and it is a source of heat loss. In an externally insulated wall, the contact area of the wall sitting on the cold rising wall is greater, therefore, imo, not only is external insulation exposed to the same flaw, it is greater here.
    The cold comes further into your house when you Dryline. The "Dew Point" is pushed nearer the outside when you Externally Insulate. We only use Poroton blocks so the problem you mention would be reduced. When we Externally Insulate existing houses we try to insulate externally down to the footings which can sometimes be 30-50 cms below finish floor level.
    Mellor wrote:
    The reveal problem also puzzles me, in drylining it is solvable, granted you end up intruding on the frame, but it solves the cold bridge.
    What is done externally? how is the external reveal formed? I'd like to see details as I am concerned about its strength.

    The windows are installed flush with the outside of the wall and the external insulation covers 50-60% of the frames improving the U-value of the windows.


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  • #22
    Mellor
    Registered Users, Registered Users 2 Posts: 40,378 ✭✭✭✭Mellor


    Thanks for the replies VH, you clear a bit up for me, the reveal detail sound alot better than the ideas in my head,


  • #23
    sas
    Registered Users, Registered Users 2 Posts: 1,282 ✭✭✭sas


    Viking House wrote:
    It looks like the only Certified Passive House in Ireland has a 9 inch "Cold Bridge" all around the house, where the walls sit on the strip foundations.

    This should not be dismissed lightly. This is a "certified" passive house which is an incredibly high standard to meet.

    Does this not suggest that the cold bridge at the foundations may not be the big issue its being made out here to be? In performance terms I mean. Obviously I'm talking about the difference between using traditional detailing to reduce the bridge and one of the specialist systems.

    You can use a specialist raft foundation system to achieve a specific u-value which in practise may make little or no difference to the cost of heating the house. Ultimately the aim is to reduce the energy requirement of the house, not to achieve a specific u-value. They may go hand in hand but given the mosart house, they may not.

    I think it was ardara that pointed out on an older thread that the difference in heating bills between a b3 and a b1 house here for example could be as little as €50 per year. Is it worth the extra cost to achieve the b1?


  • #24
    Viking House
    Registered Users, Registered Users 2 Posts: 551 ✭✭✭Viking House


    sas wrote:
    Does this not suggest that the cold bridge at the foundations may not be the big issue its being made out here to be? In performance terms I mean. Obviously I'm talking about the difference between using traditional detailing to reduce the bridge and one of the specialist systems.

    I just spoke to Tomas O'Leary and he used a row of Quinn Lite blocks where the 300mm EPS in the floor meets the rising walls.
    It is not recommended to use Poroton or AAC (Quinnlite) blocks below the DPC level so thats a bit risky unless you have a very dry site which I think he has.


  • #25
    sas
    Registered Users, Registered Users 2 Posts: 1,282 ✭✭✭sas


    Viking House wrote:
    I just spoke to Tomas O'Leary and he used a layer of Quinn Lite blocks where the insulation in the floor meets the rising walls.

    The B3 quinnlite block has the best thermal conductivity of the blocks featured in the IAB cert and that is 0.12W/mK

    So what u-value could they have achieved for that junction?

    If its a good enough detail then it would be a considerably cheaper solution than supergrund I have to imagine and alot easier to get certified too.


  • #26
    Mellor
    Registered Users, Registered Users 2 Posts: 40,378 ✭✭✭✭Mellor


    Quinnlite blocks do have the best conductivity, but they shouldn't be used below dpc in a traditional sense as they are quite porous.

    BUT that does not mean it can not be detailed correctly so that they are suitable for below DPC, This involves creating a dry area by using extra DPM


  • #27
    sas
    Registered Users, Registered Users 2 Posts: 1,282 ✭✭✭sas


    Mellor wrote:
    Quinnlite blocks do have the best conductivity, but they shouldn't be used below dpc in a traditional sense as they are quite porous.

    BUT that does not mean it can not be detailed correctly so that they are suitable for below DPC, This involves creating a dry area by using extra DPM

    Fair enough but the IAB cert makes no reference that I can recall to specific detailing when they are used for rising walls.


  • #28
    kadman
    Moderators, Home & Garden Moderators Posts: 5,134 Mod ✭✭✭✭kadman


    Viking House wrote: »
    A colleague of mine worked as an Architect in London and one of his jobs was to oversee the fitting of Combi boilers in an apartment block. In the first apartment they were coring the wall to install the flew. The walls were mass concrete with Polysterene in the middle. When the core contents fell on the ground my colleague picked up the Polysterene. He squeezed it and it was like squeezing a wet sponge.

    Poured vibrated concrete is quite dense and not very breathable and Condensation moisture was trapped between the two layers of dense concrete.

    Your image shows similar detail Kadman, with insulation trapped between two materials with similar breathability. Better to put 300mm of Polysterene on 150mm compacted Hardcord (18mm-35mm) and pour the concrete only once, on top of the insulation and in the ring beam at the same time.


    Hi VH,

    As you know EPS has varying densities, the polystyrene in the pics has a manufacturing density of between 15-30 kg. There is no possibility of water soaking into this material, and then ringing it out. Test results have proved that the water absorption rate after a 24 hour full immersion test of virtually zero. I can organise a copy of the results for you. There is no evidence of water being trapped in the polystyrene panel due to its zero water absorption rates, conducted by independent testing facilities for the Irish Agrement Board.

    This system of construction has been in use for over 30 years worldwide. In both domestic house construction , and commercial office blocks.

    It is not a poured concrete construction. The wall and floor and roof panels are erected in a similar manner to traditional timberframe, and then sprayed in one or two coats of structural concrete, using a small portable concrete pump.I have been reliably informed recently, that this system is in use in Artic regions very successfully, as soon as I get more info I will post it.

    Before you ask, Yes I do work for M2 Ireland, no I,m not touting for work, as we are run off our feet with our current projects, and yes I will send technical info , and test results ect for any one that wants some,


    kadman


  • #29
    muffler
    Registered Users, Registered Users 2 Posts: 46,876 ✭✭✭✭muffler


    Im just going to make a couple of short and simple observations here lads.

    Are we really going overboard with all the regs in relation to cold bridging etc? (Im playing devils advocate here btw).

    in the absence of full Builing Control inspection how are we ever going to achieve what is discussed here and in other threads.

    @Viking House. I havent had the time to go through all the posts in details but are you saying the methods you quoted above are in use in this country?

    Finally - damn good thread and thanks to everyone for their input so far. keep up the good work.


  • #30
    ardara1
    Closed Accounts Posts: 495 ✭✭ardara1


    muffler wrote: »
    Im just going to make a couple of short and simple observations here lads.

    Are we really going overboard with all the regs in relation to cold bridging etc? (Im playing devils advocate here btw).

    in the absence of full Builing Control inspection how are we ever going to achieve what is discussed here and in other threads.

    @Viking House. I havent had the time to go through all the posts in details but are you saying the methods you quoted above are in use in this country?

    Finally - damn good thread and thanks to everyone for their input so far. keep up the good work.

    You're right Muffler - it's doing over board.

    Under IP1/06 standards Psi values are set for thermal bridging at all junctions in a building. Passive levels (Averaging U-values in all elements of approx 0.15) are easily satisfied with thermal bridging at junctions achieving a Y value of around 0.03 - 0.04 (Current Part L regs 0.11 - draft version wanting 0.08 - UK proposing 0.04) These Y values are guite easily achieved with good standard detail - but will require drylining (Which are also tested under IP1/06 for f values that inicates the possibility for condensation forming in that junction). Floor/wall junctions are the weak areas and solutions are heading for a system of suppporting any suspended floors off an internal sleeper wall with insulation placed infront of it. Any system where the wall rests on the floor slab are having difficulty achieving th Psi value target and will necessitate separating the supporting perimeter from the main floor slab.


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  • #31
    Viking House
    Registered Users, Registered Users 2 Posts: 551 ✭✭✭Viking House


    kadman wrote: »
    As you know EPS has varying densities, the polystyrene in the pics has a manufacturing density of between 15-30 kg. There is no possibility of water soaking into this material, and then ringing it out. Test results have proved that the water absorption rate after a 24 hour full immersion test of virtually zero.

    Hi Kadman

    The 15kg EPS would be EPS 70 is that right? We were on site during the summer and there was a downpour. We built a shelter from EPS 100 (20kgs) sheets. The rain came through the sheet of EPS. The air bubbles in the EPS were not affected by the rain but the rain came through the gaps between the air bubbles. With denser EPS 300 there are less gaps between the air bubbles so that would be more moisture resistant.

    If you have a 2 degree difference between the ground and the slab you will get a capillary pull of moisture into the EPS from outside. 200mm of EPS eliminates the temperature difference and eliminates the capillary pull.
    This means in theory that with 300mm under the slab you don't need a DPC.


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