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condensation in Irish houses - are the regs wrong?

  • 08-12-2010 12:15pm
    #1
    Registered Users, Registered Users 2 Posts: 861 ✭✭✭


    Hi All,

    If you saw the recent thread on the simple u-value calc, you may have heard that I had a cold room in a TF build. I found that insulation between floors, on the outside wall had been omitted/poorly done (not TF companies fault, but ceiling slabber) - so I had my carpenter in to take up part of the floor in the room and retro-fit this insulation around the exterior wall - to see if it fixed the issue.

    The carpenter just informed me that the bit of insulation that was there was damp in parts - but he said most Irish houses have damp!

    He is from Hungary, and told me that there they insulate OUTSIDE the outer block wall, with 2-4 inches of insulation and then plaster that. Inside the walls (TF or block) is a thinner layer of insulation - while in Ireland, we generally go for one layer of insulation on the inside, then cavity, and then blocks with no exterior insulation.

    I called the TF company and they said that the wall design meets the regs - they were at a loss as to why there would be condensation.

    I did look at a program (free trial) called BuildDesk U 3.4, and I put in the exact structure of my wall in detail -
    12mm plasterbaord
    airight membrane
    200mm metac . studs at 600mm centers TF wall
    plywood
    vapour barrier
    50mm cavity
    100mm block

    and that program also said it though there was an 'interstitial condensation risk', and that the condensation may not fully evaporate during the summer months.

    This statement is curious, it seems to suggest that it's expected for condensation to form in the cavity during the winter months and then to evaporate during the summer months - and that is the 'way it works' with our regs. However - it seems other European countries prevent the condensation forming in the first place with the external insulation.

    So is this the case
    - do Irish houses expect to have condensation in the cavity for half the year and then have it evaporate?
    - what can be done about improving the condensation forming - or do I just accept this is an 'irish house'. I am not thrilled by the fact that the insulation between floors could get damp...and it will soon bring mould, and that won't evaporate in summer!

    Any advice?


Comments

  • Registered Users, Registered Users 2 Posts: 1,632 ✭✭✭heinbloed


    Well, ' Irishness ' in building is still demanded, even with new drafts comming in.

    See here a post from a different forum ( http://www.greenbuildingforum.co.uk/forum114/ ) posted by Sinnerboy:

    " The Irish Govt have just issued "Request for Tenders for Development of a Draft Code of Practice for Retrofitting Dwellings"
    Minimum standards and qualification required
    As a minimum, tenderers will be required to demonstrate: -
    (a) experience and a detailed understanding of typical methods of construction in Ireland and of the Irish Building Regulations,
    (b) an understanding of the residential construction industry in Ireland,
    (c) experience and expertise in defect analysis and condition appraisal of existing dwellings, including remedial work solutions for typical dwelling problems,
    (d) demonstrable experience of retrofit / upgrade works including their influence on existing building condition and use,
    (e) detailed knowledge of moisture control management and the control of potential ground, internal and external sources,
    (f) detailed knowledge of fire safety in dwellings, acoustic performance in dwellings, ventilation and structural stability of dwellings,
    (g) detailed knowledge of residential building services, their design and installation,
    (h) detailed knowledge of energy efficient design, construction and detailing,
    (i) detailed knowledge of energy efficient building services,
    (j) detailed understanding and experience in the use of DEAP software and methodology,
    (k) expertise and ability to evaluate and model the physics of dwellings, e.g. movement of moisture, air and heat through a dwelling,
    (l) experience, expertise, training and qualifications to carry out interstitial condensation analysis to EN 13788 and EN 15026,
    (m) experience, expertise, training and qualifications to carry out thermal bridging calculations and surface condensation risk analysis to ISO 10211, IP1/06 and BR 497,
    (n) demonstrable experience of developing Technical Documents and Standards,
    (o) competency in technical report writing, technical drawing and illustration,
    (p) demonstrable experience of construction contract selection, administration and management including programming and scheduling of works.

    I expect the end product will be of benefit beyond The Irish Sea "

    End of Quote.

    Yes, it well end IN the ocean of ignorance, where it came from.

    A simple sentence could be turned into law:

    " Where the ignorance of the laws of physics has lead to interstitial condenstation the builder/seller is fully responsible by all means. "

    And that would be the end of the cowboy trade.


  • Registered Users, Registered Users 2 Posts: 861 ✭✭✭tails_naf


    Well in fairness the TF company are far from cowboys - there are engineers involved here, and many years of building experience.

    My question really was more about is interstitial condensation not only happening, but expected to happen with the Irish style of construction, and the only requirement is that it will evaporate during the summer months, before it is deemed a problem?

    The second part of the question was more about do building to the regs currently mean interstitial condensation will not be a problem long-term with the house?

    And finally, what, if anything can be done about condensation when it is found?


  • Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    heinbloed wrote: »
    Yes, it well end IN the ocean of ignorance, where it came from.


    Or we will have delevired a usefull specification guide which is only to be encouraged . Wait for the document to be delivered first before commenting on it please .

    .


  • Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    OP try this in the software

    12mm plasterbaord
    Intello airight membrane (change SD value to 0.25) #
    200mm metac . studs at 600mm centers TF wall
    9mm plywood*
    vapour barrier Breather membrane++
    50mm cavity
    100mm block

    # allows vapour difusion to internal during summer
    * permits vapour diffusion during winter . Any thicker than this - then it acts as a vapour barrier in the wrong location i.e warm side of insulation
    ++ I hope you don't actually have a vapour barrier here


  • Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    heinbloed wrote: »
    Well, ' Irishness ' in building is still demanded, even with new drafts comming in..


    .


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  • Registered Users, Registered Users 2 Posts: 861 ✭✭✭tails_naf


    sinnerboy wrote: »
    OP try this in the software

    12mm plasterbaord
    Intello airight membrane (change SD value to 0.25) #
    200mm metac . studs at 600mm centers TF wall
    9mm plywood*
    vapour barrier Breather membrane++
    50mm cavity
    100mm block

    # allows vapour difusion to internal during summer
    * permits vapour diffusion during winter . Any thicker than this - then it acts as a vapour barrier in the wrong location i.e warm side of insulation
    ++ I hope you don't actually have a vapour barrier here



    Err - the vapour barrier i mentioned is essentially the green felt that is wrapped around the plywood on all timber frame constructions. it is the last layer before the cavity. This was all done by the TF company, so I assume it's all standard.

    Also the interior membrane (you have it down here as intello) does not allow any water through - it is air and water tight - do you think this is a problem - again I was assured by TF company it would not be, and impermeable layers are apparently ok re regs ?


  • Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    The internal layer should be a vapour barrier , the external should be vapour open . If you don't enter data like this into the software you cannot rely on the output .

    Gaps in the insulation that you described would cause condensation irrespective of the membranes specifications .

    For piece of mind hire an expert to review .


  • Registered Users, Registered Users 2 Posts: 14 readytostart


    sinnerboy wrote: »
    The internal layer should be a vapour barrier , the external should be vapour open . If you don't enter data like this into the software you cannot rely on the output .

    Gaps in the insulation that you described would cause condensation irrespective of the membranes specifications .

    For piece of mind hire an expert to review .
    This may be going off the thread but what would be the effect of putting an insulated plaster board on the inside of the vapour barrier.
    Could this have major condensation implications in years to come?
    Should all insulation be on the outside of the vapour barrier?
    Thanks for your opinions in advance


  • Registered Users, Registered Users 2 Posts: 1,632 ✭✭✭heinbloed


    Readytostart asks:
    Should all insulation be on the outside of the vapour barrier?

    Yes, in principal. But there different vapour barriers available for different conditions, climates. For example 'intelligent' ones which open once the air moisture drops to a certain level and close if the air moisture increases.

    There is a software available called " wufi ", before wasting money on a wrong job get your plans calculated.


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