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Spray Foam Insulation in Attic: Should I keep?

  • 20-04-2021 3:22pm
    #1
    Registered Users Posts: 24,062 ✭✭✭✭ noodler
    Registered User


    Hi,

    I'm in a new (very old) house where the previous owner installed open cell spray foam insulation in the attic.

    My surveyor's report said it all needed to go as there was no provision for ventilation. Another builder said he could feel a breeze.

    I can see by the guarantee left by the company in question that it is open cell and, according to the website, has a breathable vent card.

    Is there another expert one can ask on this? I put a Google next thermostat up there for a night and there was a constant humidity rating of 60% (not sure if that is RH).

    It is a cold house, the foam was expensive and it would be a shame to remove unless absolutely necessary.


Comments

  • Registered Users Posts: 4,113 ✭✭✭ Tefral
    Registered User


    noodler wrote: »
    Hi,

    I'm in a new (very old) house where the previous owner installed open cell spray foam insulation in the attic.

    My surveyor's report said it all needed to go as there was no provision for ventilation. Another builder said he could feel a breeze.

    I can see by the guarantee left by the company in question that it is open cell and, according to the website, has a breathable vent card.

    Is there another expert one can ask on this? I put a Google next thermostat up there for a night and there was a constant humidity rating of 60% (not sure if that is RH).

    It is a cold house, the foam was expensive and it would be a shame to remove unless absolutely necessary.

    If theres a vent card installed then you are ok. Get a can of expanding foam from a builders providers. Remove a hand sized amount next to a rafter all the way up to the top to see if there is indeed a vent card, you will see it stapled to the rafter. If its there, your ok. Use the can you bought to spray back in the hole you left. If not then it needs to be removed.

    Theres was alot of spray used here called Icynene and thats supoosed to be ok to spray right to the felt, but to be honest that never sat right with me. It has no NSAI cert and is against building regs, so maybe thats whats in and maybe thats why he is saying remove it.


  • Registered Users Posts: 24,062 ✭✭✭✭ noodler
    Registered User


    Just from the company's website:

    When insulating a roof, the objective is to cover the entire area, i.e, every nook, cranny and gap whilst ensuring that the wooden timbers within the roof maintain their ability to breathe. This is achieved by installing a breathable card membrane or Vent Card between the rafters.

    Open cell insulation is then sprayed onto the membrane of the vent card to the appropriate depth ensuring that an adequate level of heat retention is achieved.

    This card creates the 50mm air gap required by building regulations.


  • Registered Users Posts: 24,062 ✭✭✭✭ noodler
    Registered User


    Tefral wrote: »
    If theres a vent card installed then you are ok. Get a can of expanding foam from a builders providers. Remove a hand sized amount next to a rafter all the way up to the top to see if there is indeed a vent card, you will see it stapled to the rafter. If its there, your ok. Use the can you bought to spray back in the hole you left. If not then it needs to be removed.

    Theres was alot of spray used here called Icynene and thats supoosed to be ok to spray right to the felt, but to be honest that never sat right with me. It has no NSAI cert and is against building regs, so maybe thats whats in and maybe thats why he is saying remove it.

    Ok, useful to know it can be checked even if it is probably beyond me!

    Would the card be on every part?


  • Registered Users Posts: 4,113 ✭✭✭ Tefral
    Registered User


    noodler wrote: »
    Ok, useful to know it can be checked even if it is probably beyond me!

    Would the card be on every part?

    Yes. It should be running the whole way across the rafter and from ridge to eave.


  • Registered Users Posts: 10,991 ✭✭✭✭ Calahonda52
    Registered User


    You must be satisfied that the card is breathable


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  • Registered Users Posts: 2,597 ✭✭✭ MicktheMan
    Registered User


    noodler wrote: »

    It is a cold house, the foam was expensive and it would be a shame to remove unless absolutely necessary.

    The following comment is assuming the spray foam has been applied to between the roof rafters on the slope.

    If it was my house I would remove the foam, end of.

    Why?

    1. I don't trust any spray foam in contact with structural timber in a cold space (outside the thermal envelope) where condensation regularly occurs. The risk of timber rot is just too high for me especially if I have no idea of what product was used and how well it was installed.
    2. In any case, it is more than likely doing little or nothing to address the real reason why the house is cold. I say this because I regularly come across exactly what you describe and when tested for heat loss, its effectiveness is akin to an astray on a motorbike.


  • Registered Users Posts: 24,062 ✭✭✭✭ noodler
    Registered User


    Thanks for that.

    It was installed just over two years ago and the company in question left an 25 year guarantee for any damage arising from faulty installation of up to 12.5k.

    I might see if they can send someone to have a look and reaffirm their handiwork.


  • Registered Users Posts: 198 ✭✭ social butterfly 2020
    Registered User


    How did you get on With this?



  • Registered Users Posts: 24,062 ✭✭✭✭ noodler
    Registered User


    Left it in place, been about 18 months.

    No sign of rot but always in the back of my mind about the timbers you can't see.

    Whole road has it which gave me some reassurance, the hassle of removing it coupled with the fact there is not felt between tiles and timbers has stopped me looking into it further.



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