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Spray Foam and Wool Insulation in Attic?

  • 19-11-2024 10:49PM
    #1
    BornSkippy
    Registered Users, Registered Users 2 Posts: 62 ✭✭


    Is it bad practice to have both Spray Foam under the roof and insulation wool laid on the floor of an attic?

    The bungalow I bought has it.

    Damp was a bit of a problem.

    I cleared out some wall vents on the ground floor that had become blocked by cavity pumped insulation.

    I suspect the spray foam may lack the 50 mm ventilation clearance from the roof itself, but I don't know for sure and I'm inclined to leave it be for now anyway.

    Should I do anything about the insulation wool laid on the floor of the attic?



Comments

  • #2
    [Deleted User]
    Posts: 9,954 ✭✭✭ [Deleted User]


    Spray foamed roofs are seen as bad. In the UK some banks have stopped giving mortgages for houses with sprayed roofs. Did your surveyor say anything about it in their report, or were they the 'I am not getting my suit dirty in the attic' type?



  • #3
    BornSkippy
    Registered Users, Registered Users 2 Posts: 62 ✭✭BornSkippy


    No observations made on it in the survey.



  • #4
    muffler
    Registered Users, Registered Users 2 Posts: 47,029 ✭✭✭✭muffler


    There's an article on the BBC website from 2 days ago about spray foam and the issues with banks etc in the UK. Well worth a read.



  • #5
    SimpleQuestions
    Registered Users, Registered Users 2 Posts: 12 ✭SimpleQuestions


    We are investigating improving on the insulating in our attic.

    We have had two companies out in the past week, both contracting each other…gonna keep looking into it a while longer

    Company 1 - Spray foam applied against the underside of the roof. PVC vents included to ensure flow of ventilation and removal possibility of moisture\condensation. I asked the question - "so if I'm spray foaming against the roof would that not mean the warm air from the house still travels up, gets lost from house and gets stuck in the attic?". They had an answer but didn't really make sense (something like if the air knows it can't go past roof it'll tend to stay stagnant in the house). Also said that roll out insulation lasts 4-5 years and then needs to be replaced, spray foam doesn't

    Company 2 - Roll out insulation of 200mm (a type of fibreglass which I thought wasn't used anymore) on top of existing 100mm insulation. Half the price of the spray foam option. These guys told me that roll out insulation lasts for 20+ years. Also made the point (which makes sense to me) that getting roll out insulation means that the warmth stays in the house and doesn't move up to the attic like it would using foam spray



  • #6
    Biker1
    Registered Users, Registered Users 2 Posts: 419 ✭✭Biker1


    https://www.boards.ie/discussion/comment/122929417#Comment_122929417

    Put 250mm of Mineral wool (used to be called fibreglass) on top of what's there. Ensure attic hatch is draught stripped and seal around any pipes going up into the attic. Forget about spraying between the rafters. You need to stop the heat loss at the lowest point. i.e. ceiling level.



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  • #7
    [Deleted User]
    Posts: 353 ✭✭ [Deleted User]


    Spray foam works if it is applied correctly, the problem is you never really know.

    The biggest issue is the risk of insurance companies and banks following the UK and taking a negative view of it. If this happens then you could struggle with insurance and a bank wont lend against a house with spray foam so if you sell in the future you will be limited to cash buyers meaning your house wont be worth as much as a house without. The other obvious risk is that it is not applied correctly and you are left with damaged rafters which is a very big job to replace.

    Therefore, on the balance of risk, the potential negatives outweigh the upsides so go with option 2.

    As Biker 2 has described its an easy process to DIY. Watch a few youtubes on how to lay extra insulation, the trickiest part is where the insulation meets the roof, you have to let air into the attic so you either leave a gap at the roof or install roof vents.



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