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Attic Insulation and Flooring

  • 01-03-2023 12:44am
    Registered Users Posts: 55 ✭✭

    I have rollout insulation in my floor joists but I also want to get the attic insulated, I'm going with foam insulation sprayed on vent cards. I want to use the attic for storage, it will clean it up with no great labour involved on my part and we've had ingress of flies and birds at times over the years. A worse day to day problem is that the upstairs bedrooms are draughty and noisy with slates rattling quite loudly during storms - both problems originate in the attic. We could redo the rollout insulation get it tight but then we couldn't floor the attic directly onto the joists and those raised joists would leave very little space, we have fixed the attic door, we know long term the slates will need to be looked at but all in all we said go with attic insulation and create more space for ourselves.

    Question is: can I just lay an attic floor onto the joists compressing the insulation that's there after the attic is done instead of removing it? Obviously it doesn't matter if the insulation value is reduced. I'd prefer to leave it in situ if possible. Would humidity be a big problem and would a velux window installed in the attic be sufficient to manage it during hot periods?

    Thanks in advance for any advice provided.


  • Registered Users Posts: 393 ✭✭grimeire

    Compressing the insulation will reduce it insulation value as you mentioned.

    Not sure how old your place is but you should have at least 300mm up in the attic of wooly insulation. Inside of the wooly insulation you could use solid I believe it has far better insulation value and is around double the the insulation value of wooly insulation of the same size. Plus it is far better sound proofing but very time consuming in comparison to fit compared to the wooly insulation.