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Insulated plasterboard, how much difference will it make to solid brick walls?

Discussion in 'Building' started by MisterBoy, 28 Jan 2021.

  1. MisterBoy

    MisterBoy

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    My house is ~1860 with solid walls. My home office has two external walls and in colder months, I get a cold draft washing down the walls which leads to very cold feet :)
    I wondered about interior cladding with PIR-backed plasterboard, it's 25mm insulation on 12mm plasterboard.

    Maths or more anecdotal answers welcome, I don't need the room to be super efficient just to avoid icy-cold walls which also risk condensation/mould problems. Would this make a significant improvement to my solid brick?

    Ta.
     
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  3. Mr Chibs

    Mr Chibs

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    Can't speak for 25mm, but 50mm will make a world of difference, I've lived in old property no insulation and current old house has 50mm internal insulation and it's fantastic.
    Do the floor too if you can, with rockwool to save some lolly.

    It's cheaper to buy the insulation and plasterboard as separates if required, plus you get double sided foil barrier when done this way.
     
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  4. MisterBoy

    MisterBoy

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    Done the floor already - there is a cellar under so we put PIR between the beams when re-doing the ceiling down there. 100mm from memory.
     
  5. Mr Chibs

    Mr Chibs

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    Good, you're good to go then... my whole house has been done, it's very warm and even in the last couple of weeks, won't go below 16/17° overnight, once the heating has gone off at around 10pm (heating set to 19°)
     
  6. JohnD

    JohnD

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    Yes.
     
  7. JohnD

    JohnD

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    Measure the exterior wall area in square metres. For ease, assume a 20C difference between indoor and outdoor temperatures.

    Look up U- values

    https://www.greenspec.co.uk/building-design/u-value-introduction/#:~:text=The technical name for which,the inside and the outside.

    Also
    https://www.gov.uk/government/publi...at-losses-and-the-potential-for-energy-saving

    There might be a simpler webpage somewhere.

    There are bound to be variations and inaccuracies but it will give you a pretty good idea.

    You can knock off the old plaster first if you want.

    A wooden frame is not necessary.
     
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  9. howbut82

    howbut82

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    Personal experience... using the 38mm board from wicked, within a corner box room, wall surface temperature increased from 14 to 19 degC on a cold day (external 5C).
    Hugh difference from the radiation heat transfer perspective. Best £150 I spent to be honest.
     
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  10. MisterBoy

    MisterBoy

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    Very helpful, cheers for that.
     
  11. howbut82

    howbut82

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    To achieve Building Regulations 0.30 U-Value, you will need to use the 62.5mm board (Kingspan K118 or similar).
    Once you hit that high U-Value, make sure all gaps are sealed with tape to maintain the vapour seal, otherwise, there is a risk of condensation (and mould) form between the insulation and internal brick face.

    The K118 technical datasheet gives quite good instruction regarding detailing.
     
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  12. JohnD

    JohnD

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    The first inch of insulation saves a lot more energy than the second inch.
     
  13. Captain Nemesis

    Captain Nemesis

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    Uses a lot more too.
     
  14. Rad1o

    Rad1o

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    We moved into a house - 1930ies with solid walls - with an extension - 1970ies with cavity wall insulation. The house had always been cold while the extension felt a lot warmer. I have insulate all the rooms in the house with 50 to 60mm dry wall insulation from Kingspan or Celotex depending on price at the time. The house is very different now. Take pictures when you do it for future energy certificate purposes.
    I have also changed windows and the outside doors to frame insulated and triple glazed parts. Another big difference.
     
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