Insulating roof internally

Discussion in 'Roofing and Guttering' started by Jack07, 28 Nov 2021.

  1. Jack07

    Jack07

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    Hi, I've tried looking to see if this has been asked before but can't see anything posted.

    I have a Welsh slate roof with no felt. It's in good nick and my roofer advised me to leave it as it is but just be vigilant as any damaged slates will need to be fixed immediately.

    I'm in no rush to spend £1,000s on a new roof. Inevitably it will need to be done in the coming years but in the meantime I'm trying to Insulate the house as much as possible.

    Has anyone insulated their roof internally and if so what product did you use? Are there any negative points such as damp problems or lack of breathability?

    Regards J
     
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  3. oldbutnotdead

    oldbutnotdead

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    Why insulate the roof? Loft insulation is much cheaper and easier.
     
  4. Jack07

    Jack07

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    Hi, I have insulted the loft but being an old stone house it can be very cold. The extra loft roll doesn't seem to make a difference.

    I know it may seem a bit counter productive insulating both but I'm looking at ways to save as much energy as possible.
    If the attic space is warmer surely it would reduce the amount of warmth being pulled out of the house?

    Obviously the lack of felt really allows the wind to blow through up there. Hoping its not just the warmth but reducing the draught would help?
     
  5. datarebal

    datarebal

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    Air flow is good for the structure.
    How much fluff do you have at ceiling level ?
     
  6. RonnyRaygun

    RonnyRaygun

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    I think you’d be better adding more insulation at loft floor level. No point trapping heat in the loft where no-one ever goes, much better to trap it in the bedrooms.
    Obviously additional insulation at loft floor level becomes an issue if you use the loft for storage. You might need to use some stilts to raise the floor level before boarding out.
     
  7. oldbutnotdead

    oldbutnotdead

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    As both comments above. Your roof is in good nick partly because of the draughts- keeps the timbers dry. You are correct in one sense- the greater the temperature differential across a thermally porous barrier, the more energy per hour is lost, but it's a linear effect no exponential, the most cost-effective way to keep the heat in the bedrooms is the current standard 300mm loft insulation (if you have laid new on top of old you might want to lift the new and check the old to see how much it has crushed down over the years, older glass wool did tend to sink & lose effectiveness).
    Make sure you leave an air gap at the eaves (if you want to max your insulation and eaves are at joist height, tack bits of breathable membrane across the rafters at eaves height, you can then insulate the edges of the ceilings without risking blocking the eaves).
    Make sure any pipes, cables etc. going into the loft are well sealed. Make sure your loft hatch is well sealed, ideally insulate over it (have the Rockwool overlap the hatch for more draught reduction).
    EDIT If you have any active water tanks in the loft, consider boxing them in then insulating the outside of the boxing (and leave a gap in the loft insulation under the tanks)
    Any open fireplaces not in use- ideally cap the flues, block the fireplaces (but leave a louvre vent in the fireplace so you don't get condensation in the flue). If the fireplaces are used occasionally for a real fire, get one of those chimney sheep things.
    Once you've done that lot, have a look at your radiators and heating system (I'm assuming central heating here)- are they sized correctly for the rooms and the boiler (modern boilers run most efficiently at lower output temp so you need larger rads to get the same kWh out of them.
    Windows.
    Doors.
    Carpets.
     
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  9. Jack07

    Jack07

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    Many thanks for all the responses.
    The loft has 2x100mm which was already installed before I bought the house. Both layers look good.

    I have been up there running a new bathroom extract and was thinking of ways to limit heat loss. I'm going to buy some extra top-up rolls and lay over this week. The space isn't used for storage so I am thinking of maybe getting another 200mm.

    I also have a gas log effect fire which is awaiting a service to get up and running. This runs up the solid stone wall so it has previously helped retain the warmth in the wall.

    Thanks again
     
  10. Mr Chibs

    Mr Chibs

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    Thought the recommended thickness for loft insulation is a shade under 300mm.

    like others have said, just beef up loft not the roof.
     
  11. Notch7

    Notch7

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    seal and insulate the loft hatch

    be careful at the eves -insulate the loft floor but dont block eves ventilation

    think carefully about your water tank if its in the loft -you dont want it freezing
     
  12. catlad

    catlad

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    Overboard the bedrooms ceillings with insulated plasterboard.
     
  13. oldbutnotdead

    oldbutnotdead

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    You get into diminishing returns with insulation thickness. If you want to stick a total of 400mm up there crack on, you won't get 1/3 better heat retention than with 300mm & rockwool price is pretty much by the cubic metre so an 100mm roll will generally cover twice the area that the same manufacturers' 200mm roll will do.
     
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