insulating solid walls

Discussion in 'Building' started by RMB, 30 May 2006.

  1. RMB

    RMB

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    I live in a 1930s house with solid walls.In winter the exterior facing walls get very cold inside.What I plan to do is:
    1.Fix battens to the wall
    2.attach plasterboards to the battens
    3.fill the space between the old wall and plasterboard with insulating material

    Could this have any negative effects?
     
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  3. Darkrob_DIY

    Darkrob_DIY

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    With a configuration such as that you may well get interstitial condensation as warm moist air will penetrate through the plasterboard and condense on the cold surface of the wall. Therefore you will need to have a vapour barrier on the warm side of the insulation;

    Fix battens to wall
    Insulate between the battens
    Attach vapour barrier
    Fix plasterboard

    Hope this helps

    R Critchley :evil:
     
  4. RMB

    RMB

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    Thanks for that.Any suggestions for a vapour barrier?
     
  5. Darkrob_DIY

    Darkrob_DIY

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  6. Monsoon

    Monsoon

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    I'm insulating solid walls using celotex/kingspan.

    My method will be:-

    1. Fix 50mm treated batten to top and bottom of the wall. Leaving a gap of 2400mm

    2. In fill the gap between the battens with 50mm Kingspan. It should be a nice tight fit and each board will butt the other.

    3. Tape the joints using the heat reflective tape available from Kingspan.

    4. Place timber studs at 600mm intervals.

    The Kingspan will prevent warm air making contact with the cold wall behind.
     
  7. malhou

    malhou

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    should the plaster be removed and then insulate ?
     
  8. ajrobb

    ajrobb

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    I'm not a builder, so take the following with a pinch of salt:

    I suspect that much work would come under Local Authority Building Control (LABC). They will want you to insulate to modern regulations where possible but can make concessions as the proposed work is better than the original.

    The minimum you can do on the quiet would be to line with duplex (foil-backed) plasterboard on treated wood battens. The aluminium foil backing is a vapour barrier. The sealed reflective cavities created behind the plasterboard have an R-value of 0.6 and could reduce the U-value (and heat loss) by up to 70%, making a noticeable difference and eliminating condensation (with a bit of ventilation). It will also reduce the thermal mass, so the rooms heat up (and cool down) quicker.

    Common solutions to satisfy LABC would be to remove existing plaster and line with Celotex and plasterboard or insulated plasterboard. According to manufacturer's instructions (MI) Celotex GA4000 goes up against the brick and is held in place with untreated battens and plasterboard on the battens. Insulated plasterboard (e.g. Kingspan K18) is fixed to treated battens on the brick (MI). Personally, I'd go with the Celotex against the wall as you get a handy sealed reflective service cavity behind the plasterboard. The battens are typically 19mm thick and the cavity's R-value is equivalent to 15mm of Celotex, so you only lose 4mm and you avoid cold bridging.

    http://www.celotex.co.uk/Applications/Wall-Insulation/Solid-masonry-walls-Internal

    http://www.insulation.kingspan.com/uk/k18.htm

    If you don't remove the plaster, penetrating damp and lack of heat could damage the old plaster.
     
  9. wavetrain

    wavetrain

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    Instead of spreading rumours, why don't you first ring your local LABC and get them to confirm or deny your 'suspicion' that adding some insulation to your existing house would come under building control. Whatever they say, ask for the government website URL so we can see this in writing, since my experience of dealing with building control is they are far from 100% knowledgeable of the legislation.
     
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  11. ajrobb

    ajrobb

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    OK - my understanding is that if you replace more than 25% of the plaster on an external wall, you'll be required to insulate it to modern regulations. That is what a Building Inspector told me. I'm sorry, I neglected to get the building regulation reference off him. He was prepared to compromise on the depth as there was a restricted door opening close to the wall.

    It took a couple of minutes to find the relevant link that supports my statements:

    http://www.planningportal.gov.uk/permission/commonprojects/insulation#SolidWall
     
  12. wavetrain

    wavetrain

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    In most cases an external wall will have more than one room as part of it, so if just one room is replastered or have its plaster removed to gain a couple of cm you may be under the 25% limit.

    And unless you tell BC what you are doing, how could they know?
     
  13. ajrobb

    ajrobb

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    "Where a solid wall upgraded by the installation of insulation then it must meet the minimum energy efficiency values set out in the Approved Documents."

    Sadly, that is what the OP proposes, no 25% rule there. I didn't know that until I found the link. You live and learn...
     
  14. wavetrain

    wavetrain

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    The extract below is taken from this page: http://www.planningportal.gov.uk/permission/commonprojects/externalwalls/

    Note how they spell lintel and at the end that it is only a 'This is an introductory guide and is not a definitive source of legal information'. My feeling is if the person who wrote this does not recognise 'lintol' as a mistake, how reliable is the document as a whole?

    I remain sceptical. For example, if a homeowner decided to re plaster an external room, say a bathroom because when they removed tiles, the plaster was damaged such that it was best to replace. But if the wall was brought up to current standards, the bath would no longer fit in the room. There will be plenty of other examples one can think of: stairs no longer wide enough to meet minimum width for ease of use, small bedroom no longer big enough to fit a bed in.

    And as mentioned before, how would BC know what a householder is doing, the thought Police perhaps?
     
  15. ajrobb

    ajrobb

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    So much of what Governments do is errant nonsense but we get stuck with it in the meantime. Maybe John Prescott wrote that bit himself.

    I think there is a caveat that limits the improvement to what is technically feasible. On a good day you might persuade a BI that making the bath not fit is not technically feasible. Almost certainly not making stairs too small would take precedence over lagging.

    I'd like to know if there are grants to sweeten the bill, I thought I saw mention of one fly past. Something about getting the work done then sending off a certificate to get some cash. (Guess how much the work would be inflated.)
     
  16. alittlerespect

    alittlerespect

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    Hi

    Your not doing any structural alterations so you do not need to contact your local authority building control office, if you do you could be opening up a whole can of worms for yourself!

    Getting back to your initial enquiry, the answer would be to fix 50 x 50mm tanalised softwood timbers to the wall fixed at 600mm centres, then add 50mm PIR insulation between the battens then and only as an additional barrier fix your vapour barrier to the face of the battens ensuring to overlap joins by 150mm (horizontal and vertical overlaps) then use some duck tape and tape up the overlaps. Then fix Kingspan K18 insulated plasterboard (or similar approved product) to the battens I would recommend around a 50mm thickness of insulation but 25mm will do if space is an issue. Finish by taping and jointing and decorating to finish.

    You don't necessarily need the vapour barrier as PIR has a high vapour resistence, the choice is yours.

    Regards
     
  17. ajrobb

    ajrobb

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