internal insulation and thermal bridging

Discussion in 'Eco Talk' started by andy271, Sep 2, 2018.

  1. andy271

    andy271 New Member

    hi guys really need your advice ...its a long tale but I am in a conservation area so cant have external wall insulation and I live in a 1920 Edwardian home ..very cold ..anyhow my friend told me to do internal insulation and to get celotex 25mm .must say hear I would have got 50mm but the rooms would close in a bit to much but maybe I was wrong ..we will see. so 25mm celotex gripp fill like in a dot and dab way onto solid brick wall bricks fairly clean then attatch 12.5mm plasterboard with metal insulation fixings ...also because the rooms are upstairs the loft comes into the room so don't want a cold spot so put kingspan inbetween the rafters I couldn't reach as there was a pearling in the way I left a 25mm air gap and can carry on the rest another time my questions are numbered any advice would really be appreciated ..thank you

    1 ..window frames have timber lintel ,should I replace with concreate will this cause a thermal bridge

    2..should I seal from the windows and inside the loft all the way around the celotex and the plasterboard were there are gaps .pictures will explain a bit better

    3..will I get condensation between were the brick wall is and the celotex ..that is what worries me ..have realised the metal fixings can cause a thermal bridge also

    4.. will the eave in the loft still be able to breath with the kinspan roof has been put on with breathable membrain so im assuming it should be ok

    5.. around the window frame I would like wooden sill and wooden frame to keep with the Edwardian style but am worried this will be a thermal compromise also mdf hdf high density ..I am also going to get triple glazing as my double glazing is 30 years old and only 24mm ...I have had a good price form a local window company and they use good quality frames and glass .

    6.. should I have a themal membrane under the sill and frame before the triple glazing windows go in

    I have had joiners,electricans ,builders and the list goes on and none of them have done a job to a good standard ..I am now going to do a lot myself if I can the quality and advice I have had so far im sure has been wrong and the thought of ripping plasteboard down again is making me ill

    bare brick wall

    sbr brushed on

    25mm celotex gripp filled on similar to dot and dab method

    then 12.5mm plasterboard put on with these fixings

    if this has been done wrong I will do it again ..all my windows have no sill or frame work as I took all of these out to check for air leaks and holes etc 20180827_170446.jpg 20180827_170519.jpg 20180827_170531.jpg 20180829_202316.jpg 20180829_202400.jpg
  2. andy271

    andy271 New Member

    20160911_174543.jpg this was done last September and has been plastered and painted..some of the fixings have popped but not to many ..the reason im posting this is when I touched the walls they feeled as cold with the insulation as they did without it ..and in November when I put a cheap thermal tester on the walls they read 14% c which I thought was a bit low ..if anyone can tell me is this a botch up..i was tempted to get thermal wallpaper but don't think it will of today im tempted to take all the walls down to the brick and get the proper kingspan thermal board say 64mm ..just don't know what to do
  3. I'm bemused because I've done exactly the same and the room is lovely and warm.
  4. andy271

    andy271 New Member

    hi did you also use 25mm celotex
  5. Yes. Wood batters on dpc strips, 25mm celotex and 12mm pb.
  6. andy271

    andy271 New Member

    I didn't use wood battens as the brick walls were not that level so glued the celotex to the wall then put 12.5mm plasterboard over with the fixings..ive recently found out the fixings cause a thermal bridge and I will loose around 8% efficiency ....did your battens go directly on internal brick
  7. andy271

    andy271 New Member

    the celotex went straight on this wall

    ive asked a lot of people about the wooden lintel and should I replace it for concrete but no one knows ..

    this wall has had SBR pasted on so don't know if that is good or bad

    Attached Files:

  8. sospan

    sospan Well-Known Member

    Forget celotex. It is the wrong product and will make it so much more work for you.

    Have a look at insulated plasterboard with a built in vapour barrier. These are bonded to the wall either dot and dab or adhesive foam. You supplement this with frame fixing screws. There is a set way to deal with window openings to prevent thermal bridging - best to google it.

    I just done four stone built cottages with no cavity and have had no problems. Some of the rooms have gone from virtually inhabitable due to the cold to barely needing any heating
  9. sospan

    sospan Well-Known Member

    You should leave a 50mm gap between the felt and the back of the insulation. You have to be careful about condensation and airflow.
  10. andy271

    andy271 New Member

    hi sospan I have no felt..

    bare brick wall SBR applied
    celotex 25mm but on brick wall with gripp fill

    then 12.5mm plasterboard put on with fixings

    link to fixings that were used

    someone on another forum said the 35mm head will pop plasterboard and he was correct although only 2 have popped so far

    the reason I didn't get the kingspan with the plasterboard already on is I got the celotex for free off a friend

    so now I don't know weather to start again batten or dot and dab but instead of celotex 25mm use kingspan 50 or 60 mm thermal board

    will the wooden lintels cause a cold spot ..side of walls as seen on pics have timber and brick ..
  11. sospan

    sospan Well-Known Member

    The felt or roofing membrane is here


    The wooden lintel or concrete won't be a problem. However, I would give them a coat of timber preservative before covering.

    I am not a fan of ripping things out just because they technically aren't correct but aren't causing a problem. So I would leave it unless you have a problem.

    The frame fixings are around 15 - 20mm. Sometimes it is better to put them in at a slight angle so that is becomes harder for the material to pull through.
  12. andy271

    andy271 New Member

    hi sospan not allways near internet ..I think at the mo its a 25mm air it supposed to be 50mm..

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