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General: External wall insulation on chimney breast

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  1.  
    Hello,

    I have been reading the forum recently and managed to get my mother's property funding for external wall insulation which will hopefully be getting done soon.

    She has been told they will not insulate the chimney breasts (1.5 m and 1.7 m long) along the gable wall (9m long), because of the heat inside the chimney if it is used in the future.

    Will this not cause a big thermal bridge ?

    Would she be best to get this externally insulated at her own cost at a later date.

    The chimney stacks were both removed to below roof level last year as it was cheaper than repairing the existing render to them at the time. Front has two disused flues and rear has three disused flues. The plan was if the roof was redone to have EPs beads or glass beads poured in and potential insulation over the top??

    Chimneys have a 280 mm cavity and juts out from the 9" brick wall externally with a half brick (110mm) wall internally and externally.

    Thanks for any advice of comments
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 11th 2023
     
    Bloomin nonsense - next they'll be advising an insulated flue, to similar effect on future flue temp. A brick flue does not depend on being kept cool, rather the reverse. What if the chimney stack was fully internal?

    EWI the lot. And within the loft space, insulate the stack's inner face as well (the gable end walls too).
    • CommentAuthorbhommels
    • CommentTimeFeb 11th 2023 edited
     
    Posted By: fostertom
    EWI the lot. And within the loft space, insulate the stack's inner face as well (the gable end walls too).

    +1
    If they are worried about the thermal rating of the EWI they could use a mineral wool based EWI product for the chimney, like what is required around flues etc.
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 11th 2023
     
    Any future reinstatement of closed flues is bound to require insulated liner - or hopefully will be an idea long abandoned by then.
    • CommentAuthortony
    • CommentTimeFeb 11th 2023
     
    Yes it will leak heat and possibly collect condensation, no question that the EWI should go round all the external walls. I can’t see how it would comply with current building regs unless it did.
    •  
      CommentAuthordjh
    • CommentTimeFeb 11th 2023
     
    Posted By: listenerspeakShe has been told they will not insulate the chimney breasts (1.5 m and 1.7 m long) along the gable wall (9m long), because of the heat inside the chimney if it is used in the future.
    Who is 'they'? IIUC the chimneys have been removed or at least can't be used? Find another 'them' that knows what they're doing! Report the original 'they' to whoever is monitoring whatever programme it is.
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 11th 2023
     
    That's the trouble wich 'theys' - out of the frying pan into the fire.
  8.  
    Thanks everyone for your replies.

    Sorry I didn't specify who "they" was, it's the company that has been awarded the contract by the local council who are funding the works so it's not possible to change who is doing the work.

    Not sure how to proceed as we are grateful they are doing the EWI and don't want to throw a spanner in the works.

    Posted By: fostertom

    EWI the lot. And within the loft space, insulate the stack's inner face as well (the gable end walls too).


    Will definitely do this in the front loft space but how will this work with the rear being a room in the roof?

    Thanks again
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 13th 2023 edited
     
    Posted By: listenerspeakWill definitely do this in the front loft space but how will this work with the rear being a room in the roof?
    In that case no need, assuming the roof slopes above are insulated and join up with the 'outdoor' EWI on the gable end(s).
    Posted By: listenerspeakinsulate the stack's inner face as well (the gable end walls too)
    is only necessary if the loft is full of 'outside air' because insulation is at loft 'floor' level.
    • CommentAuthorphiledge
    • CommentTimeFeb 13th 2023
     
    If the stacks have been taken down, there are no chimneys. Maybe worth pointing this out to the contractor and or the council
    • CommentAuthorRobL
    • CommentTimeFeb 13th 2023
     
    Posted By: bhommelsIf they are worried about the thermal rating of the EWI they could use a mineral wool based EWI product for the chimney, like what is required around flues etc.


    We used 150mm platinum EPS mostly, but 150mm rockwool around the external chimney, for the avoidance of doubt.
  12.  
    Hello all,

    Just an update managed to speak to local BCO and they have agreed with the contractor saying to should not be insulated due to someone reinstating a chimney stack and putting a fireplace in future. Said the pointing might be poor and is a risk of ignition if it is clad outside?

    Also said you won't notice any difference and it doesn't need to be insulated as there won't be any thermal bridging.

    Looks like we will have to do that section ourselves at a later date?

    Thanks all
  13.  
    Posted By: fostertom
    Posted By: listenerspeakWill definitely do this in the front loft space but how will this work with the rear being a room in the roof?
    In that case no need, assuming the roof slopes above are insulated and join up with the 'outdoor' EWI on the gable end(s).
    Posted By: listenerspeakinsulate the stack's inner face as well (the gable end walls too)
    is only necessary if the loft is full of 'outside air' because insulation is at loft 'floor' level.


    Thanks, will look into the roof once the walls have been sorted
  14.  
    ''Also said you won't notice any difference and it doesn't need to be insulated as there won't be any thermal bridging.''

    You know that that is bananas, but worrying to think that they don't. The same rationale was used for not internally insulating chimney breasts ('It's a cavity wall, innit?), but that was 40+ years ago, and we knew nothing. Surely things have changed?!

    When you do it yourself, use rigid Rockwool to cover yourselves. Lots of suppliers out there, but I use a store which sells EWI.
    •  
      CommentAuthordjh
    • CommentTimeFeb 16th 2023
     
    https://www.lgo.org.uk/make-a-complaint/fact-sheets/planning-and-building-control/building-control

    helpfully points out that responsibility for meeting building regs actually lies with the owner and not with building control. It also explains how to complain when it is appropriate.
    • CommentAuthortony
    • CommentTimeFeb 16th 2023
     
    I can’t believe that building control are taking that line, it breaches part L1b. They are there to ensure that regs are met.

    Seems like the contractor is not aware of the responsibilities and are working with building control but the result is producing a proble,

    How can they say no thermal bridge, no insulation = thermal bridge.
  17.  
    Just an update as I've been busy.

    They have extended out the roofline and are definitely not doing the redundant chimney breast walls.

    They would not remove the existing render and have just gone over it but I cannot see any adhesive that has been used?

    Seem to have not stepped down from the suspended floor level to concrete slab level along the gable wall.

    I've tried to attach pictures.

    Am I being too picky or expecting too much as she has not had to contribute to the costs of the works and it will probably be better than nothing / existing blown and cracked render?

    Thanks again
      Compress_20230301_064725_5428.jpg
  18.  
    I can only add one picture at a time for some reason
      Compress_20230301_064726_6342.jpg
  19.  
    Window junction
      Compress_20230301_064745_5166.jpg
  20.  
    Boiler flue
      Compress_20230301_064742_2241.jpg
  21.  
    Window junction near flue
      Compress_20230301_064737_7318.jpg
  22.  
    I was blocked for posting too many pictures so this will be the last for now. Flat roof to wall junction.
      Compress_20230301_064740_0264.jpg
    • CommentAuthorRobL
    • CommentTimeMar 1st 2023
     
    Wow, it looks so much quicker to put up that what I did. To follow the bba approved technique for amateurs, I had to glue (5 dabs per board and bead around board perimeters) then mechanical fix every board. I think pro’s can get approval to only use one or other technique - it’s not better, but they’re perhaps less likely to screw up.
    After all of that, i went round all the gaps between ewi sheets, sprayed in a little water and then some expanding foam type glue. Cut off excess with a sharpened trowel.
    Rasped the eps a bit to rough it up a bit, i think its easier then to fix the next coat.
    Belt, braces, and then some :-).

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