Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.
Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
 Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




Housing - New Build: Unused chimneys in a party wall

Bottom of Page

1 to 16 of 16

  1.  
  1.  
    My self build project it to re-instate half of a semi detatched Victorian house that was lost during WWII.

    The existing party wall has twelve chimney pots, six to each house, and two to each of the three floors on either side. On my side four fireplaces at first and second floor level had long been covered over and rendered to protect the exposed party wall I'm building up against. Oddly the two at ground floor level had been left open.

    The current specification is to block up the chimneys, fill with verticulite to loft level, air brick in the loft and then cowl on the top of the pot.

    My builder is suggesting we should break open the blocked up fire places and have them swept before filling with verticulite to check for any issues and have them cleared out etc... Across six chimneys / fire places this is surprisingly expensive.

    It has got me thinking whether the verticulite is actually necessary? As the chimneys are in the party wall they will be warm so there is no need to insulate. If we didn't add the verticulite should we do anything different with the venting of the chimneys?

    I'd be grateful for the forum's thoughts.
  2.  
    I don't see the point of opening up and cleaning out the fireplaces/chimneys if you have no intention of ever using them at any time in the future. if you do (or if you think a future purchaser may want to), then it would make sense to do it at this stage because of the mess that it will make.
    If the chimney isn't filled with something then I guess in theory it will act as a "chimney" with the heat rising up to the highest point in the house where they are closed off. It may already be partly filled with rubble etc. which is not necessarily a problem if you never intend to use them as chimneys. LECA may be a cheaper option to fill with than vermiculite, and less likely to settle or hold any damp. The problem will be estimating how much you will need to get delivered. We are about to do a chimney (around a flue liner) and have a bulk bag of it so I can let you know how much we actually used - may help with your estimations.

    C-Cap is the cheapest way to vent the top part of the chimney (as long as you have a round chimney pot).
    • CommentAuthortony
    • CommentTimeOct 29th 2015
     
    but not in terms of heat loss!

    Close at ceiling level, ventilate to loft above this and cap

    You could knock the whole lot out and gain (valuable) floor area.
  4.  
    Posted By: tonybut not in terms of heat loss!


    Stupid question, but where would the heat loss come from? If the chimneys are in a party wall they can't lose any heat an exterior wall.

    If they are bricked up and rendered / covered in a parge coat inside the house then there shouldn't be any stack effect / air loss.


    Posted By: tonyYou could knock the whole lot out and gain (valuable) floor area.


    Would be nice, but not an expense we've budgetted for and the neighbour is strongly against. Sometimes it is easier not to put up any resistence...
    •  
      CommentAuthordjh
    • CommentTimeOct 29th 2015
     
    Posted By: richardelliotStupid question, but where would the heat loss come from? If the chimneys are in a party wall they can't lose any heat an exterior wall.

    the neighbour is strongly against

    If that implies that the neighbour uses his chimneys then they could even be a net source of heat rather than a loss, and only in the heating season!
    • CommentAuthorphiledge
    • CommentTimeOct 29th 2015
     
    <blockquote><cite>Posted By: richardelliot</cite><blockquote><cite>Posted By: tony</cite>but not in terms of heat loss!</blockquote>

    Stupid question, but where would the heat loss come from? If the chimneys are in a party wall they can't lose any heat an exterior wall.

    If they are bricked up and rendered / covered in a parge coat inside the house then there shouldn't be any stack effect / air loss.


    <blockquote><cite>Posted By: tony</cite>You could knock the whole lot out and gain (valuable) floor area.</blockquote>

    Would be nice, but not an expense we've budgetted for and the neighbour is strongly against. Sometimes it is easier not to put up any resistence...</blockquote>

    The chimney is effectively an outside wall to both sides of the party wall so the vermiculite is there to insulate both sides.
    • CommentAuthortony
    • CommentTimeOct 29th 2015
     
    Thermal bridge into the loft, how sure are you about no stack effect, thought you were using ventilating caps?
  8.  
    I think he intends to seal it off "completely" (airtight?) at ceiling/loft level and then just ventilate the very top part from the loft to the outside so that he keeps the chimney above roof (I think he said he is in a Conservation Area in another thread). C-cap would be cheaper than a (unnecessary as the chimney will not be used) cowl. Only any good if the chimney pot is round.

    I'm not sure how much of a problem a hollow chimney stack that is sealed top and bottom would present. I expect the air in it would get warmed and rise to the top, heating the highest room(s) in the house. This may or may not be a problem. If the air can continue up the chimney and out the top then yes, massive heat loss path.
  9.  
    You can get caps for square chimney pots but they are £25 and strap fixing so not as neat.
    •  
      CommentAuthordjh
    • CommentTimeOct 29th 2015
     
    Posted By: philedgeThe chimney is effectively an outside wall to both sides of the party wall so the vermiculite is there to insulate both sides.

    No, a party wall is treated as internal to both properties for heat loss purposes. That's wrong in my view since the neighbour might go away and leave his house unheated, but even PHI treat it as one thermal unit.
    • CommentAuthorgravelld
    • CommentTimeOct 30th 2015
     
    Don't they treat chimneys differently to walls? There's a clear path to outside.
    • CommentAuthorphiledge
    • CommentTimeOct 30th 2015
     
    Totally agree that a party wall without a chimney is effectivly and internal wall, so long as your neighbours heat their side.

    We're talking about a party wall with a chimney which means each house has a section of the party wall that is effectively exposed to the outside if no insulation is fitted. Even capped its still a thermal "hole".
    • CommentAuthorsnyggapa
    • CommentTimeOct 30th 2015
     
    >Totally agree that a party wall without a chimney is effectively and internal wall, so long as your neighbours heat their side.

    and as long as there is not a ventillated gap in between - so no brick cavity (not sure why there would be one) but possibly more likely a stud wall that is open to unheated the subfloor or loft
    • CommentAuthorgravelld
    • CommentTimeOct 30th 2015
     
    That reminds me. There are other reasons I think a party wall should not be considered internal - if it bridges into a cold loft for example.
  15.  
    Just for info we used a 1.2cu metre bulk bag of LECA plus 3 x small 25litre(?) bags to insulate around a 5" flexible flue liner, all the way to the top of the chimney pot. Just shy of 6m total vertical height.
    The void at the bottom of the chimney breast (just above the closure plate) was quite large, about 1m by 60cm in area so we may have used quite a bit before it even got to the bit where the chimney started narrowing.
  16.  
    Thanks

1 to 16 of 16

  1.  
Add your comments

    Username Password
  • Format comments as
 
Back to Discussions Top of Page
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press