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.

Buy individually or both books together. Delivery is free!


widget @ surfing-waves.com




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.




    • CommentAuthorskaffen
    • CommentTimeFeb 16th 2016 edited
     
    Hello All,

    After lurking and reading around the forum for a few weeks, I'm looking for advice on my proposed plan for insulating attic rooms in our Victorian house. Built 1877 it's one half of a semi that then had another house built directly adjacent, but at a lower level, a few years later.

    - External Wall 1 - 4.2m x 2.75m high (with a corner taken out due to slope of roof)

    This is a gable end wall, with the roof and attic of next door about half way up the wall. Currently brick covered with original (lime?) plaster which is very sound.

    I plan to dot and dab Cellotex PL4000 65mm+12.5mm over that wall.

    - External Wall / Ceiling Slope - 6m x 4.3m (3.3m of sloping ceiling and 1m of vertical solid wall)

    Spanning the width of the front of house this is about 1m of solid wall before the ceiling slope which extends 3.3m to the 'flat' part of the ceiling.

    The 1m height of solid wall

    Plan -> Dot & Dab Cellotex PL4000 65mm+12.5mm

    *Sloping ceiling wall* has approx 1.5" of latch and plaster over 64mmx85mm rafters with approx 380mm centres. Beyond that are slate tiles on battens. Slate tiles are 99% sound.

    Plan -> Remove lath & plaster. Insert 80mm Cellotex GA4000 board between rathers. Tape joints with metallic tape. Fix Cellotex PL4000 65+12.5mm plasterboard over the GA4000 & rafters.

    *Flat ceiling*

    This is approx 3m x 6m and extends over the other attic room and a landing/stair space. Lath & plaster (very sound) onto 3" x 2" joists with 15" centres. Above that, rafters with slate tiles on battons. Very drafty. Signs of a few missing tiles. There was no access to this loft space, when I cut a hole to inspect, the big surprise was that the loft space ran the full length of both our house and our mirror image 'twin' next door. There is no dividing wall.

    Plan -> Roll out 380mm width strips of Knauf Earthwool 100mm between joists. Overlay at 90 degrees with 200mm Knauf Earthwool, for 300mm total thickness.

    A few questions.

    1. Is there any point in removing the (sound) plaster from the solid external wall before dot & dabbing the Cellotex PL4000 on top?

    2. I plan to push the Cellotex between the rafter on the sloping wall up into the loft space to abut the 300 mm of mineral wool. Is that a good idea?

    3. Am I going to have problems with condensation? I plan to have a shower in the room (with an extractor venting outside).

    4. Will thermal bridging be a big problem from the external gable wall to the internal solid wall that forms the rear wall of the room? Anything I can do about that?

    Happy to hear thoughts on more effective / cheaper alternatives!

    I have some photos here https://www.icloud.com/sharedalbum/#B0N5ON9t3FY1xg

    Regards.

    Greg.
  1.  
    Hi Greg. Nearly identical to ours which is still in progress. I am making a video series on our youtube channel from it in the next few week but that may be too late.

    Firstly, if you can avoid removing lath and plaster, do! In hindsight we had the ceiling height to leave it in place and insulate below which would have saved alot of mess, time and waste.

    Anyway, we ripped back to rafters and slates. Then added strips of batten to the underside of all rafters allowing us to fit 100mm between and still leave an air gap on the slate side. These are friction fitted, we then have 50mm whole sheets under the rafters fitted with drywall screws and small insulation washers. This leaves us with a continuous foil on the room side which is taped as joint. We then intend to pb over that using long screws and/or adhesive. When we re roof in the future a roofing membrane will of course be added.

    Reason being, it was much cheaper to buy batches of 100mm and 50mm foiled insulation rather than the pb backed stuff. Especially if you can find it on seconds and co or a pallet deal.

    Our eaves are mineral wool between and on top.

    Gable ends I have not decided on yet, I would rather not add non breathable insulation on the external walls so will either leave with the lime plaster or even take it back to an exposed stone wall as a feature. With the amount of insulation elsewhere and roof lights, it is never going to be a cold room. Although it will be the only uninsulated surface in the roof rooms so we may need to insulate if there appears to be any condensation.

    I have no idea what if any of your questions that answers, sorry!

    Here are some before and after of the first 100mm including the additional batten.
      Between and below rafter insualtion.jpg
  2.  
    ''A few questions.

    1. Is there any point in removing the (sound) plaster from the solid external wall before dot & dabbing the Cellotex PL4000 on top?''

    * No. As long as it is lime. If it is gypsum - yes! Celotex's blurb specifically talks about maintaining a breathable 'exit' (so get rid of any impermeable paint). You also *want* the plaster as an air-tightness layer - extend it where it stops at skirting level. Please do not dot and dab! This invites thermal by-pass via air-movement behind the board, and effectively disconnects the R values of the insulation and the wall, potentially leaving the insulation value of the old wall, such as it is, 'out in the cold'. At very least use a full perimeter bead and cross-'stripes' of adhesive. (which could be adhesive grade Pu foam which does not have a tendency to 'suck' as gypsum does, in case any WV does get through.

    ''2. I plan to push the Cellotex between the rafter on the sloping wall up into the loft space to abut the 300 mm of mineral wool. Is that a good idea?''

    Yes, but you will presumably have to notch it in each rafter bay as the ties/joists are nailed to the side of the rafters.

    ''3. Am I going to have problems with condensation? I plan to have a shower in the room (with an extractor venting outside).''

    You might risk interstitial condensation. A WUFI calc will give you more comfort than the Glaser method offered by most manufs.

    Also, using a composite board, how will you ensure the VCL is perfect at the joints and perimeters? I can't, so I never use composite boards now. I usually use Pro Clima air-tightness tapes at joints and particularly at perimeters as there is little risk of it tearing, whereas foil tape carries such a risk.

    ''4. Will thermal bridging be a big problem from the external gable wall to the internal solid wall that forms the rear wall of the room? Anything I can do about that?''

    Yes, return the internal insulation of the external walls (IWI) onto that wall by about 300- 400mm.

    Happy to hear thoughts on more effective / cheaper alternatives!

    Not cheaper, but if you can use something like wood-fibre board (and lime plaster) instead of impermeable plastic, and reliance on a VCL that may not be 100% (or probably never will be!), you reduce the risks associated with IWI.
    •  
      CommentAuthorBauwer
    • CommentTimeMay 20th 2016
     
    Hello Greg,
    Answering your question on more effective and cheaper alternatives - Insulated Plaster is a reasonable, effective and cost efficient alternative. Saying that the thermal performance would be a bit inferior to Celotex, yet Insulated Plaster would provide a monolithic and vapour permeable structure which avoids the presence of thermal “cold bridges” which could potentially reduce an actual thermal performance by up to 40%. The application process of insulated plaster is much easier as well. Low weight, only 280kg/m3, Insulated plaster can be applied on any surface configuration: curved, convex, spherical. It is non-flammable and vapour permeable, which prevents the occurrence of mould and fungus growth. Moreover, it is perfectly combined with other insulation systems if applied as pre-leveled layer, creating an additional thermal and sound insulation coating for construction. We supplied insulated plaster for a large internal insulation project in central London, about 300sqm at 40mm thickness, and the insulated plaster was received very well.

    Hope this helps,

    Best regards, Alexander.
    • CommentAuthorgyrogear
    • CommentTimeMay 20th 2016 edited
     
    Posted By: BauwerWe supplied insulated plaster for a large internal insulation project in central London, about 300sqm at 40mm thickness, and the insulated plaster was received very well.


    is this advertising, or what ?

    (If so, then I think I shall start advertising my VERY WELL REGARDED ********ion, *********ing and *****ing services on here !).
    (NOT...)
    :shamed:
    gg
    • CommentAuthortony
    • CommentTimeMay 20th 2016
     
    This sounds awfully like advertising to me which is not allowed on this forum.

    Additionally it does not sound to like it would comply with building regulations
  3.  
    I think this may breach the 'no advertising' rule, but I am interested nevertheless to hear a bit about the product. What was the 'before' U value in the example you refer to, and the 'after' value? Did BC give a dispensation, or were they not aware? It seems that Part L1B would have applied (you would, I guess, have been 'adding or replacing a layer').

    More information would be good.
    • CommentAuthorGBP-Keith
    • CommentTimeMay 24th 2016
     
    I'm going too leave the posts here but Alexander, it would be good if you could ask a client that has used your products to come along to the forum to discuss how well they got on with using it. This would be by far the best way of convincing other forum members of the merits of the system.

    I will be starting a thread for Bauwer shortly on an paid advertising agreement - one which any forum user may negotiate with me. it is useful to get product manufacturer/importers onto the forum within a controlled space for a virtual face-to-face conversation.


    Regards, Keith
    •  
      CommentAuthorBauwer
    • CommentTimeMay 27th 2016
     
    Hello Keith,

    Sure, no problem, we already received very good feedback on the plasterers forum.

    I'll also ask our customer to leave their feedbacks at the Green Building forum as well.

    Also I just noticed this posts, after 3 days...any chance I could get a copy of a post on my email?

    I agree that virtual face to face conversation helps :)


    Best regards, Alexander.
    • CommentAuthortorrent99
    • CommentTimeMay 27th 2016
     
    Posted By: GBP-KeithI'm going too leave the posts here but Alexander, it would be good if you could ask a client that has used your products to come along to the forum to discuss how well they got on with using it. This would be by far the best way of convincing other forum members of the merits of the system.

    I will be starting a thread for Bauwer shortly on an paid advertising agreement - one which any forum user may negotiate with me. it is useful to get product manufacturer/importers onto the forum within a controlled space for a virtual face-to-face conversation.


    Regards, Keith


    Perhaps such advertisers could have a simple standard signature so we know who they are and don't feel we have to point out the rules to them?
  4.  
    <blockquote><cite>Posted By: restorationcouple</cite>These are friction fitted, we then have 50mm whole sheets under the rafters fitted with drywall screws and small insulation washers<div class="Attachments" id="Attachments_236537"><ul><div><img src="/newforum/extensions/InlineImages/image.php?AttachmentID=6189" alt="Between and below rafter insualtion.jpg"></img></div></ul></div></blockquote>

    Looks like you used a heap of insulation washers, can you advise if you felt these were essential? Could you have just used one or two for each board to hold in place then use the longer screws to hold the PB and insulation at the same time?
Add your comments

    Username Password
  • Format comments as
 
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press