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 - Renovation: Depth of insulation

Bottom of Page

1 to 19 of 19

  1.  
    •  
      CommentAuthorMichael1
    • CommentTimeJul 6th 2020 edited
     
    Hi all, I am about to insulate over an existing concrete floor in a very old house, is there a thickness of insulation that is not worth going pass. I’m planning on three layers of 80mm polystyrene that tongue and grooves into each other.
    Regards
    Michael
  2.  
    IMO the cold bridge at the walls is more relevant than 240mm in the middle of the floor. So what insulation is going to be provided at the wall and will this go below floor level?, (and what type of wall)
    • CommentAuthorgyrogear
    • CommentTimeJul 6th 2020 edited
     
    looks like N. France !

    what is under the floor ?

    gg
    •  
      CommentAuthorMichael1
    • CommentTimeJul 9th 2020
     
    At the wall will be 200mm Hempcrete if I can find a company to do it, the floor was a mix of all types, concrete, stone, reinforced concrete,dirt.The Walls are stone and mud. I’m in the SW of France. I’m putting 200mm insulation in the ceiling, type to be determined.
    • CommentAuthortony
    • CommentTimeJul 9th 2020
     
    Sustainability wise up to a meter of loft/roof insulation, economically it depends on many things, degree days, length of time you calculate over, cost, interest rate, energy price inflation, loss of floor area, ....

    If you start to look at the cost of future retrofit then it it pays to do it now.
    •  
      CommentAuthorMichael1
    • CommentTimeJul 9th 2020
     
    Hi Tony,
    Not looking at the economics or for a return on my money so I am happy to spend on insulation where I can, Rooms above are to be used as bedrooms and are in the roof which was recently replaced and well insulated. I will add to it also for extra.
    A question you may be able to answer for me re DPM, is it best below the insulation on the concrete or above the insulation beneath the chipboard flooring?
    Regards
    Michael
    • CommentAuthortony
    • CommentTimeJul 9th 2020
     
    What does well insulated mean? Thickness/U-value ?
    •  
      CommentAuthorMichael1
    • CommentTimeJul 9th 2020
     
    I will ask the Roofer the spec when he returns from his holidays, it’s been on for two winters and the difference is very noticeable. It’s like a foil with multiple layers and I’m going to add an additional 100mm between the rafters. I have to batten the rafters out as they are only 75mm, on top of that is going to be 21mm t&g pine boards.
    Do I DPM above or below the insolation on the floor?
    • CommentAuthorgyrogear
    • CommentTimeJul 9th 2020
     
    Posted By: Michael1It’s like a foil with multiple layers


    oh dear !

    gg
    •  
      CommentAuthorMichael1
    • CommentTimeJul 10th 2020
     
    <blockquote><cite>Posted By: gyrogear</cite><blockquote><cite>Posted By: Michael1</cite>It’s like a foil with multiple layers</blockquote>

    oh dear !

    gg</blockquote>
    Ok you have my attention! Could you explain please? What should I have done?
    Regards
    Michael.
    • CommentAuthortony
    • CommentTimeJul 10th 2020
     
    •  
      CommentAuthorMichael1
    • CommentTimeJul 10th 2020
     
    Ok I get the gist of it, it appears it isn’t much cop. I’m adding to it and will increase the amount so that should cancel the negative bit. I lost some money possibly and for what it’s worth it has made a difference to what was already there albeit not much.
    Life is a learning curve and sometimes you have to pay for your education.
    Regards
    Michael
    • CommentAuthorgyrogear
    • CommentTimeJul 10th 2020 edited
     
    You could actually remove it all, and sell it off to your neighbours for wrapping around their hot-water cylinders, which is about all it's good for - in that way you might recoup some of your "investment" :devil:

    gg
    • CommentAuthortony
    • CommentTimeJul 11th 2020
     
    Bit harsh, I would leave it but add a goodly amount of proper insulation inside it , several hundred millimetres and a vapour barrier/ air tightness layer too.
    •  
      CommentAuthorMichael1
    • CommentTimeJul 15th 2020
     
    <blockquote><cite>Posted By: gyrogear</cite>You could actually remove it all, and sell it off to your neighbours for wrapping around their hot-water cylinders, which is about all it's good for - in that way you might recoup some of your "investment"<img src="/newforum/extensions/Vanillacons/smilies/standard/devil.gif" alt=":devil:" title=":devil:"></img>

    gg</blockquote>
    Very helpful, thanks for your advice..
    Tony yes I shall add as much as I can and, what side of the insulation does the vapour barrier go? Warm or cold side?
    Regards
    Michael
  16.  
    Vapour barrier goes on the warm side.
  17.  
    I don't understand the dislike of multifoils on here. I think they are great for airtightedness in wall, roofs and ceilings. If you use rigid materials like celotex, they shrink as they age and so airgaps appear where they butt against each other or butt against timber joists or beams. If you've insulated between joists, that means a lot of airgaps. Even with foaming in, you're not immune to the celotex/kingspan shrinking away from the foam. Plus foaming can be a hit and miss affair anyway. With mutifoil you can cover these joists or beams with a large sheet and only have to pay attention to taping the edges and any perforations in the foil where you've tacked it.

    We used TLX gold on our roof to act as a breather membrane and airtighness layer and I'll be using it on the inside of the loft for airtighness.

    Plus the foil material stops NASA from beaming signals into our brains when we are at home.
    •  
      CommentAuthordjh
    • CommentTimeJul 15th 2020
     
    Posted By: Pile-o-StoneI don't understand the dislike of multifoils on here.

    I think a lot of it stems from the earlier generations of the products, where hyperbolic marketing based on multifoil performance in vacuum (i.e. spacecraft insulation) plus some shoddy products gave it a very bad name.

    For myself I would still prefer to use a soft insulant - such as rockwool or blown-in cellulose - together with an 'intelligent' vapour membrane in situations such as you describe.
  19.  
    Like you, djh, I think what I remember most is the 'over-claiming' when it first appeared on the market here. Next is the fact that (and this is no fault of the manufacturers) it is often installed in a way which does not comply with the manufacturers' instructions, in particular re air-gaps. I have also seen one of the products used as a sarking layer, along with a claim as to its thermal performance, where it seemed to me to have been fitted on the cold side of a circa 25mm ventilated void.

    A fairly common lay-up now combines PIR and multi-foil, with the PIR, taped as VCL, on the warm side. I have seen it installed the wrong way round, and at that time (not sure if it is the case now) that particular brand of M-F was stitched (for which read 'peppered with holes'), so the builder had installed it as a 'VCL' when it could not possibly perform as such.

1 to 19 of 19

  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