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.




    • CommentAuthormeigh985
    • CommentTimeJan 3rd 2021
     
    Hi there

    I did have a quick look but couldn't find the exact answer to my question /scenario.

    I'm going to be insulating the suspended timber floor of our Victorian terrace which is the middle room of the house, part of this is an external wall, part runs through to kitchen. The front room has already been insulated with Thermafleece which was lovely stuff to work with. The front room has 3 air vents which provides lots of ventilation. The subfloor was left uncovered when I did the floor in the front room as the sun floor was dry.

    In the middle room I'm using foil backed PIR boards mainly because of access issues from above. In the middle room there's one air brick along an external wall which is 1.4m long, so there is cross ventilation front front to back. The room is roughly 3.47m x 4.59m. There was no air brick before I fitted that a few years ago, I was really surprised at this but I assume this is because air could travel through the breathable earth 'slab' which is under the kitchen.

    I'm in a quandary as to whether I need to put a Dpm sheet over the earth subfloor? :confused: this would have sand blinding underneath it and concrete scattered over it to hold it down?

    Why am I considering doing it in this room compared to front room? Different materials is one, with PIR being reflective. Less ventilation is another...

    The floor *seems * dry, there are old pieces of wood sat on the floor which haven't deteriorated but the other day I left a transparent dust sheet over part of the floor and within a day or so water did bead up under the sheet.

    So to Dpm or not to Dpm, that is the question?
    • CommentAuthortony
    • CommentTimeJan 3rd 2021
     
    No DPM, keep the ventilation, air seal between void and house to eradicate cold draughts.

    I like a vapour barrier on the warm side of the insulation.

    Sounds like you are doing well, I worry about biodegradable insulation


    Weirdly even though everyone thinks damp emanates from the ground in fact even if it is wet moisture is being transported from the house into the ground! Due to differences in partial vapour pressures
    •  
      CommentAuthordjh
    • CommentTimeJan 3rd 2021 edited
     
    Posted By: tonyWeirdly even though everyone thinks damp emanates from the ground in fact even if it is wet moisture is being transported from the house into the ground! Due to differences in partial vapour pressures

    Posted By: meigh985the other day I left a transparent dust sheet over part of the floor and within a day or so water did bead up UNDER the sheet.
    • CommentAuthorSimonD
    • CommentTimeJan 8th 2021
     
    Posted By: meigh985Hi there

    So to Dpm or not to Dpm, that is the question?


    I'm guessing there is sufficient air gap under the suspended timber floor for the ventilation? e.g. 150mm ish? And that the insulation is not in contact with the ground at any point?

    If so, I doubt there is any need for a dpm. You may just want to put in an inert layer above the soil, which is required nowadays as oversite under suspended timber floors.

    If your ventilation gap under the floor is insufficient, I've seen some details that on retrofit provide fan powered forced ventilation through a below floor ventilation gap of 50mm.
Add your comments

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

© Green Building Press