Wall insulation, cavity+external?

Discussion in 'Building' started by unclebob1, 13 Aug 2014.

  1. unclebob1

    unclebob1

    Joined:
    16 Aug 2012
    Messages:
    618
    Thanks Received:
    19
    Location:
    London
    Country:
    United Kingdom
    Good Afternoon All,

    I'm looking to extend my house to the rear, the main house is solid wall, and at some point in the future i will be adding external wall insulation.

    As part of the rear extension build, i will have a cavity, the question is, should i build the exterior wall in line with the existing wall, with the cavity coming into the extension volume, Then add external insulation as i do the rest of the house to keep it a straight flat wall?

    I understand adding more insulation will reduce energy/heat loss, are there any down sides? the once outside wall of the cavity will now be insulated once, the inside wall will be insulated twice. Any ideas on moisture issues?

    Also, if i am looking to do this, any issues with me building both the inner and outer walls in thermal or otherwise blocks?

    Alternatively, should i just insulate the cavity, and leave it stepped once the external wall insulation is applied to the rest of the house?
     
  2. Sponsored Links
  3. xdave

    xdave

    Joined:
    2 Feb 2009
    Messages:
    272
    Thanks Received:
    58
    Location:
    Devon
    Country:
    United Kingdom
    Unless the extension is obviously subordinate then it may look better finished inline with the rest of the property. When I had my bungalow externally insulated (120mm PIR, ply, barrier and shingles) it went over three different wall types thanks to various extensions over the past 50 years. One was 50mm cavity with no insulation, one was 50mm cavity with blown insulation and one was 100mm cavity with full-fill fibreglass insulation. Visually it tied everything together. I had a thermal imaging survey done in January. In all three areas the walls were all within 1 degree inside and out, so from a thermal point of view the original cavity insulation made very little difference to any heat loss.
     
  4. unclebob1

    unclebob1

    Joined:
    16 Aug 2012
    Messages:
    618
    Thanks Received:
    19
    Location:
    London
    Country:
    United Kingdom
    Thanks, in which case, i should probably build in line with the existing brickwork, and render now. and when external insulation is done, cover hack off the render on both the existing and extension and finish off again the same.
     
  5. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page