1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Roof Insulation in Garden Shed -- Closed or Open Ventilation System

Discussion in 'In the Garden' started by mj62mj62, 6 Sep 2019.

  1. mj62mj62

    mj62mj62

    Joined:
    27 Jan 2010
    Messages:
    55
    Thanks Received:
    4
    Country:
    United Kingdom
    Hello,

    Shed roof insulation has been discussed on the forum before, but I'm stuck on one bit:

    Air Flow

    Please bear with me

    The shed is going to be a fully finished space for daily office and studio use.
    5.5m x 2.5m -- fairly large
    Sloped roof, felted
    Interior is a shell - we're saving by doing the interior ourselves.

    Roof insulation is the next step.

    The felt is already on so we're looking at a Cold Roof style, which I believe is:

    - Rigid insulation between the rafters
    - Choose a thickness of insulation that leaves 50mm air gap above
    - Air flows through vents from the front, through the gap, and out vents at the back

    Our rafters are 65mm and the insulation is sold in 25mm thickness, so I'm hoping a 40mm gap rather than 50 is ok... :confused:

    Our issue is that this is no air-flow:

    - the front soffit is completely sealed - no vents or air gaps.
    - the rear overhang is tiny and you can see it's not sealed well - light and air come into the roof cavity


    It seems the choices are:

    (A) Open the system - add vents at the front and back for each pair of rafters (that would need 9 vents in the front and 9 in the back - but there's no room in the back anyway!)

    (B) Close the system - seal up the rear where some air is getting in. Hopefully stop damp air getting into a place it can't escape from.

    (C) Leave it as it

    I just want to protect my investment from damp and keep it warm. Any thoughts?


    Many Thanks :notworthy: (y)
     
    Last edited: 6 Sep 2019
  2. mj62mj62

    mj62mj62

    Joined:
    27 Jan 2010
    Messages:
    55
    Thanks Received:
    4
    Country:
    United Kingdom
    p.s. there's a great video here explaining both warm and damp roofs.

    Relevant Cold roofs are covered from the 7 minute point and beyond
     
  3. conny

    conny

    Joined:
    30 Jun 2008
    Messages:
    10,840
    Thanks Received:
    269
    Location:
    Suffolk
    Country:
    United Kingdom
    Don't know much about ventilation but I would be inclined to fill the void completely, thereby eliminating the risk of cold, damp air become trapped between the insulation and underside of roof. If there is no wind/breeze blowing then there would ne no airflow to remove damp air in the void.

    Others with better knowledge may think differently.
     
Loading...

Share This Page