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Rigid Foil Faced insulation fitted to underside of rafters. Is separate VCL required

  • 04-09-2008 10:20am
    #1
    boots1
    Closed Accounts Posts: 31 ✭


    Folks,

    Per thread title, I have tacked sheets of foil faced rigid insulation to the underside of my rafters in the attic (potential future conversion). Given that the sheets are foil faced, do I need to install a separate vapour control layer underneath them (polythene) or is the kingspan sufficient? Thanks in advance, boots


Comments

  • #2
    sinnerboy
    Closed Accounts Posts: 5,433 ✭✭✭sinnerboy


    Either - foil tape all joints or use 500 gauge polythene


  • #3
    boots1
    Closed Accounts Posts: 31 ✭boots1


    Thanks sinnerboy. Tape sounds like the way to go. Just curious though, if I had have applied insulated slabs, how would I "seal" the VCL. Obviously there wouldn't have been a continuous barrier due to minor gaps between the slabs??


  • #4
    ircoha
    Closed Accounts Posts: 2,290 ✭✭✭ircoha


    because of the gaps u mention, it is becoming more common to either not use the insulated slabs or else do it in 2 layers [say 50 plus 50] with the joints on the inner layer taped and the outer joints staggered


  • #5
    ardara1
    Closed Accounts Posts: 495 ✭✭ardara1


    Put a layer of plastic on the rafters - lap and seal at joints - then apply 2nd layer of insulation - proper taping and sealing of TE plasterboard with filler will also work.


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