Another "insulating the roof in a loft" question please

Discussion in 'Builders' Talk' started by DIYDave, Jun 11, 2013.

  1. DIYDave

    DIYDave Guest

    My brother wants a hand to insulate the roof in his loft, I know this has been asked many times and I have done a search but as usual, many various answers so just some clarification required

    80% of loft floor has been boarded over for storage, on top of 100mm joists with insulation compressed under chipboard panels
    Areas where no boarding the insulation is approx 250/300mm deep

    Eaves are vented with air gaps all around but no roof vents
    Roof is cement tiles then close boarded timber, no felt, 100mm roof joists (prob wrong term)?

    Classic boiling in summer and freezing in winter, draughty when the wind blows and very dusty up there so not great for storage. The boilers up there as well and 2 shower pumps

    My brother was planning on cutting down 50mm Kingspan (or similar) boards and friction fitting them between roof timbers, leaving 50mm gap between Kingspan and boarding
    Batten between joists top and bottom and leave air gap of 150mm, top and bottom

    Finally overboard Kingspan with either hardboard sheets or 6mm MDF

    The object is to keep the dust out and keep the loft a little warmer in winter, although not a habitable space

    Is he wasting his money, his time and importantly my time as well and/or risking condensation problems (although with the above plan I believe we will  be maintaining air flow)

    As always, thanks for any input and time taken - cheers
  2. Sean_ork

    Sean_ork Screwfix Select

    overboard the rafters right down to the eaves, leaving no gap and make air tight to the joists and at the apex - fit roof vents and eaves vents at 400 or 600mm spacing to suit yours rafters

    this will allow an air flow up and out along the length of the rafters
  3. DIYDave

    DIYDave Guest

    Hi Sean and thanks for the reply
    Just to confirm you suggest that we still go with the original plan of Kingspan between the rafters but does this also go from floor level to apex with no gap now, the same as you suggest with the overboarding

    I guess that the roof and eves vents need to go in every gap between the rafters as this is now sealing them ?
    That would be around 40 of each vent and loads of work - not sure what these vents are or how fitted, will take a look in the meantime

    If you could comment on my above questions that would be helpful, many thanks
  4. Sean_ork

    Sean_ork Screwfix Select

  5. DIYDave

    DIYDave Guest

    Hi again Sean

    Sorry but I'm getting confused with the vent terminology and if I just use 1 type of vent or 2 types
    Your 1st post you mention "roof vents" and "eaves vents" and in your 2nd post you mention "eaves/soffit vents"

    Are these just different descriptions of the same vent ? ie as in the link you have supplied
    I understand how these are fitted at soffit level but do I need to vent higher up as well and if so, with what

    Thanks again for you time
  6. Sean_ork

    Sean_ork Screwfix Select

    find out who made the tiles/slating system used and they will have a solution that should be fairly seamless to the orginal, either mid roof fall or idealy a ventilated ridge

    eaves/soffit vents just a method of enabling air ingress at the lower end of the roof fall


  7. chippie244

    chippie244 Super Member

    What is your brother trying to store in his loft?
  8. DIYDave

    DIYDave Guest

    Hi chippie
    Just storing all the usual stuff up there that family life creates....... what else are lofts for ?

    He's got no skeletons up there and no he's not using the area to grow herbs !!

    Now I've answered that, any input on the insulation method mate


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