Insulation..Which way round ie. foil facing inwards or outwards?

Discussion in 'Builders' Talk' started by Lombear, Oct 11, 2007.

  1. Lombear

    Lombear New Member

    I have bought some seconds insulation to put between the rafters in my roof. It has foil on one side. What side does the foil face?

    Thanks
     
  2. Lombear

    Lombear New Member

    btw: The insulation is similar to celotex or kingspan.
     
  3. Charlie Far!ey

    Charlie Far!ey New Member

    it faces in toward the space to reflect the heat back into the space
     
  4. Stoday

    Stoday New Member

    The foil reduces heat loss through radiation. The glass fibre reduces heat loss through conduction.

    The foil side theregore goes where the temperature difference is greatest, that is it should face the space between the ceiling and the roof. The fibre side is laid in contact with the ceiling.

    If you were creating a warm attic by insulating between rafters, then you would want little temperature difference between the inside insulation surface and the room. So the foil side should face the slates and the fibre side the attic space.
     
  5. Lombear

    Lombear New Member

    Thanks, I have started to put the insulation in place with the foil facing inwards however I feel that the foil should face outwards as I have also looked on the Celotex website and their diagrams show the foil as facing outwards.

    Another question: My house was built in 30's and the rafters are not all standard dimensions apart from each other and also vary by a couple of inches from the wall plate to the ridgeboard!!! The insulatin is not stitting a snugly as I like and resulting in slight gaps along the edges. Is this a problem?
     
  6. J.T. Builders Ltd

    J.T. Builders Ltd New Member

    the foil should be on both sides!

    i would have the foil facing outwards.

    what are you doing with the insulation?

    70mm between rafters? then over board?
     
  7. ­

    ­ New Member

    > Thanks, I have started to put the insulation in place
    with the foil facing inwards however I feel that the
    foil should face outwards as I have also looked on
    the Celotex website and their diagrams show the foil
    as facing outwards.


    Celotex has foil on both sides, what exactly have you bought?


    > Another question: My house was built in 30's and the
    rafters are not all standard dimensions apart from
    each other and also vary by a couple of inches from
    the wall plate to the ridgeboard!!! The insulatin is
    not stitting a snugly as I like and resulting in
    slight gaps along the edges. Is this a problem?


    Yes, it HAS to be a tight(airtight) fit. That's why it costs lots to have professionally installed, it's a time consuming job. Best you can do is fill the gaps with expanding foam, do all the gaps in one go so as not to waste the cans of foam (half used cans are next to useless)
     
  8. Stoday

    Stoday New Member

    As ECM says, it must be airtight. If it's not, you'll get condensation.

    Warm air in the warm space holds more water vapour than cold air. If you have any gaps the warm air will move through them and the water in it will condense out when it hits a cold area, such as the tiles.
     
  9. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    The expression, 'Clear as mud' springs to mind.

    There you have it.

    It faces in, it faces out, it faces towards the roof, it faces towards the space, it faces towards the room.

    And wait for it, it should have foil on both sides, so all is correct, because it can face the room, the ceiling, the roof and the space all at the same time.


    Sorted. :(


    Mr. HandyAndy - really
     
  10. Stoday

    Stoday New Member

    You might find this link useful handy:

    *
    :)

    [Edited by: admin5]
     
  11. Lombear

    Lombear New Member

    Thanks all for your help.

    To give you an update I have so far insulated below the perlin on both sides..what a * job! Dust everywhere and crawling on my hands and knees. The gaps are not that serious, I will however fill the gaps with a can of expanding foam as per ECM.

    For info the boards I am using are 55mm with foil on one side only. The edge of the boards state 'Gyproc theraline'.

    I am only going to put 9.5mm plasterboard on the underside of the rafters, do you think I should put some kind of water barrier between the insulation/rafters and the plasterboard?

    [Edited by: admin5]
     
  12. J.T. Builders Ltd

    J.T. Builders Ltd New Member

    On the jobs i have done we have over boarded the rafters and taped the joints with foil tape, then fix 9.5mm foil back PB to this.

    A couple of times i have also used a vapour barrier fixed to the rafters then overboard then plasterboard with foil back. (i think that the correct order, it was a while ago i did it that way.

    Have you got building regs?
     
  13. J.T. Builders Ltd

    J.T. Builders Ltd New Member

  14. ­

    ­ New Member

    > Have you got building regs? / plans?

    :^O....................
     
  15. Lombear

    Lombear New Member

    No building regs or plans. This is 'deuluxe storage', if you know where I'm coming from ;)

    I have put 8" x 2" joists in the loft sitting on the wall plates and then floor boarded. I am now insulating and boarding the rafters to give a more comfortable environment. A velux window or two, some carpet tiles and voila a makeshift room.

    And I do understand this will not meet building regs etc.
     
  16. ­

    ­ New Member

    That's a lot of bovver just to store your Dulux
     
  17. Charlie Far!ey

    Charlie Far!ey New Member

    I opened my flask and thought how hot my tea was and how it kept hot for such long periods and I peeked inside and I could see my distorted eye staring back at me from the shiney surfaces within - I took it apart to discover that the outside wall was much more dull - Wonder why that is then? The only thing between the inner flask and the casing was air so how does it keep hot?

    Hmmmmmmmmmmm

    I wonder if it will stay hot if the inside were not reflective and shiney - If you're a minger and dont wash out the flask frequently to maintain a shiney inside, notice how the tea dont stay hot for such long periods.

    Hey you dont think the smarty farty pants have applied this priciple to insulation do you?

    OF COURSE THEY ***** HAVE!!!!!

    [Edited by: admin5]
     
  18. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    I opened my flask and thought how hot my tea was and
    how it kept hot for such long periods and I peeked
    inside and I could see my distorted eye staring back
    at me from the shiney surfaces within - I took it
    apart to discover that the outside wall was much more
    dull - Wonder why that is then? The only thing
    between the inner flask and the casing was air so how
    does it keep hot?

    Hmmmmmmmmmmm

    I wonder if it will stay hot if the inside were not
    reflective and shiney - If you're a minger and dont
    wash out the flask frequently to maintain a shiney
    inside, notice how the tea dont stay hot for such
    long periods.

    Hey you dont think the smarty farty pants have
    applied this priciple to insulation do you?

    OF COURSE THEY **** HAVE!!!!!





    What utter * farley. You really are a numbskull.



    Hmmm ? Let me see.


    Oh, sorry. Can't see inside a flask when the lids on.

    And oh, shiny surface in the DARK ?



    Mr. HandyAndy - really

    [Edited by: admin5]
     
  19. ­

    ­ New Member

  20. Charlie Far!ey

    Charlie Far!ey New Member

    Oh the * is here
    Still kipping under the 'van then?

    Must be getting colder there now huh? Might not make the winter this year - We live in hope I guess

    *

    [Edited by: admin5]
     

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