can anyone help me out with roof insulation (pics included)

L

liam012

Guest
ok, so i have been pricing up insulation and wondring if i am doing the right thing.
i am not drylinging the house, i have a 150mm fullfill cavity block build. slates are on and a breathable felt was used - allowing or 50mm gap between rafterloc and felt.

this is what i am thining to do:
100mm rafterlock between the rafters.
50mm xtratherm xt-tl insulated slab unde the rafters. (38mm insulation 12mm slab)



1)should there be a folil vapor check layer before i put up the slab? if so is there a better brand.
2)am iright in putting raterloc right down to where it meets the soffits and then just putting the foil and the slab along the stud wall?
3)i am some bit lost as what to do where the stud wall dissappears dues to there being a downstairs?
4)would this be considered an acceptable way of doing things!! or should i be doing this differently.

any input appreciated, thanks - here are some pics to give idea:

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Hi Liam012,

I am also building a house with 150mm fullfill cavity block with bonded bead insulation - I am still trying to decide whether to also dry-line - why did you decided not to dryline ??

Sorry cant help you with the roof insulation. Not there yet.
 
i just cant afford it.
money is fairly tight on the build due to going way over budget on the foundationsand opting for hrv.
the irony is that drylining would again improve the efficiency of the hrv! but its not an option.
anyway for now i'mpretty concerned about the roof as its very big and i think its important to get right as esentialy it will be keeping a lid on what heat we do have.
were lookin at 200 square metre of rafterlock and 210 square metre of insulated slab. about 5300 euros for those two products not including the foil if we need it - if anyone knows a cheaper or better way i'd love to heaer what people think they would do s despit my internet searching i don't think i've considered all the options.
 
Liam

The insulation backed boards are expensive. What I've done is buy the insulation (in my case 25mm) and board (12.5mm) separately and fixed the sheets of insulation first with clout nails. I have taped the joints with aluminium tale (thus forming my vapour control layer) and screwed the slabs over. It is double handling but cheaper than composite board where budgets are constrained (severely in my case!!). If you think you'll need access to the voids, then go all the way to the soffit. If not, insulate as far as the stud wall, then the stud wall itself, essentially leaving the space behind it cold. It takes a lot of compromises!
 
i had considered this but didnt think there'd b much saving - i gues your 25mm board must have an alu backing o yours just taping the joints - the xtratherm is 38.50 for a board. that gives you 38mm insulation but i cnt see is it foil backe.
i thikn i will runn rafterloc to soffit and insulate/slab the stud walls.
I must find the prices of 12mm plasterboard and 40mm PIR board to see how much cheaper it is even after the double handling .
 
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