correct use of radiant barrier in ventilated roof?

[munchingB]

seriously cannot logically understand how to make use of a radiant barrier in a ventilated roof!

reading about it online and im reading that it should go under the roof sheathing... another place says that it should lie on top of the rafters and another that it should be under the rafters between the plasterboard...

i thought i understand how they work but these contradicting examples have fuzzled my brainbox...

anyone care to add to the confusion or should i just make a spaceman suit out of it and scare the bumpkins?

cheers

 

[geraldthehamster]

should i just make a spaceman suit out of it

If you're referring to Tri-Iso type foil insulation, then yes.

cheers
Richard

 

[freddiemercurystwin]

Yes as gerry's said are you referring to the foil blanket types of insulation? if so then yes they are pointless.

 

[munchingB]

is it correct then that i dont need a vapour barrier against the plaster board of the ceiling for a ventilated roof? i feel the clue is in the word ventilated..?

would it be of any use as a vapour barrier in a timber wall with 140 kingspan behind it?

it is a superquilt that i bought of a mate who said it'd be ok to use as a vapour barrier but im a bit worried that it might do something that it isnt suppose to?

 

[freddiemercurystwin]

Ahh is this 2l2? Like a foil bubble wrap?

 

[munchingB]

it isnt the brand YBS superquilt, just what weve been calling it, it is the air bubble type yes-its a roll too many my friend used for his caravan so i took it off for for the price of a windscreen sunshield : )

i have insulation boards for a roof and for a wall-yet to actually do either so was just wondering if this material could be of any use or i'll have to buy a vapour barrier for the walls at least.

 

[freddiemercurystwin]

So this is the stuff:

 

[munchingB]

thats it pretty much yes. i only paid a tenner for a 25m2 roll so if it has any use-good. if not then car windscreen shield, super hero outfit, fish tank background...