Log cabin 'breathable membrane'

[rmwebs]

I've got a 'log-cabin' style shed on order that I'll be converting to a garden office. I've already got insulation sorted (going to be using Celotex or Kingspan) and such but just wanted to ensure I was getting the right products.

I know that I need to attach a breathable membrane internally to the log structure. I found what I think I need, however its labeled as for roofs, is this still the right stuff?

here: http://www.sandpipersupplies.co.uk/shop/buy/Cromar/Vent_3_Breathable_Membrane_50m_x_1m_Roll/

If its not, could someone provide a link to the right stuff?

Many thanks!

 

[fmck]

Breathable membrane, insulation, vapour barrier( Non breathable barrier) then your internal wall finish.

You want to have air blowing through the inside of your timber external face to allow it to remain dry and ventilated. The inside should be sealed so no warm internal air reaches the cold areas in the wall to condensate onto cold material and create damp.

 

[rmwebs]

Thanks fmck.

Would foil-backed plasterboard count as the vapor barrier after the insulation?

If so, is this correct:

1- external-facing wood
2 - breathable membrane (linked above)
3 - insulation (Celotex/Kindspan PIR in this case)
4 - Foil-backed plasterboard.

Tho, thinking about it, surely an internal barrier isnt needed as the PIR insulation has foil on both sides.

 

[fmck]

Its just important to prevent warm air entering as its surprising how much damp it produces.
If its for yourself : I have foil taped the insulation but not convinced as a seal. Polythene is a pretty inexpensive material and is the best vapour barrier sealed with duct tape. A mastic seal with the polythene to the flooring before plasterboarding is cheap and easy to. The end result is you have a very cheap, completly sealed to vapour and any drafts getting by in the ventilated areas.
I finished our loft conversion in Feb and nipped into the loft space to sort out some stuff we wanted to store. I was well chuffed how dry and ventilated it was now but within an hour I was hit by a drop of water. I looked up and all the nails from the slates pocking through now had drips of water on them. In such a short time with that wee hatch open the conditions changed.!