Hi! Sorry if this is in the wrong section, I'm planning a garden building and I'm pretty confident with the general insulation & membrane requirements for a year around room (i.e. floor, walls and roof all insulated, external breather, internal vapour barrier, plenty of ventilation beneath and in the roof/walls)
My issue is, I'm planning a long rectangular building, with about 1/3 of it partitioned as a shed, I'm trying to avoid insulating the shed to save a chunk but this leaves me with a couple of questions...
a) My general build inside to outside will be..
- Plaster board or OSB with nice cladding of some kind (save painting)
- Vapour barrier
- 50mm PIR between 100mm joists (flush to the inside face)
- 50mm cavity
- OSB
- Breather membrane secured with 25mm battens running up the joists
- Cladding fixed to battens
For the external shed walls, can I just remove the PIR, breather and vapour membranes? I'm conscious this will leave an unventilated cavity between the joists (OSB fixed to both internal and external faces) but with no insulation there should be no point that cold meets hot is this right?
b) The internal partition, I assume will need to be insulated with one side being 'warm' and the other being 'cold', but what should this make up be, I was thinking of this (from warm room to shed)
- Plaster board or OSB with nice cladding of some kind (save painting)
- Vapour barrier
- 50mm PIR between 100mm joists (flush to the inside face)
- 50mm cavity
- OSB
This is essentially just the same as the main room external walls but stopping at the OSB in the shed (to leave me with boarded internal walls in the shed) meaning no breather membrane?
c) To save the hassle is it easier to just insulate the whole thing? and leave the partition with no insulation? I'm conscious this will still leave a partition with one cold side and one warm side, no ventilation in the partition and therefor damp/rot eventually, if I insulate the partition as well then I revert back to question b.. What should the make up be!?
Thanks for any help!