Have a 1970's 3-bed detached house with quite a low pitch roof - thus making loft space and accessibility less than easy.
We are UK based.
We've got bare minimum insulation at present (seems to be 100mm rockwool/fibre wool) and we're starting to get a little condensation/mould on our master bedroom ceiling.
We've only lived here 2yrs, so slowly getting round to some jobs and this one is really getting my main mission.
We use the loft for some storage and would like to keep using it if at all possible.
I'd like to know if I can replace all the fibre wool with polystyrene or some other foam but also get the best insulation value at the same time.
I'm aware that thickness of material is going to be a factor but the fact it's a fairly low pitch roof (about 1m high) and we would like some storage I'd like to know if there is some fairly super-duper solution that's not very deep???
Can I put polystyrene sheets between the joists (directly in contact with the ceiling boards below)?
If I can then I guess I'd also need to put similar sheets at 90-degrees to cover the joists and bring the thickness up?
Would it be easier to use mineral wool between the joists and put polystyrene above?
The recommended thickness (UK 270mm) is essentially eating into loft storage space. If I have to lose storage space for a better insulated home then so be it.
Thank you all in advance!