8fx10f wooden shed insulation

[Matty353]

Goin to insulate my shed tomorrow and was wondering if I'm right in the way I'm doing it ..

50mm insulation boards in between the gaps (joists) on the walls and some plywood over the top same in the roof intky will leave a wee air gap ..??

Thinking about going and buying vapour barrier or some sort of breathable membrane to make it better ? Don't want it to sweat to much

What is my best way to go about doing this what comes first.. Breather membrane, vapour barrier ,50mm board

Or will I just stick to the 50mm board and the plywood
Thanks

 

[RobinBHM]

Simplest way is to leave a slight gap between external cladding and insulation. If you cut the insulation accurately it will push in with no gaps, you can cut a slight taper so it sits snug between studs. Too tight and you will end up breaking the insulation.

If you use silver tape to join up all the insulation sheets, ie going over each joist, that will create a vapour barrier. Im assuming you are using celetex type of insulatikn not polystrene

 

[Matty353]

I'm using polystyrene shud I put a breathable membrane first then the boards

 

[skipdiver]

I'm using polystyrene shud I put a breathable membrane first then the boards

In a word-no.

Breathable membranes generally go on the outside of the insulation and vapour control barriers on the inside. They are not the same thing and perform different functions. It's not so critical in a shed as it is in a house but you would do well to read up a bit on the differences. Even then, it's not entirely straight forward.

 

[Matty353]

I have read other forums etc about other people doing it but it's hard to get a straight answer weather its the best option or the worst in the long run with the mold etc

 

[RobinBHM]

There is not much to be gained by fixing breatheable membrane in between each stud before putting in the insulation. It would be impossible to make a full seal and also its likely the membrane would end up be pushed up agsinst the cladding which not good, its best to keep an air gap so rsinwater can escape and any damp can dry out.

Note: breatheable membrane goes on the outside of insulatiin, vapour barrier to the inside.

You can fit a vapour barrier on the inside face before plywood or osb, however Im never sure how good an idea it is in an unheated shed. The purpose is to stop warm moist air from the inside getting past gaps in the insulation and forming condensation on the cold side. That makes sense in a house, but is an unheated shed always going to be warm inside and cold outside?

 

[Paul200]

I started to do exactly this to our shed last year. I posted this - insulating-a-shed-t93376.html - but had no feedback or interest so stopped taking pictures.

Basically I attached breathable membrane to the inside of the existing framework and then built a new framework inside which contained the insulation. 11mm OSB3 was then screwed to that to create the walls. My only concern is the membrane ends on top of the floor - rather than outside - but I haven't seen any signs of damp and it's quite wet up here.

I've actually only completed one wall - other work took priority. It seems to work fine but then I haven't finished the job so it may be that it's just not doing anything yet! My intention for the ceiling was to push polystyrene insulation up between the rafters and OSB3 underneath to hold it all in. No air gap. Sort of a warm roof. Not sure how this will work though?

Whatever you do it will be a compromise but good luck with it!

Paul