Shed wall insulation

21 Jul 2019
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United Kingdom

Hello all.

Just after some advice. I am looking to insulate my shed for all year round use. I have looked on various forums and now more confused than ever.

The shed was a bespoke prefab made into a number of panels with 70mm deep stud frame, a breather membrane and then 20mm outer cladding. The breather membrane is almost tight against the inside of the cladding. (I thought normally there should be a gap, but it is what it is)

I would like a little sound proofing and so decided to go with rw3 rockwool. 35mm. And yes I do know at that thickness it wont make a huge difference. However, I have read insulation should have an air gap between the cladding and the insulation.

The next issue I have is that rockwool is to some extent flexible and will sag slighty over time and I need to somehow keep it away from the cladding, so from outside to in - I was going to put spacers on the inside of cladding(with breather membrane) then push/ fit 15mm celotex board up to this(leaving an 20mm air gap) Then push the rockwool up to the celotex filling the rest of void. Then a vapour barrier and then soundbloc plasterboard.

As I'm sure most of you will say, I have no idea what I am doing and you would be right!

How can I make this work? Or at least make the best of a bad situation, as I have already bought the materials. How do I leave an air gap and stop the rockwool falling on the cladding at some otherwise?

Many thanks
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Just stick in 70mm celotex, the rest is a waste of time .

Thanks for responding. I might have done in hindsight, but as mentioned I already have the materials now and cannot afford to just swap to 70mm celotex. I just needed to know if it would work without causing damage to shed?

So not having the airgap goes against everything I have read in relation to trapping moisture and the wood rotting?

If as you suggest and have no air gap at all, I could double up on the 15mm celotex along with the rockwool. Just trying to work with what I have really.
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