Shed insulation for heat and sound

[Robin66]

I'm building a workshop in an existing shed. It's near some adjacent flats so I want to insulate it for sound as well as heat. The shed is 10x17', t&g thickness unknown and the studs are 2" deep. I was thinking of stapling hardboard to the studs and squirting in expanding foam. I reckoned that his would be a fairly quick, cheap and effective way of insulating the walls and ceiling for sound and heat. And it'd be more fun than cutting up fibreglass board. However from reading some of the posts here it sounds like I should definitely be leaving an airgap to prevent rot.

Can anyone advise if this is really necessary or if my plan is flawed in some other way that I haven't thought of? The shed is probably only a few years old and is in good nick.

 

[Robin66]

I tried this out over the weekend and it didn't work out. The expansion ratio was no where near the upper limit of 50x claimed by the no nonsense foam which meant that I'd need about 80 cans to do the whole shed at 2" depth. I've decided to squeeze in 100mm loft insulation and cover with plasterboard which'll come in less than half the price. I'm not sure of the acoustic properties of the loft insulation, but the plasterboard is 25kg a sheet and my understanding is that weight is the enemy of acoustic transmission so I hope it'll make up for where the loft insulation is lacking

 

[r896neo]

Mineral wool insulation Increases its sound deadening properties as its compressed so no probs there.

 

[Mr Chibs]

I'm sure I read that compressing rockwool, lowers the insulation value, so it may be give 'n' take.

I think if you want sound deadening, you could double-up the plasterboard.

Not sure you'll get a 'definitive' answer about air-gap.
Insulated plasterboard was put on mother-in-laws summer house, with no gap or membrane, and it's been dry since built some 5/6 years ago.

FWIW, if you are working in their and have a window/door, keep it open, or air it afterwards, this will stop condensation.
Condensation will turn to mold spots over time if not ventilated

 

[r896neo]

Yes the thermal performance of wool decreases when compressed but the acoustic performance increases.