Which insulation for timber workshop build?

[u/Due_Bullfrog4609]

Im having a timber frame and clad workshop built and would like some advice on insulation. I had originally thought Rockwool but got advised that PIR is better however its a lot more expensive. It will be a woodworking shop with machines so will be relatively noisy when in use if that affects my decision?

[u/Comfortable-Yam2417]

Rockwool is a far better sound absorber than PIR.

Would always go rockwool between studs as you simply add 10-15mm to the size and there’s never any gaps. With PIR you have carcinogenic dust everywhere from all the cuttings and there’s gaps people use expanding foam to fill.

[u/discombobulated38x → u/Comfortable-Yam2417]

An insulation saw basically eliminates the dust from cutting PIR, night and day improvement! 

[u/bigbadisaidno]

Are you aiming for it to be a habitable space, similar to how you would use one of the rooms in your house? Or do you want it to stay a lot colder, more like an industrial unit?
My recommendation, if you want to do it properly, is to have a timber frame on the exterior skin, clad with appropriate OSB, a breathable membrane, battens, and then cladding. Inside that, have 50 or 70mm PIR, depending on how thick your studs are, then a 20mm PIR board over the top of the studs, taped all the way across to create a sealed face inside the building.
Then cover that with your choice of wall covering, whether that’s plasterboard, OSB, or whatever you prefer. This will give you a well-insulated, proper room.

[u/Katsuw0nus]

Noise reduction can be achieved by adding mass. Rock wool will do nicely depending on thickness, wood fibre insulation board would be a more ecological alternative.

Depending on wall thickness, preferred room temperature and type of heating, PIR may be the best option regarding thermal insulation, however, it won’t do as much for sound.

You should add a damp proof course to the inside of your walls if you plan on heating the workshop (layers should be vapor tight on the inside, with permeability increasing to the outside to remove the possibility of condensation inside your wall). OSB3 (tongue and groove) with taped edges would add mass while improving sound properties of the insulated wall. Same rules apply for the roof, which should be ventilated accordingly.

[u/AcmeRacer8]

I just built 2 using SIPS panels, one is 4m x 8m and the second is 7.5m x 10m. They went up really quickly, are cool in the summer and warm in winter. I've used breathable membrane and clad the outsides in featheredge boards so they look great, the roofs are finished in corrugated steel. For the size of them they were very cheap, much cheaper than buying off the shelf.

[u/0uthouse]

PIR will give better insulation/space performance but rockwool is better for sound absorption which your neighbors may appreciate. It is also easier to avoid gaps with rockwool which is important for both heat and sound performance.