Ecotherm vs Rockwool acoustic slabs

27 Nov 2013
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United Kingdom
Hi lads

I am making a music room in my loft and need to insulate the roof, the depth from felt to rafter edge is only 75mm, so I will use 25mm Ecotherm to leave the 50mm air gap behind, my question is would Rockwool acoustic slabs be better for noise reduction?
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wool is better than PIR but I'm not sure how useful 25mm would be. PIR insulates thermally twice as well. If you want warmth 50-100mm below might be needed.
If it really is felt then make sure your ventilation and vcl detailing is spot on as it can get condensation really easily trapped in there.
Thanks wonder if I can use 50mm Rokwool slabs and leave can I ventilate better, the air comes thru the tiles and felt so I am not sure what else I can do, do I need to add a vent to every ridge board topbetween every rafter? I thought the air gap is my ventilation? It would be Rockwool slabs to end rafter edges then platerboard, with the air gap behind.

Pic added for = vents (do I need a vent here for every slab?)
Green = airflow


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you'd just need plenty of breeze running through, if you've ever camped in a tent you'll know how wet the inside gets and they aren't exactly draught proof. Nowadays people avoid specifying cold roofs like that due to how easily things can get wet.
you would certainly need a path from end to end clear of obstructions that can get a bit of a breeze coming through.
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You could baton the bottom of the rafters to get extra depth.Further insulation via insulated plasterboard on top .
I called Rockwool tech and they said 50mm should be fine as long as there is an air gap and they said to leave an inch at the ridge to allow air to pass over to the other sides.

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