In this Rockwool Sound Insulation review Roger Bisby finds the product has come a long way since it’s ultra itchy conception.
It seems to me from my visits to sites that many builders and loft converters don’t attach very much importance to sound insulation. This is a great pity because good sound insulation is an important indicator of a quality extension or loft conversion.
Who wants to hear the person upstairs peeing in the loo or doing anything else for that matter? It is important enough to be included in the Building Regulations but it is rare that I see Building Inspectors taking a close interest in what is being used in between the floors and walls. Having said that I did once see one diligent inspector pick up a board and see nothing at all in between the joists and he made the builders take the whole floor up again in order to lay the sound slab and he was insistent that they use the real thing. Of course it is not just about sound, the incorporation of Rockwool Sound Insulation Slab is also important for the prevention of fire spread. It is non combustible and dense so can significantly slow the path of a fire.
As the name suggests Rockwool is made from rock fibres and the important thing is that these are non-directional fibres which means it traps airborne sound a lot more effectively than some of the straight laid glass wool general insulation products out there which are designed to be full of air. This density also slows the passage of fire you can fire a blowtorch at it and if you do it long enough it will glow but that is all. This combination of fire resistance and sound resistance is such a winning combination that it would seem to me a no brainer, but I have seen plenty of jobs where the drawing shows sound slab in the stud walls and floors and the builder grabs the nearest (and cheapest) insulation roll on the stack believing that this does the same job.
Now I have to admit that the Rockwool of old was not a builder friendly product and those with long memories may remember that you would itch for days if you had to put it in. I have a lot of that old style Rockwool in my eaves cupboards and it is a constant reminder of how things used to be. I keep clear of it if possible. The newer Rockwool is a completely different proposition. You will notice in the pictures I am not covered from head to toe in protective clothing. I am not advising anyone else to do this because it is always good practice to cover up but I am making the point visually that modern Rockwool is a lot more pleasant to use.