We needed access to the sections of the exterior walls in the utility room to get the insulation boards in, we are currently storing tools there. So today, Thursday, on April fools day, we built the first solid wall between Bedroom 3 and the Utility Room to give us more space to store tools. This wall is the usual 63mm thick but we had put on an additional fermacell plasterboard layer on the interior side of the wall, then filled up the hollow space up with 100mm thick glass wool we had lying around in our garden shed, some 10 years old (and perhaps too old as the material didn’t seems to spring back into its full 100mm thickness), to act as another sound absorbing layer. The whole thing was covered up with a layer of 18mm thick OSB board to provide a good solid first layer of sound reducing wall, between Bedroom 3 and the various noisy equipment that will live in the utility, like the washing machine and drying cabinet and the other pieces of equipment for running the air conditioner etc.
Then we moved the Ikea wooden shelving modules over to sit in front of this new wall and unscrewed the electric switchboard off the wall. We then installed the insulation in the walls and re-installed the (temporary) electric switchboard.