The sound will depend on the claddings chosen and the make up of the brick wall it is being compared with. If finished with render or brick slips, there will be very little difference vs a brick wall as the calcium silicate board does a great job of breaking up the sound.

Yes, you can extend your hup! On request hup! can provide extra parts to secure the old walls to the new walls and also the new walls if required too. 

Yes it is. Whether you want to just replace one or two windows with a hup! wall or add hup! to existing walls to create a completely new look, hup! can easily cope.  You can choose between having a cill between the dwarf wall and the hup! wall and having a different wall finishes on the hup! or you can choose the full cladding option where the wall finish can run the entire height of the building for a more premium look. hup! works on both 250mm and 300m walls -the width of the existing wall must be specified at the time of order. If Building Regulations are required, you will need to bring the entire wall to 0.18 UValue. 

0.4 kilonewtons per meter squared.

Yes - however you must consider what the room is used for. If there is high humidity, a vapour control layer may be required. This is not provided by Ultraframe and must be placed between the plasterboard and the steel clips.