You might like to get in touch with Andy Pickard: http://www.ajpengineering.com.au/ He specializes in home energy efficiency advise and retrofitting particular to the Canberra climate and issues. We have a unique climate in this region - not just because of the extreme temperatures, but also because of how vapor behaves in our walls, which makes choosing the right insulation important :) Goodluck! Should be lovely after you've installed it! (I work at Jigsaw Housing, the collaboration of architect + builder + scientist, and we specialize in energy efficient homes. I also do casual private consultations for people that are just looking for a bit of design/efficiency advice that's not really worth taking to an architect for a full service.)

What do you do when you front door opens straight into your living room? Where do you put all your bags coats and shoes?

I watched your videos and that sound is awful! I think that the clue is in that it doesn't happen in the tiled areas. Tiled floors in first floor construction is usually laid over a fibre cement sheet (called tile underlay) that is nailed to the particleboard sheet with lots of nails. This provides extra rigidity and to minimise any movement to avoid the grout between tiles opening up, or tiles cracking. Each dot on the tile underlay sheets in this photo shows where a nail should be - so your bathroom floor is rigid and strong, and won't creak. It sounds to me like there is inadequate fixing of your particleboard sheets in your carpeted areas to the floor structure. Perhaps the easiest fix would be to lift the carpet, apply wood screws through to the floor structure, and re-lay the carpet. Wood screws provide a better fix than nails, but your builder probably just used nails. Just be sure that the new screws align with the floor joists below, and you are not going through electrical wires or plumbing! It is possible that when the particleboard sheets were nailed down that the person missed getting the nails aligned with the joists. It shouldn't be this bad, but you may never get any satisfaction from the builder or VBA, so I would just spend the money to do it right. This isn't fair, but that noise is so bad, and I know I couldn't live with it. Best of luck, Dr Retro of Dr Retro House Calls and Dr Retro Virtual Visits.

i installed the bracing from underneath the floor and pushed the short lengths of timber along the bearers glued and nailed in place without any cross bracing because i wanted to use up scraps of timber at minimal extra costs and i had to install the pieces laying flat on my back underneath the house. .luckily you have much better access but didn't need to worry about the impact of my rough bracing on a plasterboard ceiling like you do...hopefully you will receive more ideas