Hi guys(and girlys)
 
Ive been robbing great ideas from the forum for a few years now i so i decided id finally show my face and ask a question rather than steal others lol
We curently live in a 70's house (it pains me to use the term house and not shed!) The type with upvc fronting instead of brickwork.
Weve ripped most of the plasterboard off and fitted 40mm of urethane behind the plasterboard and sorted coldbridging etc and will be replacing the upvc with a proper stud wall next year.
I have two main questions
Firstly we want to insulate the solid concrete floor but ideally were trying to dodge having it rescreeded due to practicalities what are the options here?
 
My first idea was to fit joist across the floor say 50mm high fit 30mm insulation between them and then fill the last 20mm with kiln dired sand or similar to keep some themal mass in the floorand then lay chipboard over the top? any other ideas? Obviously however i do it il have to lift doorframes etc so i should really have thought about this before doing the walls
 
Secondly the 3rd floor of the house is baking in summer due to the full width windows and low weight build. Are there any semi sensible ways of increasing the thermal mass of the top floor and maybe second floor without overloading the floors or walls?
 
Cheers guys i appreciate the help im sure will come
Harry