I have a "modern" UK house (approx. 15 years old, built as cheaply as possible, a wooden house with a brick shell). If it is cold outside and I heat the ground floor to the minimum I would like, then the first floor is warmer than I would like and the 2nd floor in particular is too warm.
I have installed a door to the stairwell on the ground floor and do not heat it much, so on the 1st floor it is markedly cooler than the rooms and on the second floor it is certainly no hotter.
The heating system is wet radiators with individual thermostats. When the problem is there, it is there with thermostats turned off on the second floor and set low or off on the 1st floor. Much of the problem is likely caused by the level of "insulation" being unbalanced between the ground floor with large conservatory style skylights and the other floors (see picture on related question).
Before starting on a new roof and windows for part of the house, I would like to see if insulation between the ground floor and 1st floor could help, either bonded to the ground floor ceiling or something blown with little or no adhesive into in the spaces between the load bearing joists.
Is that feasible? Would there be any pitfalls, could it be done with minimal intrusion?