What you're describing can involve a full demolition back to external walls and then hanging a thermally broken envelope from scratch (to Passivhaus standards perhaps).
But it shouldn’t, unless you are mad or the place is fucked to start with.
Carefully specc’d and fitted external, underfloor and under roof insulation with some decent windows / doors should do.
But it shouldn’t, unless you are mad or the place is fucked to start with.
Carefully specc’d and fitted external, underfloor and under roof insulation with some decent windows / doors should do.