Electrical — Heating
Replace the convectors, keep the walls.
Convector heaters from the nineteen-eighties warm the ceiling and scorch the dust. In most cases they can be replaced without major work — the supply is already there; it only needs checking.
Time
Half a day for an apartment
Benefit
Control to a tenth of a degree
Area
Paris 6th, 7th, 14th, 15th, 16th