Ray wrote:

I live in an 82-year-old six-unit apartment building, and the heat comes
from a single furnace through steam radiators... this creates a problem of
reaching an optimum temperature. Not only are there wide variations in heat
between apartments, but some like it hot, some like it cold.

We solved a problem like that in one of 25 units in a 5 story co-op with
a single thermostat in Brooklyn by adding a Danfoss mechanical thermostat
and a humidistat and a solenoid valve and a needle valve off a T that went
to a 1-pipe steam radiator vent. When the RH dropped, the valve hissed
live steam into the room, scaring the cats.

A lot of the residents wore T-shirts and shorts and left the windows open
all winter. The apartment air was extremely dry. There was no insulation on
3 steam risers in the unit we fixed up, and too many radiators. We took one
out, insulated the risers and added the thermostat after the humidity T, and
now there are only 24 units with the windows open all winter :-)

It seems to me our best solution would be to establish a very low
temperature level for the main furnace -- like 60 degrees -- and then have
each unit provide their own supplementary heat to bring the it up to the
desired level.

I've been looking at these "mini-split" systems which provide both air
conditioning and heat.

Does that sound like a good solution?

Yes. That way you get AC too, and you can turn off the split systems to get
energy savings with a setback at night and whenever units are unoccupied.

Nick