Thu, 03 Jul 2008 23:35:01 GMT from Lou :

"Stan Brown" wrote in message
t...
My mold consultant told me it was necessary to heat the house to
at least 65 to prevent the growth of mold. (Humidity should be no
more than 55%, though in winter it seems to hover in the high
30%s and low 40%s.)

I have baseboard hot-water heat, and both he and a contractor
told me it operates most efficiently if the thermostat keeps the
same setting 24/7.

The contractor wasn't trying to sell me anything, by the way. He was
the teacher of a home-maintenance class offered by a local non-profit
group.

I wonder what the definition of "most efficiently" is.

In this context, "efficient" might mean less heat lost up the
chimney, less unburned fuel passing through a cold furnace at
startup in the morning.

My understanding is that the furnace uses less fuel overall to keep
the water in the hating pipes at a constant temperature than to let
it cool down by 10 or 15 degrees in the day time (when I'm at work)
and the night (when I'm in bed) and then reheat it.

My understanding is that this is true for hot-water heat but not for
forced-air, since it takes much less energy to heat air than water.

It may also be significant that my furnace heats hot water used for
washing -- the thing in the basement that looks like a water heater
is actually just a holding tank. Maybe if I had hot water heat but a
separate water heater, the efficiency would go another way.

But it might be possible that by turning the temperature down at
night and while the house is empty during the day results in lower
overall costs because you're heating less of the time, even though
those few hours in the morning/evening might have the furnace
operating at less than peak efficiency.

I'll ask my furnace maintenance guy about this and see what he says.
Of course if I could use less energy I'd be happy about that.


--
Stan Brown, Oak Road Systems, Tompkins County, New York, USA
http://OakRoadSystems.com
Shikata ga nai...