If you have a hot water or steam boiler in a seperate room or area in
your basement, try this trick. I took a cold control (the thermostat)
from an old window air conditioner and used it to switch on a small
blower. Both items are mounted at the ceiling over the furnace, and
plug into a convienient outlet.
It goes like this: The furnace turns on and as it and it's piping get
up to temp, warms the air around it which naturally rises to the
ceiling, where the cold control senses the temp rise and turns on the
blower, sending that warm air out into the basement. I ended up using
some 3" rnd. duct to point the air where I wanted. Colder air from the
floor goes into the furnace rm. to replace the warmed air. Some of the
cold air is used for combustion, and some goes up the draft hood on the
flue (where the warm air used to go before the system started sending
it into the rest of the basement) I'm not going to pretend I got this
thing right on the first try, but it wasn't that hard to figure out
which of the salvaged fans/blowers I had was the right size, and how
much opening I needed at the top and bottom of the furnace area for
best air flow. (duct tape and plastic to start) I did this because the
idea of all that warm air going up the flue just bugged me.
The flue pipe from boiler to wall is short enough that I don't think
condensation will be a problem, so some day I'll replace a section of
it with well sealed B-vent and hook a fan to one end of the outer
section of that too. I'll let you know.