> I thought about this powered exhaust possibility.  I am thinking a
little
> plastic fan would melt in the exhaust stream depending on the
amount of
> heat that is input.

If you're venting enough heat to melt a purpose-built cooling fan
(it's *hot* inside your computer, remember) then your design does
not adequately transfer the available heat to the air inside your
van. By the time the exhaust leaves the van, it should have done its
work already -- the issue is venting harmful gases.

> Are you saying to still use the stove as the burner and run this
ducting
> all the way to the engine compartment?

Nope. I'm saying install a heater in the engine bay -- it'll double
as a block heater -- and pump the heat through a sealed duct system
which runs under the bed or in the cabin floor, but that is
airtight, relative to the cabin.

This avoids the problem of that any heat source inside the van which
requires exhaust for safety must, in practice, actually draw new
cold air *into* the van from somewhere. This is a inherent problem
with using the stove as a heater.

If your heat souce, stove or otherwise, generates harmful gases,
then the most efficient system is to decouple the air intake and
exhaust from the the cabin environment -- but run the ducting
through the cabin for radiant heating.  This conserves the heating
work that's being done by your bodies, and allows incremental
heating without drawing new cold air into the van.

Of course, if there exists such thing as a small electric space
heater which does not generate any harmful gases, then you can just
run that in the cabin and avoid all this complex ducting. The only
downsides there are fire hazard, and presumably, electrical load.

-Isaac in Cambridge