Are you sure you even *want* to try to heat it in the winter?
what do you plan to grow in it?
For most CP's in a greenhouse, winter in the greenhouse is either not feasable,
or not necessary..
For Nepenthes, its not worth it to try to heat it..it will be far too expensive to keep it 80 degrees all winter.
just bring them indoors for the winter..
a woodstove would get really old really fast..
do you really want to put more wood in the fireplace every few hours ALL winter long?
or at 3am every night? when the heat is needed most..
for VFTs and Sarracenia, you dont *need* to heat it! just leave in them in the unheated greenhouse all winter..(or even outside the greenhouse is fine in Tennessee)
Most people in North America cant reasonably use a greenhouse in the winter..
its just too cold outside..
its too difficult and expensive to heat it..
so for plants that need it warm in the winter, bring them indoors..let your furnace keep them warm..
you are already using the furnace to heat yourself anyway..no added cost to heat your plants..
for plants that need it cold in the winter, just leave them in the unheated greehouse..
either way, you dont need to heat the greenhouse in the winter..
Greenhouses are more common in England because their climate is much more mild..
a greenhouse makes sense there..
Here is NY state, greenhouses are virtually non-existant for home use..
because they simply dont work here..there is no benefit to having one..
in our climate, outside the greenhouse is better than inside it..
except for maybe a few weeks in early spring or late fall, when a greenhouse might extend the growing season slightly..but otherwise, a greenhouse is basically useless 10 months out of the year..
Tenesee is obviously warmer, so you might get more benefit from a greenhouse..
but maybe for things like starting veggie seeds early..
I dont see any great need or benefit for a greenhouse for CP's..
Scot