Jeremy Cash wrote:The best thing to do with a good theory is test it. Take lots of pictures, documentation, etc. and share your findings with us. 
I would if I had a greenhouse, or a place to build one.
C.J. Murray wrote:I would not recommend this for the following reasons:
1) People gotta be in the greenhouse at some point and there is no way to guarantee no CO was produced along with the CO2 and water vapor.
2) Plants need oxygen too, not just CO2.
3) The water vapor is gonna condense on everything and it'll be a rainforest.
Good points. The first response I have is that I am not immagining a completely sealed greenhouse. It would be normally ventillated, only with the addition of a passive one-way vent to keep the pressure equalised if the heater was burning with the service vents closed.
The CO point is a particularly good one. I personally smoke tobacco, and hope to one day heat and cook solely with wood/biomass, so I am not hugely fussy about small ammounts of CO exposure. The key would be what concentrations we are talking about. I have CO detectors in my current home in addition to smoke detectors. They are relatively inexpensive and can be run on wall current or batteries, it would probabally be a good idea to have something like one of those on my exterior "control panel".