Sensible, cheap eco-greenhouse design

Greetings to the list:

I posted this as a reply to an earlier post, thought I'd post it as a thread in case there is interest.

On the topic of compost heat, and sensible greenhouse design:

- Compost heat works, if one mixes a good "hot" pile...in addition, it would be sensible to develop, in a smaller house, some sort of chambered system, so that a relatively steady supply of heat could be maintained, by rotating fresh compost through the chambers.

-it can be extremely beneficial to plants, beyond the mere provision of heat: the composting process gives off CO2, and, if the compost itself is below the plants, this rises up to enter the stomata on the underside of leaves.

-VERY IMPORTANT: The composting process releases ammonia in concentrations high enough to damage plants, or stunt growth. Because of this, it is wise to use some sort of biofilter between the compost, and the plants....this isn't a complex thing, peat moss has been found to scrub ammonia just fine.

-In a small house, it would be difficult to have enough biomass to generate sufficient heat: what I have done is to create a box/plant table system which contains the compost in an insulated series of chambers, allowing heat and gases to escape upwards only: on top of this system is a layer of soil, and the plants sit on top of, or directly in, this. Thus the heat reaches the plant roots, and is used most efficiently.

-And finally, a truly sensible greenhouse will employ a number of passive and ecologically responsible techniques in combination: in my zone (zone 8), houses I have built combine a pit design with a straw bale back wall (for insulation: not for compost, though as previously discussed, bales will produce heat...I am presently growing some very fine watermelons directly from strawbales, inoculated with manure tea to get the bales heating up, and composting...this works well on rocky sites, and over time, the bales build up soil, if they are placed properly in natural hollows, and depressions. Anyhow, I have combined the pit structure with compost chambers, a back wall of plastic milk jugs filled with water, a stone floor, a south facing passive solar wall, and to a depth of four feet around the perimeter of the house, insulation to prevent radiant heat loss from the floor. All of this cost me exactly $150, the price of nails, and mostly, the cost of a roll of plastic: ribs were arching cedar limbs, walls were sod from the pit, cemented with a cob mix of straw, clay, and sand. Final trick I have seen used is a double layer of plastic, with an electric bathroom fan hooked up to an extension cord to inflate the space between layers...really jacks up the insulation value...but, of course, my thing is low-tech, no electricity, etc...

And, not to ramble on ad naseum, but much work has been done using greenhouse ponds to collect heat, and at the same time grow water plants, and raise fish, whose waste is used, in turn, to fertilize the greenhouse plants, and me next great experiment will use rabbits and chickens as supplemental sources of heat, fertilizer, and food.

Hope some of this helps: I'd be happy to direct interested folks to further info. on all of this...a home, or for that matter, a farm greenhouse need not be a black hole energy wise.

Regards,

David Hicks

Hi,
I have a greenhouse for the first time in my life. I would love more info on the heating processes you have mentioned.

Thanks,
Green_Leaf