Hi Mike, thanks for the reply.
I am aware that a raised bed provides some sort of coldsink. But of course Mike Oehler's idea is to extend that principle. If it is deeper it would be more effective and could offer more gradients and possibilities.More edge-effect if you will.
My idea roughly is to have a raised bed on the south side of the greenhouse. Mainly for annuals, propagation, slide-out coldframes and so on, with some sort of entrance through it for a deep litter chicken coop. Then a walk way with cold sink (coop underneath), on the east-west axis of course. North of that could have some more annuals but mainly perennials, food forest style. Pretty standard, I'd say.
According to what I understand from Eliot Coleman, a 5% slope of a terrain towards the south would "move"it about 480 kilometers (300 miles) south, by simulating a higher sun angle.That idea might work inside a greenhouse and would also enhance the coldsink-effect, I think.
Now I'd actually like to pack as many functions into the sink as possible (a tourist destination could be one of them, thank you very much)
Connected to the chicken coop inside the sink would be a closed composting system with subsoil drainpipe exhaust, providing heat, water vapor and CO2 into the soil directly under the plants. The New Alchemy Institute has an extensive report on such a compost exhaust system and it looks very promising. Of course the chickens (and maybe mushroom production) would also provide a certain amount of this heat and CO2. Exterior air intake for this system would be preheated by earth tubes or cellar-vent. I did think of connecting a cellar to the coldsink, but I don't know exactly how to deal with the fact that the cold air from the sink into the cellar might clash with the venting of that cellar, wich normaly would be situated on the north side of a building. Leaving it as a separate unit outside to pre-heat air into the greenhouse (via a small sauna as back-up?) might be a better option. Have to think about it, will search for the video you mentioned...
Thermal insulation around the perimeter of a greenhouse (extending to at least under the frost line) makes a lot of sense to me, but does provide a problem. It also totally isolates it from the soil food/fungal web outside. And we don't want that, do we? Here the cold sink could have yet another function. We could somehow create a corridor for the web, I think. Let''s say we slope the ends of the coldsink (east and west) towards the soil level of the greenhouse . Into the (also mulched) coldsink we could make a small but decent opening to the outside world into a "dry" pile of mulch, that we thouroughly protect from the weather . It would have to be large enough to give ample R-value. That could be calculated, I think it will have to be something like Huge! The moist bottom of the pile would provide the corridor for soil life, the dry mulch on top insulation. You'd have to top it off every fall or so.. Oxigenation of the pile could be done by a trombe wall, if needed. Does that make sense? Any ideas anyone?
Many good, well functioning greenhouse systems exist. But many of them seem to be depending on mechanical and electric (and digital) inputs. That's all fine really, but I think I want to learn more about biological, physiological and hydrological possibilities first. They actually represent the "passive" aspect of a greenhouse (or any house), don"t they? And they fascinate me...
Anyway, thanks. I think now I"m going to read every permie-post on greenhouses thrice. And then some...
Salut,
Michiel
