A Winter Greenhouse Construction Plan for Northerners

[Aquamaple]

First off, happy 2014 fellow aquapons! I am building a winter-ready greenhouse this spring, currently building a materials/cost list which led me to some questions you all may have valuable experience with. I hope this thread will be invaluable to others such as I who wish to grow year round in cold climates. It is currently January 2, 2014, and it has been below 20°F for a couple weeks now with air temperatures monday expected dropping to 5°F, possibly below 0°F for the rest of the week. I need serious thought to go into this greenhouse, and I have thus far researched much and pondered greatly on the topic. If I remember correctly, I live along the 42nd parallel, in Michigan.
Please excuse the jumbled communication, I'm using my phone and apparently it doesn't like the mobile interface because I can't scroll up to edit my text. I will add to this thread and edit at home, when possible.
I have found successful designs I plan to base my greenhouse off, and I will soon link those so you may have an idea where I am headed. Essentially, it will be tall and insulated on the North side, a steep glazed roof sloping toward the South with a shorter wall there. I will explain more of my ideas later, but that is the gist of it. I plan on using a combination of SHC and geothermal energy.
My first questions:
1. I am capable of building, but not too knowledgeable about building trades, as of yet. WHAT would be the benefit of using a concrete perimeter foundation as opposed to just planting my treated posts in the dirt? I plan on using foam board underground all the way around to assist with insulation. Im sure a concrete foundation would look prety and work well, but I currently see it as an unnecessary cost. Am I right? The inside square footage of my GH will be dirt, for many reasons I will later explain.

Thanks for all your help, this is going to be a fun project!

[Sonja Martin Young]

I chatted with our local guy about geothermal in our area. His take is that the systems that he uses would not be able to keep up with the temperature extremes in our area so I would still have to have a conventional heater and he ran some numbers with me and we decided it would not be cost effective. Might be different in a different area.

I like Jim's idea of using used furniture bubble wrap on the inside for extra insulation. Thought I would check to see what is available here.

[Jeremiah Robinson]

I did a bunch of research on SCHS for a customer recently.  They're gangbusters for cooling, but heating gain is minimal.  The real winter advantage is that they heat up the ground earlier in the season, which doesn't do much for aquaponics.  When I have time I'm going to make a calculator for how much heat/cooling to expect given your design.  Maybe over the winter I'll do it.

Geothermal for water heat would be an interesting idea - haven't seen it before.  Beware of geothermal sellers over-promising.  The way efficiency for them is rated (COP) doesn't include pumping power, which can be a big part of their load.  They're great, but not as great as they've been made to seem by some.

[Jeff S]

Last year when cold weather hit I rushed and built an 8x10 GH. I was happy with the results but struggled to keep it warm. This year I am expanding to 14x21 but will be able to reuse the walls. I am anticipating no further growth but will be building in a way that the GH can be expanded if needed. No deep digging to undo if there are changes of any kind. I have a sunken sump now and that will be the hardest item to relocate.

Aquamaple said:

I'm kind of thinking like Sonja where I plan to do it once. The structure I am planning will be too big to dig it all up a second time.

[Aquamaple]

I forgot to relay one of my most exciting developments! My wife wants a cellar for food storage and a place for me to store all my homemade wine. SO... I think I'll just build it deep undergound and big enough that it can accommodate sump tanks big enough for all the AP expansion on my property! The sump system will be very close to my water supply and my electrical source. Also, the geothermal water conditioning can be installed way over near the cellar instead of under the greenhouse. This could be done way cheaper than an underground bunker with poured walls and a poured ceiling, but since I'm going to build a cellar, I might as well make it multi-purpose and get the best "bang" for my buck!

So, SHC will actually be subterranean cooling for the summer, not so much for winter heating in the greenhouse. I like the idea of the concrete floors, sloped to drains, dyed or painted black for winter energy absorption, and covered with something like crushed limestone in the warm months. My wife and I are replacing our indoor forced air wood furnace with an outdoor boiler system where I plan to burn sawdust/horse manure logs from our farm (PM me if you are interested, or we can start a discussion about it in a furnace thread). I plan to make the boiler big enough to heat the greenhouse to some extent, since they will be in close proximity. I am also a fan of rocket mass heaters, I don't have plans for one in the greenhouse yet, but maybe someday one would be incorporated. I'm more likely to reverse the SC air flow into the heat exchanger with the boiler water so I'm never heating air cooler than 55°F as opposed to trying to heat <40° greenhouse air... I am also building a very nice waste oil furnace for my shop at this very moment that could potentially be used for supplemental heat in a greenhouse. (These are VERY hot and VERY clean, lookup a gentleman I follow on Youtube called, "Gerry's Waste Oil Burner" if you are interested.)
So my hope is to have my trout water always 55° or so, warm water tanks I have other plans for temperature control. My plan is that the GH will always be at least slightly warmer than the coolest [trout] FT. But my gut tells me with adequate weatherproofing combined with all the other things it will be fairly easy to maintain warmer temperatures ALL winter.

[Aquamaple]

I never said it would be cheap, but it WILL work!

[Jeremiah Robinson]

That sounds great!  Love to see pictures as it comes along!