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!

[Aquamaple]

Jeremiah, I like the idea of dyed black concrete. I would hate sand and the resultant mess when there was moisture on the floor. I would probably be way more willing to put down an inch or so of some crushed white colored stone in the summer months. Then water on the ground (and small dirt particles) could be washed down the drain under the stone. In the winter the stone could be used as additional thermal mass, or simply stored elsewhere.

[Aquamaple]

Maybe just a thick layer non-toxic paint instead of dyed concrete.

[Jeremiah Robinson]

I like the white gravel idea.  I've been kicking around in my head ways of covering a dark surface in the summer to avoid heat absorption.  That seems like the best one yet!

You could use paint with some texture in it.  You'd have to find a very uv-resistant paint though.

An even better way of storing heat would be phase change materials.  

[Aquamaple]

what are your thoughts about phase change materials?

[Jeff S]

 I figure something like gravel would allow water to drain through as well in the event of a spill or leak. Not sure how it would be for walking. I'll have to keep asking around.

[Jeremiah Robinson]

I don't have any special thoughts on them, other than that they store a lot of heat.  I wrote up the theory behind it here.  You might find some out there with a google search.

I'm working on a PCM product that freezes at about 55 degF.  Not ready yet though.

[Aquamaple]

Jeff,

My thinking is an angular aggregate (like crushed limestone) set to a minimum pack-able depth might work very well. While a smooth floor surface might possibly allow a more free flow of liquids on their way to the drain, the benefit of textured concrete might be less movement from the crushed stone. Brushed concrete might be easier and cheaper than a textured paint. Also, the brushed concrete texture would probably last longer than an added texture. I like where this is going...

[Robert C. Wood]

has anyone considered using geothermal floor heating and cooling. the reason that I ask is that in winter it heats the floor and in summer it cools the floor. it is a lot cheaper than natural gas and more environmentally friendly then using wood or gas to heat.

[Jeremiah Robinson]

Do you mean geothermal using a heat pump, or subterranean heating and cooling using air?

[Aquamaple]

I plan on geothermal heating / cooling for my water, and subterranean heating and cooling for the greenhouse.

[Jeff S]

Some how all this takes away the "hobby" aspect of aquaponics. But I'm just as guilty as anyone.I see an idea and I have to try it.

[Aquamaple]

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.