Greenhouse planning and prep continues slowly

I posted about a year ago that we wanted to build a greenhouse.  After Wifey found a great deal on some windows and a door, I scraped most of the windows to remove flaking paint and we worked to clear a space for it.  Then we got a ton of rain over the year and progress ground to a halt.

Since then, things have changed a bit.  Wifey convinced me to move the site from adjacent to the driveway pad, between the garage and the garden to the other side of the house and nearby to the pool deck.  I'm still not exactly certain it's going to get as much sunlight, but the new site should allow for us to build it in such a way to have a wider frontage facing the south sun.

We cleared a spot for it, as well.  We had a bulge of overgrown juniper, camillas that didn't flower, and dogwood all competing for space that were removed.  I removed a tree that was leaning toward the house that, unfortunately, turned out to be an American Persimmon.  Not a huge loss, though, since no fruit ever reached the ground that I'm aware of.  I also trimmed up the canopy of another adjacent tree to ensure we got a fair amount of sunlight to the site.

Wifey contacted the county to find out where the line was about whether we needed to get permits.  Based on what she found out, we don't need a permit for anything under 150 sq ft.  If we follow the guidance of the golden ratio of design, we could have a structure with the footprint of 9 1/2' x 15 3/8'.  That would yield a foot print of 146 sq ft.

I've been reading about ways to heat the greenhouse.  As much as I love the idea of having a geothermal setup, with all the trees we have in the area, I'm concerned about how to run the piping without damaging roots.  There's also the issue of power which doesn't exist out at the site and which I'd rather not have to pay for.  For now, I'm leaning toward trying composting as a means of heating it and using water barrels for thermal mass to help retain the heat collected inside.  I'd eventually like to try to have a solar-powered setup to give bonus heat on especially cold periods.

I'm torn about the plan for the foundation.  On one hand, I think that elevating everything and building on posts would simplify things considerably.  On the other hand, if we sunk the foundation down a few feet under ground (frost line in Maryland is 30"), we would get the benefit of having a modicum of consistent temperature thanks to soil temps at that depth being relatively stable.  Digging to that depth would also allow for us to have the option of small trees (dwarf banana, dwarf avocado to name two) with the benefits of added height.  The obvious downside is that working at depth also complicates things.  I don't know that that's an undertaking (and potential expense) we're going to be willing to undertake.

So, we're making some slow progress, but still have a ways to go before we can seriously tackle construction.