So, with this information, what would YOU do? I wonder if just one oil-filler radiant heater would be enough in the winter to keep the greenhouse warm enough? I plan on digging down about 3 feet, for the bottom of the green house (below frost level - to provide more heat), and building the greenhouse above. I have not decided how I would insulate the area where greenhouse meets ground. Possibly straw. Would I need added ventilation, with the auto vents?

As far as summer goes, I am thinking of having misters, to maintain humidity (NO humidity where I live) and keeping all doors and windows/vents open constantly. Plants, such as tomatoes, peppers, squash, etc... would all be moved to my outdoor garden.

What am I missing here??

Will you be getting a water line installed? And electricity? (I assume yes if you are considering a radiant heater.)
I assume you'll add shade cloth in the summer too?

For winter, what will you be growing and what minimum temperature will you be aiming for?

If you dig your foundation deep into the ground and insulate the perimeter (underground), then you can skip insulating the floor. This method is warmer than insulating the floor because you are making use of the fact that the ground is warmer than the air in winter. You can learn more about this by searching here or in Shane Smith's greenhouse book.

As far as what I am growing... good question! I figure this year I am just going to give everything a try and see what happens! I keep getting conflicting information from people on what will, or will not grow, so I want to learn for myself. BUT, I am certainly open for suggestions! As far as plants like squash, watermelon, pumpkins, etc... I will just start seeds, and plant those outdoors next spring.

Thoughts?? My thinking is, try to keep the greenhouse above 50 F. I do not think that will be THAT hard to achieve, and I think the majority of the time it will easily stay around 70 inside (during the winter) because of the location. It is also very protected from the wind (not that we get that much wind anyway) so I do not have to worry about that.

Am I way off??

As for the heat and the winter growing - before you commit to heating your greenhouse all winter, and paying the money that goes along with that, I would give some serious thought to why you want to do that and what will be possible. I agree, experimenting is a great way to proceed. But I'd caution you to not get yourself locked into something that ends up being a lot of energy use for a small gain. Sounds like you are in a warm spot anyway, which is great. Another book for you is Elliot Coleman's 'Four Season Harvest.' He discusses various methods to keep your winter greenhouse productive without adding heat.

My approach to getting the most out of the greenhouse is to be as clever and efficient as possible, and to use added electricity only as a last resort - that way I am not dependent on having added heat to make it all work. Everyone's approach is different - that is just my viewpoint!

Enjoy the planning - certainly it is all very exciting.

Now my thoughts are - double doors...necessary? I am assuming to get proper ventilation in the summer, that is a must-have.

Providing that the Rion greenhouse structural members are assembled with a lot of care and attention to detail, the end result is an unbelievably strong structure. But another 'secret' to this strength is attaching the base members of the Rion greenhouse to an 'immovable' surface. If the base isn't absolutely rigid and allows the sidewalls to 'bow out', the roof can 'sag' slightly which can allow roof panels to shift and roof 'caps' to pop. This is the primary cause of the roof leaks. In my own case, I used a 4 x 4 base frame with cross braces supporting a cedar deck 'floor'. If you plan on excavating down a couple of feet, something like poured concrete 'side walls' which cannot / will not 'bow out' is highly recommended.

I run an overhead mist system that works beautifully ... providing that you have plenty of water pressure available to allow the mister nozzles to spray properly.

I also run a 16" ventilator fan on a thermostat behind a side wall vent panel installed next to the double door ... because the 16 ft length makes for too many 'dead air' zones if you're depending on just the roof vents and side wall vents during the peak heat of summer. I actually keep the double doors closed when the temperature starts pushing 90 degrees in order to allow the ventilator fan to create an end-to-end cross-draft ( drawing outside air from sidewall vent panels at the opposite end of the greenhouse.

If I open the door and the roof vent, then it usually stays in the high 80's to low 90's, but it makes me wonder what it will be when the outside temp is in the 90's.

I have been looking at ventilation, shade cloth (inside or outside), and am just not sure the best way to proceed.

I'm not really sure that I will actually grow anything in the hottest part of summer in the greenhouse, but I also don't want it to get so hot it damages the greenhouse.

My primary use will be seed starting in the spring (although I still have all that indoors right now, even though the greenhouse is complete), and then would like to attempt to grow greens year round, so start some in the greenhouse each fall (I left a 42" x 96" section of the floor soil so I could just grow in the floor, the rest of the floor is pavers).

I also keep two inexpensive rotating fans running inside, 24-7, for air circulation.

I grow plants (cacti and succulents) that tolerate a lot of heat. If we have a 100F day, the temp inside my greenhouse can get to 110-115 even with all of the above, for brief periods.

I use Aluminet shadecloth, but there's a lot of good info in this forum on other types of shadecloth as well. I started with enough to cover the roof, then added as I learned what my plants needed, and as I learned how the sun intensity changes throughout the year.

If you don't get enough response to this post, you might consider starting a new thread about cooling, since your questions are good ones that affect any type of greenhouse (not just Rion.)

Pretty greenhouse!