Howdy, I too have an 8x12 green house. Wish it was larger, or better yet, a solarium built to the house. Inside are larger plants that no longer fit in the house. Citrus, Agaves, a few Aloes, Olive tree, variegated Ginger, and a few other odds and ends. Plants are kept in the gh during winter months..once temps warm up, plants are set outdoors. With utility prices, why pay extra when plants do well outside, not to mention easier to manage...? The first year it was erected, 'December, Christmas present,) on the coldest night of the year, the heater went out. In the process, I lost either 32 or 37 plants which froze. I cried, literally cried. After that dreadful night, we figured the problem and made sure the gas heater was working. We added an electric heater in case something went wrong with the gas again. We also purchased a temp/guage/alarm. The guage displays indoor, outdoor and gh temps and humidity. If temp drops to 45F, the alarm beeps. The guage is kept in the house. Mike, although Feb is cold, 'usually the coldest month of the year,' the sun is stronger and will burn certain plants. I hesitate adding shading since most plants are sun lovers, and eventually adapt to strong rays. During summer, gh temps reaches 117F+. This last summer, especially July, temps rose 140 and higher. Even with two opened vents and the storm/screen door ajar. Although my gh is on the small side, it's great having extra space. Don't know what I'd do without the extra room. It's a great investment, especially for those of us who have, more than a few, plants. lol. Toni

The extra height is intended to let the 13' back wall be fully enclosed in the greenhouse so it would reflect light throughout as well as retain/release solar heat. I've since done the heating calculations and I think I'm fine heat-wise, however now I'm quite concerned that the 30 degree slope is too shallow for my zone(6). A 48-60 degree slope would be ideal given my suns path throughout the year, but here I am with a 30 degree poised to reflect away a whole bunch of crucial growing light. Is it as big a deal as I'm thinking? You're so, so right about the ease of covering! The logistics involved in double glazing some of those improved structures are INTENSE.. and I would prefer to just glaze the way it is and maybe rebuilt next season if it's a huge problem. (And then again if snowload is a problem? haha)

Thank you Cactusfreak! That's what I was afraid of. I do have another alternative. I've had to construct a concrete water storage tank (for a sprinkler system), a 28' octagon, mostly below grade, containing 27000 gallons of water and also a pump room, which has to be heated to a minimum of 52 degrees at all times. In winter, the snow or ice melts above the pump room, about 1/3 of the total octagonal top of the tank. The plan was always to build a pavillion there, I have most of the materials, basically glass doors and windows, framed with tree trunks and milled lumber. Again, I have no idea what the temperature of this enclosure will be when it's 15 degrees outside, assuming fairly tight-fitting sinle pane doors and windows. Do you know of a way to find out? I was hoping to overwinter at least zone 7 plants, is that unrealistic? Any suggestions would be very welcome. I will look for the thread you're referring to as well.

What Mini-Splits Look Like in Your Home what do these systems look like in your home, you ask? https://www.ductless-mini-split-air-conditioner.org/ Indoor Here are a couple of pictures of “indoor units” installed in customer homes. As you can see, the indoor unit is mounted near the ceiling. mini split in home mini split home stock Inside the unit is a fan and a set of self-adjusting louvers. The louvers can be configured by the remote control to sweep back and forth and up and down, or point the cool air in a specific direction or directions. The louver directions are easily set with the remote control. We love our mini-splits because they are quieter than the industrial-strength fans we used to have, and they provide near instantaneous cooling. When the unit is off, the louvers close, making the unit look even sleeker. In this photo, the louvers are closed almost all the way: indoor unit closed The indoor unit is connected to the outdoor unit by two insulated refrigerant pipes and a power line. We only have to drill a 3″ hole through the wall to run the pipes and wire. And, of course, the hole is behind the indoor unit and made weather tight from the outside.