Welcome to TEG, RD

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It has been a long time since I had a coldframe. I made very poor use of it. Controlling the temperature just seemed very difficult.
I have had a hoophouse in my backyard for about 15 years . . . or, 15 springs. Twice it collapsed under heavy snow but I pulled it back together. The hoophouse is just put together with pvc pipe held in the ground with re-bar and covered with construction-grade 6-mil plastic. The whole thing is held down with twine stretched over the top. There's a framed-in window at one end and a door at the other. The center aisle is excavated about 16" and it only stands about 5' tall.
The hoophouse is in a very protected place - I would hate to see what the wind would do to it, otherwise! The thing is only set up from March until June. The rest of the year, it magically becomes just two 20' beds in my backyard garden

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Beside the hoophouse is a greenhouse. Once again, it is plastic covered but with UV-resistant film. Really, it is a "sunhouse" in that it is under an insulated roof and has an insulated northwall. Only the southwall and parts of the east and west walls are open to sunlight.
The greenhouse has natural gas furnace so that makes it the best choice for starting plants. Some of those plants are moved into the beds under the hoophouse. Most go out into the open garden. Actually, some plants are started in the beds of the hoophouse and also are transplanted out into the garden. Of course, it is easiest to use a heated greenhouse for early starts.
Also, the hoophouse has much more variable temperatures during the day. That thing can really heat up if I don't pay attention to it!
So, I guess if I was voting - I'd vote for a "sunhouse" :coolsun as the most suitable for a gardener, whether it has a heater or not. During the summer, it can serve as a shed. As far north as I live, it doesn't get a tremendous amount of sunlight during the summer months. The roof shades a good part of the interior when the sun is very high in the sky.
Steve
Edited to add: Here is a rather rambling accounting of temperatures for about a month this spring in the greenhouse and hoophouse. Also, some pictures . . .
http://www.theeasygarden.com/forum/viewtopic.php?id=27920