My experience with Greenhouses has been nothing less than great. Even a lower shelf GH that proved less than desirable. I didn’t know if I needed or wanted a GH but an opportunity came up in the mid 1970s to get many used church basement windows free including delivery. The frames were made of steel and had matching holes on all 4 sides for mounting. I used the windows as they were without any additional frame work on the walls. The only frame work was a steel angle for the peak of the roof. Through the mid 70s to 1980 we had some hellish summer storms and snow loads, the GH just sat there without a wimper. The GH was only used to support a vegetable garden but I spent many enjoyable hours there with much success and nice garden plants. The GH/kennels had to eventually give way to a Garage/shop but I had plans for another GH. I apologize for the photo but it is a scanned Polaroid.
The second GH is a simple lean-to on the back side of a tool shed. The GH isconstructed using 2 X 4s and fiberglasssheeting. There is a shelf with a heated sand bed and worked very well for starting garden plants and storing semi hardy perennials and tubers through the winter. But things never stay the same, the neighbors trees have grown to the point the GH is now in dense shade. I have added florescent lights and continue to use it for seed propagation in the early spring and hardwood stem propagation in the fall. You will have to excuse all the junk setting around I’m geting ready to pressure wash the garage and GH
My fourth and hopefully my last GH is a Rion GH44 the rigidity and air tightness is very impressive. I am heating a larger GH with the same gas heater at a substantially lower setting for the same temps inside the GH. I was concerned enough to install a carbon monoxide detector but every thing is ok. If any of the polycarb panels need replacing, the roof will be easy but the walls will be a bear to replace.