I can imagine in Texas you have often no clouds even in winter. I heard you can put just Rocks into the Grenhouse, where The Sun shines on, and they will store some sungenereated heat, wich they will give away at start of night. Easy trick, just place them in. Also the greenhouse-heatup does only happen IF sun shines, and again you in Texas do Profite more than in a more clowdy place. Third Thing is you can Build a wall at the northern Side of the greenhouse, and partly a the Roof, where no sunshine Comes from to SUBSTENTIALLY Isolate the greenhouse. I also agree, that some cannabisstrains can survive minustemperatures quiet well. They might stagnate Abit, but they dont die. Some Thais, or Nepal Strains can handle that quiet good. So i see not that big of Problem growing even equatorial thaistrains. If it gets 100 Percent topquality is questionable, but 80 percent Quality is enough , no? What you envision?
Oh and shure double glass would hold more warmth in, as plastic, but they filter uv wich is debatted to be important for resinproduction.. So, i would still take plastic, and it holds in Abit of heat (5 degrees celcius) . To my understanding intense sun could be same important if you want to have 100 percent Quality bud..
For that i have a possible solution on this exact page, preflowering the plants indoor (this is for 18 weeker Sativas rahter) : https://www.icmag.com/ic/showthread....360394&page=15