Generally speaking, the solar gain differences between a vertical and slightly sloping wall are not that significant; other considerations generally take over. Things like wall material/construction demands, desire for more headroom near the wall, how it looks, and the like. On my first GH I made the south wall at a slight angle. It probably does have slightly better solar performance, however it required quite a bit more labor to build and seal properly. In hindsight, I suspect it wasn't worth it, except maybe for the aesthetics.

Hi Rocky Mountain Corn Project. Thanks for the informative post. I have a 12" long x 8" wide shed that I want to retrofit for a 3-season greenhouse or even a 4-season greenhouse eventually if that's possible with thermal mass and planning, and further retrofitting over time. Just like plantladyco I live at 6000 feet elevation. It has, as you described, two angled south-facing roof surfaces (roughly 30 and 60 degrees from the ground, respectively. Should I plan to glaze the south-facing vertical section below the roof as well? How much do you think this project will run me in materials? I'm pretty handy.

the moss will like something a little cooler. Are you going to put down any soil at all? the moss will need something to feed off of and the paper will only last a season. I'd spray my milkshake, but painting it on will work well too.

My first greenhouse was a wooden structure. Took glass out of old windows and put around the sides. Then I found several old patio sliding glass doors, took those apart and used that for roof. That was was when I was living at my parents house as a teen. It lasted for over 10 years. Have a lean-to greenhouse attached to my own house which I made out of angle iron. I use the polycarbonate panels all the way around. The panels are over 12 years old and are still durable and clear! So both options of glass doors and polycarbonate sheets have worked well for me!