In the book, Health and Light, the author, John Ott explains that plants (and
people) need full-spectrum light, which includes UV (both visible and invisible to the naked eye) light in order for proper ripening to take place. Using glass, as in a
greenhouse situation, is not the best. Glass blocks
UV light, at least to the extent plants need to undergo proper ripening and ethylene production.
Clinical trials found sheet plastic a better (as well as cheaper) method to screen wind, rain and airborne contaminants like bugs and particles, while still allowing the proper full-spectrum lighting needed by growing organisms, plants in this case.
I build welded steel buildings on my ranch in North Texas, which is noted for high winds. I use "red iron" tubes. Red iron is primed (red) steel and I generally use 2" x 2" square. I have a pneumatic driver, which pounds the steel deep into the ground, having first dug a 30" hole with an auger, then pounding said steel post into the ground another 4 feet.
Concrete is then poured into the upper 30 inches and left to hydrate before further fabricating. Once a superstructure, including solid steel gussets at corners and welded trusses at the roof is fabricated and welded into place, the structure is nearly indestructible. The posts (on 10-foot centers) are anchored 6.5 feet into the earth!
Sheet plastic can then be stretched over the building's sides and top, tacked in place with staples driven into "sleepers" (wood boards bolted to the surface of the exterior structural steel), to create the "greenhouse".
The cost is far and away less than using pre-fabricated, bolted- and screwed-together galvanized carports. Primed red iron resists weather just as well as galvanized. Many of my buildings are over 30 years old and show no signs of weather-related decay (rust).
Hope this helps someone.