Ok, so this WAS counting as a greenhouse, I had the +5 C from it on the planted crops. NONE of the blocks are on top of the glass, they're only on the sides.
I put some decorative blocks on top (WAY less than 50% of the roof and also chiseled small) and it stopped counting as a greenhouse. I removed the blocks and it still won't count as a greenhouse anymore. I tore the glass out, tore the doors out, and re-placed them. No good. Slept, restarted game, still nothing.
I ran the debug rooms command and the whole inside shows green, but it also says I'm standing in 9 rooms? Standing on the ground, my hud shows a cellar. Pillaring up near the ceiling, the hud shows a house?
The inside dimensions are 10x10x6 tall. Is there any command to just make the game re-check the building? Or re-check the chunk? I honestly don't know what's wrong here and why it changed.