Would it benefit to add some skylight for humidity?

My cactus seem to love this spot even though it only gets half a days sunlight the brick wall heats up and stays warm into the evening, it is coming into winter where I live and I thought that they might like a slight greenhouse effect if I added a peice of clear plastic skylight to the railing if anyone has done anything similar or has some knowledge on what humidity these beautiful plants like your opinion would be greatly appreciated, thanks 🙏 🌵