Mason bees in a greenhouse may not work well due to the elevated temperature of the greenhouse. Mason bees typially begin to emerge at about 54 degrees. I seggets that you build a mason bee box outside and allow the natural bees to populate it. Then, when your are ready to polinate in the greenhouse (assuming that the bees growth cycles are complete, move it into the greenhouse. I believe that they need a cold period, so you should move the box into a cold shed for the winter and back into the greenhouse for polination.

Thanks, I currently have my bees in my refrigerator, I need to check on the humidity as I understand they require about 70% humidity while in storage.
Dan