Will mobs spawn from dark ceilings?

Question

I'm trying to cut back on having so many torches but it leaves my ceilings rather dark, light level 7 to be exact. As long as the ground is well lit, will that be enough to prevent monsters from spawning?

Answer 1

As you can see on the image bellow, a mob need an opaque block bellow his feet to spawn, so it can't spawn in the air. Also, the light level is only checked at the ground level, so only the floor needs to be lit to avoid mob spawning.

Image source