[masraum]

Are you certain that they are paper wasps and not mud daubers?

We get wasps in the house during the summer. Most of the wasps that we get in the house are "mud daubers". The mothers make nests that they hide inside the walls/roof/anywhere that they can find access to. The new wasps hatch out and don't know how to get outside since they've never been anywhere but in their mud tube. I assume some make it outside, but others find their way into the house instead. I do think we've had a few paper wasps get into the house, but they are much more rare compared to the solitary mud daubers.

If you want to keep them from finding their way in, my suggestion is to check around any ceiling fan/light fixture on the ceiling. You'll have to take the fixture down to see if there's any open space around the boxes that they are connected to and seal those up with something (spray foam in a can maybe). The bathroom vent (and maybe kitchen vent) is probably a good idea too.