Every fall and spring the inside of my house gets overrun with large
orange wasps. They are all pretty sluggish and congregrate along the
top corners of west-facing windows where it is obviously warmer late
in the day. I have no idea how they are getting inside--i will
sometimes burn my gas fireplace and will get a handful that fall down
into the fire, but I keep the damper closed otherwise so I don't think
it is likely they get in through the fireplace. I live in a two story
house, and I'd guess 99% of the wasps I find are on the first floor.

Any thoughts on how to find where they are getting into the house?

assuming I can't find where they are coming in (if I could, I'd just
seal the entry up), any suggestions on how to keep them out?