The first few years after we finished our cabin, there were lots and lots of flies that ended up dying on the window sills. I figured most of this was due to eggs that were somehow attached to the materials and hatched over time. I figured eventually, the number would go to zero but that is not the case. Seems like every couple of weeks we vacuum up a hundred or so dead ones and a week or two later, they start to show up again. We have even tried bug bombing them but that wasn't a long term solution.
Our place is pretty tight and we don't see any flying around inside usually so anyone know where they are coming from and how to get rid of them once and for all!