wasps tend to sort out sheltered, hot locations. They are commonly found around attic beams, outside trim, chimneys or exhaust pipes, and attic vents. It is impossible to seal your attic because you need to have the airflow but you could add screens to prevent the wasps from entering and exiting. The best bet would be to hire an exterminator/pesticide treatment company to remove the wasp nests every few months and give suggestions on how to better bee proof your home.