Like we’ve mentioned before, insects and spiders are crafty. They’ve had to be! After hundreds and thousands of years competing with each other and with other organisms for food, water, and shelter they’ve adapted to be very successful.
In the urban environment, paper wasps are particularly crafty. In order to be protected from the wind, rain, humans, and the weather, they’ve had to locate their nests in places that are hidden and protected:

Without carefully observing we might not of seen this one, we had to watch for several minutes and observe workers flying in and out of that particular shutter.

As with most other insect problems, consistent, regular pest control treatment is best to prevent and take care of established problems.