In June saw the activation of a wasp nest in the ridge of the roof. At first I thought the species to be Vespula germanica since many specimen of this species were active at that moment, see here. Every now and then squeaking noises from the nest penetrate through the wall.
Meanwhile for some time it has become clear judging by the two to three wasps per day that fly around indoors the species is actually Vespula vulgaris. It is not yet entirely clear where they enter. It seems the entry points are on the top floor, where the nest resides, and the floor below it. Which may indicate they enter the space between as that is connected to the wall. They are passively buzzing around so we’re fine with that. Most of them fly on windows looking for an exit. Besides brisk specimen that mainly fly around there are many that give an exhausted impression. They are sluggish and walk a lot. Perhaps they took a long time to find an exit, because I’m checking every day so they will not be there for a long time. The sluggish specimen are first nurtured with sugar water before they are set free through the roof window like their energetic brethren.
Now in October males start to appear as well.
References1 Nederlands Soortenregister