Huge amounts of flies in the house

We had a lot of fruit flies last year after moving in, even though we didn’t have anything standing around in the kitchen. Since many other builders had the same problem, we attributed it to the moisture in the house. This year, we haven’t had the problem so far. Instead, we have regular flies in the house. For us, they mainly come in through the patio door, as we installed insect screens on all the windows in the entire upstairs. Solution = fly swatter