They are old windows- you can see one set on the south facing side are like little french doors so were meant to open, the others are single pane windows that have hinges on the top only and I prop them open. I need to put hooks on the outside so I can bungee the french door windows open, they blow around in the wind a lot. The other mistake I made is not allowing enough clearance for the windows. They had been in storage at my dad's forever and were really dry. One wet Oregon winter and they were so swollen we had to take them down and plane off the edges. Same with the door.
It doesn't get cold here often so I usually keep the windows open for ventilation. The "screens" are hardware cloth.