How are the vents in my home's vinyl windows used?

[sandman2s2]

The casing of my home's vinyl windows have a small ventilation slit that slides open to vent to the outside. Why? How do I best utilize this vent?

 

[Jan]

You want to keep the vents open but still covered with small breathable foam pieces to keep out insects but let some air in and moisture out too. I flush mine out in the spring and summer by pouring water in through them and replacing the little pieces of foam. You want your home to breath some and not be sealed too tight or it is not healthy. My home is well insulated and the windows are the vinyl thermo- panes and all I do is keep the tracks clean and the slider vent pieces. The little foam pieces do have to be replaced as they deteriorate with time. You can purchase new foam at fabric stores and cut it to size.