Actually, now that I'm thinking of it... does this mean a fan will have the opposite effect in the summer? I don't intentionally blow it at the chickens (more at the roofline to knock the hot air out), but I've noticed they enjoy roosting right in the crosshairs on a warm day. After they get over the indignity of having their feathers rustled, of course.You are thinking about drafts in mammalian terms not avian. As long as any gentle breezes or drafts that pass through roost space do not open their outer feathers that is fine. Their feathers getting blown open is what allows their heat to escape.