Yeah, winters down here aren't much, are they? I'm not sure how much ventilation that actually provides or if it is in both gables or just the front one. Silkies are typically bantams. With only three in that area I'd think yo'd be OK in the winter down here but summers is what would bother me.
If those louvers are on both front and back gables you might be OK in the summer. Since Silkies can't fly your nests and roosts will probably be really close to the floor. I'd be real tempted to put a window on one or both sides up fairly high. Instead of glass or Plexiglas maybe use louvers to help keep the rain out. If you don't feel they are predator-proof enough, like for snakes, put hardware cloth behind them.
Welcome to the forum from Belle Chasse, glad you joined. Your location was pretty important to this. You might modify your profile to show general location so that info is always available.