Hi OS,

There are always vents in any worm bin. Cut off the airflow, and only anaerobic bacteria survives. That said, air vents are often overrated. As long as some oxygen can get in the bin, the worms do fine.

You can protect a plastic bin with a sheet of plywood. But, realize that if you do not do a good enough job of protecting it, and if the outside gets warm to the touch for a short time, your worms will cook. It can be a challenge to protect something outside with just a sheet of plywood.