Flow through worm bins

Here are some designs for efficient harvests of vermicompost. Lots of folks start with the beginner rubbermaid worm bins, but the flow-through design is a lot better for harvesting castings.

http://vermicomposters.ning.com/forum/topics/diy-flow-through-bins-a?id=2094123%3ATopic%3A41256

I was originally considering the stacking method but I think I like the flow through better. Has anyone attempted to have an outside bin during winter before? Obviously temperature is an issue, but I'm wondering if you made a rig with hay bales and tarps if it would keep the temp up enough for them to survive/thrive. Experiences anyone? Oh and thank you Abe for the link, got some good design ideas from it!

I have a couple of outside bins that do well in winter, but we have mild winters.

Insulate, bury in the ground, and add some hot compost material on top to help with the temps.