I normally store my bananas in my attached, unheated but insulated garage over winter. However, the last couple of winters I have had quite a few casualties due to rot. I have been storing bare root.

Should I be washing the dirt off the roots?
Replanting in sphagnum peat moss?
Do I need to cut more of the pseudostem back?
Store in a black trash bag and tie it?(read this, but seems like it would promote mold)
Is it getting too cold?
Should I be putting a paper bag over the pseudostem to block out light?
I could keep them in the basement and they would stay dark, but it stays relatively warm during winter, around 65-68 degrees.

The garage usually stays in the mid 30s on the coldest nights of the year to mid 50s the rest of winter. Is it getting too cold? They have been rotting and molding. The garage gets plenty of natural light.