Conventional wisdom is to increase 10% per week, but 13 miles isn't very far on a bike. I would suggest to start with riding for an hour at a moderate pace and see how you feel. If that feels easy, increase a little bit and try again.
The 10% number comes from running though. With cycling you can dial it up a lot faster. My coach said up to 50% would be fine for cycling when starting out. Then again, I'm having hamstring trouble right now, so who knows.
I'd say 30% per week would be safe.