One of the reasons I believe that having /home on a separate hard drive was that it would be easier to maintain you're data if you need to do a re-install.
My question though is it as simple as just running a new install on the OS hard drive or do you need to do certain steps (apart from a back-up) before re-installing Ubuntu?
For example do you need to use same username/computername and passwords?
In my case Ubuntu 14.04 is the only OS used and I have encrypted the OS but not /home.