A door with a lock on it would be the best solution for me to be productive. I agree whole heartedly with you when you say

So the "best" environment for writing a lot of code is one that minimizes interruptions.

And I also want to re-itterate another thing you said

Most research shows that (most) programmers produce the most code when they can spend 3-4 hours at a stretch on a problem, uninterrupted. You know, that midnight-hacking zone we've all experienced, when the ideas are right there in your head and the code is flowing freely... After an interruption, it takes (on average) about 10-15 minutes to get your head back to where it was pre-interrupt.

These are both very important topics to me and I am betting to most of you...

Thanks for the feedback