When we sketch a wall we can provide an offset value on the Options Bar and then use the Space Bar to flip the side of the reference points we provide during sketching.
That flows pretty well (pun intended). It's not so fluid when using the Duct and Pipe tools. The Offset feature is hiding in the Justification Settings dialog AND the Space Bar concept doesn't work. We have to provide a negative value or be careful to start sketching in a specific direction to get the opposite offset.
This makes sketching pipe with a specific offset value relative to walls and other elements tedious. I think it is very likely (even much more so) to want to create pipe and duct taking into account adjacent elements like walls and structure AND provide an offset while doing so...it would be a lot more fun if there wasn't this extra little dialog hassle to do so.