Same rule applies as everywhere else. If you want contrast in your negatives and the contrast is low in the scene, you must create it, and the only way to do that is to underexpose your film and then over-develop it.

If there are no real black values in the scene, you will push the darkest values that DO exist, further toward normal shadow values by under-exposing.

Then you stretch the tonality of the scene by over-developing, so that your mid-tone contrast doesn't suck, and your highlight intensity isn't weak.


But then again, you may wish to focus on conveying the light that is there in a manner that is truthful to the scene, which could be equally effective.