Here is a 0.233 ball penetrating 8 walls and not fragmenting.
While I am sure that most would opt to select .223/5.56 NATO over .22LR for home defense, but I have heard the argument that .22 would be better for home defense since its reduced energy would mean that it would penetrate through fewer walls. On the flip side, others argue that the 5.56 would be better as the round would tumble dissipating its energy and thus penetrate less.
Fortunately, both have now been put to the test in relatively similar conditions. A few tests come to mind on 5.56 through drywall (my favorite being the slow-motion from RichardBeck). I like the slow motion as it shows that the round does indeed start to loose stability. Still, the round is able to penetrate through nearly 8 walls, coming to rest on the inside of the last piece of drywall. (Interestingly, the 9mm Critical Defense load actually penetrates one drywall section less).