From the comments, I understand that the window shutters are actually empty wood boxes, or must be in order to hang from the hinges.
However, one I spotted before I read the comments: the roller shutter on the rear facing looks a bit flimsy and is probably the main point of attack for the walking dead. If I was going with that, I'd want some sort of trench in front. Hell, I'd settle for a one-floor concrete drawbridge dropping to fill said trench, with steel roller shutter on the top section. Same wide-open view effect, but significantly more secure.
I also thought it was a 3D render on a photo backdrop but it does appear to be a real mockup. Totally impressive for that but I think I'll stick to designing my own zombie-proof bunker, with more layers of protection for starters (and that's without the obvious need for sentry guns).