Also from that article is this.
But this source says that AMC had its own ideas about how to make the show more cheaply. The show shoots for eight days per episode, and the network suggested that half should be indoors. "Four days inside and four days out? That's not Walking Dead," says this insider. "This is not a show that takes place around the dinner table." That was just one of what this person describes as "silly notes" from AMC. Couldn't the audience hear the zombies sometimes and not see them, to save on makeup? The source says Darabont fought "a constant battle to keep the show big in scope and style."
If true, this Attack of the Bean Counters
is the kind that has cluelessly killed many projects.
AMC's star could fall as fast as it rose.
Those suggestions aren't really all that terrible (especially if they're just on-the-cuff questions rather than a directives from above). There are certainly creative ways to spend a couple episodes in closed sets. Hell, these guys are trying to survive a zombie outbreak. It's perfectly reasonable to have them hiding in enclosed spaces occasionally or arguing with other survivors over how to best protect their hiding places.
Most SF/F shows depend upon having a few bottle episodes in order to save money for the big smash-em-up episodes. I get that they're trying to make every episode special, but bottle episodes can be special in the right hands (check out Babylon 5's "Intersections in Real Time" as an example).
Sure, it might have been excessive to put half the episodes indoors, but that's (hopefully) just a starting point for some discussions.
Edit: Also, I've read the comics, and there are certainly plot-lines that lend themselves to long-term (even indoor) sets. They could even plan ahead (assuming the script-writers can get ahead of the filming a bit) and have a few outdoor scenes in-the-can for the periods without out-door filming.