Forum:"House is not suitable" - All Requirement Met. What to do?

I've recently added more rooms to my house, so it could house all the eventual NPCs i'd find at some point. But after the adding everything required for a suitable home (walls, background walls, chair,table, lighting and so on) Its stil isnt suitable. The rooms im talking about are the bottom 6, i have no idea what i need to change to make them suitable. I've though it might have something to do with the snow blocks as walls, but cba to change that unless im certain...

Thanks for the help in Advance

- Nediarph