Now I'm trying to think if we can see anything out the windows. I've always assumed they're up a few floors -- possibly because the establishing shot looks up at the building, as though we're looking at the second floor. It looks like there's a hallway outside their door, so I'd guess there's an elevator and/or stairs out there.

On the other hand, I'm not sure if they could have gotten the christmas tree into an elevator or up the stairs. So... I think it's up to you, since it hasn't been well established. :)