Alison and Mike move to the house in the summer, as she tells Kitty in the previous episode that it's currently June, and Barclay says he and Bunny were away for the summer when he comes to introduce himself two episodes later. But the newspaper clipping in the pantry says Pat died on October 25th, which would make his death day well after the events of this episode when the builders were working on the house early on.
When Pat goes outside to see his family, he casts a shadow on the ground which a ghost, obviously, would not do.
Pat is supposed to be a ghost, but his breath can be seen in the exterior scenes.