My intuition says make offerings of incense outside of that room, Good tobacco even, on that side of the house. If it is an old spirit on the land then you have to make peace with it as best you can. Partly by learning, and partly by peaceful offerings.
Obviously he's pretty peed off there is a house there at all, and wants the land back for his people, but failing that - just recognise this and offer a peaceful alternative. This needs to be ceremonial. Maybe you can get help with this from a shaman.
This is just my personal opinion.