The Farmhouse Is a "Savupirtti" Smoke House
The smoke house was a common dwelling in Finland in the 1800s and earlier. Often it had a main room and four bedrooms. The walls were built with fitted logs, with the upper log being carved to fit over the lower log, which was left round. In the corners the logs were interlocked with traditional "salmon tail" joints. The floor consisted of thick planks. An historical drawing of another smoke house is shown below.
The smoke house was dominated by a massive stone fireplace, shown in the drawing above on the right, and in the photograph below.
The fireplace was built without a chimney. The smoke from the fire in the fireplace came directly into the room, conducting the heat, and rose to the top of the room. Later, someone in the room would move a pole to release a flap in the ceiling, which covered a hole. The smoke was drawn through the hole and out of the house, leaving the heat behind. This, along with smaller openings, was used to ventilate the house.