Back wall with vapor retarder and battens

Most of the picture is taken up by the back wall of the sauna, shaped like a rectangle with the upper left corner cut off by the sloping ceiling. On the right we see some of a side wall. Both walls are covered in a blue paper-like nmaterial held together with lines of yellow tape from floor to ceiling. Over the blue material there are pieces of wood of varying lengths and widths attached to the walls. On the right wall there are four horizontal pieces visible: one close to the tope of the wall, one close to the bottom, one somewhat higher than the middle, and one somewhat lower than the middle, which is appreciably wider than the others. At the bottom of the back wall there is one batten across the whole width of the room close to the floor. At the top there is one from the left wall up to the end of the sloping part of the ceiling and a horizontal one from the right wall to around half way across the level part of the ceiling. Just below the gap between the two top battens there are two set at angles, sloping the same direction as the ceiling but at a steeper angle. The bottom end of sloping batten 1 is below the end of the sloping ceiling, the bottom end of sloping batten 2 beneath the top end of sloping 1, and the top end of sloping 2 at the end of the top right horizontal batten. Half way up the wall on the right is a horizontal batten with its left end under the lower end of the sloping batten 2 and its right end at the wall. Lower down the wall on the left there is a horizontal batten reaching from the left wall with its right end a little to the left of the lower end of sloping batten 2. Above the lower batten on the left a number of small pieces of wood are attached to the wall with gaps between them.