What do I do if the properties of a wall vary along the egde of a room?

If the properties of a wall vary along the edge of a room, you can split the wall using the blue handles. This may be necessary ifif, for instanceinstance, one half of the wall has an unheated space behind it (for example a garage), and the other half is external. Simply drag and drop the blue handle to the point where the wall needs to be split. You can then set different properties for each section of the wall.