Where temperatures regularly drop below freezing, outside pipes are buried (300 mm in the 2003 text) or insulated with waterproof insulation, pipes on metal roofs are insulated and kept off the roof sheet, and pipes in cold spaces inside buildings are kept away from the roof covering and outer walls and insulated to the thickness tables (2003 text).
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.