This International Standard provides methods of calculation of heat transfer coefficients and heat flow rates for building elements in thermal contact with the ground, including slab-on-ground floors, suspended floors and basements. It applies to building elements, or parts of them, below a horizontal plane in the bounding walls of the building situated. for slab-on-ground floors, suspended floors and unheated basements, at the level of the inside floorsurface;NOTE In some cases, external dimension systems define the boundary at the lower surface of the floor slab.. for heated basements, at the level of the external ground surface.This International Standar