In construction this purely refers to the ground area utilised by construction, however the meaning of footprint has been taken up by the ecological and sustainability sector to refer to the effect of man’s activity on the planet, like a footprint on the moon! Conventionally in construction the building footprint is the area of a building measured from the outer surface of the exterior of the building multiplied by the depth measured in the same manner to give a square area. There can be variations in agreed measure in different countries in that patios, paths, external components of the building which are not part of the structure maybe included/excluded. In pad foundations the outer edge of the foundation may project outside this line but would normally be disregarded. The use of building footprint can be distorted by commercial concerns for example the greater the footprint declared so the cost per square area of construction is reduced Likewise a smaller declared footprint area may incur less planning/building tax when calculated on footprint area. The variation this makes is often very small but it is still worth confirming the definition. In some Mediterranean countries the definition simply is taken as the ground shadow from an overhead sun, but large over hanging roofs distort this measured area. Carbon Footprinting for sustainability is not an exact science and is subject to many national variations. A definition by Carbon Management states; A measure of the total amount of carbon dioxide (CO2) and methane (CH4) emissions of a defined population, system or activity, considering all relevant sources, sinks and storage within the spatial and temporal boundary of the population, system or activity of interest. Calculated as carbon dioxide equivalent (CO2e) using the relevant 100-year global warming potential (GWP100). So the intention is obvious but the methodology is not so rigorously defined, though there are some agreed standards being introduced and accepted.