In the developed world, the number of products now used in building construction projects is much higher than in the past, and the distances that products are transported to reach building sites are much greater. This can be deduced from delivery notes for supplies arriving at building sites every day. In 2010, the LiTA research group carried out a preliminary detailed study of this issue, with regard to a building type for a fast food chain of restaurants built around the region of Catalonia. The results of the study led to the proposal of a numerical indicator called KxK. This indicator is calculated by multiplying the number of kilogrammes of each product used in the construction of the building type by the kilometres that the product is transported from its point of supply to the building site.