31 1 “How Much Does Your Building Weigh, Mr. Foster?” 1 R. Buckminster Fuller posed this question, used as the title of a recent documentary, as Norman Foster showed him designs for the ultra- lightweight Sainsbury Gallery at the University of East Anglia. The question implies that lighter is better—and that reducing the amount of material in a project also reduces the embodied energy of a given structure. This principle is useful to apply in an apples-to-apples scenario: a building with less steel will probably have less embodied energy than a building with more steel. However, in an apples- to-oranges scenario, this principle can be misleading. A lightweight steel-and-glass structure does not necessarily have less embodied energy than heavy masonry. Some lightweight materials require high energy expenditure for their production, others do not. Timber may be both lightweight and low energy, while aluminum is lightweight and recyclable but energy- intensive. It may be useful to think of material use in terms of performance: What is the minimum of any given material needed to perform a certain function, and how would another material’s performance compare? 1 How Much Does Your Building Weigh, Mr. Foster? , Norberto Lopez Amado and Carlos Carcas, Art Commissioners, documentary, 2010.