International audienceEnvironmental concerns are increasingly seen a not only raising a threat to which firms need to adapt by becoming "greener" and more "socially esponsible", but also as offering opportunities or new business development. Instead of being relinquished to the status of externalities, which firms more or less willingly come to internalize, environmental qualities (or deficiencies) now sometimes happen to be brought to he enter of the calculation of the value of new products. The emergence of a "clean tech" sector epitomizes this move towards the economization (Callon and Caliskan 2009) of concerns which have hitherto been considered as lying outside of the market. This paper proposes to investigate the construction of clean tech markets by examining the mechanisms through which new technologies succeed (or fail) to be transformed into goods which possess a twofold value: environmental quality (their "cleanliness") and economic worth (their price)