Grey energy is often defined as the energy necessary for manufacturing, transport, life and the elimination of constructions and/or buildings (1). Beyond this definition, some people consider «grey energy»to be «hidden energy»(2), others as «lost» energy (3).
The new challenge of (very) energy efficient building.
Calculation of the energy consumption of a building takes operating energy and grey energy into account. Whereas the contribution of grey energy was lower than 10% in old buildings (thermal colander), in new buildings that comply with French thermal regulation RT2012 it represents between 30 and 50% and by 2020 it will account for almost all of the energy consumption in top-rate energy efficient buildings such as positive energy buildings (BPOS).
Grey energy of primary zinc: relatively low grey energy.
The energy necessary to manufacture primary zinc (from extraction of mineral resources until the end product leaves the factory) is 2 to 4 times less than that required to manufacture other primary metals used in building envelope applications (4). The order of magnitude of the comparison can be nuanced by the «primary metal»/«secondary metal» mix used in the manufacture of metal applications.
The benefit of recycling used rolled zinc for grey energy in VMZINC solutions.
With an actual recycling rate that is higher than 98% (5), VMZINC solutions have low grey energy. The grey energy of 1 kg of rolled natural zinc used in roofing corresponds to the energy balance used from extraction of mineral resources to production of rolled (47.6 MJ), less the grey energy saved thanks to its recycling (34.2 MJ), i.e. 13.4 MJ.
(1) « Construction et énergie – Architecture et développement durable », Manfred Hegger, Matthias Fuchs, Thomas Stark and Martin Zeumer, Published by Presses polytechniques et universitaires romandes, 2011 (2) Cahier Technique, CT 2032, Published by Société suisse des Ingénieurs et des Architectes – SIA, 2010 (3) « L’énergie grise des matériaux et des ouvrages » - Les guides BIO-TECH – Published by ICEB et ARENE IDF, November 2012 (4) - « European study on the Ecoprofile fo primary zinc production", Dr I.Boustead and Dr Dove for the International Zinc Association, 1998 - « The recycling of non ferrous metals", Michael E.Henstock, A publication by the International Council of Metals and the Environment, May 1996 - « Metaux pour toits et façades" Recommandation 2000/1 du KBOB, Suisse (5) (5) Study of rolled zinc recycling, Institut i+c, September 2011
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