But what about the grey energy of these buildings? This claim of zero net energy homes seems dubious when one does not factor in the embedded energy of the buil

But what about the grey energy of these buildings? This claim of zero net energy homes seems dubious when one does not factor in the embedded energy of the building with all this metal. You can go a long way of heating your wooden house till this building will break even in terms of total energy consumed including building materials and shipping.