31. ‘cost-optimal level’ means the energy performance level which leads to the lowest cost during the estimated economic lifecycle, established by applying the cost-optimal methodology where:
(a) the lowest cost is determined taking into account:
(i) the category and use of building concerned:
(ii) energy-related investment costs based on official forecasts
(iii) maintenance and operating costs, including energy costs taking into account the cost of greenhouse gas allowances
(iv) environmental and health externalities of energy use
(v) earnings from energy produced on-site, where applicable
(vi) waste management costs, where applicable
▌ (via) social externalities of building renovations, construction, demolition including the modification of built areas
(b) the estimated economic lifecycle is determined by each Member State and refers to the remaining estimated economic lifecycle of a building where energy performance requirements are set for the building as a whole, or to the estimated economic lifecycle of a building element where energy performance requirements are set for building elements. The cost-optimal level shall lie within the range of performance levels where the cost benefit analysis calculated over the estimated economic lifecycle is positive