This report focuses on methodological issues related to the determination, assessment and presentation of the environmental performance of buildings. The purpose of this report is to provide the foundations to responsible parties for further developing their specific methods to assess the primary energy demand, GHG emissions and further environmental impacts of buildings and to increase the mainstreaming of practice globally. As far as possible, this should lead to a standardization of methods used worldwide. Where this goal cannot be achieved, methodological differences can be at least identified. The specific objectives of this report are to: clarify methodological questions that have been shown as significant but are under-addressed i...