The aim of this study is to assess the consistency of Portuguese thermal building legislation in terms of energy and environmental performance. To illustrate this, a case study has been carried out for different scenarios of a dwelling home located in an extreme climate zone (I3, V1 north) in Portugal with a T3 typology: four occupants and net floor area of 150 m(2), modelled according to Regulation Thermal Performance Characteristics of Buildings and a Life Cycle Assessment approach. The results show that the Portuguese thermal building legislation can be considered consistent in terms of energy efficiency and environmental performance if we take the damage categories into account - "human health" or "ecosystem quality" or the impact category -"emission into air". It cannot be considered consistent if we take the damage category into account - "resources" or the impact category -"CO2 eq" (equivalent carbon dioxide emissions)/"climate change"/"global warming". (C) 2011 Elsevier B.V. All rights reserved.