A life-cycle (LC) model has been implemented for a Portuguese single-family house. The first goal is to characterize the main LC processes (material production and transport, heating, cooling, maintenance) assessing seven alternative exterior walls for the same house to identify environmentally preferable solutions. The second goal is to compare the results of three life-cycle impact assessment (LCIA) methods - CED (cumulative energy demand), for primary energy accounting; CML 2001 (Institute of Environmental Sciences of Leiden University) and EI'99 (Eco-indicator'99), for multiple environmental impacts - to determine the extent to which the results of a life-cycle assessment are influenced by the method applied. The results show that the most significant LC process depends on the operational pattern assumed. Regarding the assessment of the exterior wall alternatives, the results indicate the wood-wall is the preferable solution. Non-renewable CED shows results similar to abiotic depletion (CML 2001) and resources (EI'99) categories, as well as some correlation with climate change/global warming potential (GWP), acidification and eutrophication. However, no correlation was found with the remaining impact categories. Comparing CML 2001 and EI'99 categories, GWP, ozone layer depletion, abiotic depletion, acidification, and eutrophication present robust results that permit a straightforward comparison between the two LCIA methods. Nevertheless, CML results present slightly higher impacts for the use phase, while EI'99 for material production. In addition, the two LCIA methods can present inconsistent results between similar categories (different ranking of alternatives), which ultimately can influence the choice among solutions. (C) 2011 Elsevier B.V. All rights reserved.