Rating systems for sustainability (R.S.), started to be largely used in the assessment of built environment since the early '90s,. The diffusion of these tools led to several benefits but also underlined some critical issues. One of the main hitches is the difficulty in comparing methods and results of different assessments, which have been developed at different times and places, following specific approaches. This paper aims at proposing a method to compare different R.S. and their outcomes,

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... y mapping what and how much they have in common, to identify a shared core of elements that could be considered the most representative in assessing the sustainability of the built environment, focusing particularly on residential buildings. The predictable loss of accuracy due to the reduction of the considered indicators is analyzed, to define an acceptable level of reliability of the resulting concise R.S., whose simplification can, however, help to facilitate its wider application.