By 2020, different European Directives on the energy performance of buildings (EPBD) aim to reduce energy consumption by 20%, reduce greenhouse gas emissions by 20% and endorse a target of a 20% share of energy from renewable sources. These Directives have led EU Member States to develop systems, following their corresponding transposition into national law, to evaluate the energy efficiency of buildings, and create different Energy Performance Certificates (EPCs). This has led to different energy efficiency measurement systems in the EU and a CO2 emissions scale has not been included by some Member States. Just as EPC is aimed at influencing the demand for energy-efficient buildings, this study is aimed at developing a straightforward procedure to obtain the environmental impact in the use phase of a building in kgCO(2)/m(2) year in order to influence the demand for buildings with a low impact on climate change. By applying this methodology to different case studies, we can conclude that obtaining the formula drastically simplifies the calculation of CO2 emissions in KgCO(2)/m(2) year. The results obtained from applying this methodology will serve to record CO2 emission rates in single-family houses on a yearly basis, thus contributing to the study of applications that address climate change mitigation. (C) 2015 Elsevier B.V. All rights reserved.