This paper focuses on the ex post evaluation of national energy efficiency policy mixes in the building sector, more specifically the effectiveness of implemented policy packages on helping to achieve energy savings and avoided greenhouse gas emissions (GHGs). The analysis covers all Policies and Measures (PaMs) affecting heating and cooling of residential buildings. Main research questions are: Is there a relationship between improvements in energy efficiency and GHG mitigation and the PaM history set-up within a Member State (MS)? Which are the driving factors behind the latest energy consumption trends? Hereto, the analysis starts from a literature review on effectiveness of implemented PaMs for the building sector. Afterwards, six Member States, namely France, the Netherlands, Czech Republic, Cyprus, Sweden and Bulgaria, are assessed in more detail. The detailed assessment includes gathering of existing PaMs as implemented in the six cases, and an index decomposition analysis (IDA) of CO2 emissions. The IDA of CO2 is applied to evaluate whether the different policy packages in different cases are effective on reducing energy consumption and mitigating CO2 in the residential sector. Hence, the approach followed in this paper will enable the correlation between currently adopted policy packages and quantified CO2 savings, providing a consistent approach to assess how effective MS policies are on reaching energy efficiency and climate goals. The paper brings together two recent assessments in frame of the European Topic Centre for Air Pollution and Climate Change Mitigation under the authority of the European Environment Agency.