Open Access

Reaching the climate goals for the building sector requires to improve insulation and to increase air tightness of buildings in order to minimize heat loss. To achieve these goals and to prevent risks to the health of occupants and damages to the building fabric due to insufficient removal of pollutants and humidity, broad implementation of Mechanical Ventilation and Heat Recovery (MVHR) systems is crucial. Comparable and up to date figures on the market penetration of MVHR systems across the EU are hardly available. However, figures point to only a small share of residential buildings being currently equipped with such systems (cf. Riviere et al. 2009). For the German building stock the figure is estimated to be below 5% (Händel 2011). The paper presents insights into the reasons for the slow diffusion of HRV technologies in the German building stock. It builds on the results of a recently completed research project whose central aim was to identify actor-specific and structural barriers for the diffusion of efficient ventilation systems in apartment buildings and to examine how these barriers can be addressed. The analysis is based on 40 semi-structured expert interviews with energy consultants, HVAC craftsmen, and housing companies, as well as guided in-depth interviews with private owners of apartment buildings or apartments that were evaluated by means of qualitative content analysis. Based on the collected data, seven barrier categories were identified, each containing a range of single barriers for the diffusion of efficient ventilation systems within the residential building stock. Results of the analysis were quantitatively validated by means of online surveys and a household survey among 1,008 households. The paper points out interdependencies within the chain of effects leading up to the investment decision of building owners. Furthermore, based on good practice examples identified within the data collection process, it proposes different measures to address these barriers.

In 2016, the European Commission presented the Clean Energy for all Europeans Package , comprising legislative proposals to facilitate the clean energy transition within the EU, such as the revised EPBD 2010/31/EU and EED 2012/27/EU.Besides putting energy efficiency first and achieving global leadership in renewable energy, a third goal of the package was to provide a "fair deal to consumers" with "no one left behind"., While in some Member States the issue of energy poverty already was on the political agenda, enabling affordable access to basic energy services for all households and thus reducing energy poverty is now an explicit policy target of the revised EU Directives. In order to assess and monitor the extent of the issue across the EU and address it by suitable measures, the concept of energy poverty needs to be defined, operationalised and measured. The paper aims to investigate the role of energy poverty indicators for policy making. To do so, it provides an overview on existing measurement approaches.Furthermore, the paper presents the development and current state of energy poverty across the EU using a set of four complementary indicators used by the EU Energy Poverty Observatory. These consensual and expenditure-based indicators are calculated using data from the EU Survey on Income and Living Conditions and the Household Budget Survey. In addition, the paper highlights peculiarities of results on the different indicators, describes persisting issues with regard to their calculation and interpretation against the background of the underlying data base. Based on the results of this analysis, further necessities of data collection and research are pointed out.