Diffusion of energy-efficient technologies in EU residential buildings

Doctoral thesis, 2020

Residential buildings constitute approximately 75% of the European building stock, accounting for around 30% of the EU´s overall energy demand and emissions. They also represent one of the biggest sources of energy saving potential, thus holding a crucial role in achieving EU carbon targets. Technology options to decrease residential building’s energy demand to nZEB standards are readily available and, in many cases, economically viable. However, they are not being deployed at the required rate to achieve GHG emission reduction targets. The divergence between the techno-economic potential and actual market behaviour suggests that in the European housing context the economic viability of energy-efficiency technologies (EETs) is not sufficiently acknowledged or appealing to motivate the necessary investments. In order to bridge the energy-efficiency gap and favour the low-carbon transformation of residential buildings in Europe, additional policy measures need to be developed. In a diverse national organisation such as the EU, it is particularly essential to have a national and cross-national scale knowledge to generate an appropriate combination of common and country-specific policies. This knowledge should be based on solid comprehension of the current national and cross-national market conditions affecting the diffusion of EETs.

Against this background, this PhD thesis builds on the research field of technology diffusion with the overall goal of advancing the understanding of the EET adoption in EU residential building stock. In particular, the following research questions are posed: (1) Who are the key decision-makers and persuaders in the technology selection, across building typologies, project types, and EU member states? (2) What are the drivers and barriers for EETs across the EU member states? and (3) What are the EET diffusion gradients across building typologies, project types and EU member states?

To address these research questions while allowing for cross-country comparison of the results, a methodology framework is developed. First, an online survey addressing these research questions is designed and distributed across eight European countries, namely Italy, Spain, Germany, Poland, United Kingdom, France, Belgium, and the Netherlands. The retrieved information is then analysed using a bundle of quantitative methods, specifically social network analysis (SNA), discrete choice modelling, and Chi2 and Cramers V tests.

Results from this study show that the individual level of power and communication varies across the different cases and countries. However, in all instances, multiple stakeholders interact, thereby potentially influencing each other during the technology selection. The potential technology adopters are identified as having the highest power in the decisions, often followed by engineers, architects, and installers. In terms of barriers and drivers, techno-economic arguments are most relevant across most of the geographies and technology solutions, with the exception of electric storage in Germany. Finally, the most often implemented EET measures across the sampled countries and building projects are maintenance of the wall and envelope, new energy-generation systems, and maintenance of the roof or envelope combined with an upgrade of the energy generation system.

Findings from this thesis can contribute to the understanding of EET diffusion in the EU residential building stock. This information, in turn, can support the formulation of evidence-based policies and actions, aimed at stimulating the adoption of these technologies.