How deep does the retrofitting have to be? A cost-benefit analysis of two different regional programmes

International audienceThe recent European energy proposals for the revision of the Energy Efficiency and the Energy Performance of Buildings Directives emphasize the importance of driving investments into the renovation of building stocks and stimulating retrofitting demand. Moreover, the ambitious targets on Green House Gas' abatement and energy consumption reduction require refurbishments to a high level of performance. This high level of performance subsequently represents high cost for households. Thus, with the necessity to lead to ambitious renovations, the question about the cost-effectiveness of the relevant level of performance has to be tackled. Unfortunately, the absence of reliable data often makes it difficult to answer this key question. In this paper, we rely on two different regional energy efficiency programmes providing incentives for performing refurbishment with a great importance dedicated to thermal insulation and air tightness. Covering a sample of around 50 households per programme, data on energy consumption and the characteristics of individual dwellings were collected as well as on refurbishment costs. Comparisons between the two programmes and within each programme provide information on the economic relevance of ambitious targets (in terms of energy and carbon). Both programmes pursue similar objectives but the cost associated were different. The first programme presents an average retrofit cost of 290 €/m² compared to an average cost of 415 €/m² for the second one, but both programmes present a large margin of uncertainty. On average the energy savings were 63 kWh/m² (final energy) for the less costly programme compared to 88 kWh/m² for the second programme. Concerning the non-energy impacts, the households express satisfaction about comfort increase and green value of their refurbished real estate property. The findings underline the crucial importance of both financial incentives and extra benefits such as asset value to enhance the accessibility of deep retrofit potential