Optimizing the Retrofitting Paths for Vulnerable Residential Buildings in Spain: Modeling Shallow Renovations for Net-Zero 2050

J.P. Chaparro Ramírez, J.C. Romero, R. Barrella

38th Young Energy Economists & Engineers Seminar - YEEES Delft 2026, Delft (Países Bajos). 29-30 octubre 2026

Resumen:

This paper uses openMASTER, an open-source model of the entire Spanish energy system [1], to analyze how home energy renovations could be carried out based on cost savings. We add renovation to the model as an endogenous investment and study what the optimization says about how much to renovate and whether the pace of renovation or its cost is the limiting factor.
Almost half of Spanish dwellings (45%) were built before any thermal regulation (pre-1980) and require up to ten times more heating than recent ones [1]. The draft National Building Renovation Plan (PNRE) sets a renovation path, but the current pace lags behind [2]. We divide dwellings into four efficiency levels set by Spanish regulation (Very Low, Low, Medium, High) and let the model decide when and where to renovate. We call a building vulnerable when its efficiency level is Very Low or Low; the model does not yet disaggregate households by income. We take the renovation costs from the shallow renovation studies of Fundación Naturgy (the technical report and the VAREX 2022 and 2024 evaluations) [3], [4], [5]. Besides, the PNRE renovation rates are used as the maximum number of renovations that the construction sector can deliver. The model uses energy service demand (for this specific case, the heat a home needs).
By 2050, the model makes 16.6 million renovation steps, and no Very Low Efficiency (VLE) dwelling remains after 2035. The heating service demand falls 36% in 2050 against a case without renovation, and residential emissions in 2030–2050 fall 56%. Each euro invested in renovation (8.6 G€ in total over the whole modeling period, discounted to its first year) returns 4.3 € in avoided energy system costs. Renovation would stop only at a cost 8 to 39 times the package costs, so the pace of renovation, not its cost, is the limit.

Resumen divulgativo:

Muchos hogares españoles tienen problemas para mantenerse calientes. Con el modelo openMASTER se estudió su mejora gradual hasta 2050. Renovar con límites realistas reduce un tercio la demanda de calefacción y a la mitad el CO₂ residencial desde 2030; cada euro invertido ahorra 4 euros al sistema.

Fecha de publicación: 29-oct-2026

Cita:
J.P. Chaparro Ramírez, J.C. Romero, R. Barrella, "Optimizing the Retrofitting Paths for Vulnerable Residential Buildings in Spain: Modeling Shallow Renovations for Net-Zero 2050", presentado en 38th Young Energy Economists & Engineers Seminar - YEEES Delft 2026, Delft, Países Bajos, 29-30 octubre 2026

IIT-26-313C