Leveraging the Transfer of Development Rights for housing retrofit financing: International insights and the opportunity for Spain

The transition to carbon neutrality by 2050 requires energy retrofits of existing residential stock, yet Spain's retrofit rate remains at 0.1% annually—far below the 1% required to meet national climate targets. Due to their aging, the residential sector also faces accessibility and habitability issues. High upfront costs represent the primary barrier to comprehensive retrofits, while current financing mechanisms suffer from limited accessibility and sustainability. This paper explores the potential of adapting Transfer of Development Rights (TDRs) as a financing mechanism for multifamily private housing retrofits in Spain. While TDRs have been used internationally to support heritage preservation and acquire land for public purposes, their application to fund housing retrofits remains largely underexplored. To address this gap, the study investigates two questions: (1) whether the Spanish planning system provides a favorable regulatory framework for the implementation of TDRs, and (2) what key factors should be considered for their potential adaptation. Based on a diverse literature review, our findings show that Spain has historically included instruments that separate development rights from land ownership, suggesting regulatory compatibility with TDRs. The case review further identifies five key stages in TDRs implementation—planning integration, area designation, transactions design, monitoring, and evaluation—each involving critical design decisions. These include not only operational factors but also safeguards against speculative practices. This approach introduces a meaningful innovation: leveraging the planning system itself to manage planning gains as a viable financing mechanism for private multifamily housing retrofits. • Spain's legal framework supports separating development rights from land ownership • Land readjustment provides historical precedent for TDRs adaptation • Selling DRs from vulnerable areas funds retrofits, redistributing urban value fairly • A potential TDRs implementation must take care to prevent speculative practices • TDRs allow shifting focus from public-space retrofits to private housing upgrades