Embodied environmental impacts and labour intensity of four compatible heritage rehabilitation projects: A budget-based multi-indicator life cycle assessment

The refurbishment of traditional buildings is often associated with environmental benefits, yet the performance of compatible rehabilitation—interventions that retain existing fabric and employ materials and techniques consistent with it—remains comparatively underexplored. This study assesses four compatible rehabilitations of traditional buildings carried out in the Valencian Community, Spain, between 2008 and 2022, differing markedly in scale, setting and scope of intervention. Life cycle inventories were built from itemised bills of quantities, providing physical quantities, costs and labour hours from a single traceable source. The assessment covers product manufacturing, transport to site and replacement-material burdens over a 50-year reference study period, considering global warming potential, net fresh-water use and renewable and non-renewable primary energy. Within the assessed embodied-impact scope, minimally processed traditional materials generally combined high physical or economic presence with comparatively low reported GWP, with timber representing 27–33% of material cost in three cases but only 3–8% of GWP and stone and aggregates showing particularly low impacts per unit mass. Replacement burdens were concentrated mainly in short-lived finishes and treatments rather than long-lasting construction components. Global warming potential expressed per square metre varied by a factor of 22.5 across cases; decomposition of this area-based result showed that intervention expenditure per square metre varied by a factor of 19.2, whereas GWP per unit of initial expenditure varied by a factor of 1.65. The contrast between the two normalisation bases remained stable under sensitivity tests of the reference study period, service lives and replacement convention. Labour exceeded half of direct construction cost in two cases. The results show that compatible rehabilitation can combine material retention with construction resources exhibiting comparatively low reported GWP, while expenditure-based normalisation provides a complementary reference for comparing interventions of heterogeneous intensity without representing avoided emissions.