Influence of urban density on energy retrofit of building stock: case study of Spain

Energy retrofitting of existing buildings plays a key role in the European targets of Green House Gas reduction. The addition or substitution of construction materials is needed to improve energy performance of buildings and its environmental impact must be considered. This paper proposes a model for the assessment of the environmental impact of neighborhood retrofit in relation with urban density. The model is based on the decomposition of buildings into functional elements and the quantification of construction materials used in building energy retrofitting. As a novelty, the need of road rehabilitation was also considered. The environmental impact was assessed in terms of Embodied Energy (EE) and Embodied Carbon (EC). The operational energy after retrofit was also calculated. The results bring the evidence of the relation between the urban density and the EE and EC derived from building retrofit, which can be up to 60% higher in low density areas. The sensitivity analysis carried out demonstrates the influence of the urban compactness on the environmental assessment results. The model proposed can assist in the design of retrofit plans at urban level by highlighting those retrofit measures with most significant environmental impact depending on the urban density.