C31 -- The Environmental Impact of Step-by-Step Renovation: A Single-Family Dwelling PDF

To achieve a climate-neutral building stock by 2050, a substantial number of renovations will be necessary in the upcoming years. Because of these large numbers, the Flemish government has proposed a strategic approach that systematically phases out dwellings with the poorest Energy Performance Certificate labels. Whereas existing literature on the environmental impact of renovation projects predominantly addresses renovations as a single-step intervention, the more common step-by-step renovation approach is missing in current state-of-the-art. Therefore, this paper examines the environmental impact of a step-by-step renovation of an uninsulated single-family dwelling by means of life cycle assessment (LCA). Within this study, four distinct sets of renovation measures, hereafter referred to as “renovation packages”, are considered. These packages all include the insulation of the building envelope in line with the current Flemish EPBD-regulations combined with two types of heating systems (i.e., a gas condensing boiler and air-water heat pump) and two types of ventilation systems (i.e., an exhaust ventilation system and balanced ventilation system). In addition, three main parameters are distinguished in the context of a stepwise approach: (1) the renovation sequence, (2) the number of renovation steps, and (3) the interval between renovation steps. First, the environmental impact of a stepwise approach under fixed parameter conditions is calculated. Subsequently, the influence of varying these three parameters on the environmental impact is assessed. The findings indicate that, when evaluating identical renovation packages and conducting the one-step renovation at the start of the study period, a step-by-step renovation consistently results in a higher environmental impact than a one-step deep renovation. Nonetheless, a stepwise renovation approach can be preferred over a one-step renovation in case the latter employs a less efficient renovation package or is conducted at a later moment in time.