Energy-Efficient Retrofits on an Existing Home in Coimbra, Portugal : A dynamic assessment of environmental performance for future climate and energy mix scenarios

Abstract: This work introduces a method, called the dynamic building life cycle, to evaluate theenvironmental performance for residential renovation products. The method goes beyond a fullbuildinglife cycle by accounting for the changing dry bulb temperature and greenhouse gas (GHG)intensity over a 30-year period between 2020 and 2050. This method is a combination of using (1) lifecycle assessment and environmental product declarations to determine environmental impact fromrenovation products, (2) climate projections and the morphing algorithm to determine future drybulb temperature, (3) GHG intensity projections based on five different e-Highway2050 (eHW) projectscenarios to predict the future state of national energy mix and (4) whole building energy simulationsto calculate final energy demand. The work focuses on a case-study comparing renovation productsapplied to a single-family home located in Coimbra, Portugal. Renovations include replacing existingwindows with double-glazed and triple-glazed windows along with three different insulationmaterials for Exterior Thermal Insulation Composite Systems (ETICS).The results show that all renovation products reduced the overall emissions over the dynamicbuilding life cycle compared to base model, however, improving the thermal insulation wassignificantly more effective than upgrading the windows across all eHW scenarios. From theinsulation materials, XPS provided the best combination of low environmental impact and thermalproperties to reduce the total GHG emissions, although EPS and mineral wool insulation performedsimilarly well. Despite having a low overall effect compared to the ETICS, triple-glazed windowsoutperformed double-glazed windows with 26% more reduction in GHG emissions on average acrossall eHW scenarios. The impact of using a dynamic building life cycle was compared to simplifiedmethods. For instance, depending on the eHW scenario a comparison where the GHG intensity wereto remain constant over the building life cycle could lead to a 5% under estimation or 30% overestimation for final GHG emissions compared to the dynamic method. Whereas if the climate were toremain constant the final emissions would be about 5% overestimation compared to the dynamicmethod.