Energy saving policies and low energy residential buildings: a LCA case study to support decision-makers in Piedmont (Italy)

Background, aim and scope A low-energy family house recently built in Northern Italy was selected by Regione Piemonte as an outstanding example of resource efficient building. An economic incentive was awarded to cover the extra costs of the thermal insulation, windows and equipment in order to decrease the yearly winter heat requirement from the legal standard of 109 to 10 kW h/m2, while existing buildings in the study area typically require 200 kW h/m2. As the building was claimed to be sustainable on the basis of its outstanding energy-saving performance, an ex post life cycle assessment (LCA) was set up to understand whether, and to what extent, the positive judgement could be confirmed in a life cycle perspective. Materials and methods After an analysis of the literature on LCA of whole buildings, a detailed life cycle assessment has been conducted by encompassing all the life cycle phases. Emphasis was given on the end-of-life stage, too often disregarded due to lack of data or heavily simplified. Virtually all the materials used in the building structure, finishes and equipment were considered, paying attention to their expected service duration and the recycling potential. In order to increase transparency and therefore credibility and acceptance of LCA in the building sector, an uncertainty analysis was carried out. Results and discussion The dramatic contribution of material-related impacts emerged. Structure and finishes materials represented the highest relative contribution, but maintenance operations also played a major role. The contributions of equipment, construction stage and transportation were minor. The important role of the recycling potential also emerged. Unlike standard buildings, where heating-related impacts overshadow the rest of the life cycle, there is no single dominating item or aspect. Rather, several of them play equally important roles. Conclusions The study confirmed that the initial goal of resource and environmental efficiency was reached, but to a much lower extent than previously thought. In comparison to a standard house, while the winter heat requirement was reduced from 109 to 10 kW h/m2 (10:1 ratio), the life cycle energy was only reduced by 2.1:1 and the carbon footprint by 2.2:1. Recommendations and perspectives The findings emphasise the need for incorporating the life cycle approach in energy-saving policies and economic incentives schemes in the building sector, in Italy and elsewhere, as single-step improvements might not be effective in a life cycle perspective and could even disappoint expectation

The assessment of the relevance of building components and life phases for the environmental profile of nearly zero-energy buildings: life cycle assessment of a multifamily building in Italy

Purpose: Since the construction sector is a considerable energy consumer and greenhouse gas (GHG) producer, the EU rules strive to build nearly zero-energy buildings, by reducing the operative energy and yearning for on-site energy production. This article underlines the necessity to go beyond the energy evaluations and move towards the environmental assessment in a life cycle perspective, by comparing the impacts due to building materials and energy production devices. Methods: We compared the operational energy impacts and those of technologies and materials carrying out a life cycle assessment (LCA; ISO 14040, ISO 14044, EN 15643–2, EN 15978) on a nearly zero-energy building (ZEB), a residential complex with 61 apartments in four buildings, situated near Milan (Italy). We consider all life cycle phases, including production, transport, building site activities, use and maintenance; the materials inventory was filled out collecting data from invoices paid, building site reports, construction drawings and product data sheets. To make the assessment results comparable, we set a functional unit of 1 m2 of net floor area in 1 year (1 m2y), upon a lifespan of 100 years. The environmental data were acquired from Ecoinvent 2.2. Results and discussion: The results highlight the important role of the pre-use and maintenance phases in building life so that in a nearly ZEB, the environmental impacts linked to the use are no longer the major proportion: the pre-use phase accounts for 56 %, while the operative energy is only 31 % of the total. For this reason, if the environmental assessment of the case study was shrunk to the operational consumption, only one third of the impacts would be considered. The consumption of non-renewable resources after 100 years are 193,950 GJ (133.5 kWh/m2y); the GHG emissions are 15,300 t (37.8 kg of CO2 eq/m2y). In the pre-use phase, structures have the major impacts (50 %) and the load of system components is unexpectedly high (12 %) due to the ambition of on-site energy production. Conclusions: Paying attention to the operative energy consumption seems to address to only one third of the environmental impacts of buildings: the adoption of LCA as a tool to guide the design choices could help to identify the solution which ensures the lowest overall impact on the whole life, balancing the options of reducing the energy requirements, the on-site production from renewable sources and the limitation of the impacts due to building components (simpler and more durable)