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The need to improve the energy efficiency of buildings has introduced the concept of nearly zero-energy buildings into European energy policies. Moreover, a percentage of the building stock will have to be renovated annually to attain high energy performance. Conventional passive interventions in buildings are focused on increasing the insulation of the building envelope to increase its energy efficiency during the operating phase. Often, however, intervention practices imply the incorporation of embodied energy into the building materials and increase the associated environmental impacts. This paper presents and evaluates a comparison of two different proposals for a real-world building renovation. The first proposal was a conventional project for energy renovation, while the second was a low-energy building proposal (following the Passivhaus standard). This study analysed the proposals using an integrated life cycle and thermal dynamic simulation assessment to identify the adequacy of each renovation alternative regarding the post-renovation energy performance of the building, including an evaluation of the introduction of a renewable insulation material into the low-energy building proposal, specifically a specific cork solution. The most significant conclusion was the convenience of the renovation, achieving energy savings of 60% and 80% for the conventional and Passivhaus renovations (ENERPHIT), respectively. The former supposed less embodied energy and environmental impacts but also generated less energy savings. The latter increased the embodied impacts in the building, mainly for the large amount of insulation material. The environmental implications of both proposals can be compensated for within a reasonable period of time, over 2 years in the majority of alternatives and impact categories. However, the ENERPHIT project was 30% better than the conventional proposal when the total lifespan of the building was considered. The introduction of cork did not fit the requirements for competing with the common non-renewable insulation materials because it did not imply better environmental performance in buildings, but cork insulation solutions currently present ample room for improvement. [ABSTRACT FROM AUTHOR]

Windows are central for the development of liveable nearly zero-energy homes and require careful consideration. Various studies have indicated that the effect of windows on energy consumption may change significantly with improved building insulation levels. Current guidelines on windows may therefore not apply in very well-insulated buildings, and more up-to-date information is needed about window solutions that are appropriate for the new conditions. This study maps the effect of multiple combinations of window size and basic glazing—and frame properties on energy, daylighting and thermal comfort in nearly zero-energy houses located in the European cities Rome and Copenhagen. The aim was to identify options that can support the easy and robust design of future homes with typical use of roof and façade windows. Hourly daylight levels were calculated in DAYSIM, while space heating demand and operative temperatures were calculated in EnergyPlus. The results support previous findings on the limited ability of nearly zero-energy buildings to utilise solar gains. It was found that U -values are becoming increasingly important for the energy performance of windows. The paper sketches the increased flexibility and related possibilities that may appear with improved roof window frame constructions and glazing U -values far lower than currently standard levels. [ABSTRACT FROM AUTHOR]

Abstract: Energy efficiency in buildings is essential for economic, social, and environmental reasons. Under current European legislation, buildings have to be certified with an energy efficiency index. To provide a fair comparison of the energy performance in buildings we need a global and unified representation. In this paper we propose the Energy Efficiency Ontology (EEOnt) to provide a foundation upon which this requirement can be built. EEOnt extends the applicability of other ontological models of buildings incorporating energy efficiency data and knowledge that can be calculated with high spatial and temporal resolution in what we call an Energy Efficiency Landscape (EELB). These EELB''s provide significant information which allows a detailed diagnosis of the energy efficiency within the building. Consequently, EEOnt is capable of representing buildings and energy efficiency in a unified way. Furthermore, it supplies a tool for managing the energy efficiency in buildings and constructing national inventories. These two features link the global and particular needs of governments and users, thus becoming key to both improve the energy efficiency in buildings and to implement viable certification schemes. [Copyright &y& Elsevier]

Abstract: The age of European existing building stock and the very low growth rate make energy retrofit a critical issue at the moment. The spreading of good practices is strongly hampered by their cost effectiveness. National legislation thermal requirements for retrofitting works play a fundamental role. If they are too strict, the initial economic investment could be too high if compared with energy savings achievable. The paper refers to a case study of improving fabric thermal performance of stone masonry buildings located in Cagliari – Italy. They were built in 1950s. The economic feasibility of different energy efficiency retrofits is evaluated. Two different scenarios are analyzed: the former according to the earlier Italian legislation (valid from 2006 to 2008), the latter according to the latest and strictest measures (valid from 2010). The results show that heavy thermal performance upgrades, even though compulsory, are not completely cost-effective in a mild Mediterranean climate area as far as payback time is concerned. National subsidy policies can improve the economic return on the investment. The impact of present Italian incentives has also been evaluated. [Copyright &y& Elsevier]