tThe paper presents a methodology to define reference values regarding building environmental impacts,energy outputs, and global costs. Four exemplary Italian residential categories were analyzed, focusingon the recent existing stock and on the most common kinds of houses. Buildings were subjected to LifeCycle Assessment (LCA) analyses, through SimaPro software, in order to define specific values linkedto the environmental impacts and to the total energy spent. The amount of energy related to the usephase, including heating, domestic hot water, and cooling systems, was estimated by using the energysimulation program EnergyPlus. Building economic performance was analyzed through Life Cycle Costing(LCC) analyses, with the global cost approach. The results showed that the use phase implied the largestcontribution to the environmental and energy impacts; instead the pre-use phase was predominant inlife cycle costs. Furthermore, since a considerable amount of consistent data was used for this study, theoutcomes could be treated as reliable for the definition of benchmarks. For instance, the results indicatedthat, during the whole life cycle, Italian residential buildings could spend around 140 kWh/m2, with aproduction of about 35 kg CO2eq/m2each year, reaching a global cost of nearly 1420 D/m2

Highlights:• Business models and sustainability analyses in building projects are investigated.• An analytic process towards sustainable business models of such projects is proposed.• The application of the analytic process to a case study is shown.• Quantitative analyses can foster sustainable business models in building projects.

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Buildings currently play a fundamental role for the achievement of the sustainable development goals as they are responsible for several environmental, social, and economic impacts. Energy renovation projects of existing buildings can support the reduction of environmental impacts by leading, at the same time, to economic and social advantages. In this paper, the life cycle assessment and life cycle costing methodologies were used in a combined performance assessment applied to a case study, i.e., the energy renovation project of a single-family house in Norway. Several scenarios based on alternative energy efficiency measures were analyzed, and life cycle environmental and economic indicators were computed, i.e., global warming potential (GWP), cumulative energy demand (CED), and net present cost (NPC). The results demonstrated the close to negative linear regression between the environmental and economic indicators computed. However, the values of CED and GWP for the best scenarios in environmental terms were respectively 50% and 32% lower than the values of the worst scenarios, while their NPC was around 6% higher than the lowest values. The findings can be helpful in the decision-making context towards a meaningful combination of environmental and economic assessments in building energy renovation projects for selecting the most sustainable scenario.

The paper investigates the effects on building indoor air quality (IAQ) resulting from the choice of different design ventilation rates. A reference residential building was analysed by means of the multizone modelling software CONTAM, by monitoring the concentration of two pollutants: occupant-generated carbon dioxide (CO 2) and total volatile organic compounds (TVOC) from indoor sources. A demandcontrolled ventilation strategy based on building occupancy was implemented and users' presence schedules were defined. Specifically, the evolution of indoor pollutant concentrations was investigated when the design ventilation rates, recommended by two IAQ-related standards (the Italian UNI 10339 and the European EN 15251), were implemented through a mechanical ventilation system. Different results regarding the IAQ level were achieved accordingly to the dissimilar ventilation rates. After a statistical analysis on the distributions of CO 2 and TVOC concentrations, EN 15251 outcomes showed overall better results of the analysed statistical metrics, i.e. prevalence, sensitivity and accuracy. Indeed, the EN 15251 design airflows led to indoor conditions that were more often classified either in the correct air quality class or in a higher class. Finally, a better alignment between the national and European IAQ standards is recommended, especially in terms of airflows, air quality classes and pollutant limit values.

As the existing building stock is responsible for high energy use and greenhouse gas emissions, energy upgrading projects have been acknowledged as crucial for the energy performance improvement of existing buildings, as well as for environment preservation and rational use of resources. The aim of this article is to investigate the definition of a nearly zero-energy building (nZEB) level for the energy upgrading of single-family houses. In particular, the findings from a research project, i.e., “energy upgrading of wooden dwellings to nearly zero energy level” (OPPTRE), are presented and discussed. A core task of OPPTRE was to carry out an architectural competition, where six interdisciplinary teams proposed innovative solutions for upgrading to a nZEB level representative Norwegian wooden single-family houses, from the period 1950-1990. The upgrading measures proposed in the OPPTRE competition focused on several aspects, such as architectural quality, indoor thermal environment, energy use/generation, carbon footprint, and cost effectiveness. General principles for a nZEB level achievement in upgrading projects are discussed in this article, as deducted from the evaluation of the results of the OPPTRE architectural competition. In particular, the focus is on examining the solutions proposed for upgrading building envelope and technical building systems. Energy use, energy generation, investment costs, and CO2 emissions are examined across the various OPPTRE projects, striving to define a trade-off among different parameters for the achievement of a nZEB level. The findings of this paper support the creation of knowledge in nearly zero-energy upgrading of wooden single-family houses, aiming to a more systematic definition of a nZEB level in such projects. This can be relevant for several stakeholders, such as governmental institutions, homeowners, builders, and private or public decision makers, towards the market uptake of nZEB upgrading by 2030.

Wooden ventilated pitched roofs represent a widely spread construction solution in Nordic countries. They have several benefits, including the drainage of excessive moisture from the construction and the reduction of the surface temperature to prevent snow melting and thus icing at the eaves and gutters. Modelling ventilated components is complex and requires a thorough understanding of the phenomena occurring in the air cavity, where convection plays a central role in the heat transfer process. The approach and the assumptions adopted for the roof model are therefore crucial to investigate the thermo-fluid dynamics in the air cavity. A literature review showed the need for comprehensive numerical and experimental research focusing on ventilated roof constructions, especially for Nordic climates. This article presents the thermo-fluid dynamic modelling of a ventilated pitched roof, which belongs to a full-scale experimental building located in Trondheim (Norway), the ZEB Test Cell Laboratory. A model of the roof was created using the finite element method-based software COMSOL Multiphysics. Transient simulations were performed in different climate conditions and the results of temperature and air flow speed along the cross section of the roof were compared with measurement data for validation. The simulation results show a good agreement with measurement data for both air speed and temperature in the air cavity, particularly in the summer day. The deviations in the numerical results will be object of study in future research, where the modelling approach will be further explored by testing different inputs, including boundary conditions and turbulence models.