Fabrizio Ascione

Transient heat transfer through walls and thermal bridges. numerical modelling: methodology and validation

The current advanced numerical codes for the energy audits carry out 0-dimensional simulation (i.e., one computational node representing the thermal zone), underestimating the effects of thermal bridges on the seasonal heating demand of buildings. The paper suggests a numerical resolution model, implemented in Matlab, aimed to be transferred in numerical engines for the hourly energy simulation. The proposed methodology solves common thermal bridges in buildings, evaluating their effects on the energy demand. Typical thermal bridges have been studied and implemented, analyzing the reliability of the methodology, in terms of accuracy, computational time, required sources, comparing the solutions with those derived by computational fluid dynamic codes. The method reveals very satisfactory results, both as regards the computational time and CPU sources required, as well as with reference to the reliability. Moreover, the solution stability is commonly very high, regardless the chosen computational time-step.

Technical and economic analysis of green roofs to reduce building cooling needs

Several public/private institutions, at international and national levels, consider green roofs effective energy efficiency measures. A large feasibility study of their technical and economical profitability is proposed here. The main heat transfer phenomena and a brief literature state of the art are presented. Congruent with the cost-optimal approach, the economic indicators are described, as well as the physical set of equations for evaluating the energy performances of green roofs. Moreover, the case studies are shown by describing the various climates considered, energy and water costs, efficiency of power systems, emissions factors, and all parameters necessary for suitable feasibility studies. Various climates and building technologies are taken into account, as well as common typologies of extensive green roofs. The results show a relative feasibility of green roofs, when the watering costs are limited, and if the buildings are not properly insulated, so that the installation of greenery, combined with the added thermal insulation, provides energy savings for both heating and cooling. A final section proposes some considerations for improving the profitability of green roofs by adopting rainwater harvesting systems.

Artificial Neural Networks for Predicting the Energy Behavior of a Building Category

Abstract The reliable assessment of building energy performance requires significant computational times. The chapter handles this issue by proposing an original methodology that employs artificial neural networks (ANNs) to predict the energy behavior of all buildings of an established category. The ANNs are generated in MATLAB by using EnergyPlus simulations for testing and training purposes. The inputs are properly set by means of a thorough preliminary sensitivity analysis. The final aim is a reliable assessment of the global cost for space conditioning as well as of the potential global cost savings produced by energy retrofit measures for each category’s building. The benefit is a huge reduction of computational times compared to standard reliable simulation tools. Definitely, this can support the diffusion of rigorous approaches for cost-optimal energy retrofits. Beyond the presentation of the methodology, this is applied to the office building stock of South Italy built in the period 1920–1970. The results show a high ANN reliability compared to EnergyPlus simulations, with regression coefficients ( R ) always higher than 0.98.

Cost-Effective Refurbishment of Italian Historic Buildings

Abstract This chapter investigates strategies for approaching the energy refurbishment of historic buildings, by proposing, beyond a general methodology aimed at guaranteeing feasibility of the design, its application to two cases studies in the context of South Italy, in a typical Mediterranean climate according to the Koppen classification. According to the latest international guidelines in matter of building energy efficiency and future trends, by 2020, a great effort should be applied to both new constructions and building refurbishments, to achieve goals of nearly zero-energy impacts or very low energy demand. Of course, the energy refurbishment of architectures characterized by historical or artistic values should not determine damage of the valuable peculiarities. In this study, by means of the proposed case studies, and thus an admirable Italian building, examples of an approach toward cost-effective and architecturally compatible actions are proposed, according to the European methodology of cost optimality. Moreover, by comparison with the feasible refurbishment of an existing building, the difference in energy retrofit designs of historical or modern edifices is evidenced. The proposed case studies are an educational ancient palace built beginning in the 12th century and, as an existing building, a railway station located in the same city. In both cases, replacement of components of thermal envelope and active energy systems will be applied, by evidencing that, based on the building peculiarities, technologies, architectural values, and kinds of loads, different boundary conditions imply different cost-optimal energy conservation measures.

Cost-Effective Energy Refurbishment of Health Care Facilities in Heating Dominated Climates of Italian Backcountry. The Case Study of the Hospital Veneziale of Isernia

Maximizing energy efficiency within hospitals and healthcare facilities is a major challenge for sustainable development and energy saving objectives. In this study, the case study of the public hospital of Isernia (Italian backcountry city) is proposed, being typical of the hospital building stock developed in reinforced concrete all around Italy in the last 40 years. Starting from deep on-site investigations, based on direct surveys and documents, a transient energy model has been developed and calibrated, in order to reproduce the present scenario. This, in a next phase, has been modified for proposing a multi-target optimization of energy performances, by taking into consideration all main uses (heating, cooling, ventilation, lighting, domestic hot water), by refurbishing the building envelope, active energy systems and providing energy conversion from renewables. The whole energy retrofit, formulated on the basis of a multi-stage optimization problem, resulted technically efficient and economically feasible. Moreover, the peculiarities of the case study and of the method make that investigation repeatable with reference to both studying approach and outcomes.