Preliminary Energy Audit of the Historical Building of the School of Engineering and Architecture of Bologna

AbstractEnergy efficiency has become a common target for every building: the European Directive 2010/31 provides that by 2020 every new building must consume very little fossil energy (Nearly Zero Energy Building) and from 2018 also public buildings will have to meet this requirement. Although the objectives imposed by the new legislative references are very clear, modify the existing heritage in many cases is not easy. For example, many buildings, including public ones, in addition to consuming a lot of energy, are also constrained by the Superintendence for Architectural, Landscape, Historical and Artistic Assets; therefore it becomes difficult to improve their energy performance. This paper presents a preliminary energy audit of the historical building of the School of Engineering and Architecture in Bologna (Italy). It was built in the 30s, is one of several public buildings of particular historical and architectural interest for the city of Bologna and it is constrained architecturally. Special attention has been focused on the energy consumption for heating during the winter season. The audit was carried out taking into account the European standard EN 15603, using the method of energy signature based on actual consumption. The results of the energy analysis show an energy saving of about 15% with operations building management and over 30% with improvements of the heating system and the windows

Overall Indoor Quality of a Non-renewed Secondary-school Building

This work is the result of a field study about overall comfort aspects performed in a secondary-school building in the surroundings of Bologna during the winter season. The campaign aimed at describing overall comfort aspects of the school both from an objective and a subjective point of view, thus a questionnaire was administered to pupils during ongoing lessons to compare physical measurements and subjective responses. The monitored attributes and items concerned typical indoor quality aspects: acoustical, thermal, indoor air, and visual quality. As weak points emerged from the data analysis, possible solutions are illustrated, focusing on acoustics and optimizing effectiveness and cost

Acoustical comfort in university lecture halls: simulating the dynamic role of occupancy

The acoustic comfort in teaching environments is generally determined through requirements concerning reverberation time, speech intelligibility and HVAC noise. The presence of students reduces the reverberation time but concurrently increases the background noise, that undermines the focus of students and the vocal effort of teachers. A double set of measures were acquired in two university lecture halls in unoccupied and occupied state to investigate the consequences of occupancy variations. Acoustic simulations allowed to assess the dynamic effects of the occupancy detecting the differences of speech intelligibility. Predicting the student activity may return reliable outcomes improving the quality of lessons

Acoustic Measurements on a Sonic Crystals Barrier

Abstract This paper describes the measurements carried out over a sonic crystal at normal incidence according to EN 1793-6, which allows to cancel ground reflection and edge diffraction by applying suitable windowing techniques. The sample was made of hollow PVC pipes with an outer diameter of 160 mm arranged in a square lattice with lattice constant 0.2 m. FE predictions were computed in order to verify the experimental campaign. A good match between simulations and measurements was found in the first sonic Bragg band gap. As expected, increasing the number of rows does not translate into a shift of the Bragg band gap but into an increase of the insulation properties

Acoustic design of a multipurpose hall inside a former church

The present work is about an acoustic design for a former church converted into a multi-purpose auditorium. The current status of the hall has been classified by means of an acoustic measurements campaign complying with technical standards requirements. A numerical model, which has been calibrated through the measured values, led to the development of the acoustic design that includes sustainable and not-invasive interventions. In contrast with the practical habits, which would use a large amount of sound absorbing materials, an array of suspended reflecting panels over the musicians positions has been introduced. Exploiting the reflecting and scattering properties of those objects, sound clarity and speech definition improve. All the treatments are validated using numerical simulation softwares in order to estimate the efficiency of the whole improvement proposal

A trial acoustic improvement in a lecture hall with MPP sound absorbers and FDTD acoustic simulations

Sound absorbing micro-perforated panels (MPPs) are being increasingly used because of their high quality in terms of hygiene, sustainability and durability. The present work investigates the feasibility and the performance of MPPs when used as an acoustic treatment in lecture rooms. With this purpose, three different micro-perforated steel specimens were first designed following existing predictive models and then physically manufactured through 3D additive metal printing. The specimens\u2019 acoustic behavior was analyzed with experimental measurements in single-layer and double-layer configurations. Then, the investigation was focused on the application of double-layer MPPs to the ceiling of an existing university lecture hall to enhance speech intelligibility. Numerical simulations were carried out using a full-spectrum wave-based method: a finite-difference time-domain (FDTD) code was chosen to better handle time-dependent signals as the verbal communication. The present work proposes a workflow to explore the suitability of a specific material to speech requirements. The measured specific impedance complex values allowed to derive the input data referred to MPPs in FDTD simulations. The outcomes of the process show the influence of the acoustic treatment in terms of reverberation time (T30 ) and sound clarity (C50 ). A systematic comparison with a standard geometrical acoustic (GA) technique is reported as well

Fixed Grid Numerical Models for Solidification and Melting of Phase Change Materials (PCMs)

Phase change materials (PCMs) are classified according to their phase change process, temperature, and composition. The utilization of PCMs lies mainly in the field of solar energy and building applications as well as in industrial processes. The main advantage of such materials is the use of latent heat, which allows the storage of a large amount of thermal energy with small temperature variation, improving the energy eciency of the system. The study of PCMs using computational fluid dynamics (CFD) is widespread and has been documented in several papers, following the tendency that CFD nowadays tends to become increasingly widespread. Numerical studies of solidification and melting processes use a combination of formulations to describe the physical phenomena related to such processes, these being mainly the latent heat and the velocity transition between the liquid and the solid phases. The methods used to describe the latent heat are divided into three main groups: source term methods (E-STM), enthalpy methods (E-EM), and temperature-transforming models (E-TTM). The description of the velocity transition is, in turn, divided into three main groups: switch-o methods (SOM), source term methods (STM), and variable viscosity methods (VVM). Since a full numerical model uses a combination of at least one of the methods for each phenomenon, several combinations are possible. The main objective of the present paper was to review the numerical approaches used to describe solidification and melting processes in fixed grid models. In the first part of the present review, we focus on the PCM classification and applications, as well as analyze the main features of solidification and melting processes in dierent container shapes and boundary conditions. Regarding numerical models adopted in phase-change processes, the review is focused on the fixed grid methods used to describe both latent heat and velocity transition between the phases. Additionally, we discuss the most common simplifications and boundary conditions used when studying solidification and melting processes, as well as the impact of such simplifications on computational cost. Afterwards, we compare the combinations of formulations used in numerical studies of solidification and melting processes, concluding that “enthalpy–porosity” is the most widespread numerical model used in PCM studies. Moreover, several combinations of formulations are barely explored. Regarding the simulation performance, we also show a new basic method that can be employed to evaluate the computing performance in transient numerical simulations

PROGETTO INVOLUCRO: TRASMISSIONE LATERALE ATTRAVERSO GIUNTI IN CLT E GIUNTI MISTI MURATURA-CLT

Il progetto Involucro è un progetto di ricerca finanziato dalla Regione Emilia-Romagna nell’ambito del POR-FESR 2014-2020 ed ha lo scopo di ottenere un sistema di facciata ventilata ad alte prestazioni termiche ed acustiche attraverso un’indagine sperimentale in condizioni reali, provando diverse soluzioni innovative. In questo articolo verranno mostrati i primi risultati della campagna di misure di trasmissione laterale condotta sulla struttura degli edifici test realizzati per il progetto

Criteri metodologici di valutazione e valori guida per il rumore: una proposta per gli ambienti scolastici che considera l’apprendimento degli allievi e lo sforzo vocale degli insegnanti

Introduzione: il Sottogruppo coordinato da AIA con la collaborazione di AIDII e SIMLII si po-ne l’obiettivo di affrontare le tematiche poco note attinenti il disturbo da rumore nei luoghi di vita e di lavoro. Il primo lavoro del Sottogruppo riguarda gli ambienti scolastici. In questi ambienti, condizioni acustiche inadeguate, quali l’elevato rumore di fondo e l’eccessiva riverberazione, producono perdita di concentrazione e affaticamento nei docenti e discenti (1), riducono l’intelligibilità della parola compromettendo l’apprendimento degli allievi (2), determinano negli insegnanti un elevato sforzo vocale i cui effetti si manifestano come sintomi di una vera e propria malattia professionale (3). Obiettivi: nel lavoro si riportano i metodi di misurazione e di calcolo dei parametri acustici fondamentali per la valutazione dell’adeguatezza degli ambienti scolastici (livello del rumore di fondo, rapporto segnale-rumore, tempo di riverberazione, chiarezza, speech transmission index, livello di sforzo vocale), nonché i valori guida riferiti a detti parametri e indicazioni sulla ristrutturazione-progettazione acustica delle scuole. Metodi: l’intelligibilità del parlato è una precondizione essenziale in un ambiente destinato all’apprendimento; si valuta tramite alcuni dei parametri sopra indicati, misurabili e oggetto di norma. È possibile inoltre ricorrere a prove soggettive che consistono in test d’ascolto con materiale vocale registrato da svolgersi in campo o in laboratorio simulando condizioni acustiche ambientali differenti. Il livello di sforzo vocale è valutato tramite monitoraggio dell’attività vocale degli insegnanti per l’intera giornata lavorativa, mediante un dispositivo (Voice Care) costituito da un microfono a contatto da fissare in corrispondenza della fossetta giugulare e da un data logger. Da osservare che il monitoraggio dell’attività vocale può costituire uno strumento di prevenzione d’insorgenza di patologie della voce. Nell’ambito dello studio sono stati rilevati i requisiti acustici di circa cinquanta aule, sono stati eseguiti test d’ascolto su circa ottocento bambini e ragazzi, è stato monitorato lo sforzo vocale di alcune decine di insegnanti. Risultati e discussione: i valori guida sono stati ripresi dalla legislazione straniera e dalla letteratura scientifica e sono stati verificati e validati sperimentalmente al fine di giungere a una proposta integrata nazionale. In Italia la normativa sugli ambienti scolastici risale al 1975: oltre a non essere applicata, essa soffre del fatto di definire requisiti acustici meno stringenti di altri Paesi dove tali requisiti sono aggiornati con il progredire della ricerca. L’AIA sta operando affinché i valori guida proposti siano adottati in sede legislativa al fine di migliorare l’apprendimento e la salute nelle scuole