Numerical analysis of passive strategies for energy retrofit of existing buildings in Mediterranean climate: thermal mass and natural ventilation combination

Carlotta Cecchini,Letizia Martinelli,Filippo Calcerano

doi:10.1051/sbuild/2017003

Abstract

The study investigates the potential of coupling natural ventilation and thermal storage systems to improve hygrothermal comfort and reduce energy consumption during summer season in an existing building in the Mediterranean. It aims at bridging the knowledge gap between designers, researchers and building scientists, fostering a multidisciplinary approach and promoting numerical simulation of the energy performance of buildings within architectural professional practice. The study analyses the interaction between six natural ventilation systems (single sided ventilation through facade openings; cross ventilation through facade openings, inlet wind tower, thermal chimney, evaporative cool tower, earth pipes) and with two thermal storage typology (heavy and medium-light) within four strategic Italian location (Rome, Naples, Messina and Catania). For each interaction we perform a numerical dynamic simulation of indoor comfort, indoor air quality and energy consumption during the summer period, on a reference building model corresponding to the most common Italian typology. Results show that the use of the chosen systems ensures significant reductions of discomfort hours and energy consumption in all configurations. The study also highlights the high efficiency of non invasive systems (single-sided and cross ventilation with automatic control present discomfort hours reduction and energy consumption reduction above 68% for all combinations) and the significant influence of the daily thermal range value on the performance of systems without air pre-treatment.

Highlights

The global consumption of primary energy in Europe depends for over 40% on buildings’ demand: the existing building stock uses approximately 40% of economy’s incoming materials and is responsible for over 45% of the total amount of greenhouse gases produced [1].An increasing concern about rational use of energy and the limits of land urbanization identifies the great potential of energy refurbishment of existing buildings [2,3] for energy consumption reduction and environmental impact mitigation
Single-sided ventilation (SSV) with automatic control shows a Discomfort Hours Reduction Potential (DRP) higher than 68.6% for all scenarios and a general better performance of the heavy envelope compared to the medium-light envelope, but the percentage performance difference between the two scenarios varies among the cities
The present study analyses the contribution of natural ventilation systems, coupled with thermal storage building elements, to summer indoor comfort for different cities in Italy with different climatic condition and thermal ranges

Summary

Introduction

The global consumption of primary energy in Europe depends for over 40% on buildings’ demand: the existing building stock uses approximately 40% of economy’s incoming materials and is responsible for over 45% of the total amount of greenhouse gases produced [1].An increasing concern about rational use of energy and the limits of land urbanization identifies the great potential of energy refurbishment of existing buildings [2,3] for energy consumption reduction and environmental impact mitigation. Since the industrial revolution and its confidence in the limitless availability of low-cost energy, environmentally conscious design weakened, while the overall use of HVAC systems replaced traditional know-how based on passive thermal and hygrometric control [8].

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