PSI - Issue 11

Fabiana Silvero et al. / Procedia Structural Integrity 11 (2018) 52–59 Silvero, et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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consumption, being one of the largest end-use sectors worldwide, and a large share of this consumption is used for space conditioning (Lucon et al., 2014). Considering this, Levine, et al. (2007) analysed the global potential reduction of greenhouse gases (GHG) emission around the world for the building sector and found that there is a global potential to reduce approximately 29% of the projected emissions by 2020 cost-effectively in this sector, through the implementation of energy efficiency (EE) measures. Some developed countries have already managed to reduce their total energy use through the implementation of stricter building codes. In developing countries like Paraguay, GHG emissions from buildings sector are not very representative, however, considering future climate scenarios, is very likely that the air temperature in the country will increase due to CC effects, affecting the buildings’ indoor thermal comfort and leading to a higher energy consumption for space cooling (ECLAC, 2014). Thus, EE is presented as an adaptation and mitigation strategy to these effects. Nevertheless, finding the most suitable intervention for heritage buildings represents a challenge since the best ene rgy retrofit solution has also to achieve the preservation of the building’s original characteristics. Currently, one of the most used methods to improve the buildings EE is the use of thermal insulation. Indeed, in the last years, the use of thermal insulation materials has increased significantly because of EE requirements set in construction standards of several countries. These standards set specific requirements for the buildings’ envelope to achieve indoor thermal comfort without large energy needs. One of the most analysed parameters is the thermal transmittance (Noailly, 2012). This parameter represents the heat transfer occurring through a building envelope component considering a one-dimensional steady-state thermal conduction without considering any dynamic behaviour (Verbeke et al., 2017). However, building envelope components are subject to variable boundary conditions, since they are exposed to variations in usage and environmental conditions such as time-varying outdoor temperature and solar radiation, which cause a variable heat flow rate through the components over time (CEN, 2007). Thus, to guarantee a suitable thermal response to the external heat fluxes and ensuring adequate internal comfort it must be considered the dynamic thermal properties of the envelope components (Gasparella et al., 2011). The Standard EN ISO 13786:2007 (CEN, 2007) accounts for the dynamic thermal characteristics of a building component considering sinusoidal boundary conditions, where the boundaries are submitted to sinusoidal variation of heat flow rate. Some of the parameters considered are: thermal mass ( ); thermal transmittance ( ); time shift ( ); periodic thermal transmittance ( ); decrement factor, ( ) and internal areal heat capacity ( ). The current study aims to understand the interdependency between the cited thermal parameters and to analyse the influence of these thermal parameters on the indoor comfort level of a residential heritage building located in a hot-humid climate, aiming to achieve better levels of EE. The first stage involves evaluating the thermal performance of the dwelling in its original state. Subsequently, several retrofitting solutions for the building envelope were simulated resourcing Energy Plus software and Design-Builder interface. In a general approach, this research proposes energy efficient solutions that guarantees better living conditions for inhabitants and collaborates with the general objective of the city, which is to return to the Historic Centre its character of residential nucleus lost in the last decades. 2. Methodology The development of this research has mainly three steps: to calculate the thermal parameters ( , , , , , 1 ) of the envelope components in the building original state and the improved solutions designed; to evaluate the thermal comfort of the building through dynamic simulations in the original state and in the energy efficient versions; and finally, to analyse and discuss the results and draw up the main conclusions. In this way, a parametric study is proposed, where dynamic simulations of a building are carried out using Energy Plus software and Design Builder interface. The weather file used corresponds to the default one available in Design-Builder for Asunción. In the following subsection, the description of the case study, the input parameters for the thermal comfort evaluation of the building and the evaluation indicators are defined.

2.1. Description of the case study

The case study corresponds to a residential heritage building with Italian neoclassical architecture. It was constructed between the years 1900-1930 and is listed as cultural property of the city, reason why the external facade cannot be modified. The building consists of a two-storey structure and, according to their area and