A Parametric Study and Performance Evaluation of Energy Retrofit Solutions for Buildings Located in the Hot-Humid Climate of Paraguay—Sensitivity Analysis

Abstract

Nowadays, awareness concerning the need to use energy efficiently is increasing significantly worldwide, thus, improving the energy efficiency levels in the building sector has acquired high importance because of their energy saving potential. However, several intervention options are available to achieve high energy efficiency levels in buildings, and the choice must be made considering the efficiency of the solution and the costs involved. Considering this, the present research aimed to develop a parametric study of several energy retrofit solutions for buildings located in the hot-humid climate of Paraguay, in order to analyse their efficiency in terms of comfort rates and cooling energy needs. Furthermore, the Analytic Hierarchy Process (AHP) is employed as a decision-making method to choose the most suitable intervention considering the investment costs required. Thus, threshold values of thermal transmittance for the building thermal envelope components are established through a parametric study and sensitivity analysis of the simulations results. Considering that Paraguay does not have national building energy codes, the outcomes of this research will constitute a support and contribute for the thermal parameters regulation of buildings aiding to improve the energy efficiency of Paraguayan buildings.A parametric study is developed in this research, in which dynamic energy simulations of a building performed using the EnergyPlus software and DesignBuilder interface. The weather data employed is the default one available in DesignBuilder for Asunción (Paraguay). The weather station corresponds to the Silvio Pettirossi airport, and the dataset cover a period of 18 years, from 1982 to 1999 for most stations. These hourly weather data are 'typical' data derived from hourly observations which correspond to a record of multiple years, where each selected month is representative of that month for the period of record [21]. The parameters used as evaluation indicators were operative temperature (T op ), which is employed to determine the discomfort rates, and the energy requirement of the thermal zone under analysis. The internal and external surface temperatures (T si . and T se , respectively), and the heat transfer through the building's envelope are also studied.The discomfort rate is computed considering two methods: the former, according to the acceptable indoor operative temperatures for buildings in the Category II of the standard EN 15251 for the design of buildings without mechanical cooling systems [22], which employs the adaptive method [23]; and the latter, applying the statistic method, using fixed threshold values of comfort temperature. This approach was already adopted for the thermal comfort assessment of buildings by several scientific research [24][25][26][27][28][29].In order to set the fixed range for the city of Asunción, which does not have a national standard energy code, a scientific literature analysis was performed. The static models usually set fixed thresholds values of comfort tempera...

Assessment of Different Envelope Configurations via Optimization Analysis and Thermal Performance Indicators: A Case Study in a Tropical Climate

“…The authors in [30] compared various roof insulation layouts and achieved a reduction in energy consumption higher than 10%. Likewise, by considering four different roof configurations, the authors [18] found it possible to reduce the annual discomfort rate by 7.4% and the annual energy requirement by 37%.…”

“…A parametric study in hot-humid Paraguayan buildings [18] concluded that reinforcing exterior walls with 5 cm insulation may increase the annual comfort rate 7% and decrease the requirements of annual energy by 37%. Moreover, with WWR up to 15%, there is no need to improve glazing areas; simple shading devices can help increase natural ventilation rates, and thus comfort rates.…”

Economic and Energy Analysis of Building Retrofitting Using Internal Insulations

“…Energy consumption for hot water preparation was not analyzed. For the climatic data of Warsaw, for room type (1), the heating season reduction is from the value of E K,H,0 = 46.0 to E K,H,n = 42.9 kWh/(m 2 •a), for room type (2) from E K,H,0 = 61.1 to E K,H,n = 56.0 kWh/(m 2 •a) and for room type (3) from E K,H,0 = 83.1 to E K,H,n = 72.2 kWh/(m 2 •a). For all cases, the lowest final energy value was for insulation type B.…”

“…Reducing energy consumption in existing buildings has now become one of the most critical challenges in building construction, not only in cold climate region [1,2]. Activities undertaken in the area of building's retrofitting focus mainly on improving the thermal insulation of external walls.…”