Energy analysis of a residential building in Southern Brazil

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Energy analysis of a residential building in Southern Brazil 
 
Felipe De Oliveira Correa1, Letícia Mara Beliski2 
 
Energy Engineering, Federal University of Santa Catarina 
Araranguá – SC 88905-355, Brazil. 
 
 
Abstract 
 
The residential sector accounts for most of electricity consumption in Brazil. In addition, in 
order to compensate for poor architectural designs, air conditioning systems are used to 
increase the thermal comfort, consequently increasing the expense with electric energy. In this 
context, this paper evaluates the consumption of electricity and thermal comfort in a 
residential building with a popular profile located in the city of Araranguá, Santa Catarina. 
Also, this paper proposes improvements that would suit the building in the climate location 
that the building belongs. The results show that improvements aimed at protecting the 
building of solar radiation in the summer and increasing thermal inertia generate energy 
savings and increase thermal comfort. The proposed improvement that made the better result 
was the utilization of reflective paint on the roof, generating electricity savings of 11.9 kWh / 
year and reducing the internal average temperature of the building by up to 2ºC. 
 
Keywords: Energy simulation. Energy efficiency. Constructive guidelines. 
 
 
 
1 Introduction 
 
The consumption of electricity in buildings is quite significant in Brazil, reaching 50% 
of the total electricity consumed in this country. In addition, existing buildings have potential 
savings of 30%, and savings can reach 50% in new buildings [1]. Among the many factors 
that cause such large energy consumption are inefficient lighting systems, outdated equipment 
and improper scaling of air conditioning systems. In fact, generally such air conditioning 
systems are used to correct poor architectural designs [2]. 
Another important point of analysis to be evaluated in buildings is thermal comfort. 
This aspect often does not receive the necessary attention in residential architectural projects, 
especially in popular houses [2]. 
Many studies have evaluated the effectiveness of actions to reduce electric energy 
consumption and thermal comfort. A study by Matos (2007) evaluated constructive 
 
1
 Corresponding author: felipedeoliveiracorrea@hotmail.com 
2
 Corresponding author: leticiapuhl@hotmail.com 
 
2 
 
techniques aiming at a better thermal comfort in a building in the city of Florianópolis, Brazil. 
In that study the author evaluated recommendations of technical standards and carried out 
simulations to evaluate its effectiveness. The study showed that actions such as protection of 
solar radiation and better utilization of natural ventilation have significant results [3]. 
A study by Tavares and Martins (2007) evaluated different possible improvements to 
modernize a public building in the central region of Portugal. The simulations evaluated 
constructive materials, lighting system, air conditioning system, window frames, etc. In that 
paper, the authors emphasize the importance of correct size and model of Heating, Ventilation 
and Air Conditioning (HVAC) system selected for different buildings, since these equipments 
are responsible for a big amount of energy consumption in buildings [4]. 
Insulation is often analyzed as one of the main potentials of savings in buildings. Also, 
insulations is considered as one of the main alternatives to increase thermal comfort. This is 
largely due to the poor quality of thermal insulation of the building materials used in most of 
the buildings, especially in Brazil. As Boyano et al explain, there are many factors that 
influence HVAC expenditure such as location, climatic conditions, construction techniques, 
and technologies used. However, improvements in thermal envelope usually carry out energy 
savings and better thermal comfort [5]. 
Although there are studies that evaluate improvements in buildings to reduce energy 
consumption, studies focused on different locations with different constructive 
recommendations still have to be developed. This will contribute for technological 
development of HVAC systems, lighting, materials and other human comfort-designed 
systems specific for different locations [6]. 
In view of the importance of better energy use and techniques to increase thermal 
comfort in buildings, this paper proposes to perform an energy analysis in a residential 
building located in South of Santa Catarina State, Brazil. The analysis includes both energy 
consumption and thermal comfort of the occupants. This study is based on relevant literature, 
constructive guidelines and eQUEST, CST and Energy3D simulations. 
 
 
2 Methods 
 
First, the simulation of the building was made with the actual parameters. Second, 
the results were validated comparing them with real consumption data. Then, the 
3 
 
improvements to save energy and increase thermal comfort were simulated and the results 
were analyzed. 
The energy efficiency improvements proposed by this paper were evaluated through 
computational simulations. The simulations were done through eQUEST software. This 
software was developed by James J. Hirsch to perform energy analyzes of buildings [7]. 
Therefore, eQUEST will be used to evaluate the energy consumption and thermal 
performance of the building. 
The simulations were validated comparing the results with the real consumption data 
of the building. In this step, the simulation was done with the actual parameters of the 
building to obtain the actual values and the end use of electric energy consumption. In 
addition, the simulation provides the internal temperatures of the building, time of maximum 
thermal load, heat rate exchanges and several other results of interest. 
In order to obtain a valid comparison, it is necessary to obtain a history of 
consumption of long periods to minimize atypical deviations during a certain period [8]. For 
example, one week of atypical consumption has more influence on one year than in five year 
of consumption data history. 
Increasing thermal comfort of the building analyzed is one of the goals of this paper. 
Therefore, this paper presents improvements to reduce the internal temperature of the building 
in the summer. The values of higher internal temperature were used to perform a thermal 
comfort analysis using Analysis CST software. Analysis CST is a software that uses the 
Predicted Average Voting method to estimate the comfort feeling of occupants in a building. 
As Lamberts et al (2007) explains, this method uses information such as occupant dress, wind 
speed and environmental information to calculate the discomfort of occupants in an 
environment. 
 
 
3 Experimental details 
 
The building chosen for this energy analysis is located in the city of Araranguá, Santa 
Catarina, Brazil (Lat.:-28.56.05/Long.:-49.29.09). The building and the footprint is shown in 
Figures 1a and 1b respectively. In the footprint shown in Figure 1b, number 1 is the living 
room and kitchen. Number 2 is an office. Number 3 is the bathroom. Number 4 is the 
bedroom. Number 5 is the laundry. Number 6 is the garage. 
 
4 
 
 
Figure 1 – a: Image of the building; b: Footprint of the building. 
 
In this energy efficiency analysis, the first step was to obtain all the parameters that 
affect the energy consumption and thermal comfort of the building. Among the parameters of 
interest are construction materials properties, air conditioning system, occupation, electric 
equipments, fenestration, building location, geometry, and energy use profile. 
The building has electrical and electronic equipment that does not consume large 
amounts of energy. The lighting system is basically formed by bulb fluorescent
lamps. The 
walls are made with clay brick and plaster. The foundation is in contact with the ground and it 
has 10 cm of concrete before ceramic floor. The roof has wood ceiling without thermal 
insulation and fiber cement tiles. The doors are hard wood and simple glass windows without 
film. The occupation is stable throughout the year. There are air conditioning systems in the 
bedroom and office. Both air conditioning systems are Split type with cooling capacity of 
9,000 Btu, but only the office has heating system by heat pump. 
The occupation of the building consists of two adults. One of them remains in the 
building 24 hours and the other 12 hours, from 6 pm to 6 am. The occupation is continuous 
throughout the year, however there is only one atypical period during the last week of the 
year, corresponding to vacations. 
Table 1 gives some parameters used in the simulation. It shows the Global Heat 
Transfer Coefficient of walls and roof, the Solar Factor of the window glasses and the 
installed electric load. 
 
 
 
 
3 
1b1a
6 
2 
 
4 
5 1 
1 
5 
 
Table 1 – Parameters used in the simulation [2] [9]. 
Parameter Value 
Wall Global Heat Transfer Coefficient 2.28 W/m2K 
Roof Global Heat Transfer Coefficient 2.00 W/m2K 
Glasses Global Heat Transfer Coefficient 8.35 W/m2K 
Glasses Solar Factor 0.914 
Installed Eletric Load 5,700 W 
Air Conditioning System Coefficient of Performance 5.31 
Fundation 10 cm concrete 
 
The first simulation was made to compare the results with the real consumption data. 
Figure 2 shows an image of the building generated by software eQUEST. 
 
Figure 2 – Image generated by software eQUEST. 
 
The comparison between the simulation results and the real consumption data can be 
seen in Table 2. Although there are some differences between the values, the consumption 
profiles in each month follow the same trend. The main factor that influences the energy 
consumption of the building is the weather. In the summer there is big energy consumption 
for cooling. On the other hand, in the winter there is big energy consumption due to space 
heating and water heating. In fact, the water heating system in this building uses electricity as 
energy source. 
 
 
 
 
 
 
6 
 
Table 2 – Comparison between real consumption data e simulation results. 
Month Real consumption data Simulation results 
 January 131 kWh 127 kWh 
 February 124 kWh 115.1 kWh 
 March 138 kWh 123.8 kWh 
 April 129 kWh 114.6 kWh 
 May 124 kWh 122.8 kWh 
 June 128 kWh 121.7 kWh 
 July 120 kWh 122.1 kWh 
 August 135 kWh 119.5 kWh 
 September 132 kWh 118.1 kWh 
 October 136 kWh 120.5 kWh 
 November 136 kWh 121.4 kWh 
 December 131 kWh 125.8 kWh 
Total 1.704 kWh 1,452.5 kWh 
 
The values on Table 2 show that the simulation follows the same trends of real 
consumption data, where the annual energy consumption is 1,452.5 kWh. Also, the software 
provides the end use of electric energy. The results are shown in Figure 3. 
 
 
Figure 3 – End use of electric energy. 
 
Figure 3 clearly shows the influence of weather on the end use of electric energy. In 
the summer, due to the higher temperatures, the cooling consumption increases. On the other 
hand, during winter the energy consumption for space heating and water heating are higher. 
Expenses with lighting and electric equipment are practically constant throughout the year. 
Furthermore, the software provides the maximum thermal load value for each space, 
as can be seen in Table 3. The higher thermal load occurs in the living room and kitchen. 
7 
 
Basically, there are five spaces in the building. Two of them have split air conditioning 
system. 
 
Table 3 – Maximum thermal load value of the building. 
Space Maximum thermal load 
Maximum temperature Minimum temperature 
Dry bulb Wet bulb Dry bulb Wet bulb 
Living room and 
kitchen 
11,101 Btu 34 ºC 27 ºC 5ºC 4ºC 
Bedroom 3,603 Btu 28 ºC 22 ºC 5ºC 4ºC 
Office 6,316 Btu 29 ºC 24 ºC 5ºC 4ºC 
Bathroom 1,649 Btu 28 ºC 22 ºC 5ºC 4ºC 
Laundry 4,396 Btu 31 ºC 26 ºC 5ºC 4ºC 
 
The results in Table 3 show that the split air conditioning systems in the bedroom and 
office, both of 9,000 Btu, are somewhat oversized, because these spaces have maximum 
thermal loads lower than the cooling capacity. However, the results show that the present air 
conditioning systems guarantee the conditioning of these spaces. Therefore, for those spaces 
where there are air conditioning systems, the improvements proposed by this paper aim to 
reduce the values of thermal load. Consequently, the improvements proposed by this paper 
aim to reduce electric energy consumption for cooling. 
To perform the thermal comfort analysis through Analysis CST software, the dressing 
parameter of the occupants was considered as 0.31 clo and they were doing office activities 
(0.70 W/m2 and 1.2 met). The ambient air temperature parameter was obtained through 
simulations by eQUEST software. The average radiant temperature was considered equal to 
ambient air temperature, air velocity equal to zero and air humidity of 60%. 
When analyzing thermal comfort of the building before the proposed improvements, 
it shows that the building has a high rate of discomfort. The month that presented the highest 
average temperature was January with 28.1ºC in the living room and kitchen. The analysis 
with Analysis CST software using this temperature and other parameters shows that the 
Percentage of Unsatisfied People (PPD) reaches 22%. In other words, this result shows that 
the building has a high rate of discomfort. 
 
3.1 Proposed improvements 
 
8 
 
In order to propose improvements to reduce electric energy consumption and increase 
thermal comfort, some guidelines were taken as a basis. First, the software Analysis Bio was 
used to help in choosing improvements for this building. Analysis Bio is a software that 
assists in the process of adapting buildings to the local climate [10]. In this software the user 
has to choose the location of the building to be analyzed, and then the software gives building 
guidelines to safe electric energy based on the climate characteristics of the location. 
According to the recommendations given by Analysis Bio software for the building analyzed 
in this paper, the improvements should be increase ventilation, high thermal inertia, 
evaporative cooling and passive solar heating. 
Second, the constructive recommendations given by Brazilian Standard NBR 15.220 
were used to obtain constructive guidelines based on the climate of the city of Araranguá. The 
building guidelines guiven by Brazilian Standard NBR 15.220 are solar heating, thermal 
inertia, cross ventilation and reflecting surfaces [11]. 
Finally, because a big amount of the thermal load in summer comes from the solar 
radiation incident in the building, efficiency improvements involving solar protections are 
strongly recommended [10]. For this, it is important to know which surfaces of the building 
receive the highest radiation incidence. This information was obtained through Energy 3D 
software that provides heat maps indicating which walls suffer the highest incidence of solar 
radiation. A heat map of the building in a typical summer day (December 4) generated by 
Energy 3D software can be seen in Figure 4a and 4b. 
 
 
Figure 4 – a: Heat map of the North view; b: Heat map of the West view. 
 
4a 
4b 
9 
 
It is possible to see in Figure 4 that the Northwest and Southwest surfaces are the ones 
that have the greatest solar radiation incidence, so these are the surfaces that need solar 
radiation protection. 
Therefore, three improvements were simulated with the objectives of increasing 
thermal comfort of the occupants and
save electric energy for cooling. The improvements 
presented in this paper are installation of thermal insulation on the ceiling, utilization of solar 
reflective paint on the roof and utilization of vegetation as a solar radiation protection. 
 
3.1.1Thermal insulation on the ceiling 
 
The installation of thermal insulation on the ceiling aims to improve the thermal 
performance of the building in relation to the thermal conductivity. The constructive 
guidelines of NBR 15.220 and the guidance provided by Analysis Bio software indicate that 
buildings located in that climate must have high thermal inertia. Therefore, this will be done 
with the addition of a thermal insulation on the ceiling. The thermal insulation used is a 50 
mm polyethylene foam with a reflective surface and a thermal conductivity of 0.041 W/mK. 
Therefore, the Global Heat Transfer Coefficient, U (W/m2K), which was 2.0 
W/m2K, became 1.36 W/m2K after the installation of the thermal insulation. 
 
 
3.1.2 Solar reflective paint on the roof 
 
Another NBR 15.220 constructive guideline and Analysis Bio suggestion is the 
utilization of reflective surfaces. For this, one of the improvements analyzed in this paper is 
the utilization of a reflective paint on the roof. The paint chosen is roof paint with high 
reflectivity and mechanical resistance available on the market. The purpose is to increase the 
reflectivity of solar radiation incident on the roof of the building. Consequently, the building 
will get less thermal energy in indoor spaces. 
In this sense, the roof reflectivity prior to utilization of the reflective paint was 0.9. 
After the utilization of reflective paint, the roof reflectivity was considered as 0.2 as Lamberts 
et al explains [10]. 
 
3.1.3 Vegetation as a solar radiation protection 
 
10 
 
The utilization of vegetation is an option to protect the building of solar radiation in 
the summer [12]. Therefore, the third improvement proposed by this paper consists in the 
implantation of a tree in the front of the building. 
The simulation will be done with a tree positioned in order to block the solar radiation 
mainly in the external walls of the space 2. These are the surfaces that receive great amount of 
solar radiation. As a consequence, it generates thermal discomfort during the summer. 
The simulation of the radiation incidence in the building was done through Energy 3D 
software and the variation of internal temperature of the building was simulated through 
eQUEST software. For this, a rectangular structure with dimensions 2.15x2.45m was 
simulated at a distance of 1.2m from the ground in front of the building to block the solar 
radiation, as shown in Figure 5a and 5b. 
 
 
Figure 5 – a: Heat map of the building after a tree as protection; b: Structure to simulate a tree in eQUEST 
software. 
 
It is possible to see in Figure 5 that the exterior wall temperature of space 2 is smaller 
compared to the building without a tree as solar radiation protection. 
 
 
4 Results and discussion 
 
The results will be discussed separately for each simulated improvement. 
5a 
5b 
11 
 
 
4.1 Results of thermal insulation on the ceiling 
 
The results of the simulation using the thermal insulation on the ceiling show that the 
savings due to the lower thermal load in the internal spaces is 11.1 kWh/year. This savings of 
electric energy represents the savings in air conditioning system due to lower heat transfer to 
the environment. 
Regarding thermal comfort, the thermal insulation slightly reduced the internal 
temperature variation in the summer months. Table 4 shows the internal average temperatures 
of each space in January. Typically, this month has the highest temperatures of the year. 
 
Table 4 – Internal average temperature in January for thermal insulation on the ceiling. 
Spaces Before thermal insulation After thermal insulation 
 Space 1 27.5ºC 26.6ºC 
 Space 2 26.9ºC 26.6ºC 
 Space 3 27.3ºC 27.0ºC 
 Space 4 28.1ºC 27.4ºC 
 Space 5 26.8ºC 26.5ºC 
 
The information in Table 4 can be used to calculate PPD through simulation with 
Analysis CST. For space 1, for example, PPD reduced from 15.79% to 8.13%. In other words, 
the new environmental conditions of the building resulted in greater thermal comfort. 
 
4.2 Results of solar reflective paint on the roof 
 
The reduction of electric energy consumption due to utilization of reflective paint was 
11.9 kWh/year. In the same way of thermal insulation, this result represents the reduction of 
electric energy required for cooling by the air conditioning system. 
Regarding the thermal comfort, the thermal paint improvement results a reduction in 
the internal average temperature of the building. Table 5 shows the internal average 
temperatures of each space in January. 
 
 
 
 
12 
 
Table 5 – Internal average temperature in January for solar reflective paint on the roof. 
Spaces Before solar reflective paint After solar reflective paint 
 Space 1 27.5ºC 25.5ºC 
 Space 2 26.9ºC 25.6ºC 
 Space 3 27.3ºC 25.6ºC 
 Space 4 28.1ºC 26.0ºC 
 Space 5 26.8ºC 25.3ºC 
 
The increase of the reflectivity of the roof consequently decreases the internal average 
temperatures of the spaces, because the absorbed energy due to solar radiation is smaller. 
Through the simulation, the PPD in Space 1, which was 15.79% before using 
reflective paint on the roof, became 5.00%. That is, the new internal average temperature 
results in better thermal comfort. 
 
4.3 Results of vegetation as solar radiation protection 
 
The reduction of electric energy consumption due to utilization of vegetation as solar 
radiation protection was 4.3 kWh/year and the temperature summary can be seen in Table 6. 
In this table, the average temperatures of each space are detailed for the month of January. 
 
Table 6 – Average internal temperature in January for vegetation as solar radiation protection. 
Spaces Before protection After protection 
 Space 1 27.5ºC 27.1ºC 
 Space 2 26.9ºC 25.8ºC 
 Space 3 27.3ºC 27.2ºC 
 Space 4 28.1ºC 27.7ºC 
 Space 5 26.8ºC 26.6ºC 
 
The results in Table 6 show that the space with the greatest influence is Space 2, that is 
because Space 2 is closer to the three. The protection of solar radiation in the building by the 
tree results in a decrease of 1.1ºC in the internal temperature of Space 2. As a result, the PPD 
decreases from 10.96% to 5.18% with a tree as a sun protection. 
 
 
5 Conclusions 
 
13 
 
In this paper, improvements were proposed to reduce energy consumption and 
increase the thermal comfort of a popular building in Southern Brazil. The simulations 
quantified the reduction of electric energy consumption and the influence on the thermal 
comfort. The summary of the results can be seen in Table 7. 
 
Table 7 – Summary of results. 
Improvement Energy savings PPD reduction 
 Thermal insulation on the ceiling 11.1 kWh/year 7.66% 
 Solar reflective paint on the roof 11.9 kWh/year 10.79% 
 Vegetation as solar radiation protection 4.3 kWh/year 5.78% 
 
The improvement that generated the greatest impact was the utilization of reflective 
paint on the roof. It resulted in an electrical energy saving of 11.9 kWh/year and a reduction 
of up to 2ºC in the internal temperature of the building in the summer months. As a result, the 
thermal comfort sensation increased, reducing the PPD from 15.79% to 5.00%. The 
improvements of using thermal insulation on the roof and using tree as solar protection 
generated similar results in relation to thermal comfort. They both reduced the Percentage of 
People Dissatisfied. 
The reduction in electricity consumption through the proposed improvements was not
greater due to the number of air-conditioned spaces in the building. The reduction in energy 
consumption presented is related to the energy expended by the air conditioning units in 
Spaces 2 and 4. However, since these spaces represent only 28% of the total area of the 
building and they are not used for long periods, the savings in electric energy is limited. 
Finally, the results show that the proposed improvements presented in this paper 
generate positive results for both electric energy consumption and thermal comfort for 
residential buildings located in that specific area. However, the savings in electricity would be 
greater if all spaces in the building had air conditioning system. In addition, the methodology 
used in this paper can be used for buildings in any other location. 
 
 
REFERENCES 
 
[1] Procel-Centro Brasileiro de Informação de Eficiência Energética. [Online] Available: 
<http://www.procel.gov.br/main.asp?View={8E03DCDE-FAE6-470C-90CB-
922E4DD0542C}> 2016. 
14 
 
[2] Lamberts, Roberto; Dutra, Luciano; Pereira, Fernando E. R. “Energy Efficiency in 
Architecture (Eficiência Energética na Arquitetura).” Federal University of Santa 
Catarina. Florianopolis, Brazil. 2011. 
[3] Matos, Michele. “Computation simulation of the thermal performance of residences 
in Florianópolis using natural ventilation (Simulação computacional do desempenho 
térmico de residências em Florianópolis utilizando a ventilação natural).” M. Eng. 
Thesis, Federal University of Santa Catarina. Florianopolis, Brazil. 2007. 
[4] Tavares, Paulo Filipe de Almeida Ferreira; Martins, António Manuel de Oliveira 
Gomes. “Energy efficient building design using sensitivity analysis—A case 
study.” Energy and Buildings. Elsevier. 2007. 
[5] Boyano, A.; Hernandez, P.; Wolf, O. “Energy demands and potential savings in 
European office buildings: Case studies based on EnergyPlus simulations.” Energy 
And Buildings. Elsevier. 2013. 
[6] Al-Homoud, Mohammad Saad. “Computer-aided building energy analysis 
techniques. Building and Environment.” Pergamon. 2000. 
[7] James J. Hircsh& Associates “eQUEST - Introductory tutorial, Version 3.65.” James J. 
Hircsh& Associates. California. 2012. 
[8] Wang, Shan K. “Hand book of air conditioning and refrigeration.” 2. ed. New York: 
Mcgraw-hill. 2001. 
[9] Milbratz, Juliana Helena. “Construction, enviromental comfort and responssible 
energy and water consumption (Construção, conforto ambiental e uso racional de 
energia e água)” Federal University of Santa Catarina. Florianopolis. Brazil. 2007. 
[10] Lambertz, Roberto. et al. “Thermal performance of buildings (Desempenho térmico de 
edificações)” Federal University of Santa Catarina. Florianopolis. Brazil. 2007. 
[11] BRASILIAN STANDART NBR. “ABNT15.220: Thermal performance of buildings 
(Desempenho térmico de edificações).” Rio de Janeiro. Brazil. 2003. 
[12] BUENO, Carolina Lutofo. “Influence of vegetation on urban thermal comfort and 
built environment (Influência da vegetação no conforto térmico urbano e no ambiente 
construído).” Campinas State University. Campinas, Brazil. 2003.