PSI - Issue 55

Andréa R. Souza et al. / Procedia Structural Integrity 55 (2024) 143–150

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Andrea R. Souza et al ./ Structural Integrity Procedia 00 (2019) 000–000

• e is constant for all conditions, defined as 0.90, an average value for the ETICS system (Alonso et al. 2017). • T sky is calculated according to the procedures of Costanzo et al. (2014), considering Brunt's equation. • The external convective heat transfer coefficient is 25 W/m 2 K (WUFIPro value). • The climate data, i.e., air temperature, irradiation, and humidity, were taken from the EnergyPlus Weather Format – EPW (Climate.OneBuilding 2023). The ST value was calculated for different Portuguese climatic zones using the numerical model for 17 Portuguese cities, with climate variables in Table 2. In addition, the impact of retrofitting was estimated considering two different expositions, horizontal (roofs) and vertical (façades), in four orientations (west, east, south, and north).

Table 2. Distribution of used cities for each climate (IPMA 2011).

Annual Average Ta( o C)

Annual Cumulative Horizontal Irradiation (Wh/m 2 )

Annual Average Ta( o C)

Annual Cumulative Horizontal Irradiation (Wh/m 2 )

Climate classification

Climate classification

City

City

Castelo Branco

Funchal

Csb

19.7

1836.64

Csa

16.3

1719.06

Pico

Cfa

18.0

1578.54

Porto Alegre Csa

15.3

1710.64

Flores

Cfb

17.9

1488.21

Coimbra

Csb

15.4

1610.90

Beja

Csa

16.2

1789.12

Viseu

Csb

13.4

1619.66

Faro

Csa

17.8

1843.08

Porto

Csb

15.1

1654.06

Sagres

Csa

25.4

1762.7

Vila Real

Csb

13.6

1593.63

Lisboa

Csa

17.1

1771.56

Bragançca Csb

12.5

1612.39

Sintra

Csa

15.8

1753.39

Viana do Castelo

Csb

14.3

1645.02

Peniche

Csb

15.4

1619.09

3. Results and Discussion 3.1. Experimental reflectance measurements The average and standard deviation of the reflectance measurements are listed in Table 3.

Table 3. Reflectance results. Sample ID Condition

Reflectance

Original 0 year

New

0.120 ± 0.009

Natural aged 3 years

Aged

0.076 ± 0.007

Res 0.250 ± 0.003 The 3-year aged reflectance value is 36% lower than the original value. This reflectance loss is below the expectations of the Cool Roof Rating Council (CRRC), which estimates a threshold of 23% loss after three years of natural degradation (CRRC 2019). However, the reflectance variation in time will result from chemical and physical stress in combination with matter depositions (Shi et al. 2019). In some cases, dark surfaces with low initial reflectance can increase aged reflectance, as demonstrated by Sleiman et al. (2011). Furthermore, the increase in reflectance due to the use of a paint with high NIR reflectance as a retrofit solution was 108% compared to the initial condition and 228% compared to the aged condition. The change in reflectance due to NIR reflectance was also demonstrated in Mazhar et al. (2020) and Ramos et al. (2021). Restored