PSI - Issue 13

Barbara Šubic et al. / Procedia Structural Integrity 13 (2018) 503–510 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Table 3. Comparison of thermal characteristics of window mullion WB1 with different reinforcing materials. Samples U [W/m 2 K] U f [W/m 2 K] T min [°C]

U w [W/m

2 K]

WB1_AL WB1_ST WB1_CF WB1_GF Reference

1.44 1.44 1.43 1.33 1.17

1.24 1.24 1.24 1.21 1.17

12.02 12.04 12.07 12.68 13.52

0.94 0.94 0.94 0.94 0.93

U, U f and T min of WB1_AL, WB1_ST and WB1_CF are practically the same and differ from the reference for 21 %, 6 % and -11 %, respectively (Table 3). This means that using reinforcements in window profiles U and U f increases, but T min decreases. U, U f and T min of the profile WB1_GF differ the least compared to the reference that is for 14 %, 3 %, and - 6 %, respectively, due to the lowest λ of all reinforcing materials used in this study. The influence of any reinforcing material on U w with WB1 mullion is minimal (1 %).

Table 4. Comparison of thermal characteristics of window mullion WB2 with different reinforcing materials. Samples U [W/m 2 K] U f [W/m 2 K] T min [°C]

U w [W/m

2 K]

WB2_AL WB2_ST WB2_CF WB2_GF Reference

3.10 3.07 3.00 1.93 1.17

1.79 1.62 1.44 1.22 1.17

3.35 6.04 8.80

1.01 0.99 0.97 0.94 0.93

12.49 13.52

When the reinforcement extends across the entire cross-section height (WB2), the influence of the type of reinforcing material on thermal characteristics is higher. The highest thermal losses are at WB2_AL where the parameters U, U f and T min differ from referenced values for 166 %, 53 % and -75 %, respectively ( Table 4 ). Reinforcements have the highest influence on U and T min as this present local thermal losses, whereas lower influence on U f and U w was found, due to low percentage of mullion area (7 %) compared to entire window area. The smallest deviation of parameters U, U f and T min , from the reference values are observed for WB2_GF at 66 %, 4 %, and -8 %, respectively. The increases of U w for windows with window mullions WB2_AL, WB2_ST, WB2_CF, and WB2_GF are 8 %, 6 %, 4 % and 1 % respectively, compared to reference profile. The minimal temperature difference between reinforced mullion and reference mullion increases with the increase of reinforcement’s λ, and is the highest with WB2_AL, that is 75 %. For reinforcements where λ is lower than 1 W/mK (WB2_GF) T min differs from T min of reference mullion for 8 %. Table 5 shows a comparison of limited outside temperature (T limit ) at which T min is higher than 13 °C for different reinforced window profiles WB1 and WB2. If outside temperature is lower than T limit this means that T min is lower than 13 °C and consequently to condensation and mould growth occurs. With reference window the condensation appears on the inner side of the window when outside temperature is lower than -7 °C. However at WB1_AL, WB1_ST and WB1_CF this criteria is reached already at -2 °C, and with WB2_AL already at outside temperature of 9.5 °C. In the latter case this means that criteria for condensation and mold growth are fulfilled almost through half of the year, and that such windows should not be installed in modern buildings.

Table 5. The limit outside temperature (T limit ) when criteria of T min >13 °C, on the inner side of the window is met. Samples T limit [°C] Samples T limit [°C] WB1_AL -2 WB2 _AL 9.5 WB1_ST -2 WB2_ST 7.5 WB1_CF -2 WB2_CF 4.5 WB1_GF -4 WB2_GF -3 Reference -7 Reference -7