PSI - Issue 13

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

506

= ∗ + ∗ + ∗

4

(1)

U f was calculated with WinIso 2D software according to EN ISO 10077-2: 2017 using a two-dimensional numerical method conforming to ISO 10211 and anisotropic cavity algo rithm. λ values were taken from EN ISO 10077 -2: 2017 and are presented in Table 1. The standard specifies that the calculation of U f must be made using the following parameters: outside temperature 0 °C, relative humidity 80 % and surface resistance 0.04 m 2 K/W. For the inside conditions, temperature 20 °C, relative humidity 50 % and surface resistance 0.13 m 2 K/Wmust be used. Inside surface resistance at edges or junctions between surfaces was 0.20 m 2 K/W, due to reduced radiation/convection. Insulated glass unit was replaced by so- called calibration panel with λ = 0.035 W/mK. The length of the panel was 190 mm. Linear thermal transmittance (U) presents the thermal transmittance through the middle symmetry line of the analyzed cross sections. The criteria for condensation and mold growth was defined based on the 13 °C isotherm, when the temperature and relative humidity are -5 °C and 80 % on the outside and 20 °C and 50 % on the inside, respectively. This means that minimal inside surface temperature of window profile (T min ) should not be less than 13 °C. If this criteria is not reached, condensation appears, which can lead to mold growth (Ruediger et al. 2016).

Fig. 3. Different thermal transmittance parameters on double sashed window

Table 2. Thermal transmittance values of components for double casement wooden window. Thermal transmittance [W/m 2 K] Window element width [mm] U f,l 1.2 b f,1 122 U f,t 1.2 b f,2 122 U f,b 1.3 b f,3 137 U f,m 1.2 b f,4 190 U g 0.6

U w as a total is calculated from different U f values (left, right, top, bottom and middle cross section as seen on Fig. 3), multiplied by associated surface (Table 2). Left, top and right window profiles are identical and therefore there are only three different U f values: left (U f,1 ), bottom (U f,b ) and middle (U f,m ). U f,m differ with different reinforcing materials used, and it is the main parameter which was observed in the study.

3. Analysis of the results 3.1. Thermal transmittance of hybrid beams

Window mullions WB1 and WB2, with four different reinforcing materials (aluminium - AL, steel - ST, CFRP – CF, and GFRP - GF) were compared to the reference window mullion made only of wood. Three different parameters were analyzed: U, U f and T min . Additionally, the effect of reinforcements on the U w of double casement window, with dimensions 1500 mm × 2500 mm and U g of 0.6 W/m 2 K was compared. The results are presented in Table 3 – 4.