Determine the overall U-factor for a double-door type wood-framed double-pane window with 13-mm air space and metal spacers, and compare your result with the value listed in Table 9–6. The overall dimensions of the window are 2.00 m × 2.40 m, and the dimensions of each glazing are 1.92 m × 1.14 m.

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Overall U-factors (heat transfer coefficients) for various windows and skylights in W/m².K (from ASHRAE Handbook of Fundamentals, Chap. 27, Table 5) Aluminum frame (without thermal break) Type → Frame width →→ Spacer type → Glazing Type Single Glazing 3 mm (in) glass 6.4 mm (in) acrylic 3 mm (in) acrylic Glass section (glazing) only Center- Edge-of- of-glass glass 6.30 5.28 5.79 Triple Glazing (no coating) 6.4 mm air space (Not applicable) Fixed 32 mm (1 in) Metal Insul. All 6.30 5.28 5.79 Double Sloped door skylight 1.53 0.97 1.19 0.80 53 mm (2 in) All 12.7 mm air space 2.96 2.35 2.97 3.66 2.67 2.02 2.62 3.33 6.4 mm argon space 2.79 2.16 2.77 3.47 12.7 mm argon space 1.65 2.58 1.92 2.52 3.23 2.16 1.76 1.93 19 mm (in) All 5.93 6.63 7.16 9.88 5.69 6.27 8.86 5.02 6.16 6.71 2.23 1.56 2.12 2.85 1.92 1.25 1.77 2.51 Wood or vinyl frame Double door Fixed 41 mm 88 mm (13 in) (3 in) Metal Insul. Metal Insul. 5.57 4.77 9.94 5.48 - 5.17 6.04 6.04 5.62 5.71 Double Glazing (no coating) 6.4 mm air space 12.7 mm air space 3.24 3.71 3.34 3.90 4.55 6.70 3.26 3.16 3.20 3.09 4.37 4.22 2.78 3.40 2.91 3.51 4.18 6.65 2.88 2.76 2.86 2.74 4.32 4.17 6.4 mm argon space 2.95 3.52 3.07 3.66 4.32 6.47 3.03 2.91 2.98 2.87 4.14 3.97 12.7 mm argon space 2.61 3.28 2.76 3.36 4.04 6.47 2.74 2.61 2.73 2.60 4.14 3.97 Double Glazing [e = 0.1, coating on one of the surfaces of air space (surface 2 or 3, counting from the outside toward inside)] 6.4 mm air space 12.7 mm air space 6.4 mm argon space 3.21 3.89 3.37 2.44 3.16 2.60 1.82 2.71 2.06 2.67 1.99 2.83 2.21 2.82 3.52 12.7 mm argon space 1.53 2.49 1.83 2.42 3.14 Sloped skylight 23 mm (in) Metal Insul. 7.57 6.57 7.63 2.46 2.60 2.59 2.47 3.73 3.53 2.06 1.92 2.13 1.99 3.73 3.53 2.21 2.07 2.26 2.12 3.32 3.09 1.82 1.67 1.91 1.78 3.41 3.19 Triple Glazing [z = 0.1, coating on one of the surfaces of air spaces (surfaces 3 and 5, counting from the outside toward inside)] 6.4 mm air space 12.7 mm air space 6.4 mm argon space 12.7 mm argon space 5.81 2.34 2.18 2.36 2.21 3.48 3.24 5.67 2.01 1.84 2.07 1.91 3.34 3.09 5.57 2.15 1.99 2.19 2.04 3.25 3.00 5.53 1.91 1.74 1.98 1.82 3.20 2.95 2.49 1.83 2.42 3.14 5.24 1.81 1.64 1.89 1.73 2.92 2.66 2.05 1.38 1.92 2.66 5.10 1.33 1.15 1.46 1.30 2.78 2.52 4.90 1.52 1.35 1.64 1.47 2.59 2.33 4.86 1.18 1.01 1.33. 1.17 2.55 2.28