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Polystyrene Foam Insulation in Long-Term Building Applications – Effective R-values Page 16 Example 2 Effective R-value in long-term (50-year), above-grade wall applications for a winter condition with an outside temperature of 5°F (-15°C) and an interior temperature of 75°F (24°C). The mean temperature will be (5°F +75°F)/2 = 40°F [(-15°C +24°C)/2 = 4.5°C]. Table 9. R EFFECTIVE for Long-term, Above-grade Winter Wall Applica on of EPS and XPS Equation Term ASTM C578 Material Type EPS XPS II IX X, IV R-value RSI R-value RSI R-value RSI R LAB (Table 1) 4.0 0.70 4.2 0.74 5.0 0.88 F age (Table 4) 1.0 1.0 1.0 1.0 0.86 0.86 F Temp (Table 6) 1.10 1.10 1.10 1.10 1.08 1.08 F h2o (Table 7) 1.0 1.0 1.0 1.0 1.0 1.0 R EFF 4.4 0.77 4.6 0.81 4.6 0.82 % Change +10% +10% -7% Example 3 Effective R-value in long-term (50-year), below-grade wall applications with a ground temperature of 50°F (10°C) and an interior temperature of 70°F (22°C). The mean temperature will be (50°F +70°F)/2 = 60°F [(10°C +22°C)/2 = 16°C]. Table 10. R EFFECTIVE for Long-term, Below-grade Wall Applica on of EPS and XPS Equation Term ASTM C578 Material Type EPS XPS II IX X, IV R-value RSI R-value RSI R-value RSI R LAB (Table 1) 4.0 0.70 4.2 0.74 5.0 0.88 F age (Table 4) 1.0 1.0 1.0 1.0 0.86 0.86 F Temp (Table 6) 1.05 1.05 1.05 1.05 1.04 1.04 F h2o (Table 7) 0.89 0.93 0.89 0.89 0.93 0.93 R EFF 3.7 0.65 3.9 0.69 4.1 0.73 % Change -7% -7% -17%