Table 21 Inside Surface Resistance (Table A3.5 CIBSE Guide)
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Surface resistance (m²K/W)
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Building element
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Heat flow
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High emissivity
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Low emissivity
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factor
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factor
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Walls
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Horizontal
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0.12
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0.3
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Ceilings or roofs,
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Upward
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0.1
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0.22
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flat or pitched
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floors
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Ceilings and floors
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Downward
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0.14
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0.55
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Notes:
1. High emissivity factor assumes ε 1 = ε 2 = 0.90 (most building materials),
Low emissivity factor assumes ε 1 = 0.90, ε 2 = 0.05,
2. Surface temperatures are 20°C
3. Air speed at the surface is assumed to be less than or equal to 0.1 m/s
