WHERE:
T = insulation thickness for material with conductivity K, inches.
PR = actual outside radius, inches.
t = Insulation thickness from Table 120.3-A, inches.
K = Conductivity of alternate material at the mean rating temperature indicated in Table 120.3-A for the applicable fluid temperature range, in Btu-inch per hour per square foot per °F.
k = The lower value of the conductivity range listed in Table 120.3-A for the applicable fluid temperature range, Btu-inch per hour per square foot per °F.
Fluid Operating Temperature Range | Insulation Conductivity | Nominal Pipe Diameter (in inches) | |||||||||
Conductivity | Mean Rating Temperature (°F) | ||||||||||
< 1 | 1 to <1.5 | 1.5 to < 4 | 4 to < 8 | 8 and larger | |||||||
Space heating and Service Water Heating Systems (Steam, Steam Condensate, Refrigerant, Space Heating, Service Hot Water) | Minimum Pipe Insulation Required (Thickness in inches or R-value) | ||||||||||
Above 350 | 0.32-0.34 | 250 | Inches | 4.5 | 5.0 | 5.0 | 5.0 | 5.0 | |||
R-value | R 37 | R 41 | R 37 | R 27 | R 23 | ||||||
251-350 | 0.29-0.32 | 200 | Inches | 3.0 | 4.0 | 4.5 | 4.5 | 4.5 | |||
R-value | R 24 | R 34 | R 35 | R 26 | R 22 | ||||||
201-250 | 0.27-0.30 | 150 | Inches | 2.5 | 2.5 | 2.5 | 3.0 | 3.0 | |||
R-value | R 21 | R 20 | R 17.5 | R 17 | R 14.5 | ||||||
141-200 | 0.25-0.29 | 125 | Inches | 1.5 | 1.5 | 2.0 | 2.0 | 2.0 | |||
R-value | R 11.5 | R 11 | R 14 | R 11 | R 10 | ||||||
105-140 | 0.22-0.28 | 100 | Inches | 1.0 | 1.5 | 1.5 | 1.5 | 1.5 | |||
R-value | R 7.7 | R 12.5 | R 11 | R 9 | R 8 | ||||||
Space cooling systems (chilled water, refrigerant and brine) | Minimum Pipe Insulation Required (Thickness in inches or R-value)1 | ||||||||||
40-60 | 0.21-0.27 | 75 | Inches | Nonres 0.5 | Res 0.75 | Nonres 0.5 | Res 0.75 | 1.0 | 1.0 | 1.0 | |
R-value | Nonres R 3 | Res R 6 | Nonres R 3 | Res R 5 | R 7 | R 6 | R 5 | ||||
Below 40 | 0.20-0.26 | 50 | Inches | 1.0 | 1.5 | 1.5 | 1.5 | 1.5 | |||
R-value | R 8.5 | R 14 | R 12 | R 10 | R 9 | ||||||
Footnote to Table 120.3-A: 1 These thickness are based on energy efficiency considerations only. Issues such as water vapor permeability or surface condensation sometimes require vapor retarders or additional insulation. |