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.  | |||||||||||
        