Piping with a nominal diameter greater than 1/4 inch (6.4 mm), including associated valves, fittings and piping system components, in heating, ventilating and air-conditioning (HVAC) systems shall be thermally insulated in accordance with Table 606.4. For insulation outside of the conductivity ranges specified in Table 606.4, the minimum thickness of the insulation shall be determined in accordance with Equation 6-4.
entered all_borders">
| T = r [(1 + t/r)K/k - 1] | (Equation 6-4) |
where:
| T | = | minimum insulation thickness (inches). |
| r | = | actual outside radius of pipe (inches). |
| t | = | insulation thickness specified in Table 606.4 for applicable fluid temperature and pipe size. |
| K | = | Conductivity of alternate material at mean rating temperature indicated for the applicable fluid temperature (Btu × in/h × ft2 × °F). |
| k | = | the upper value of the conductivity range specified in Table 606.4 for the applicable fluid temperature. |
Building cavities and interstitial framing spaces shall be large enough to accommodate the combined diameter of the pipe plus the insulation, plus the full thickness of the insulation plus any other objects in the cavity that the piping must cross.
Exception: Piping insulation is not required for the following:
- Factory-installed piping within HVAC equipment tested and rated in accordance with Section 606.2.
- Piping conveying fluids not heated or cooled such as roof and condensate drains, cold water supply, and natural gas piping.
- Where heat gain or heat loss will not increase energy usage such as liquid refrigerant piping.
- Piping having an outside diameter of 1 inch (25 mm) or less, associated with strainers, control valves, and balancing valves.
TABLE 606.4
MINIMUM PIPE INSULATION THICKNESS
| ntered uc_vertical_align_bottom">FLUID | CONDUCTIVITY Btu-in/(h × ft2 × F) | RATIO OF WALL THICKNESS OF PIPE INSULATION TO NOMINAL PIPE DIAMETERa, b |
| Steam | 0.27 — 0.34 | ≥ 2:1 |
| Hot Water | 0.22 — 0.29 | ≥ 1:1 |
| Chilled Water | 0.22 — 0.28 | ≥ 1:1 |
For SI: 1 inch = 25.4 mm, 1 Btu-in = W/m × K.
- The proportions apply to all nominal pipe diameters greater than 1/4 inch and less than or equal to 2 inches. For nominal pipe diameters larger than 2 inches, outside diameter, the minimum wall thickness of the insulation shall be equal to the wall thickness required for 2-inch pipe.
- These thicknesses are based on energy-efficiency considerations only.