Department of Energy Adopts Standards for Manufactured Housing Based on 2021 IECC

The Department of Energy (DOE) published it's final rule on energy efficiency standards for manufactured housing on May 30, 2022. The new standards are based on the 2021 International Energy Conservation Code (IECC) and set a tiered set of building thermal envelope requirements for single-section and multi-section homes in each of the four HUD climate zones. Texas is wholly in Climate Zone 1 and homes built on or after May 31, 2023 will need to comply with the adopted rules.

The climate zones can be seen in Figure 460.101.

The building thermal envelope requirements lay out prescriptive and performance paths for compliance with the new standards.

For the prescriptive path a home must meet either the minimum R-value, and the glazing max U-factor and solar heat gain coefficients (SGHC) laid out in Table 460.102-1 if the home is single-section and Table 460.102-2 if the home is multi-section.

Component U-values can also be used as alternatives to the R-value requirements as laid out in Table 460.102-3 for single-section homes and Table 460.102-4 for multi-section homes. The U-factor values "reflect the thermal transmittance of the component, excluding fenestration, and not just the insulation of that component."

Manufacturers can also comply with the rule by meeting the performance requirements by having a building thermal envelope Uo value that is less than or equal to Table 460.102-5 for single-section homes and Table 460.102-6 for multi-section homes.

There are more details needed to fully meet compliance and additional requirements laid out in the rule that are specific to the other climate zones.

The rule goes on to outline insulation installation requirements (460.103), building thermal envelope air leakage requirements (460.104), duct leakage requirements setting a max of less than or equal to 4 cubic feet per minute (cfm) (460.201), mandatory programmable thermostat requirements (460.202), service hot water requirements (460.203), ventilation fan efficacy requirements (460.204), and heating and cooling sizing requirements (460.205).

The final rule is published online at