10 C.F.R. § 460.104
Manufactured homes must be sealed against air leakage at all joints, seams, and penetrations associated with the building thermal envelope in accordance with the component manufacturer's installation instructions and the requirements set forth in table 1 to 460.104. Sealing methods between dissimilar materials must allow for differential expansion, contraction and mechanical vibration, and must establish a continuous air barrier upon installation of all opaque components of the building thermal envelope. All gaps and penetrations in the exterior ceiling, exterior floor, and exterior walls, including ducts, flue shafts, plumbing, piping, electrical wiring, utility penetrations, bathroom and kitchen exhaust fans, recessed lighting fixtures adjacent to unconditioned space, and light tubes adjacent to unconditioned space, must be sealed with caulk, foam, gasket or other suitable material. The air barrier installation criteria are adapted from section R402 of the 2021 IECC.
Table 1 to § 460.104 -Air Barrier Installation Criteria
| Component | Air barrier criteria |
| Ceiling or attic | The air barrier in any dropped ceiling or dropped soffit must be aligned with the insulation and any gaps in the air barrier must be sealed with caulk, foam, gasket, or other suitable material. Access hatches, panels, and doors, drop-down stairs, or knee wall doors to unconditioned attic spaces must be weather-stripped or equipped with a gasket to produce a continuous air barrier. |
| Duct system register boots | Duct system register boots that penetrate the building thermal envelope or the air barrier must be sealed to the subfloor, wall covering or ceiling penetrated by the boot, air barrier, or the interior finish materials with caulk, foam, gasket, or other suitable material. |
| Electrical box or phone box on exterior walls | The air barrier must be installed behind electrical and communication boxes or the air barrier must be sealed around the box penetration with caulk, foam, gasket, or other suitable material. |
| Floors | The air barrier must be installed at any exposed edge of insulation. The bottom board may serve as the air barrier. |
| Mating line surfaces | Mating line surfaces must be equipped with a continuous and durable gasket. |
| Recessed lighting | Recessed light fixtures installed in the building thermal envelope must be sealed to the drywall with caulk, foam, gasket, or other suitable material. |
| Rim joists | The air barrier must enclose the rim joists. The junctions of the rim board and the subfloor must be air sealed. |
| Shower or tub adjacent to exterior wall | The air barrier must separate showers and tubs from exterior walls. |
| Walls | The junction of the top plate and the exterior ceiling, and the junction of the bottom plate and the exterior floor, along exterior walls must be sealed with caulk, foam, gasket, or other suitable material. |
| Windows, skylights, and exterior doors | The rough openings around windows, exterior doors, and skylights must be sealed with caulk or foam. |
10 C.F.R. §460.104