SUBPART - Subpart B—Building Thermal Envelope

Collapse to view only § 460.104 - Building thermal envelope air leakage.

§ 460.101 - Climate zones.
§ 460.102 - Building thermal envelope requirements.
§ 460.103 - Installation of insulation.
§ 460.104 - Building thermal envelope air leakage.

§ 460.101 - Climate zones.

Manufactured homes subject to the requirements of this subpart must comply with the requirements applicable to one or more of the climate zones set forth in figure 1 to § 460.101 and table 1 to § 460.101.

Table 1 to § 460.101—U.S. States and Territories per Climate Zone

Zone 1	Zone 2	Zone 3	Alabama	Arkansas	Alaska	American Samoa	Arizona	Colorado	Florida	California	Connecticut	Georgia	Kansas	Delaware	Guam	Kentucky	District of Columbia	Hawaii	Missouri	Idaho	Louisiana	New Mexico	Illinois	Mississippi	North Carolina	Indiana	South Carolina	Oklahoma	Iowa	Texas	Tennessee	Maine	The Commonwealth of Puerto Rico		Maryland	U.S. Virgin Islands		Massachusetts			Michigan			Minnesota			Montana			Nebraska			Nevada			New Hampshire			New Jersey			New York			North Dakota			Ohio			Oregon			Pennsylvania			Rhode Island			South Dakota			Utah			Vermont			Virginia			Washington			West Virginia			Wisconsin			Wyoming

§ 460.102 - Building thermal envelope requirements.

(a) Compliance options. The building thermal envelope must meet either the prescriptive requirements of paragraph (b) of this section or the performance requirements of paragraph (c) of this section.

(b) Prescriptive requirements. (1) The building thermal envelope must meet the applicable minimum R-value (nominal value of insulation), and the glazing maximum U-factor and SHGC, requirements set forth in table 1 to § 460.102(b)(1) and table 2 to § 460.102(b)(2) or component U-values set forth in table 3 to § 460.102(b)(5) and table 4 to § 460.102(b)(5).

Table 1 to § 460.102(b)(1)—Tier 1 Building Thermal Envelope Prescriptive Requirements

Climate zone	Exterior wall insulation R-value	Exterior ceiling insulation R-value	Exterior floor insulation R-value	Window U-factor	Skylight U-factor	Door U-factor	Glazed fenestration SHGC	1	13	22	22	1.08	0.75	0.40	0.7	2	13	22	19	0.5	0.55	0.40	0.6	3	19	22	22	0.35	0.55	0.40	Not applicable.

Table 2 to § 460.102(b)(1)—Tier 2 Building Thermal Envelope Prescriptive Requirements

Climate zone	Exterior wall insulation R-value	Exterior ceiling insulation R-value	Exterior floor insulation R-value	Window U-factor	Skylight U-factor	Door U-factor	Glazed fenestration SHGC	1	13	30	13	0.32	0.75	0.40	0.33	2	21	30	19	0.30	0.55	0.40	0.25	3	21	38	30	0.30	0.55	0.40	Not applicable.

(2) For the purpose of compliance with the exterior ceiling insulation R-value requirement of paragraph (b)(1) of this section, the truss heel height must be a minimum of 5.5 inches at the outside face of each exterior wall.

(3) A combination of R-21 batt insulation and R-14 blanket insulation may be used for the purpose of compliance with the floor insulation R-value requirement of table 2 to § 460.102(b)(1), Climate Zone 3.

(4) An individual skylight that has an SHGC that is less than or equal to 0.30 is not subject to the glazed fenestration SHGC requirements established in paragraph (b)(1) of this section. Adapted from section R402 of the 2021 IECC.

(5) U-factor alternatives to R-value requirements. Compliance with the applicable requirements in paragraph (b)(1) of this section may be determined using the applicable maximum U-factor values set forth in table 3 to § 460.102(b)(5) and table 4 to § 460.102(b)(5), which reflect the thermal transmittance of the component, excluding fenestration, and not just the insulation of that component, as an alternative to the minimum nominal R-value requirements set forth in table 1 to § 460.102(b)(1) and table 2 to § 460.102(b)(1), respectively.

Table 3 to § 460.102(b)(5)—U-Factor Alternatives to Tier 1 R-Value Requirements

Climate zone	Exterior ceiling U-factor	Exterior wall U-factor	Exterior floor U-factor	1	0.061	0.094	0.049	2	0.061	0.094	0.056	3	0.061	0.068	0.049

Table 4 to § 460.102(b)(5)—U-Factor Alternatives to Tier 2 R-Value Requirements

Climate zone	Exterior ceiling U-factor	Exterior wall U-factor	Exterior floor U-factor	1	0.043	0.094	0.078	2	0.043	0.063	0.056	3	0.037	0.063	0.032

(c) Performance requirements. (1) The building thermal envelope must have a Uo that is less than or equal to the applicable value specified in table 5 to § 460.102(c)(1) and table 6 to § 460.102(c)(1).

Table 5 to § 460.102(c)(1)—Tier 1 Building Thermal Envelope Performance Requirements

Climate zone	Single-section Uo	1	0.110	2	0.091	3	0.074

Table 6 to § 460.102(c)(1)—Tier 2 Building Thermal Envelope Performance Requirements

Climate zone	Multi-section Uo	1	0.082	2	0.066	3	0.055

(2) Area-weighted average vertical fenestration U-factor must not exceed 0.48 in Climate Zone 2 or 0.40 in Climate Zone 3. Adapted from section R402 of the 2021 IECC.

(3) Area-weighted average skylight U-factor must not exceed 0.75 in Climate Zone 2 and Climate Zone 3. Adapted from section R402 of the 2021 IECC.

(4) Windows, skylights and doors containing more than 50 percent glazing by area must satisfy the SHGC requirements established in paragraph (b)(1) of this section on the basis of an area-weighted average. Adapted from section R402 of the 2021 IECC.

(d) [Reserved].

(e) Determination of compliance with paragraph (c) of this section. (1) Uo must be determined in accordance with Overall U-Values and Heating/Cooling Loads—Manufactured Homes (incorporated by reference; see § 460.3)

(2) [Reserved]

§ 460.103 - Installation of insulation.

Insulating materials must be installed according to the insulation manufacturer's installation instructions and the requirements set forth in table 1 to 460.103, which is adapted from section R402 of the 2021 IECC.

Table 1 to § 460.103—Installation of Insulation

Component	Installation requirements	General	Air-permeable insulation must not be used as a material to establish the air barrier.	Access hatches, panels, and doors	Access hatches, panels, and doors between conditioned space and unconditioned space, such as attics and crawlspaces, must be insulated to a level equivalent to the insulation of the surrounding surface, must provide access to all equipment that prevents damaging or compressing the insulation, and must provide a wood-framed or equivalent baffle or retainer when loose fill insulation is installed within an exterior ceiling assembly to retain the insulation both on the access hatch, panel, or door and within the building thermal envelope.	Baffles	For air-permeable insulations in vented attics, a baffle must be installed adjacent to soffit and eave vents. Baffles, when used in conjunction with eave venting, must be constructed using a solid material, maintain an opening equal or greater than the size of the vents, and extend over the top of the attic insulation.	Ceiling or attic	The insulation in any dropped ceiling or dropped soffit must be aligned with the air barrier.	Narrow cavities	Batts to be installed in narrow cavities must be cut to fit or narrow cavities must be filled with insulation that upon installation readily conforms to the available cavity space.	Rim joists	Rim joists must be insulated such that the insulation maintain permanent contact with the exterior rim board.	Shower or tub adjacent to exterior wall	Exterior walls adjacent to showers and tubs must be insulated.	Walls	Air permeable exterior building thermal envelope insulation for framed exterior walls must completely fill the cavity, including within stud bays caused by blocking lay flats or headers.

§ 460.104 - Building thermal envelope air leakage.

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.