15A-3-203. Amendments to Chapters 6 through 15 of IRC.

1,345 words·~6 min read·/ut/title-15a/chapter-3/15a-3-203

A research copy — for the controlling text, always check the official state or federal source. Not legal advice.

Effective 7/1/2026

(1)IRC, Section R609.4.1, is deleted.

(2)IRC, Section R702.7, is deleted.

(3)In IRC, Chapter 11, is deleted and replaced with the following:

"Chapter 11, Energy Efficiency (Revised)

R1101.1 Scope. This chapter establishes minimum thermal-performance requirements for the building envelope of residential structures regulated by this code.

R1101.2 General. The building envelope shall be constructed to limit heat loss and gain through its components by providing insulation values not less than those specified in this chapter.

R1101.3 Compliance Paths. Compliance with this chapter shall be demonstrated by one of the following methods:

R1101.3.1 Prescriptive Compliance. The building thermal envelope shall meet or exceed the minimum R-values and maximum U-factors in Section R1102.2.

R1101.3.2 Performance Compliance. As an alternative to Section R1101.3.1, compliance may be demonstrated using U.S. DOE REScheck, provided the proposed design achieves an overall envelope performance not less than 5% above the current Utah 2012 REScheck standard, as documented on the REScheck compliance certificate or achieve a HERs rating of 67 or better.

R1102.1 Building Thermal Envelope. The building thermal envelope shall include exterior walls, roof/ceiling assemblies, floors over unconditioned spaces, windows, doors, and other elements that enclose conditioned space.

R1102.2 Minimum Thermal Resistance (R-Values) and U-Factors. Insulation for each component of the building envelope shall meet or exceed the following minimum R-values and U-factors:

Component Minimum R-Value/

Maximum U-Factor Notes

Above-grade exterior walls R-21 Applies to all framed or masonry walls separating conditioned and unconditioned space or the exterior environment.

Ceilings / roof assemblies R-38 Applies to the thermal boundary between conditioned space and unconditioned attic or exterior air.

Floors over unconditioned space R-30 Includes floors over crawl spaces, garages, or open air.

Basement walls (conditioned basements) R-10 continuous or R-13 cavity Required for any portion of basement walls enclosing conditioned space.

Windows and glazed doors Maximum U-factor = 0.32 Applies to all fenestration enclosing conditioned space.

Skylights Maximum U-factor = 1.3 Applies to all skylights over conditioned space.

Opaque doors Minimum U-factor = 0.6 Applies to solid doors separating conditioned and unconditioned spaces.

R1102.2.1 Conversion for Imported Windows and Doors. A conversion factor of 5.678 shall be used to convert U-values expressed in SI units to IP units: U(IP) = U(SI) / 5.678.

R1102.3 Installation. Insulation materials shall be installed in substantial contact with the surface they are intended to insulate and in accordance with the manufacturer's instructions. Compressed or poorly fitted insulation shall not be permitted where it reduces effective thermal resistance.

R1102.4 Verification. Compliance with the requirements of this chapter shall be verified by inspection prior to the installation of interior finishes. No additional energy modeling, trade-off analysis, or performance-based documentation shall be required.

R1103 Mechanical Room Requirements. Mechanical rooms that receive combustion air from unconditioned space shall be insulated and sealed to prevent uncontrolled air infiltration. Such rooms shall:

be separated from unconditioned spaces by an insulated thermal barrier equal to the minimum wall R-value of R13; and

be sealed to limit air leakage through joints, penetrations, and construction openings with the air-sealing provisions.

R1104 Duct System Testing and Insulation.

R1104.1 Duct Leakage Testing. Duct systems located in unconditioned attics shall be tested for total air leakage.

R1104.1.1 Air Handler Installed at Time of Test. Where the air handler is installed at the time of the leakage test, the total leakage shall be less than or equal to 6.0 cubic feet per minute (170 L/min) per 100 square feet (9.29 m) of conditioned floor area.

R1104.1.2 Air Handler Not Installed at Time of Test. Where the air handler is not installed at the time of the test, the total leakage shall be less than or equal to 5.0 cubic feet per minute (141 L/min) per 100 square feet (9.29 m) of conditioned floor area.

R1104.2 Duct Insulation. Duct systems located outside conditioned space shall be insulated to a minimum of R-8. Ducts buried beneath concrete floors do not require insulation.

R1104.1.3 Building Thermal Envelope Air Leakage Testing. The building thermal envelope shall be tested to determine air leakage rate. Testing shall be conducted in accordance with ASTM E779 or ASTM E1827. A written report of the results of the test shall be signed by the party conducting the test and shall be provided to the code official. Testing shall be performed at a pressure differential of 0.2 inch water gauge (50 Pascals).

R1104.1.3.1 Mechanical Ventilation. Where the tested air leakage rate is not greater than 3 air changes per hour, the dwelling unit shall be provided with whole-house mechanical ventilation in accordance with Section M1505.

R1104.1.3.2 Mechanical Ventilation as an Alternative. In lieu of the testing required by Section R1104.1.3, the dwelling unit shall be provided with mechanical ventilation in accordance with Section M1505.

R1105 Building Thermal Envelope Air Leakage Testing. The building thermal envelope shall be tested to determine air leakage rate. The maximum air leakage rate shall not exceed 5.0 air changes per hour or 0.25 cubic feet per minute

(CFM)per square foot [0.00127 m3/(s x m2)] of dwelling unit enclosure area for single family construction and 6.0 air changes per hour or 0.28 cubic feet per minute

(CFM)per square foot [0.0079 m3/(s x m2)] of dwelling unit enclosure area for multifamily construction.

Testing shall be conducted in accordance with ASTM E779 or ASTM E1827. A written report of the results of the test shall be signed by the party conducting the test and shall be provided to the code official. Testing shall be performed at a pressure differential of 0.2 inch water gauge (50 Pascals).

The following parties shall be approved to conduct testing: Parties certified by BPI or RESNET, or licensed contractors who have completed training provided by Blower Door Test equipment manufacturers or other comparable training.

Exception to air leakage testing: Table R41105 may be used as an alternative to conducting air leakage testing.

Table R41105: Air Barrier, Air Sealing, and Insulation Installation Checklist

Insulation and air barriers installed in accordance with manufacturers instructions.

Air-permeable insulation (fiberglass, rock-wool, cellulose) is not used for air sealing.

Closed-cell foam is the only insulation that also serves as an air barrier.

Continuous air barrier installed at the building thermal envelope. Breaks & joints sealed.

Dropped ceilings/soffits, shafts, and chases shall be capped with an air barrier lid and sealed (attic insulation does not drop down into soffits).

Walls shall be framed to allow insulation in corners and in headers.

Wall insulation shall be enclosed on 6 sides. Includes an air barrier, backside of knee-walls.

Wall batt insulation shall be cut all pipes, wiring and boxes in cavity (recommend blown insulation).

All gaps and voids sealed between conditioned and un-conditioned spaces, including garages, crawlspaces, around windows and doors, and all penetrations.

Rim joist insulation shall include a sealed air barrier on the inside face of insulation, or closed cell spray foam.

Floor insulation in contact with sheathing/lid below. Air barrier underside of cantilevers. Fill floor cavities rooms over garages.

Recessed can lights, boxes and HVAC boots penetrating the thermal envelope shall be sealed.

Air barrier behind electrical boxes or closed cell foam, caulk, gaskets, or air sealed boxes.

Exterior walls adjacent to fireplaces, tubs, showers shall include an inside surface air barrier."

(4)In IRC, Section M1401.3 the word "approved" is deleted in the first sentence and the following is added after the word "methodologies," "complying with M1401.3.1."

(5)A new IRC, Section M1401.3.1, is added as follows:

"M1401.3.1 Qualifications. An individual performing load calculations shall be qualified by completing HVAC training from one of the following:

1. HVAC load calculation education from ACCA;

2. A recognized educational institution;

3. HVAC equipment manufacturer's training; or

4. Other recognized industry certification."

(6)In IRC, Section M1402.1, the following is added at the end of the second sentence: "or UL/CSA 60335-2-40."

(7)In IRC, Section M1403.1, the characters "/ANCE" are deleted.

(8)IRC, Section M1411.9, is deleted.

(9)In IRC, Section M1412.1, the characters "/ANCE" are deleted.

(10)In IRC, Section M1413.1, the characters "/ANCE" are deleted.

Amended by Chapter 47 , 2026 General Session