If you're building in Utah, mark your calendar. Starting July 1, 2026, the new IRC Chapter 11 energy code takes effect — and it brings meaningful changes to insulation, air sealing, duct systems, and testing requirements. The good news? Compliance is straightforward when you know what's expected.
Here's a plain-language breakdown of what's changing and how to stay on the right side of code.
Insulation Minimums Are Non-Negotiable
Under Section R1102.2, minimum R-values are clearly defined:
Exterior Walls
R-21
Ceiling / Roof
R-38
Floors (unconditioned)
R-30
Basement Walls
R-10/R-13
Windows and glazed doors must meet a U-factor of 0.32 or better. Opaque doors require a minimum U-factor of 0.6.
Air Sealing: The Details That Matter
A tight building envelope is central to the new code. Key requirements include:
- Continuous air barrier across the entire thermal envelope — all breaks and joints sealed
- Dropped ceilings, soffits, shafts, and chases must be capped with an air-barrier lid
- Rim joists sealed with an air barrier or closed-cell spray foam
- All penetrations sealed — recessed lights, electrical boxes, HVAC boots
- Exterior walls at fireplaces, tubs, and showers require an interior air barrier
- Air-permeable insulation (fiberglass, rock wool, cellulose) cannot serve as the air barrier
Skip the Blower Door Test — If You Qualify
Not every project needs a blower door test. Table R41105 offers an alternative for builders who follow a prescriptive air-sealing checklist — including proper installation per manufacturer instructions, enclosed wall insulation on all 6 sides, and full-contact floor insulation. Follow the checklist, document it, and you may be able to skip the test altogether.
If you do test, maximum air leakage is capped at 5.0 ACH (6.0 for multifamily).
Duct Systems & Mechanical Rooms
Ducts outside conditioned space must be insulated to a minimum of R-8 (exception: ducts buried under concrete floors). Duct systems in unconditioned attics must be tested for total air leakage:
- With air handler installed: max 6.0 CFM per 100 sq ft of conditioned floor area
- Without air handler: max 5.0 CFM per 100 sq ft
Mechanical rooms drawing combustion air from unconditioned space must be separated from those unconditioned spaces. And if tested air leakage is at or below 3.0 ACH, mechanical ventilation is required.
Two Paths to Compliance
Under Section R1101.3, builders can choose their compliance approach:
Prescriptive
Meet or exceed all minimum R-values and U-factors in R1102.2. No modeling required at plan check.
Performance
Use U.S. DOE REScheck showing ≥5% better than Utah 2012 baseline, or achieve a HERS rating of 67 or better. Verified at finale.
Bottom Line for SLHBA Members
The new code rewards builders who are detail-oriented with their air sealing and insulation practices. Start reviewing your standard specs now, train your crews on the checklist alternative to blower door testing, and work with your inspectors early. July 1 will be here before you know it — and great homes really do start with good code.