Quality Insulation Installation (QII): What It Is and How to Pass the Inspection

Quality Insulation Installation (QII) is a Title 24 field verification that checks insulation was installed properly and that the building's air barrier is continuous. It is not enough for the right R-value to be on site. Insulation has to be installed without gaps, voids or excess compression, and air leaks through framing have to be sealed. The insulation installer follows the procedure in Reference Residential Appendix RA3.5, and an ECC-Rater (formerly HERS rater) verifies it in the field, mostly before drywall goes up. Under the 2025 Energy Code, QII is required under the prescriptive path for newly constructed single-family homes in all 16 climate zones.

Gaps, voids and compressed batts can cut an insulated wall's real performance well below its label. QII is how the code checks that the insulation and air barrier are installed well enough to support the performance assumed in your energy documents. It is a visual inspection of the installation, not a measurement of the wall's R-value.

Table 150.1-A of the 2025 Standards marks QII as required in every climate zone under the prescriptive path for new single-family homes, including detached ADUs. Additions over 700 square feet must meet the Section 150.1(c) prescriptive requirements, with a few addition-specific modifications, and those include QII. When an addition over 700 square feet is a conversion of unconditioned space, such as a garage, QII doesn't require insulating the existing window and door headers, or air sealing where the existing air barrier isn't removed or replaced. For additions of 700 square feet or less, Section 150.2(a)1Bv says QII does not apply.

On the performance path, QII becomes a required ECC verification whenever the energy model includes QII credit. Because QII is part of the prescriptive package, skipping it on a new home generally means making up the difference elsewhere in the model. Your energy consultant can tell you what dropping it would cost.

Check the ECC or HERS feature summary on your CF1R. If QII is listed, it is required for your permit.

RA3.5 applies to the whole thermal envelope of a new building, covering walls, ceilings and roofs, and floors. Every insulation type is included, from batts and loose fill to spray foam, rigid board, structural insulated panels (SIPs) and insulating concrete forms (ICFs). The rater checks two things.

The air barrier. Wall cavities must be caulked, foamed or otherwise sealed against the outdoors, attic, garage and crawlspace. That includes plumbing and wiring penetrations through top and bottom plates, electrical boxes that penetrate the sheathing, and bottom plates sealed to the subfloor or slab.

The insulation installation. RA3.5 has criteria for each insulation type. Batts and loose fill must fill each cavity side to side, top to bottom and front to back, while spray foam, rigid board and other assemblies have their own thickness, coverage and air-barrier criteria. Batts should touch the sheathing behind and the wallboard in front, with no gaps or voids. They must be cut or split around wiring and plumbing, with compression limited to 30 percent of nominal thickness at obstructions. Narrow spaces at corners and wall intersections must be filled, and single-member window and door headers generally must be insulated (R-3 minimum in 2x4 walls, R-5 in other assemblies). RA3.5 has an exception for a single-member header that is the same width as the wall when the whole wall has at least R-2 insulation.

QII takes more than one visit. Appendix RA2 says the measure requires inspecting the air barrier and the insulation behind tubs and showers at framing rough-in. Wall, floor and ceiling insulation must be verified before drywall, and attic insulation may need a follow-up. A typical sequence:

• Rough-in or framing stage: air sealing at plates and penetrations, insulation and air barrier behind tub and shower enclosures, hard-to-reach cavities at corners. Some of these spots can only be insulated before the tub, exterior sheathing or stucco lath goes on.
• Insulation stage, before drywall: all wall, floor and ceiling insulation installed and visible.
• Final or attic stage: blown attic insulation depth and coverage, attic access, and any items deferred from earlier visits.

Rater pricing reflects the multiple visits. Some raters quote QII as one price that covers several trips, while others charge per visit, so ask whether your quote covers every stage. See what a HERS rater costs.

The biggest scheduling mistake is letting the drywall crew in before the rater signs off on the insulation stage. If walls get closed first, the rater cannot verify them. That can mean opening walls or reworking the compliance approach.

• Missing or incomplete sealing at top and bottom plates, plumbing and wiring penetrations, and electrical boxes.
• Uninsulated or poorly insulated spaces behind tubs and showers, with no air barrier on the inside of the exterior wall there.
• Batts stuffed behind wiring or pipes instead of split around them, leaving compression or voids.
• Batts not fully filling the cavity front to back, or inset-stapled faced batts left with gaps.
• Empty narrow cavities at corners, wall intersections and beside window and door jambs.
• Uninsulated single-member headers that don't qualify for the same-width-as-the-wall exception.
• Kneewalls, skylight shafts and the house-to-garage wall left without a complete air barrier.
• Missing insulation certificates or R-value markings for loose fill, such as depth markers in the attic.

Fixing these is usually cheap before drywall and expensive after. Give your insulation subcontractor a copy of the RA3.5 criteria and do a walk-through yourself before calling the rater.

The insulation installer completes the installation certificate (CF2R) and registers it with the ECC-Provider's data registry. The ECC-Rater inspects and registers the certificate of verification (CF3R). The building inspector checks that the registered documents are complete at final. Our guide to CF2R vs CF3R explains the paperwork.

QII has to be scheduled around your framing and insulation dates, so line up your rater early. Search certified raters by city, county or climate zone in the Title 24 Directory, or start with a local page like San Bernardino County.