7.2 Table R402.4.1.1: Openings, Penetrations, Tubs, Garages & Boxes
Key Takeaways
- Duct and flue shafts to exterior or unconditioned space shall be sealed; utility penetrations shall be caulked or gasketed to allow expansion, contraction, and vibration, with insulation fitted tightly to maintain the required R-value.
- Narrow cavities of 1 inch or less that cannot be insulated shall be air sealed; batts in narrow cavities shall be cut to fit, or the cavity shall be filled with insulation that conforms to the space.
- A shower or tub on an exterior wall needs an air barrier that separates the wall from the shower or tub, and that exterior wall shall be insulated.
- Electrical and communication boxes on exterior walls need an air barrier behind the box or an air-sealed box; HVAC register boots that penetrate the envelope shall be sealed to the subfloor, wall, or ceiling.
- Concealed fire sprinklers, where required to be sealed, may be sealed only as the manufacturer recommends; caulk shall not fill voids between cover plates and walls or ceilings.
7.2 Table R402.4.1.1: Openings, Penetrations, Tubs, Garages & Boxes
Quick Answer: After the big assemblies in Section 7.1, Table R402.4.1.1 scores the openings. Duct and flue shafts to exterior or unconditioned space shall be sealed; utility penetrations shall be caulked or gasketed so they can move; insulation shall be fitted tightly around those utilities. Cavities 1 inch or less that cannot be insulated shall be air sealed. Garage-to-house air sealing is required. Recessed lights in the envelope shall be sealed per R402.4.5, airtight and IC-rated, and buried or surrounded with insulation. A tub on an exterior wall needs an air barrier that separates the wall from the tub, and that wall shall be insulated. Boots that penetrate the envelope shall be sealed to the finish they pass through. Concealed sprinklers take manufacturer-recommended sealing only.
Independent OpenExamPrep material for ICC Exam 79 keeps this half of the table separate because the fails look like "the insulation was installed" until you open a tub surround or look behind a garage-ceiling boot. The national 2021 IECC first printing is the exam text. Do not import a state's energy-subcode amendments from a public viewer.
Where required by the code official, an approved third party still verifies both columns of the table. A visual "looks insulated" pass is not a substitute when that third-party inspection is required.
Shafts and penetrations
| Column | 2021 Table R402.4.1.1 rule |
|---|---|
| Air barrier | Duct and flue shafts to exterior or unconditioned space shall be sealed. Utility penetrations of the air barrier shall be caulked, gasketed, or otherwise sealed and shall allow for expansion, contraction, and mechanical vibration. |
| Insulation | Insulation shall be fitted tightly around utilities passing through shafts and penetrations in the building thermal envelope to maintain the required R-value. |
A metal flue chase that opens into a vented attic is a stack-effect highway if the chase is not sealed where it leaves the conditioned envelope. The seal has to tolerate flue temperature and movement; random polyurethane foam against a hot flue can be a listing and fire-separation fail as well as a poor seal. Plumbing and electrical penetrations need a seal that can move. Rigid, brittle caulk that cracks after the first heating season does not meet the expansion-and-vibration sentence.
Tight-fit insulation around a waste pipe or a cluster of cables is the other column. Leaving a 4-inch uninsulated halo around a tub valve or a dryer vent because "the batt wouldn't fit" drops the assembly R-value at the exact hole the air barrier is trying to close. Cut the batt, dense-pack the halo, or use a conforming insulation.
Narrow cavities
Air barrier: narrow cavities of 1 inch (25 mm) or less that are not able to be insulated shall be air sealed.
Insulation: batts to be installed in narrow cavities shall be cut to fit, or narrow cavities shall be filled with insulation that on installation readily conforms to the available cavity space.
The 1-inch trigger is easy to miss on a plans exam. A leftover 3/4-inch space beside a tightly packed shower valve or a doubled king stud is not an excuse to leave an open slot. If you cannot insulate it, you air-seal it. If you can insulate it, you do not compress a 3-1/2-inch batt into a 1-inch slot and call it R-13. Cut the batt to the cavity, or use a product that fills the space (foam, dense pack).
Garage separation
Air barrier: air sealing shall be provided between the garage and conditioned spaces.
Insulation: insulated portions of the garage separation assembly shall be installed in accordance with Sections R303 and R402.2.7.
R303 is the materials-identification chapter (marked R-value, installed thickness). R402.2.7 is the floor-insulation contact rule you already used above garages in Section 7.1. The air-leakage table adds the house-garage air seal: common wall, common ceiling, rim, and any ducts or wires that cross. An attached garage that is unconditioned is outside the thermal envelope. The envelope is the common assemblies, not the overhead door. If the garage is later heated, Chapter 4's conditioned-space test moves the envelope to the garage's exterior walls — and this table's garage-separation row still describes how the remaining common assemblies are sealed.
Recessed lighting (table row)
Air barrier: recessed light fixtures installed in the building thermal envelope shall be air sealed in accordance with Section R402.4.5.
Insulation: those fixtures shall be airtight and IC-rated, and shall be buried or surrounded with insulation.
This row is a pointer plus two field checks. The leakage number (2.0 cfm at 1.57 psf / 75 Pa, ASTM E283) and the gasket-or-caulk-to-finish rule are R402.4.5 in Section 7.4. At the Table R402.4.1.1 inspection you still fail a non-IC can that cannot be buried, a can sitting in an empty drywall box with no insulation around it, or a housing that was never sealed to the ceiling air barrier.
Plumbing, wiring, or other obstructions
Air barrier: all holes created by wiring, plumbing, or other obstructions in the air barrier assembly shall be air sealed.
Insulation: insulation shall be installed to fill the available space and surround wiring, plumbing, or other obstructions, unless the required R-value can be met by installing insulation and air barrier systems completely to the exterior side of the obstructions.
The unless clause is the exterior-continuous-insulation path. If the designer puts the air barrier and the full required R-value entirely outboard of the plumbing and wiring, you do not have to pack every interior bay around those pipes. If the R-value still lives in the cavity, you fill around the obstructions and you seal every hole the plumber or electrician cut in the air barrier. A cluster of wires stuffed through an unsealed hole in the top plate is both an air-barrier fail and a place the batt will never fill.
Shower or tub on an exterior wall
Air barrier: the air barrier installed at exterior walls adjacent to showers and tubs shall separate the wall from the shower or tub.
Insulation: exterior walls adjacent to showers and tubs shall be insulated.
Field scenario: tub on an exterior wall
A Climate Zone 4 hall bath sets a garden tub against the rear exterior wall. The plumber sets the tub, the drywall crew stops at the tub flange, and the insulator never returns. The inspector opens the access panel and sees exterior sheathing, no insulation, and no air barrier — the tub apron is the interior finish. That is a two-column fail.
The air barrier (typically gypsum, a rigid panel, or a listed membrane) must run behind the tub or shower so it separates the exterior wall from the fixture. That wall cavity must still be insulated. Sequencing is the real construction problem: the air barrier and the insulation have to be in place before the tub is set, or the tub has to come back out. A bead of caulk at the tub flange does not replace the wall air barrier, and it does not insulate the cavity.
Electrical and communication boxes on exterior walls
Air barrier: the air barrier shall be installed behind electrical and communication boxes. Alternatively, air-sealed boxes shall be installed. The insulation cell is an em dash.
Two listed methods:
- Continue the wall air barrier behind the box so the box is not a hole in the barrier (box putouts, membranes, or airtight drywall with a sealed box opening).
- Use an air-sealed box. When that product path is used, R402.4.6 (Section 7.4) adds NEMA OS 4, the 2.0 cfm leakage cap, marking, and installation with supplied components.
A standard plastic box with an unsealed hole saw through the exterior sheathing, and with no membrane behind it, meets neither method.
HVAC register boots
HVAC supply and return register boots that penetrate the building thermal envelope shall be sealed to the subfloor, wall covering, or ceiling penetrated by the boot. There is no insulation cell. A boot that dumps supply air into a floor cavity over a garage, or a boot sitting in a saw-cut with daylight around the flange, is an envelope penetration. Seal the boot to the finish, not merely tape the duct to the boot in the joist bay.
Concealed sprinklers
Where required to be sealed, concealed fire sprinklers shall only be sealed in a manner that is recommended by the manufacturer. Caulking or other adhesive sealants shall not be used to fill voids between fire sprinkler cover plates and walls or ceilings.
This row overrides the inspector's instinct to "caulk every hole." A caulk ring around a concealed-sprinkler cover plate can glue the plate down, change the spray pattern, or void the listing. If the listing says a specific gasket or escutcheon, that is the seal. If the listing says do not seal the cover plate, you do not seal the cover plate. Energy sealing happens at a manufacturer-approved location, not in the finish ring.
Inspection sequence for this half of the table
- Shafts and flues: sealed where they leave conditioned space, with movement allowed at utilities.
- Narrow leftover slots: air-sealed if 1 inch or less and uninsulated; otherwise cut-to-fit or conforming fill.
- Garage common wall and ceiling: air-sealed; insulated portions match R303 markings and R402.2.7 contact.
- Recessed cans: IC, airtight, buried or surrounded, with R402.4.5 sealing still due.
- Tubs and showers on exterior walls: air barrier behind the fixture; wall insulated.
- Boxes: barrier behind or air-sealed box. Boots: sealed to the finish they penetrate.
- Concealed sprinklers: manufacturer method only — no caulk between cover plate and finish.
Independent OpenExamPrep study material for Exam 79 treats these rows as sequencing items. If the tub is set before the wall is insulated, the fail is already built in.
A garden tub is set on an exterior wall. The access panel shows exterior sheathing, no insulation, and no air barrier behind the tub. What does Table R402.4.1.1 require?
Concealed fire sprinklers are installed in a gypsum ceiling that is part of the thermal envelope. Which sealing method matches Table R402.4.1.1?
The framer leaves a 3/4-inch slot beside a shower valve in an exterior wall. The slot cannot accept cavity insulation. What does Table R402.4.1.1 require?
A supply boot comes through the subfloor over an unconditioned garage. The duct is taped to the boot in the joist bay, but daylight is visible around the boot at the finish floor. What does Table R402.4.1.1 require?