5.4 Crawl Spaces, Masonry Veneer, Sunrooms & Heated Garages (R402.2.10–R402.2.12)

Crawl Spaces, Masonry Veneer, Sunrooms, and Heated Garages

Quick Answer: Insulate crawl space walls to Table R402.1.3 unless the crawl is vented to the outdoors and the floor overhead meets the table and R402.2.7. Fasten crawl-wall insulation permanently, run it from the floor to finished grade, then continue vertically or horizontally at least 24 inches. Unvented crawls also need a continuous Class I vapor retarder on exposed earth, overlapped 6 inches and turned 6 inches up the stem wall. Masonry veneer ledges skip insulation on that horizontal step. Thermally isolated sunrooms and heated garages that enclose conditioned space may use ceiling R-19 (Climate Zones 0–4) or R-24 (Climate Zones 5–8) and wall R-13; the wall between that space and the house still takes the full envelope.

R402.2.10 through R402.2.12 close the envelope chapter’s specialty assemblies. Exam 79 items often pair a vented versus unvented crawl with a sunroom that is “just a three-season room” until the drawings show a heat run. The definitions of sunroom and thermal isolation in Chapter 2 [RE] decide which R-value table actually applies.

Crawl space walls (R402.2.10)

Crawl space walls shall be insulated in accordance with Table R402.1.3.

Exception: Crawl space walls associated with a crawl space that is vented to the outdoors and whose floor overhead is insulated in accordance with Table R402.1.3 and Section R402.2.7 do not take the crawl-wall R-value. Both halves of the exception are required. A vented crawl with no floor insulation, or with floor batts sagging away from the subfloor in violation of R402.2.7, still needs crawl-wall insulation (or a repaired floor). An unvented, conditioned, or “encapsulated” crawl is not this exception; those walls stay on the table.

Choosing the exception moves the thermal envelope to the floor. Choosing wall insulation moves the envelope to the stem wall and usually implies an unvented crawl with ground cover. Mixing the two—vents open, walls insulated, floor empty, or vents closed, floor insulated, walls empty—leaves a hole in the envelope.

Installation (R402.2.10.1)

Where crawl space wall insulation is installed, it shall be permanently fastened to the wall and shall extend downward from the floor to the finished grade elevation and then vertically or horizontally for not less than an additional 24 inches (610 mm).

A 30-inch crawl with grade 24 inches below the floor needs insulation down those 24 inches plus another 24 inches turned out on the interior grade or continued down the wall if the wall goes deeper. Loose batts leaned against the concrete without fasteners fail “permanently fastened.” Foam boards with only a few dabs of adhesive that will release in a damp crawl also fail the fastening test at inspection.

Unvented crawl ground cover

Exposed earth in unvented crawl space foundations shall be covered with a continuous Class I vapor retarder in accordance with the IBC or IRC as applicable. Joints shall overlap by 6 inches (153 mm) and be sealed or taped. Edges shall extend not less than 6 inches (153 mm) up the stem walls and shall be attached to the stem walls.

Class I means a permeance of 0.1 perm or less in the referenced IRC/IBC vapor-retarder classification (polyethylene sheeting is the usual product). A Class II kraft facing on a batt is not the ground cover. Unsealed laps, a sheet that stops at the mud sill, or a vapor retarder that is not attached to the stem wall fail R402.2.10.1 even if the R-value on the wall is correct.

Masonry veneer (R402.2.11)

Insulation shall not be required on the horizontal portion of a foundation that supports a masonry veneer. The brick or stone ledge is a shelf. The code does not demand a wedge of foam on that shelf. Vertical foundation walls still follow basement, crawl, or slab-edge rules as applicable. Inspectors should not fail a job because the brick ledge itself is bare, and they should not skip the vertical edge insulation just because veneer is present.

Sunrooms and heated garages (R402.2.12)

Sunrooms enclosing conditioned space and heated garages shall meet the insulation requirements of this code.

Chapter 2 [RE] defines a sunroom as a one-story structure attached to a dwelling with a glazing area in excess of 40% of the gross area of the structure’s exterior walls and roof. A heated garage is a garage provided with space heating. Conditioned space is space enclosed within the building thermal envelope and directly or indirectly heated or cooled—including space that shares openings with conditioned rooms, is separated only by uninsulated assemblies, or contains uninsulated ducts, piping, or other heating or cooling sources.

If a sunroom or heated garage encloses conditioned space and is not thermally isolated, its ceiling, walls, and (where applicable) floors use the same Table R402.1.3 values as the dwelling. A “sunroom” with a duct, a baseboard, or an uninsulated opening to the family room is inside the envelope.

Thermal isolation exception

Thermal isolation (Chapter 2 [RE]) is physical and space-conditioning separation from conditioned spaces. The conditioned spaces shall be controlled as separate zones for heating and cooling or conditioned by separate equipment.

For sunrooms and heated garages provided thermal isolation and enclosed conditioned space, the following exceptions to the insulation requirements apply:

1. Minimum ceiling insulation R-values: R-19 in Climate Zones 0 through 4, and R-24 in Climate Zones 5 through 8.
2. Minimum wall insulation R-value: R-13 in all climate zones.

Walls separating a sunroom or heated garage with thermal isolation from conditioned space shall comply with the building thermal envelope requirements of this code. The shared wall, shared ceiling, or shared floor is still a full Table R402.1.3 (or U-factor) assembly. The reduced R-19 / R-24 / R-13 numbers apply to the sunroom or garage envelope that faces the outdoors, not to the wall that protects the house.

Fenestration for these spaces is in R402.3.5 (taught with Chapter 6), not here: thermally isolated sunrooms and heated garages in Climate Zones 2 through 8 may use fenestration U-0.45 and skylight U-0.70, while new fenestration in the separating wall still meets the dwelling table. Do not import those U-factors into an R402.2.12 insulation answer.

Heated attached or detached private garages also appear in the R402.4.1.2 testing exception: field verification of Table R402.4.1.1 may substitute for a blower-door number when those garages are thermally isolated per R402.2.12 and R402.3.5. That testing trade is Chapter 7 material; the insulation prerequisite is this section.

Field scenario: thermally isolated sunroom

A Climate Zone 6 two-story adds a 12-foot by 16-foot sunroom with glazing over 40% of its exterior walls and roof. The sunroom has its own ductless mini-split. A weatherstripped, labeled exterior-grade door and an insulated wood-frame wall separate the sunroom from the dining room. The dining-room thermostat does not control the mini-split.

That is thermal isolation plus enclosed conditioned space. The sunroom’s exterior ceiling may be R-24 and its exterior walls R-13 under R402.2.12. The separating wall toward the dining room must still meet Climate Zone 6 wood-frame options (R-30 or R-20+5ci or R-13+10ci or R-0+20ci), not R-13. If the contractor leaves a 4-foot cased opening with no door, thermal isolation fails: the sunroom is then simply more conditioned space, and the sunroom ceiling jumps to Table R402.1.3 R-60 (or the R402.2.1 attic trade if it has a qualifying attic).

A heated garage with a unit heater, a tight fire-rated door to the mudroom, and no shared uninsulated ducts can use the same reduced garage-envelope R-values, while the house-to-garage wall stays a full envelope assembly and still needs the air-sealing required of garage separation.

Masonry-veneer-plus-crawl combinations

A Climate Zone 4 house on a vented crawl with brick veneer often shows three details on one foundation sheet:

1. Floor overhead insulated to R-19 in permanent contact with the subfloor (vented-crawl exception + R402.2.7).
2. No crawl-wall insulation, because the exception applies.
3. A bare brick ledge under R402.2.11, which does not excuse skipping slab-edge or stem insulation on a different part of the same building if that part is a slab-on-grade wing.

Read the assembly in front of you. Veneer, crawl, and slab rules do not override each other; they occupy different surfaces.

Plan-review checklist

• Crawl: vented or unvented; floor R-value and R402.2.7 method versus wall R-value, fastening, and 24-inch turn; Class I ground sheet with 6-inch laps and 6-inch stem attachment if unvented.
• Veneer: horizontal ledge may be uninsulated; vertical walls still follow their section.
• Sunroom / heated garage: confirm Chapter 2 sunroom glazing percentage if claimed; confirm thermal isolation (physical separation plus separate zone or equipment); apply R-19/R-24 and R-13 only to that enclosure; keep the shared wall on the full table.

Independent OpenExamPrep study material for ICC Exam 79 covers 2021 IECC residential Sections R402.2.10 through R402.2.12. It is not an ICC or IECC publication; match the first-printing text in the bound book you bring to the open-book exam.