11.3 Tropical Climate Region Option (R407)
Key Takeaways
- R407.1 applies only in the tropical climate region at elevations less than 2,400 feet (731.5 m) above sea level.
- Not more than one-half of the occupied space may be air conditioned, and the occupied space shall not be heated.
- Solar, wind, or other renewable energy shall supply at least 80 percent of the energy for service water heating.
- Conditioned-space glazing needs SHGC ≤ 0.40 or an overhang projection factor ≥ 0.30; operable fenestration must provide ventilation area ≥ 14 percent of each room's floor area, or an equivalent fan.
- The roof must slope at least 1/4 : 12 without ponding, and the roof must meet IECC commercial Table C402.3 or the roof/ceiling must have at least R-15, with attics above insulation vented and attics below insulation unvented.
11.3 Tropical Climate Region Option (R407)
Quick Answer: R407 is available only to residential buildings in the tropical climate region at elevations less than 2,400 feet (731.5 m). Compliance requires all of the listed R407.2 items—not a majority, and not "enough shading to offset a furnace." An inland Climate Zone 2 house cannot use R407 because Climate Zone 2 is not the tropical climate region.
Independent OpenExamPrep material for ICC Exam 79 treats R407 as a scope-and-checklist path. Chapter 3 already warned that tropical is not a warm-summer nickname for R405. This section is the field list you walk when someone actually claims R401.2.4.
Scope comes first: region and elevation
R407.1 establishes alternative criteria for residential buildings in the tropical region at elevations less than 2,400 feet above sea level. Both limits apply. A dwelling in a mapped tropical climate region (Hawaii, Puerto Rico, Guam, the U.S. Virgin Islands, American Samoa, the Northern Mariana Islands, and other locations Chapter 3 of the IECC assigns to the tropical climate region) still fails R407 if the site is at 2,400 feet or higher. A house at 80 feet of elevation in inland Georgia, Dallas, or Birmingham is in Climate Zone 2 or 3, not the tropical climate region, and cannot use this option at any elevation.
R401.2.5 still applies. Because R407 is the R401.2.4 primary option, the additional-efficiency overlay remains on the project; the R401.3 certificate must identify the path and the additional-efficiency option selected. R407 does not erase lighting (it expressly points to R404) and does not authorize a silent skip of the certificate.
All of the R407.2 items
R407.2 says compliance with this section requires the following. Teach it as a closed list. Missing one item fails the path.
| # | 2021 R407.2 requirement | What the examiner or inspector actually looks for |
|---|---|---|
| 1 | Not more than one-half of the occupied space is air conditioned | Floor-area takeoff of occupied rooms versus the rooms served by cooling equipment. A fully ducted two-story house with every bedroom on the air handler fails this item even if the porch is open |
| 2 | The occupied space is not heated | No furnace, heat pump heating mode serving occupied rooms, electric baseboard, or similar heating of occupied space. A "small bathroom heater" that heats occupied space still heats occupied space |
| 3 | Solar, wind, or other renewable energy supplies not less than 80 percent of the energy for service water heating | Renewable production sized to service water heating, not a token collector. Ask for the calculation that 80 percent of DHW energy is renewable |
| 4 | Glazing in conditioned spaces has SHGC ≤ 0.40, or an overhang with projection factor ≥ 0.30 | NFRC SHGC on conditioned-space glass, or a dimensioned overhang where PF = A/B ≥ 0.30. Unconditioned lanai glass is not the test; the conditioned rooms are |
| 5 | Permanently installed lighting is in accordance with R404 | High-efficacy sources in permanently installed fixtures (kitchen-appliance lighting excepted) and the R404 control rules taught in Chapter 10 |
| 6 | Exterior roof complies with one option in IECC commercial Table C402.3, or the roof or ceiling has insulation ≥ R-15. Where attics are present, attics above the insulation are vented and attics below the insulation are unvented | Cool-roof / Table C402.3 documentation or an R-15 roof/ceiling. Attic venting must match which side of the insulation the attic occupies |
| 7 | Roof slope not less than 1/4 : 12 (2 percent). The finished roof does not have water-accumulation areas | Slope on the roof plan and a finished roof without birdbaths or scupper-less low spots |
| 8 | Operable fenestration provides ventilation area not less than 14 percent of the floor area in each room, or equivalent ventilation by a ventilation fan | Room-by-room operable area (sash opening, not just rough opening) ≥ 0.14 × that room's floor area, or a fan schedule that is equivalent |
| 9 | Bedrooms with exterior walls facing two different directions have operable fenestration on exterior walls facing two directions | A corner bedroom needs operable glass on both exposed walls, not a single window wall |
| 10 | Interior doors to bedrooms are capable of being secured in the open position | Hold-opens, hooks, or hardware that keeps the door open so cross-ventilation can use the bedroom |
| 11 | A ceiling fan or ceiling fan rough-in is provided for bedrooms and the largest space that is not used as a bedroom | Count bedrooms plus the largest living, dining, or family room. A fan in every bedroom with none in the great room fails this item |
Projection factor is the overhang depth divided by the vertical distance from the underside of the overhang to the sill of the glazed opening. A 2-foot overhang over an 8-foot drop is PF = 0.25 and does not satisfy the 0.30 alternative; that house needs SHGC ≤ 0.40 on conditioned-space glazing or a deeper (or lower) overhang.
Item 6's attic sentence is easy to invert. Insulation at the ceiling with a vented attic above is the common tropical assembly. Insulation at the roof deck with an attic below the insulation must be an unvented attic. A vented attic below roof-deck insulation is the wrong pairing.
Why an inland Climate Zone 2 house cannot borrow R407
Scenario. A builder in an inland Climate Zone 2 subdivision (for example, a Dallas- or Atlanta-area lot at 600 feet) submits an R407 checklist: half the house on mini-splits, no furnace, a solar water heater claimed at 80 percent, SHGC 0.40, R404 lighting, R-15 ceiling, 1/4 : 12 roof, 14 percent operable glass, corner-bedroom windows, door hold-opens, and ceiling-fan rough-ins. The packet is tidy and the elevation is under 2,400 feet.
The path still fails. R407.1 is limited to residential buildings in the tropical climate region. Inland Climate Zone 2 is a warm-humid or mixed classification on the IECC climate map; it is not the tropical climate region. Elevation below 2,400 feet does not convert a Climate Zone 2 county into Hawaii. Tell the applicant to pick R401.2.1, R401.2.2, or R401.2.3 and to bring the matching R401.2.5 method. Do not field-approve R407 because the house "lives like a tropical house."
The same rejection applies to a coastal Climate Zone 2 mainland county that is not mapped as tropical. Humidity and palm trees are not the Chapter 3 tropical designation.
How to inspect a real tropical claim
When the site is in the tropical climate region and below 2,400 feet, walk the list instead of sampling it. Measure occupied-space area versus conditioned area so that air-conditioned occupied space is not more than one-half. Confirm there is no occupied-space heating equipment. Review the service-water renewable fraction, not only the presence of a panel. Check SHGC labels in conditioned rooms or measure overhangs for PF ≥ 0.30. Open operable sashes and compare free area to each room's floor area (14 percent), or read the fan schedule. In a two-exposure bedroom, look for operable fenestration on both exposures. Latch a bedroom door open. Count ceiling fans or listed rough-ins in every bedroom and in the largest non-bedroom space. Sight the roof slope and look for ponding. If an attic exists, match venting to the insulation location.
R407 does not create a simulated reference home and does not produce an ERI. If the only energy sheet is an R405 printout or an ERI certificate, the applicant has declared a different path. Ask for a revision that either completes the R407.2 list or redeclarates R405 or R406.
A high-elevation tropical site is the mirror-image reject. A house on a 2,600-foot tropical ridge fails R407.1 even if every R407.2 checkbox is ticked, because the elevation is not less than 2,400 feet. Move that project to R405, R406, or the prescriptive option.
This is independent OpenExamPrep teaching of 2021 IECC residential provisions for Exam 79 study, not a claim of ICC endorsement.
What elevation limit does 2021 IECC R407.1 place on the tropical climate region option?
An inland Climate Zone 2 house at 600 feet submits a complete-looking R407.2 checklist (half the occupied space cooled, no heat, 80 percent renewable water heating, SHGC 0.40, R404 lighting, R-15 ceiling, 1/4 : 12 roof, 14 percent operable glass, two-direction bedroom windows, door hold-opens, and ceiling-fan rough-ins). Can the house use R407?
On a dwelling that is in the tropical climate region and below 2,400 feet, which statement matches R407.2?
A tropical-region bedroom has exterior walls facing two directions. Which R407.2 ventilation and door rules apply to that room?