International Energy Conservation Code 2018 (IECC 2018)

Heads up: There are no amended sections in this chapter.

Table R301.1 shall be used in determining the applicable requirements from Chapter 4. Locations are assigned a climate zone based on Section R301.3.

Figure R301.1 Climate Zones.


TABLE R301.1


Key: A — Moist
Asterisk (*) indicates a warm-humid location.
2A Alachua*
2A Baker*
2A Bay*
2A Bradford*
2A Brevard*
1A Broward*
2A Calhoun*
2A Charlotte*
2A Citrus*
2A Clay*
1A Collier*
2A Columbia*
2A DeSoto*
2A Dixie*
2A Duval*
2A Escambia*
2A Flagler*
2A Franklin*
2A Gadsden*
2A Gilchrist*
2A Glades*
2A Gulf*
2A Hamilton*
2A Hardee*
1A Hendry*
2A Hernando*
2A Highlands*
2A Hillsborough*
2A Holmes*
2A Indian River*
2A Jackson*
2A Jefferson*
2A Lafayette*
2A Lake*
1A Lee*
2A Leon*
2A Levy*
2A Liberty*
2A Madison*
2A Manatee*
2A Marion*
2A Martin*
1A Miami-Dade*
1A Monroe*
2A Nassau*
2A Okaloosa*
2A Okeechobee*
2A Orange*
2A Osceola*
1A Palm Beach*
2A Pasco*
2A Pinellas*
2A Polk*
2A Putnam*
2A Santa Rosa*
2A Sarasota*
2A Seminole*
2A St. Johns*
2A St. Lucie*
2A Sumter*
2A Suwannee*
2A Taylor*
2A Union*
2A Volusia*
2A Wakulla*
2A Walton*
2A Washington*
Warm humid counties are identified in Table R301.1 by an asterisk.

The climate zone for any location outside the United States shall be determined by applying Table R301.3(1) and then Table R301.3(2).

TABLE R301.3(1)


Marine (C) Definition—Locations meeting all four criteria:
  1. Mean temperature of coldest month between -3°C (27°F) and 18°C (65°F).
  2. Warmest month mean < 22°C (72°F).
  3. At least four months with mean temperatures over 10°C (50°F).
  4. Dry season in summer. The month with the heaviest precipitation in the cold season has at least three times as much precipitation as the month with the least precipitation in the rest of the year. The cold season is October through March in the Northern Hemisphere and April through September in the Southern Hemisphere.
Dry (B) Definition—Locations meeting the following criteria:
Not marine and Pin < 0.44 × (TF - 19.5) [Pcm < 2.0 × (TC + 7) in SI units]
Pin = Annual precipitation in inches (cm)
T = Annual mean temperature in °F (°C)
Moist (A) Definition—Locations that are not marine and not dry.
Warm-humid Definition—Moist (A) locations where either of the following wet-bulb temperature conditions shall occur during the warmest
six consecutive months of the year:
  1. 67°F (19.4°C) or higher for 3,000 or more hours; or
  2. 73°F (22.8°C) or higher for 1,500 or more hours.

For SI: °C = [(°F) - 32]/1.8, 1 inch = 2.54 cm.

TABLE R301.3(2)


IP Units SI Units
1 9000 < CDD50°F 5000 < CDD10°C
2 6300 < CDD50°F ≤ 9000 3500 < CDD10°C ≤ 5000
3A and 3B 4500 < CDD50°F ≤ 6300 AND HDD65°F ≤ 5400 2500 < CDD10°C ≤ 3500 AND HDD18°C ≤ 3000
4A and 4B CDD50°F ≤ 4500 AND HDD65°F ≤ 5400 CDD10°C ≤ 2500 AND HDD18°C ≤ 3000
3C HDD65°F ≤ 3600 HDD18°C ≤ 2000
4C 3600 < HDD65°F ≤ 5400 2000 < HDD18°C ≤ 3000
5 5400 < HDD65°F ≤ 7200 3000 < HDD18°C ≤ 4000
6 7200 < HDD65°F ≤ 9000 4000 < HDD18°C ≤ 5000
7 9000 < HDD65°F ≤ 12600 5000 < HDD18°C ≤ 7000
8 12600 < HDD65°F 7000 < HDD18°C

For SI: °C = [(°F) - 32]/1.8.

The tropical climate zone shall be defined as:

  1. Hawaii, Puerto Rico, Guam, American Samoa, U.S. Virgin Islands, Commonwealth of Northern Mariana Islands; and
  2. Islands in the area between the Tropic of Cancer and the Tropic of Capricorn.
The interior design temperatures used for heating and cooling load calculations shall be a maximum of 72°F (22°C) for heating and minimum of 75°F (24°C) for cooling.
Materials, systems and equipment shall be identified in a manner that will allow a determination of compliance with the applicable provisions of this code.
The thermal resistance (R-value) of insulation shall be determined in accordance with the U.S. Federal Trade Commission R-value rule (CFR Title 16, Part 460) in units of h • ft2 • °F/Btu at a mean temperature of 75°F (24°C).

R-values referenced in Chapter 4 of this code refer to the R-values of the added insulation only. The R-values of structural building materials such as framing members, concrete blocks or gypsum board shall not be included.

Exception: R402.1.5 Total UA Alternative.

When installing two layers of bulk or board insulation, the R-values of each material may be added together for a total R-value. When installing two separate reflective insulation products in layers, the total R-value of the system shall have been achieved by testing under FTC regulations, 16 CFR Part 460.
The thermal resistance (R-value) of insulated siding shall be determined in accordance with ASTM C1363. Installation for testing shall be in accordance with the manufacturer's instructions.
An R-value identification mark shall be applied by the manufacturer to each piece of building thermal envelope insulation 12 inches (305 mm) or greater in width. Alternately, the insulation installers shall provide a certification listing the type, manufacturer and R-value of insulation installed in each element of the building thermal envelope. For blown or sprayed insulation (fiberglass and cellulose), the initial installed thickness, settled thickness, settled R-value, installed density, coverage area and number of bags installed shall be listed on the certification. For sprayed polyurethane foam (SPF) insulation, the installed thickness of the areas covered and R-value of installed thickness shall be listed on the certification. For insulated siding, the R-value shall be labeled on the product's package and shall be listed on the certification. The insulation installer shall sign, date and post the certification in a conspicuous location on the job site.
The thickness of blown-in or sprayed roof/ceiling insulation (fiberglass or cellulose) shall be written in inches (mm) on markers that are installed at least one for every 300 square feet (28 m2) throughout the attic space. The markers shall be affixed to the trusses or joists and marked with the minimum initial installed thickness with numbers not less than 1 inch (25 mm) in height. Each marker shall face the attic access opening. Spray polyurethane foam thickness and installed R-value shall be listed on certification provided by the insulation installer.
Insulating materials shall be installed such that the manufacturer's R-value mark is readily observable upon inspection.
Minimum equipment efficiency rating identification for heating, cooling, hot water, swimming pool heating and filtration, and lighting shall be in accordance with industry standards and as described in Chapter 4 of the Commercial Provisions of this code, as applicable, for such equipment.

U-factors of fenestration products shall be determined as follows.

  1. For windows, doors and skylights, U-factor ratings shall be determined in accordance with NFRC 100.
  2. Where required, garage door U-factors shall be determined in accordance with either NFRC 100 or ANSI/DASMA 105.

U-factors shall be determined by an accredited, independent laboratory, and labeled and certified by the manufacturer.

Products lacking such a labeled U-factor shall be assigned a default U-factor from Table R303.1.3(1) or R303.1.3(2). The solar heat gain coefficient (SHGC) and visible transmittance (VT) of glazed fenestration products (windows, glazed doors and skylights) shall be determined in accordance with NFRC 200 by an accredited, independent laboratory, and labeled and certified by the manufacturer. Products lacking such a labeled SHGC or VT shall be assigned a default SHGC or VT from Table R303.1.3(3).

TABLE R303.1.3(1)


Single Double
Metal 1.20 0.80 2.00 1.30
Metal with Thermal Break 1.10 0.65 1.90 1.10
Nonmetal or Metal Clad 0.95 0.55 1.75 1.05
Glazed Block 0.60

TABLE R303.1.3(2)


Uninsulated Metal 1.20
Insulated Metal 0.60
Wood 0.50
Insulated, nonmetal edge, max 45% glazing,
any glazing double pane

TABLE R303.1.3(3)


Clear Tinted Clear Tinted
SHGC 0.8 0.7 0.7 0.6 0.6
VT 0.6 0.3 0.6 0.3 0.6
Materials, systems and equipment shall be installed in accordance with the manufacturer's instructions and the Florida Building Code, Building or Florida Building Code, Residential, as applicable.

Insulation materials shall comply with the requirements of their respective ASTM standard specification and shall be installed in accordance with their respective ASTM installation practice in Table R303.2.1 in such a manner as to achieve rated R-value of insulation. Open-blown or poured loose-fill insulation shall not be used in attic roof spaces when the slope of the ceiling is more than 3 in 12. When eave vents are installed, baffling of the vent openings shall be provided to deflect the incoming air above the surface of the insulation.

Exception: Where metal building roof and metal building wall insulation is compressed between the roof or wall skin and the structure.

TABLE R303.2.1


Mineral Fiber Batt/Blanket ASTM C665 ASTM C1320
Mineral Fiber Loose Fill ASTM C764 ASTM C1015
Cellulose Loose Fill ASTM C739 ASTM C1015
Polystyrene Foam ASTM C578
Polyisocyanurate Foam ASTM C1289
Reflective ASTM C1224 ASTM C727
Radiant Barrier ASTM C1313 ASTM C1158
Vermiculite ASTM C516
Perlite ASTM C549
Spray-applied Rigid Cellular Polyurethane Foam ASTM C1029
Interior Radiation Control Coating Systems ASTM C1321

Insulation that has been compressed to 85 percent or less of the manufacturer's rated thickness for the product shall use the R-values given in Table 303.2.1.1. These values are to be used except where data developed by an independent testing laboratory are provided.

TABLE R303.2.1.1


% OF ORIGINAL THICKNESS R-5 R-7 R-11 R-14 R-19 R-30 R-38
90 5 6 10 13 18 28 36
80 4 6 10 12 17 26 33
70 4 5 9 11 15 24 30
60 3 5 8 10 14 22 27
50 3 4 7 9 12 18 24
40 2 4 6 8 10 15 20
30 2 3 4 6 8 12 16
20 2 2 2 3 4 10 10

Insulation shall be installed in a permanent manner in substantial contact with the inside surface in accordance with manufacturer's recommendations for the framing system used. Flexible batt insulation installed in floor cavities shall be supported in a permanent manner by supports no greater than 24 inches (610 mm) on center (o.c.).

Exception: Insulation materials that rely on airspaces adjacent to reflective surfaces for their rated performance.

Exterior insulation shall be covered with a protective material to prevent damage from sunlight, moisture, landscaping operations, equipment maintenance and wind. In attics and mechanical rooms, a way to access equipment that prevents damaging or compressing the insulation shall be provided. Foundation vents shall not interfere with the insulation. Insulation materials in ground contact shall have a water absorption rate no greater than .3 percent when tested in accordance with ASTM C272, shall cover the exposed exterior insulation and shall extend a minimum of 6 inches (153 mm) below grade.
Maintenance instructions shall be furnished for equipment and systems that require preventive maintenance. Required regular maintenance actions shall be clearly stated and incorporated on a readily accessible label. The label shall include the title or publication number for the operation and maintenance manual for that particular model and type of product.
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