International Energy Conservation Code 2015 (IECC 2015)

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

Table C301.1 shall be used in determining the applicable requirements from Chapter 4. Locations are assigned a climate zone based on Section C301.3.

Figure C301.1 Climate Zone.

TABLE C301.1


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 C301.1 by an asterisk.

The climate zone for any location outside the United States shall be determined by applying Table C301.3(1) and then Table C301.3(2).

TABLE C301.3(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 C301.3(2)


IP UnitsSI Units
19000 < CDD50°F5000 < CDD10°C
26300 < CDD50°F ≤ 90003500 < CDD10°C ≤ 5000
3A and 3B4500 < CDD50°F ≤ 6300 AND HDD65°F ≤ 54002500 < CDD10°C ≤ 3500 AND HDD18°C ≤ 3000
4A and 4BCDD50°F ≤ 4500 AND HDD65°F ≤ 5400CDD10°C ≤ 2500 AND HDD18°C ≤ 3000
3CHDD65°F ≤ 3600HDD18°C ≤ 2000
4C3600 < HDD65°F ≤ 54002000 < HDD18°C ≤ 3000
55400 < HDD65°F ≤ 72003000 < HDD18°C ≤ 4000
67200 < HDD65°F ≤ 90004000 < HDD18°C ≤ 5000
79000 < HDD65°F ≤ 126005000 < HDD18°C ≤ 7000
812600 < HDD65°F7000 < 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.
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.

U-factors of fenestration products (windows, doors and skylights) shall be determined in accordance with NFRC 100.

Exception: 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 C303.1.3(1) or C303.1.3(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 C303.1.3(3).

TABLE C303.1.3(1)


Metal with Thermal Break1.100.651.901.10
Nonmetal or Metal Clad0.950.551.751.05
Glazed Block0.60

TABLE C303.1.3(2)


Uninsulated Metal1.20
Insulated Metal0.60
Insulated, nonmetal edge, max 45% glazing,
any glazing double pane

TABLE C303.1.3(3)


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).
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.
Materials, systems and equipment shall be installed in accordance with the manufacturer's instructions and the Florida Building Code, Building.
Insulation applied to the exterior of basement walls, crawlspace walls and the perimeter of slab-on-grade floors shall have a rigid, opaque and weather-resistant protective covering to prevent the degradation of the insulation's thermal performance. The protective covering shall cover the exposed exterior insulation and extend not less than 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.

R-values for building materials used to demonstrate code compliance with Chapter C4 shall be taken from ASHRAE 90.1 Normative Appendix A, from manufacturer's product literature or from other nationally recognized engineering sources. Assembly U-factor calculations shall follow the procedure(s) detailed in Section C304.3 or be tested in accordance with procedure(s) described in Section C304.2.

Concrete block R-values shall be calculated using the isothermal planes method or a two-dimensional calculation program, thermal conductivities from ASHRAE 90.1 Normative Appendix A and dimensions from ASTM C90. The parallel path calculation method is not acceptable.

Exception: R-values for building materials or thermal conductivities determined from testing in accordance with Section C304.2.

If building material R-values or thermal conductivities are determined by testing, one of the following test procedures shall be used:

  1. ASTM C177
  2. ASTM C236
  3. ASTM C518

For concrete, the oven-dried conductivity shall be multiplied by 1.2 to reflect the moisture content as typically installed.

If assembly U-factors are determined by testing, ASTM C1363 shall be used. Product samples tested shall be production line material or representative of material as purchased by the consumer or contractor. If the assembly is too large to be tested at one time in its entirety, then either a representative portion shall be tested or different portions shall be tested separately and a weighted average determined. To be representative, the portion tested shall include edges of panels, joints with other panels, typical framing percentages and thermal bridges.
The following procedures and assumptions shall be used for all Chapter 4 code calculations. R-values for air films, insulation and building materials shall be taken from Section C304.3.1 or C304.3.2, respectively. In addition, the appropriate assumptions listed, including framing factors, shall be used.

Prescribed R-values for air films shall be as follows:

0.17All exterior surfaces
0.46All semi-exterior surfaces
0.61Interior horizontal surfaces, heat flow up
0.92Interior horizontal surfaces, heat flow down
0.68Interior vertical surfaces
Exterior surfaces are areas exposed to the wind.
Semi-exterior surfaces are protected surfaces that face attics, crawl spaces and parking garages with natural or mechanical ventilation.
Interior surfaces are surfaces within enclosed spaces.
The R-value for cavity airspaces shall be taken from ASHRAE 90.1 Normative Appendix A. No credit shall be given for airspaces in cavities that contain any insulation or less than 0.5 inch (12.7 mm). The values for 3.5 inch-cavities (84 mm) shall be used for cavities of that width and greater.
The U-factors, C-factors, F-factors, and heat capacities for typical construction assemblies from ASHRAE 90.1 Normative Appendix A shall be used for all calculations unless otherwise allowed by applicant-determined assembly U-factors, C-factors, F-factors or heat capacities. Interpolation between values for rated R-values of insulation, including insulated, sheathing is allowed; extrapolation beyond values in the ASHRAE 90.1 Normative Appendix A tables is not.

If the building official determines that the proposed construction assembly is not adequately represented in the appropriate table of ASHRAE 90.1 Normative Appendix A, the applicant shall determine appropriate values for the assembly using the assumptions in ASHRAE 90.1 Normative Appendix A. An assembly is deemed to be adequately represented if:

  1. the interior structure, hereafter referred to as the base assembly, for the class of construction is the same as described in Normative Appendix A and
  2. changes in exterior or interior surface building materials added to the base assembly do not increase or decrease the R-value by more than 2 from that indicated in the descriptions in ASHRAE 90.1 Normative Appendix A.

Insulation, including insulated sheathing, is not considered a building material.

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