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About this chapter: Chapter 3 covers general regulations for energy conservation features of buildings. The climate zone for a building is established by geographic location tables and figures in this chapter.

R301.1 General

AMENDMENT
This section has been amended at the state or city level.
In Table R301.1, warm humid counties are identified 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)

INTERNATIONAL CLIMATE ZONE DEFINITIONS

MAJOR CLIMATE TYPE DEFINITIONS
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. Not fewer than 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 not less than 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 P in < 0.44 × (TF - 19.5) [Pcm < 2.0 × (TC + 7) in SI units]

where:

P in = 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.
  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)

INTERNATIONAL CLIMATE ZONE DEFINITIONS

ZONE
NUMBER
THERMAL CRITERIA
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 that is 12 inches (305 mm) or greater in width. Alternatively, the insulation installers shall provide a certification that indicates the type, manufacturer and R-value of insulation installed in each element of the building thermal envelope. For blown-in or sprayed fiberglass and cellulose insulation, the initial installed thickness, settled thickness, settled R-value, installed density, coverage area and number of bags installed shall be indicated on the certification. For sprayed polyurethane foam (SPF) insulation, the installed thickness of the areas covered and the R-value of the installed thickness shall be indicated on the certification. For insulated siding, the R-value shall be on a label on the product's package and shall be indicated on the certification. The insulation installer shall sign, date and post the certification in a conspicuous location on the job site.

Exception: For roof insulation installed above the deck, the R-value shall be labeled as required by the material standards specified in Table 1508.2 of the International Building Code or Table R906.2 of the International Residential Code, as applicable.

The thickness of blown-in or sprayed fiberglass and cellulose roof and ceiling insulation shall be written in inches (mm) on markers that are installed at not less than 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. The thickness and installed R-value of sprayed polyurethane foam insulation shall be indicated on the certification provided by the insulation installer.
Insulating materials shall be installed such that the manufacturer's R-value mark is readily observable at inspection.

U-factors of fenestration products such as 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 R303.1.3(1) or R303.1.3(2). The solar heat gain coefficient (SHGC) and visible transmittance (VT) of glazed fenestration products such as 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)

DEFAULT GLAZED WINDOW, GLASS DOOR AND SKYLIGHT U-FACTORS

FRAME TYPEWINDOW AND
GLASS DOOR
SKYLIGHT
Single
pane
Double
pane
SingleDouble
Metal1.200.802.001.30
Metal with Thermal Break1.100.651.901.10
Nonmetal or Metal Clad0.950.551.751.05
Glazed Block0.60

TABLE R303.1.3(2)

DEFAULT OPAQUE DOOR U-FACTORS

DOOR TYPEOPAQUE
U-FACTOR
Uninsulated Metal1.20
Insulated Metal0.60
Wood0.50
Insulated, nonmetal edge, not exceeding 45%
glazing, any glazing double pane
0.35

TABLE R303.1.3(3)

DEFAULT GLAZED FENESTRATION SHGC AND VT

SINGLE GLAZEDDOUBLE GLAZEDGLAZED
BLOCK
ClearTintedClearTinted
SHGC0.80.70.70.60.6
VT0.60.30.60.30.6
The thermal resistance, R-value, of insulation shall be determined in accordance with Part 460 of US-FTC CFR Title 16 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 International Building Code or the International Residential Code, as applicable.
Insulation applied to the exterior of basement walls, crawl space 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.
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