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The building thermal envelope shall comply with the requirements of Sections N1102.1.1 through N1102.1.5.
Exceptions:
  1. The following low-energy buildings, or portions thereof, separated from the remainder of the building by building thermal envelope assemblies complying with this section shall be exempt from the building thermal envelope provisions of Section N1102.
    1. 1.1. Those with a peak design rate of energy usage less than 3.4 Btu/h • ft2 (10.7 W/m2) or 1.0 watt/ft2 of floor area for space-conditioning purposes.
    2. 1.2. Those that do not contain conditioned space.
  2. Log homes designed in accordance with ICC 400.
N1102.1.1 (R402.1.1) Vapor Retarder
Wall assemblies in the building thermal envelope shall comply with the vapor retarder requirements of Section R702.7.
N1102.1.2 (R402.1.2) Insulation and Fenestration Criteria
The building thermal envelope shall meet the requirements of Table N1102.1.2 based on the climate zone specified in Section N1101.7.
INSULATION AND FENESTRATION REQUIREMENTS BY COMPONENTa
CLIMATE
ZONE
FENESTRATION
U-FACTORb
SKYLIGHTb
U-FACTOR
GLAZED
FENESTRATION
SHGCb, e
CEILING
R-VALUE
WOOD
FRAME WALL
R-VALUE
MASS
WALL
R-VALUEi
FLOOR
R-VALUE
BASEMENTc
WALL
R-VALUE
SLABd
R-VALUE
& DEPTH
CRAWL
SPACEc
WALL
R-VALUE
1NR0.750.2530133/413000
20.400.650.2538134/613000
30.320.550.253820 or 13 + 5h8/13195/13f05/13
4 except
Marine
0.320.550.404920 or 13 + 5h8/131910/1310, 2 ft10/13
5 and
Marine 4
0.300.55NR4920 or 13 + 5h13/1730g15/1910, 2 ft15/19
60.300.55NR4920 + 5h or 13 + 10h15/2030g15/1910, 4 ft15/19
7 and 80.300.55NR4920 + 5h or 13 + 10h19/2138g15/1910, 4 ft15/19
For SI: 1 foot = 304.8 mm.
NR = Not Required.
  1. R-values are minimums. U-factors and SHGC are maximums. Where insulation is installed in a cavity that is less than the label or design thickness of the insulation, the installed R-value of the insulation shall be not less than the R-value specified in the table.
  2. The fenestration U-factor column excludes skylights. The SHGC column applies to all glazed fenestration.
    Exception: In Climate Zones 1 through 3, skylights shall be permitted to be excluded from glazed fenestration SHGC requirements provided that the SHGC for such sky lights does not exceed 0.30.
  3. "10/13" means R-10 continuous insulation on the interior or exterior of the home or R-13 cavity insulation on the interior of the basement wall. "15/19" means R-15 continuous insulation on the interior or exterior of the home or R-19 cavity insulation on the interior of the basement wall. Alternatively, compliance with "15/19" shall be R-13 cavity insulation on the interior of the basement wall plus R-5 continuous insulation on the interior or exterior of the home.
  4. R-5 insulation shall be provided under the full slab area of a heated slab in addition to the required slab edge insulation R-value for slabs. as indicated in the table. The slab edge insulation for heated slabs shall not be required to extend below the slab.
  5. There are no SHGC requirements in the Marine Zone.
  6. Basement wall insulation shall not be required in warm-humid locations as defined by Figure N1101.7 and Table N1101.7.
  7. Alternatively, insulation sufficient to fill the framing cavity providing not less than an R-value of R-19.
  8. The first value is cavity insulation, the second value is continuous insulation. Therefore, as an example, "13+5" means R-13 cavity insulation plus R-5 continuous insulation.
  9. Mass walls shall be in accordance with Section N1102.2.5. The second R-value applies where more than half of the insulation is on the interior of the mass wall.
N1102.1.3 (R402.1.3) R-Value Computation
Insulation material used in layers, such as framing cavity insulation or continuous insulation, shall be summed to compute the corresponding component R-value. The manufacturer's settled R-value shall be used for blown-in insulation. Computed R-values shall not include an R-value for other building materials or air films. Where insulated siding is used for the purpose of complying with the continuous insulation requirements of Table N1102.1.2, the manufacturer's labeled R-value for insulated siding shall be reduced by R-0.6.
N1102.1.4 (R402.1.4) U-factor Alternative
An assembly with a U-factor equal to or less than that specified in Table N1102.1.4 shall be permitted as an alternative to the R-value in Table N1102.1.2.
EQUIVALENT U-FACTORSa
CLIMATE
ZONE
FENESTRATION
U-FACTOR
SKYLIGHT
U-FACTOR
CEILING
U-FACTOR
FRAME
WALL
U-FACTOR
MASS WALL
U-FACTORb
FLOOR
U-FACTOR
BASEMENT
WALL
U-FACTOR
CRAWL
SPACE WALL
U-FACTOR
10.500.750.0350.0840.1970.0640.3600.477
20.400.650.0300.0840.1650.0640.3600.477
30.320.550.0300.0600.0980.0470.091c0.136
4 except Marine0.320.550.0260.0600.0980.0470.0590.065
5 and Marine 40.300.550.0260.0600.0820.0330.0500.055
60.300.550.0260.0450.0600.0330.0500.055
7 and 80.300.550.0260.0450.0570.0280.0500.055
  1. Nonfenestration U-factors shall be obtained from measurement, calculation or an approved source.
  2. Mass walls shall be in accordance with Section N1102.2.5. Where more than half the insulation is on the interior, the mass wall U-factors shall not exceed 0.17 in Climate Zone 1, 0.14 in Climate Zone 2, 0.12 in Climate Zone 3, 0.087 in Climate Zone 4 except Marine, 0.065 in Climate Zone 5 and Marine 4, and 0.057 in Climate Zones 6 through 8.
  3. In warm-humid locations as defined by Figure N1101.7 and Table N1101.7, the basement wall U-factor shall not exceed 0.360.
N1102.1.5 (R402.1.5) Total UA Alternative
Where the total building thermal envelope UA, the sum of U-factor times assembly area, is less than or equal to the Total UA resulting from multiplying the U-factors in Table N1102.1.4 by the same assembly area as in the proposed building, the building shall be considered to be in compliance with Table N1102.1.2. The UA calculation shall be performed using a method consistent with the ASHRAE Handbook of Fundamentals and shall include the thermal bridging effects of framing materials. In addition to UA compliance, SHGC requirements shall be met.

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