Page 504 - 2018_IRC

ENERGY EFFICIENCY

electric furnace, or baseboard electric heater is installed in the bridging effects of framing materials. In addition to UA
residence, the certificate shall indicate “gas-fired unvented compliance, SHGC requirements shall be met.
room heater,” “electric furnace” or “baseboard electric N1102.2 (R402.2) Specific insulation requirements (Pre-
heater,” as appropriate. An efficiency shall not be indicated scriptive). In addition to the requirements of Section
for gas-fired unvented room heaters, electric furnaces and N1102.1, insulation shall meet the specific requirements of
electric baseboard heaters.
Sections N1102.2.1 through N1102.2.13.
N1102.2.1 (R402.2.1) Ceilings with attic spaces. Where
SECTION N1102 (R402) Section R1102.1.2 requires R-38 insulation in the ceiling,
BUILDING THERMAL ENVELOPE installing R-30 insulation over 100 percent of the ceiling
area requiring insulation shall satisfy the requirement for
N1102.1 (R402.1) General (Prescriptive). The building
thermal envelope shall comply with the requirements of Sec- R-38 insulation wherever the full height of uncompressed
tions N1102.1.1 through N1102.1.5. R-30 insulation extends over the wall top plate at the
eaves. Where Section N1102.1.2 requires R-49 insulation
Exceptions: in the ceiling, installing R-38 insulation over 100 percent
1. The following low-energy buildings, or portions of the ceiling area requiring insulation shall satisfy the
thereof, separated from the remainder of the building requirement for R-49 insulation wherever the full height of
by building thermal envelope assemblies complying uncompressed R-38 insulation extends over the wall top
with this section shall be exempt from the building plate at the eaves. This reduction shall not apply to the U-
thermal envelope provisions of Section N1102. factor alternative approach in Section N1102.1.4 and the
Total UA alternative in Section N1102.1.5.
1.1. Those with a peak design rate of energy
2
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usage less than 3.4 Btu/h • ft (10.7 W/m ) or N1102.2.2 (R402.2.2) Ceilings without attic spaces.
2
1.0 watt/ft of floor area for space-condition- Where Section N1102.1.2 requires insulation R-values
ing purposes. greater than R-30 in the ceiling and the design of the roof/
1.2. Those that do not contain conditioned space. ceiling assembly does not allow sufficient space for the
2. Log homes designed in accordance with ICC 400. required insulation, the minimum required insulation R-
value for such roof/ceiling assemblies shall be R-30. Insu-
N1102.1.1 (R402.1.1) Vapor retarder. Wall assemblies lation shall extend over the top of the wall plate to the
in the building thermal envelope shall comply with the outer edge of such plate and shall not be compressed. This
vapor retarder requirements of Section R702.7. reduction of insulation from the requirements of Section
2
N1102.1.2 (R402.1.2) Insulation and fenestration crite- N1102.1.2 shall be limited to 500 square feet (46 m ) or 20
ria. The building thermal envelope shall meet the require- percent of the total insulated ceiling area, whichever is
ments of Table N1102.1.2 based on the climate zone less. This reduction shall not apply to the U-factor alterna-
specified in Section N1101.7. tive approach in Section N1102.1.4 and the Total UA
alternative in Section N1102.1.5.
N1102.1.3 (R402.1.3) R-value computation. Insulation
material used in layers, such as framing cavity insulation N1102.2.3 (R402.2.3) Eave baffle. For air-permeable
or continuous insulation, shall be summed to compute the insulations in vented attics, a baffle shall be installed adja-
corresponding component R-value. The manufacturer’s cent to soffit and eave vents. Baffles shall maintain an
settled R-value shall be used for blown-in insulation. opening equal or greater than the size of the vent. The
Computed R-values shall not include an R-value for other baffle shall extend over the top of the attic insulation. The
building materials or air films. Where insulated siding is baffle shall be permitted to be any solid material.
used for the purpose of complying with the continuous N1102.2.4 (R402.2.4) Access hatches and doors. Access
insulation requirements of Table N1102.1.2, the manufac- doors from conditioned spaces to unconditioned spaces
turer’s labeled R-value for insulated siding shall be such as attics and crawl spaces shall be weatherstripped
reduced by R-0.6. and insulated to a level equivalent to the insulation on the
N1102.1.4 (R402.1.4) U-factor alternative. An assembly surrounding surfaces. Access that prevents damaging or
with a U-factor equal to or less than that specified in Table compressing the insulation shall be provided to all equip-
N1102.1.4 shall be permitted as an alternative to the R- ment. Where loose-fill insulation is installed, a wood-
value in Table N1102.1.2. framed or equivalent baffle or retainer shall be installed to
prevent the loose-fill insulation from spilling into the liv-
N1102.1.5 (R402.1.5) Total UA alternative. Where the
total building thermal envelope UA, the sum of U-factor ing space when the attic access is opened. The baffle or
times assembly area, is less than or equal to the Total UA retainer shall provide a permanent means of maintaining
resulting from multiplying the U-factors in Table the installed R-value of the loose-fill insulation.
N1102.1.4 by the same assembly area as in the proposed Exception: Vertical doors providing access from con-
building, the building shall be considered to be in compli- ditioned spaces to unconditioned spaces that comply
ance with Table N1102.1.2. The UA calculation shall be with the fenestration requirements of Table N1102.1.2
performed using a method consistent with the ASHRAE based on the applicable climate zone specified in Sec-
Handbook of Fundamentals and shall include the thermal tion N1101.7.

2018 INTERNATIONAL RESIDENTIAL CODE ® 479
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