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N1102.2 (R402.2) Specific Insulation Requirements (Prescriptive)
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N1102.2.1 (R402.2.1) Ceilings With Attic Spaces
Where Section R1102.1.2 requires R-38 insulation in the ceiling, installing R-30 insulation over 100 percent of the ceiling area requiring insulation shall satisfy the requirement for R-38 insulation wherever the full height of uncompressed R-30 insulation extends over the wall top plate at the eaves. Where Section N1102.1.2 requires R-49 insulation in the ceiling, installing R-38 insulation over 100 percent of the ceiling area requiring insulation shall satisfy the requirement for R-49 insulation wherever the full height of uncompressed R-38 insulation extends over the wall top plate at the eaves. This reduction shall not apply to the U-factor alternative approach in Section N1102.1.4 and the Total UA alternative in Section N1102.1.5.
N1102.2.2 (R402.2.2) Ceilings Without Attic Spaces
Where Section N1102.1.2 requires insulation R-values greater than R-30 in the ceiling and the design of the roof/ceiling assembly does not allow sufficient space for the required insulation, the minimum required insulation R-value for such roof/ceiling assemblies shall be R-30. Insulation shall extend over the top of the wall plate to the outer edge of such plate and shall not be compressed. This reduction of insulation from the requirements of Section N1102.1.2 shall be limited to 500 square feet (46 m2) or 20 percent of the total insulated ceiling area, whichever is less. This reduction shall not apply to the U-factor alternative approach in Section N1102.1.4 and the Total UA alternative in Section N1102.1.5.
N1102.2.3 (R402.2.3) Eave Baffle
For air-permeable insulations in vented attics, a baffle shall be installed adjacent to soffit and eave vents. Baffles shall maintain an opening equal or greater than the size of the vent. The baffle shall extend over the top of the attic insulation. The baffle shall be permitted to be any solid material.
N1102.2.4 (R402.2.4) Access Hatches and Doors
Access doors from conditioned spaces to unconditioned spaces such as attics and crawl spaces shall be weatherstripped and insulated to a level equivalent to the insulation on the surrounding surfaces. Access that prevents damaging or compressing the insulation shall be provided to all equipment. Where loose-fill insulation is installed, a wood-framed or equivalent baffle or retainer shall be installed to prevent the loose-fill insulation from spilling into the living space when the attic access is opened. The baffle or retainer shall provide a permanent means of maintaining the installed R-value of the loose-fill insulation.
N1102.2.5 (R402.2.5) Mass Walls
Mass walls where used as a component of the building thermal envelope shall be one of the following:
N1102.2.6 (R402.2.6) Steel-Frame Ceilings, Walls, and Floors
Steel-frame ceilings, walls, and floors shall comply with the insulation requirements of Table N1102.2.6 or the U-factor requirements of Table N1102.1.4. The calculation of the U-factor for a steel-frame envelope assembly shall use a series-parallel path calculation method.
TABLE N1102.2.6 (R402.2.6)
STEEL-FRAME CEILING, WALL AND FLOOR INSULATION R-VALUES
|WOOD FRAME |
|Steel Truss Ceilingsb|
|R-30||R-38 or R-30 + 3 or R-26 + 5|
|R-38||R-49 or R-38 + 3|
|R-49||R-38 + 5|
|Steel Joist Ceilingsb|
|R-30||R-38 in 2 × 4 or 2 × 6 or 2 × 8 R-49|
in any framing
|R-38||R-49 in 2 × 4 or 2 × 6 or 2 × 8 or 2 × 10|
|Steel-Framed Wall, 16 inches on center|
|R-13||R-13 + 4.2 or R-21 + 2.8 or|
R-0 + 9.3 or R-15 + 3.8 or R-21 + 3.1
|R-13 + 3||R-0 + 11.2 or R-13 + 6.1 or R-15 + 5.7 or|
R-19 + 5.0 or R-21 + 4.7
|R-20||R-0 + 14.0 or R-13 + 8.9 or R-15 + 8.5 or|
R-19 + 7.8 or R-19 + 6.2 or R-21 + 7.5
|R-20 + 5||R-13 + 12.7 or R-15 + 12.3 or R-19 + 11.6 or|
R-21 + 11.3 or R-25 + 10.9
|R-21||R-0 + 14.6 or R-13 + 9.5 or R-15 + 9.1 or|
R-19 + 8.4 or R-21 + 8.1 or R-25 + 7.7
|Steel-Framed Wall, 24 inches on center|
|R-13||R-0 + 9.3 or R-13 + 3.0 or R-15 + 2.4|
|R-13 + 3||R-0 + 11.2 or R-13 + 4.9 or R-15 + 4.3 or|
R-19 + 3.5 or R-21 + 3.1
|R-20||R-0 + 14.0 or R-13 + 7.7 or R-15 + 7.1 or|
R-19 + 6.3 or R-21 + 5.9
|R-20 + 5||R-13 + 11.5 or R-15 + 10.9 or R-19 + 10.1 or|
R-21 + 9.7 or R-25 + 9.1
|R-21||R-0 + 14.6 or R-13 + 8.3 or R-15 + 7.7 or|
R-19 + 6.9 or R-21 + 6.5 or R-25 + 5.9
|Steel Joist Floor|
|R-13||R-19 in 2 × 6, or R-19 + 6 in 2 × 8 or 2 × 10|
|R-19||R-19 + 6 in 2 × 6, or R-19 + 12 in 2 × 8 or 2 × 10|
N1102.2.7 (R402.2.7) Walls With Partial Structural Sheathing
Where Section N1102.1.2 requires continuous insulation on exterior walls and structural sheathing covers 40 percent or less of the gross area of all exterior walls, the required continuous insulation R-value shall be permitted to be reduced by an amount necessary, but not more than R-3, to result in a consistent total sheathing thickness on areas of the walls covered by structural sheathing. This reduction shall not apply to the U-factor alternative in Section N1102.1.4 and the Total UA alternative in Section N1102.1.5.
N1102.2.8 (R402.2.8) Floors
Floor framing-cavity insulation shall be installed to maintain permanent contact with the underside of the subfloor decking.
Exception: As an alternative, the floor framing-cavity insulation shall be in contact with the topside of sheathing or continuous insulation installed on the bottom side of floor framing where combined with insulation that meets or exceeds the minimum wood frame wall R-value in Table N1102.1.2 and that extends from the bottom to the top of all perimeter floor framing members.
N1102.2.9 (R402.2.9) Basement Walls
Walls associated with conditioned basements shall be insulated from the top of the basement wall down to 10 feet (3048 mm) below grade or to the basement floor, whichever is less. Walls associated with unconditioned basements shall comply with this requirement except where the floor overhead is insulated in accordance with Sections N1102.1.2 and N1102.2.8.
N1102.2.10 (R402.2.10) Slab-on-Grade Floors
Slab-on-grade floors with a floor surface less than 12 inches (305 mm) below grade shall be insulated in accordance with Table N1102.1.2. The insulation shall extend downward from the top of the slab on the outside or inside of the foundation wall. Insulation located below grade shall be extended the distance provided in Table N1102.1.2 by any combination of vertical insulation, insulation extending under the slab or insulation extending out from the building. Insulation extending away from the building shall be protected by pavement or by not less than 10 inches (254 mm) of soil. The top edge of the insulation installed between the exterior wall and the edge of the interior slab shall be permitted to be cut at a 45-degree (0.79 rad) angle away from the exterior wall. Slab-edge insulation is not required in jurisdictions designated by the building official as having a very heavy termite infestation.
N1102.2.11 (R402.2.11) Crawl Space Walls
As an alternative to insulating floors over crawl spaces, crawl space walls shall be insulated provided that the crawl space is not vented to the outdoors. Crawl space wall insulation shall be permanently fastened to the wall and shall extend downward from the floor to the finished grade elevation and then vertically or horizontally for not less than an additional 24 inches (610 mm). Exposed earth in unvented crawl space foundations shall be covered with a continuous Class I vapor retarder in accordance with this code. Joints of the vapor retarder shall overlap by 6 inches (153 mm) and be sealed or taped. The edges of the vapor retarder shall extend not less than 6 inches (153 mm) up the stem walls and shall be attached to the stem walls.
N1102.2.12 (R402.2.12) Masonry Veneer
N1102.2.13 (R402.2.13) Sunroom Insulation
Exception: For sunrooms with thermal isolation, and enclosing conditioned space, the following exceptions to the insulation requirements of this code shall apply:
- The minimum ceiling insulation R-values shall be R-19 in Climate Zones 1 through 4 and R-24 in Climate Zones 5 through 8.
- The minimum wall insulation R-value shall be R-13 in all climate zones. Walls separating a sunroom with a thermal isolation from conditioned space shall comply with the building thermal envelope requirements of this code.
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