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# A4.2 C-Factors for Below-Grade Walls

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*C-factors* for *below-grade walls* shall be taken from Table A4.2.1 or determined by the procedure described in this subsection.

**Table A4.2.1 Assembly C-Factors for Below-Grade Walls**

Framing Type and Depth |
Rated R-Value of Insulation Alone |
Specified C-Factors( Wall Only, without Soil and Air Films) |
---|---|---|

No Framing | R-0 | C-1.140 |

Exterior Insulation, Continuous and Uninterrupted by Framing |
||

No Framing | R-5.0 | C-0.170 |

No Framing | R-7.5 | C-0.119 |

No Framing | R-10.0 | C-0.092 |

No Framing | R-12.5 | C-0.075 |

No Framing | R-15.0 | C-0.063 |

No Framing | R-17.5 | C-0.054 |

No Framing | R-20.0 | C-0.048 |

No Framing | R-25.0 | C-0.039 |

No Framing | R-30.0 | C-0.032 |

No Framing | R-35.0 | C-0.028 |

No Framing | R-40.0 | C-0.025 |

No Framing | R-45.0 | C-0.022 |

No Framing | R-50.0 | C-0.020 |

Continuous Metal Framing at 24 in. on Center Horizontally |
||

3.5 in. | R-11.0 | C-0.182 |

3.5 in. | R-13.0 | C-0.174 |

3.5 in. | R-15.0 | C-0.168 |

5.5 in. | R-19.0 | C-0.125 |

5.5 in. | R-21.0 | C-0.120 |

1 in. Metal Clips at 24 in. on Center Horizontally and 16 in. Vertically |
||

1.0 in. | R-3.8 | C-0.233 |

1.0 in. | R-5.0 | C-0.201 |

1.0 in. | R-5.6 | C-0.189 |

1.5 in. | R-5.7 | C-0.173 |

1.5 in. | R-7.5 | C-0.147 |

1.5 in. | R-8.4 | C-0.138 |

2.0 in. | R-7.6 | C-0.138 |

2.0 in. | R-10.0 | C-0.116 |

2.0 in. | R-11.2 | C-0.108 |

2.5 in. | R-9.5 | C-0.114 |

2.5 in. | R-12.5 | C-0.096 |

2.5 in. | R-14.0 | C-0.089 |

3.0 in. | R-11.4 | C-0.098 |

3.0 in. | R-15.0 | C-0.082 |

3.0 in. | R-16.8 | C-0.076 |

3.5 in. | R-13.3 | C-0.085 |

3.5 in. | R-17.5 | C-0.071 |

3.5 in. | R-19.6 | C-0.066 |

4.0 in. | R-15.2 | C-0.076 |

4.0 in. | R-20.0 | C-0.063 |

4.0 in. | R-22.4 | C-0.058 |

It is acceptable to use the *C-factors* in Table A4.2.1 for all *below-grade walls.*

If not taken from Table A4.2.1, *below-grade wall C-factors* shall be determined from Tables A3.1-2, A3.1-3, or A3.1-4 using the following procedure:

- If the
*below-grade wall*is uninsulated or only the cells are insulated:- For concrete
*walls*, determine the*C-factor*from Table A3.1-2 based on the concrete density and*wall*thickness. - For concrete block
*walls*, determine the*C-factor*from Table A3.1-3 based on the block size, concrete density, degree of grouting in the cells, and whether the cells are insulated.

- For concrete
- If the
*mass wall*has additional insulation:- For concrete
*walls*, determine the*R*from Table A3.1-2 based on the concrete density and_{c}*wall*thickness. Next, determine the effective*R-value*for the insulation/framing layer from Table A3.1-4 based on the*rated R-value of insulation*installed, the thickness of the insulation, and whether it is installed between wood or*metal framing*or with no framing. Then determine the*C-factor*by adding the*R*and the effective_{c}*R-value*together and taking the inverse of the total. - For concrete block
*walls*, determine the*R*from Table A3.1-3 based on the block size, concrete density, degree of grouting in the cells, and whether the cells are insulated. Next, determine the effective_{c}*R-value*for the insulation/framing layer from Table A3.1-4 based on the*rated R-value of insulation*installed, the thickness of the insulation, and whether it is installed between wood or*metal framing*or with no framing. Then determine the*C-factor*by adding the*R*and the effective_{c}*R-value*together and taking the inverse of the total.

- For concrete

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