ASHRAE-90.1-2022- - Page 067
Extracted Content
| Allowable Area per Point Thermal Bridge, in.2 | Common Material Name |
|---|---|
| 3 | Carbon steel |
| 9 | Stainless steel |
| 65 | Concrete and masonry |
16
Table 5.5.5.5 Allowable Point Thermal Bridge Cross-Sectional Area
shall have a thermal break with a thermal conductivity of 3.6 Btu·in/ h·ft [2] ·°F or less. Exception to 5.5.5.4: Intersections between vertical fenestration and uninsulated opaque walls .
5.5.5.5 Other Elements and Building Assembly Intersections. Individual point thermal bridges and
Above grade area of the building envelope ≥ ( k 1 × A 1) + ( k 2 × A 2) + ( k 3 × A 3) … (5.5.5.5)
where k 1, k 2, k 3 … = thermal conductivity of material 1, material 2, material 3, etc., expressed in Btu·in./ (ft [2] ·h·°F) for point thermal bridge material 1, material 2, material 3, etc. (e.g., concrete, carbon steel, stainless steel, wood) A 1, A 2, A 3, … = the total cross-sectional area of point thermal bridges and linear thermal bridges of material 1, material 2, material 3, etc., expressed in ft [2]
Exceptions to 5.5.5.5:
- Service penetrations, including mechanical, electrical, plumbing, telecommunications, and fire services, that pass through the opaque building envelope .
- Insulated roof curbs and blocking.
- Individual point thermal bridges that are less than the allowances in Table 5.5.5.5.
( Informative Note: See ASHRAE Handbook—Fundamentals Appendix A, Chapter 26, or Chapter 33 for typical material thermal conductivity.)
5.6 Building Envelope Trade-Off Compliance Path 5.6.1 The building envelope complies with the standard if
a. the proposed design satisfies the provisions of Sections 5.1, 5.4, 5.7, 5.8, and 5.9 and b. the proposed envelope performance factor of the proposed design is less than or equal to the proposed
envelope performance factor of the base design .
5.6.1.1 All components of the building envelope shown on architectural drawings or installed in existing buildings shall be modeled in the proposed design . The simulation program model fenestration and opaque
5.6.1.2 Trade-Offs Limited to Building Permit. When the building permit being sought applies to less than the whole building, parameters relating to unmodified existing conditions or to future building components shall be identical for both the proposed envelope performance factor and the base envelope perfor- mance factor . Future building components shall meet the prescriptive requirements of Section 5.5.
5.6.1.3 Envelope performance factor shall be calculated using the procedures of Normative Appendix C.
5.7 Submittals 5.7.1 General. Compliance documentation and supplemental information shall be submitted in accordance with Section 4.2.2 of this standard.
ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 65
