ASHRAE-90.1-2022- - Page 239

Extracted Content

b. Advanced framing: Wood framing at 24 in. on center with cavities filled with 22.5 in. wide insulation for

both 3.5 in. deep and 5.5 in. deep wall cavities. Double headers leave uninsulated cavities. Weighting factors are 78% insulated cavity, 18% studs, plates, and sills, and 4% headers. c. Advanced framing with insulated headers: Wood framing at 24 in. on center with cavities filled with 22.5

in. wide insulation for both 3.5 in. deep and 5.5 in. deep wall cavities. Double header cavities are insulated. Weighting factors are 78% insulated cavity, 18% studs, plates, and sills, and 4% headers.

A3.4.2 Rated R-Value of Insulation for Wood-Framed and Other Walls

A3.4.2.1 The first rated R-value of insulation is for uncompressed insulation installed in the cavity between wood studs. It is acceptable for this insulation to also be continuous insulation uninterrupted by framing.

A3.4.2.2 If there are two values, the second rated R-value of insulation is for continuous insulation uninterrupted by framing, etc., to be installed in addition to the first insulation.

A3.4.3 U-Factors for Wood-Framed Walls

A3.4.3.1 U-factors for wood-framed walls shall be taken from Table A3.4.3.1. A3.4.3.2 For wood-framed walls with framing at less than 24 in. on center, use the standard framing values as described in Section A3.4.1(a).

A3.4.3.3 For wood-framed walls with framing from 24 to 32 in. on center, use the advanced framing values as described in Section A3.4.1(b) if the headers are uninsulated, or the advanced framing with insulated header values as described in Section A3.4.1(c) if the headers are insulated.

A3.4.3.4 For wood-framed walls with framing greater than 32 in. on center, U-factors shall be determined in accordance with Section A9.

ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 237