ASHRAE-90.1-2022- - Page 237
Extracted Content
A3. ABOVE-GRADE WALLS
A3.1 Mass Wall
A3.1.1 General. For the purpose of Section A1.2, the base assembly is a masonry or concrete wall . Con- tinuous insulation is installed on the interior or exterior or within the masonry units, or it is installed on the interior or exterior of the concrete. The brick cavity wall has continuous insulation between the brick and the concrete or masonry. The U-factors include R-0.17 for exterior air film and R-0.68 for interior air film, vertical surfaces. For insulated walls, the U-factor also includes R-0.45 for 0.5 in. gypsum board. For the cavity wall, the U-factor includes R-0.74 for brick. U-factors are provided for the following configurations:
a. Concrete wall : 8 in. normal weight concrete wall with a density of 145 lb/ft [3] . b. Solid grouted concrete block wall : 8 in. medium weight ASTM C90 concrete block with a density of 115
lb/ft [3 ] and solid grouted cores. c. Partially grouted concrete block wall : 8 in. medium weight ASTM C90 concrete block with a density of
115 lb/ft [3] having reinforcing steel every 32 in. vertically and every 48 in. horizontally, with cores grouted in those areas only. Other cores are filled with insulating material only if there is no other insulation.
A3.1.2 Mass Wall Rated R-Value of Insulation
A3.1.2.1 Mass wall HC shall be determined from Table A3.1-2 or A3.1-3. A3.1.2.2 The rated R-value of insulation is for continuous insulation uninterrupted by framing other than 20 gage 1 in. metal clips spaced no closer than 24 in. on center horizontally and 16 in. on center vertically. A3.1.2.3 Where other framing, including metal and wood studs, is used, compliance shall be based on the maximum assembly U-factor .
A3.1.2.4 Where rated R-value of insulation is used for concrete sandwich panels, the insulation shall be continuous throughout the entire panel.
A3.1.3 Mass Wall U-Factor
A3.1.3.1 U-factors for mass walls shall be taken from Table A3.1-1 or determined by the procedure in this subsection. It is acceptable to use the U-factors in Table A3.1-1 for all mass walls, provided that the grouting is equal to or less than that specified. HC for mass walls shall be taken from Table A3.1-2 or A3.1-3.
A3.1.3.2 Determination of Mass Wall U-Factors. If not taken from Table A3.1-1, mass wall U-factors shall be determined from Tables A3.1-2, A3.1-3, or A3.1-4 using the following procedure:
a. If the mass wall is uninsulated or only the cells are insulated:
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For concrete walls, determine the U-factor from Table A3.1-2 based on the concrete density and wall thickness.
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For concrete block walls, determine the U-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. b. If the mass wall has additional insulation:
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For concrete walls, determine the Ru from Table A3.1-2 based on the concrete density and 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 U-factor by adding the Ru and the effective R-value together and taking the inverse of the total.
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For concrete block walls, determine the Ru 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 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 U-factor by adding the Ru and the effective R-value together and taking the inverse of the total.
ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 235