Mich. Admin. Code R. 408.31063 - [Rescinded effective 8/29/2025] Insulation and fenestration criteria

Rule 1063. Insulation and fenestration criteria. Table R402.1.1 of the code is amended to read as follows:

TABLE R 402.1.1 INSULATION AND FENESTRATION REQUIREMENTS BY COMPONENTa

CLIMATE ZONE

FENESTRATION U-FACTOR

SKYLIGHTb

U-FACTOR

CEILING R-Value

WOOD FRAME WALL R-VALUE

MASS WALL R-VALUEg

FLOOR

R-VALUE

BASEMENTc

WALL R-VALUE

SLAB d

R-VALUE

AND DEPTH

CRAWL

SPACEc

WALL R-VALUE

5A

0.32

0.55

38

20 or 13 + 5f

13/17

30e

10/13

10, 2ft

15/19

6A

0.32

0.55

49

20 or 13 + 5f

15/20

30e

15/19

10, 4ft

15/19

7

0.32

0.55

49

20 or 13

+ 5f

19/21

38e

15/19

10, 4ft

15/19

a. R-values are minimums. U-factors are maximums. When insulation is installed in a cavity that is less than the label or design thickness of the insulation, the installed R-value of the insulation shall not be less than the R-values specified in the table.

b. The fenestration U-factor column excludes skylights.

c. "15/19" means R-15 continuous insulation on the interior or exterior of the home or R-19 cavity insulation at the interior of the basement wall. "15/19" may be met with R-13 cavity insulation on the interior of the basement wall plus R-5 continuous insulation on the interior or exterior of the home. "10/13" means R-10 continuous insulation on the interior or exterior of the home or R-13 cavity insulation at the interior of the basement wall.

d. R-5 shall be added to the required slab edge R-values for heated slabs.

e. Or insulation sufficient to fill the framing cavity, R-19 minimum.

f. First value is cavity insulation, second is continuous insulation or insulated siding, so "13 + 5" means R-13 cavity insulation plus R-5 continuous insulation or insulated siding. If structural sheathing covers 40 % or less of the exterior, continuous insulation R-value may be reduced by no more than R-3 in the locations where structural sheathing is used to maintain a consistent total sheathing thickness.

g. The second R-value applies when more than half the insulation is on the interior of the mass wall.

Notes

Mich. Admin. Code R. 408.31063
1998-2000 AACS; 2008 AACS; 2010 AACS; 2015 AACS; 2025 MR 10, Eff. 8/29/2025

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