Wis. Admin. Code Department of Safety and Professional Services SPS 322.31

Current through November 25, 2024

Section SPS 322.31 - Prescriptive insulation and fenestration criteria

(1) REQUIREMENTS.

(a) Except as specifically provided under this subchapter, dwellings using the prescriptive method shall meet the requirements of Table 322.31-1 or 322.31-2.

(b) In Tables 322.31-1 and 322.31-2, zone 2 consists of the following 15 northern counties: Ashland, Bayfield, Burnett, Douglas, Florence, Forest, Iron, Langlade, Lincoln, Oneida, Price, Sawyer, Taylor, Vilas and Washburn. Zone 1 consists of all other counties not included in zone 2.

(2) THERMAL ENVELOPE.

(a)General. If the total dwelling thermal envelope UA is less than or equal to the total UA resulting from using the U-factors in Table 322.31-2 multiplied by the same assembly area as in the proposed building, the dwelling is in compliance with this chapter. The UA calculation shall be done using a method consistent with the ASHRAE Handbook of Fundamentals and shall include the thermal bridging effects of framing materials.

Note: UA is equal to the product of the U-factor times the assembly area.

Note: REScheck is an acceptable software program for determining compliance with this section.

(b)Software version. If a REScheck software program is used to show compliance with this section, a version approved by the department shall be used.

Note: The IECC 2009 version of REScheck meets the thermal envelope requirements of this code.

(3) APPLIANCE EFFICIENCY.

(a) Except as allowed under par. (b) and s. SPS 322.46, oil-fired and gas-fired furnaces and boilers shall meet the minimum efficiency requirements in Table 322.31-3.

(b) In new construction, an oil-fired or gas-fired furnace or boiler meeting the federal efficiency standard but not the requirements of Table 322.31-3 may be installed if the dwelling thermal envelope requirements of Table 322.31-4 are met.

TABLE 322.31-1

INSULATION AND FENESTRATION REQUIREMENTS BY COMPONENT^a

Zone	Fenestration U-Factor	Skylight U-Factor	Ceiling R-Value	Wood Frame Wall R-Value	Mass Wall R-Valuei	Floor R-Value	Basement Wall R-Valueb	Crawl Space Wall R-Valueb	Heated Slab R-Valuec	Unheated Slab R-Valued
1	0.35	0.60	49e	20f or 13+5g	15/19	30h	15/19	10/13	10/15	10
2	0.35	0.60	49e	21f	19/21	38h	15/19	10/13	10/15	10

^a R-values are minimums. U-factors are maximums.

^b "15/19" means R-15 continuous insulated sheathing on the interior or exterior of the home or R-19 cavity insulation at the interior of the basement wall. "15/19" shall be permitted to be met with R-13 cavity insulation on the interior of the basement wall plus R-5 continuous insulated sheathing on the interior or exterior of the home. "10/13" means R-10 continuous insulated sheathing on the interior or exterior of the home or R-13 cavity insulation at the interior of the basement wall.

^c The first R-value applies under the entire slab, regardless of depth below grade. The second R-value applies to the slab edge where the bottom of the slab is less than 12 inches below adjacent grade. Slab edge insulation shall extend downward from the top of the slab for a minimum of 48 inches or downward to at least the bottom of the slab and then horizontally to the interior or exterior for a minimum total distance of 48 inches. Also, see s. SPS 321.16 for protection against frost for slabs with supports less that 4 feet below grade.

^d The R-value applies to any slab, the bottom of which is less than 12 inches below adjacent grade. Also, see s. SPS 321.16 for protection against frost for slabs with supports less than 4 feet below grade.

^e See s. SPS 322.32(1) for application and permitted reduced R-value.

^f R-20 and R-21 may be compressed into a 2X6 cavity.

^g "13+5" means R-13 cavity insulation plus R-5 insulated sheathing. If structural sheathing covers 25% or less of the exterior, insulating sheathing is not required where structural sheathing is used. If structural sheathing covers more than 25% of the exterior, structural sheathing shall be covered with insulated sheathing of at least R-2.

^h Or insulation sufficient to fill the framing cavity with a minimum of R-19.

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

TABLE 322.31-2

EQUIVALENT U-FACTORS

Zone	Fenestration U-Factor	Skylight U-Factor	Ceiling U-Factor	Wood Frame Wall U-Factor	Mass Wall U-Factor	Floor U-Factor	Basement Wall U-Factor	Crawl Space U-Factor	Unheated Slab U-Factor
1	0.35	0.60	0.026	0.057	0.060a	0.033	0.050	0.065	10
2	0.35	0.60	0.026	0.057	0.057a	0.028	0.050	0.065	10

^a When more than half the insulation is on the interior, the mass wall U-factors shall be the same as the frame wall U-factor.

TABLE 322.31-3

WARM AIR FURNACES AND BOILERS, MINIMUM EFFICIENCY REQUIREMENTS

Equipment Type	Minimum Efficiency	Test Procedure
Natural gas and propane furnace	90% AFUE	DOE 10 CFR Part 430 or ANSI Z21.47
Natural gas and propane hot water boilers	90% AFUE	DOE 10 CFR Part 430
Oil-fired furnaces	83% AFUE	DOE 10 CFR Part 430 or UL 727
Oil-fired hot water boilers	84% AFUE	DOE 10 CFR Part 430

TABLE 322.31-4

COMPONENT DWELLING THERMAL ENVELOPE REQUIREMENTS FOR DWELLINGS USING LOWER EFFICIENCY APPLIANCES^a

Fenestration U-Factor	Skylight U-Factor	Ceiling R-Value	Wood Frame Wall R-Value	Mass Wall R-Value	Floor R-Value	Basement or Crawl Space Wall R-Valueb	Heated Slab R-Valuec	Unheated Slab R-Valued
0.30	0.60	49e	21f or 19+5g	19	30h	15/19	10/20	15
Equivalent U-Factors
0.30	0.60	0.026	0.057	0.057	0.033	0.045	0.033	0.047

^a R-values are minimums. U-factors are maximums.

^b The first R-value applies to continuous insulation. The second R-value applies to framing cavity insulation.

^c The first R-value applies under the entire slab, regardless of depth below grade. The second R-value applies to the slab edge. Slab edge insulation shall extend downward from the top of the slab for a minimum of 48 inches or downward to at least the bottom of the slab and then horizontally to the interior or exterior for a minimum total distance of 48 inches.

^d The R-value applies to the slab perimeter insulation, where the bottom of the slab is less than 12 inches below adjacent grade. Slab edge insulation shall extend downward from the top of the slab for a minimum of 48 inches or downward to at least the bottom of the slab and then horizontally to the interior or exterior for a minimum total distance of 48 inches. Also, see s. SPS 321.16 for protection against frost for slabs with supports less than 4 feet below grade.

^e See s. SPS 322.32(1) for application and permitted reduced R-value.

^f R-21 may be compressed into a 2X6 cavity.

^g "19+5" means R-19 cavity insulation plus R-5 insulated sheathing. If structural sheathing covers 25% or less of the exterior, insulating sheathing is not required where structural sheathing is used. If structural sheathing covers more than 25% of the exterior, structural sheathing shall be covered with insulated sheathing of at least R-2.

^h Or insulation sufficient to fill the framing cavity with a minimum of R-19.

Wis. Admin. Code Department of Safety and Professional Services SPS 322.31

CR 08-043: cr. Register March 2009 No. 639, eff. 4-1-09; EmR0917: emerg. am. (2) (b), eff. 9-5-09; CR 09-072: am. (2) (b) Register March 2010 No. 651, eff. 4-1-10; CR 09-104: am. Tables 22.31-1 and 22.31-4 Register December 2010 No. 660, eff. 1-1-11; correction in (1) (a), (b), (2) (a), (b), (3) (a), (b), Table 322.31-1, Table 322.31-4 made under s. 13.92(4) (b) 7, Stats., Register December 2011 No. 672.

Amended by, CR 15-041: am. Table 322.31-1, Table 322.31-2, Table 322.31-4 Register December 2015 No. 720, eff.1/1/2016