FIELD NOTE · SUPPLEMENTAL SET
Three or four inches of polyiso: the reroof requirement that moved
ISSUEDJULY 11, 2026DRAWN BY THE NIGHTLY SWEEP
A roll of single-ply membrane leaves the plant carrying two solar reflectance numbers, and only the second describes a roof anybody will stand on. The first is initial, measured in a laboratory on material that has never been outdoors. The second is aged. Title 24 buys the aged number, and it has asked a low-sloped commercial roof for 0.63 since January 1, 2020. So the reflective surface stopped being an upsell six years ago, and what moved the price of a reroof is the polyiso underneath it.
Aged reaches the label two ways, and the first is three years of exposure at a Cool Roof Rating Council test farm, then a return to an accredited lab for a second measurement. The other is arithmetic under Section 110.8(i)2, which the code supplies for any product the council has not weathered. Both routes end in the same cell: Section 140.3(a)1A of the 2025 California Energy Code sets the prescriptive minimum for a nonresidential low-sloped roof at an aged solar reflectance of 0.63 with a thermal emittance of 0.75, or an SRI of 75, in climate zones 1 through 16. The 2022 standards print those values, and so do the 2019 standards, which took effect on January 1, 2020.
Six years, and no movement.
The 2025 code, CEC-400-2025-010-F, applies to permit applications submitted on or after January 1, 2026, and for the nonresidential roofing sections it reprints its predecessor. The layer that actually moved sits one subchapter over, in Table 141.0-C, and it moved in the cycle before this one.
Section 140.3(a)1A, Table 140.3-C and Table 141.0-C, 2025 California Energy Code, CEC-400-2025-010-F; zone labels from Reference Appendix JA2.
The low-sloped row of that matrix runs flat across all eight Southern California columns. A commercial roof at a rise to run under 2:12 owes 0.63 aged reflectance and 0.75 emittance, or SRI 75, in Torrance in Climate Zone 6, in Palm Springs in 15 and in the six other Southern California columns.
Steep-sloped roofs, at 2:12 and above, carry the one reflectance value in the matrix that did move: Climate Zones 1 and 3 owe 0.20 and 0.75, or SRI 16, while Climate Zones 2 and 4 through 16 owe 0.25 and 0.80, or SRI 23, which puts every Southern California zone in the second band. The 2019 code had asked 0.20 and 0.75 of every zone in the state, and the 2022 cycle raised it.
Guest rooms of hotel and motel buildings get their own rows and their own zone lists: low-sloped at 0.55 and 0.75, or SRI 64, in Climate Zones 9, 10, 11, 13, 14 and 15, and steep-sloped at 0.20 and 0.75, or SRI 16, in Climate Zones 2 through 15. So a hotel in Torrance recovering a low-sloped guest-room roof has no prescriptive aged reflectance to hit at all, because Table 140.3-C prints NR in that cell, and NR is the code declining to require rather than the code forgetting. The insulation lands on that roof anyway, because Table 141.0-C carries no occupancy column.
A membrane rated 0.80 initial runs 0.2 plus 0.70 times 0.60, which is 0.62. It misses by 0.01.
Then Section 140.3(a)1Aia offers a second way through, because the requirement is written as a choice, and the alternative to 0.63 with 0.75 is a minimum SRI of 75. Section 110.8(i)3 pins how that gets calculated, at ASTM E1980-11 approach I, equations 1 and 3 only, at a moderate wind velocity, and SRI reads thermal emittance as well as reflectance, so run at those settings the two branches disagree with each other. A product sitting exactly on the prescriptive 0.63 and 0.75 returns an SRI of 72, and fails the alternative the same sentence offers it. The 0.80 membrane, at 0.62, returns 74.8 at an emittance of 0.90 and 75.0 at 0.91.
Which branch the plan checker runs is what decides a borderline product, and the emittance printed on the label is what decides which way it breaks.
That exception is gone. It was deleted in the 2022 cycle, effective January 1, 2023, and the recover language was broadened at the same time to the whole area of the recover or the replacement.
So a roof in Climate Zone 9 goes from R-8 to R-23 and one in Climate Zone 6 goes from R-8 to R-17, which at the R-5.7 per inch the supporting analysis assumed is four inches of above-deck insulation and three.
INSTALLED COST OF ABOVE DECK POLYISO, 2020 ANALYSIS DOLLARS PER SQ FT R-8, THE 2019 MINIMUM IN CLIMATE ZONES 1 AND 3 THROUGH 9 0.97 R-14, THE 2019 MINIMUM IN CLIMATE ZONES 2 AND 10 THROUGH 16 1.47 R-17, REQUIRED NOW IN CLIMATE ZONES 6, 7 AND 8 1.71 R-23, REQUIRED NOW IN EVERY OTHER ZONE 2.19
The Statewide CASE Team report prepared for the Energy Commission priced that material at $0.97 per square foot installed at R-8, $1.47 at R-14, $1.71 at R-17 and $2.19 at R-23. Those are 2020 dollars off RSMeans 2020 and contractor interviews, produced to justify a rulemaking, not a quote.
The code wrote an exception around the rooftop units, and the exception is what decides the crane. Exception 2 to Section 141.0(b)2Bii says that where existing mechanical equipment will not be disconnected and lifted, what gets added is the greater of R-10 or the maximum thickness that still keeps the distance from membrane surface to top of base flashing inside the manufacturer's instructions. Lifting is therefore a code decision before it is a cost decision, and leaving the units down drops a Climate Zone 9 roof from R-23 to whatever the flashing height allows, with R-10 as the floor. The CASE Team put $1,500 on lifting a five-ton unit and assumed one unit per 2,000 square feet of roof, which is $0.75 per square foot of roof area.
A recoat isn't required to be insulated at all, under Exception 4, so its polyiso line is zero, and a recover that adds new R-10 above deck escapes Table 141.0-C under Exception 1. A full replacement carries the table, the thickness, the flashings and the crane, which in Climate Zone 9 is $2.19 a square foot of polyiso against the $0.97 the same roof would have cost under the 2019 minimum, plus $0.75 if the units come off.
None of that makes the prescriptive numbers unavoidable: Exception 1 to Section 141.0(b)2Bi sells a lower aged reflectance against a tighter assembly, and Section 141.0(b)3 is the other way out, an energy budget in place of a table. A darker roof is purchasable. What buys it is insulation.
An owner whose last reroof was permitted before 2023 has priced none of this; the contractor pricing the work has, on every commercial replacement that crossed the trigger since January 2023.
Permits filed on or after January 1, 2023 have carried them, and the 2025 cycle reprinted the sections without changing a digit.
Aged reaches the label two ways, and the first is three years of exposure at a Cool Roof Rating Council test farm, then a return to an accredited lab for a second measurement. The other is arithmetic under Section 110.8(i)2, which the code supplies for any product the council has not weathered. Both routes end in the same cell: Section 140.3(a)1A of the 2025 California Energy Code sets the prescriptive minimum for a nonresidential low-sloped roof at an aged solar reflectance of 0.63 with a thermal emittance of 0.75, or an SRI of 75, in climate zones 1 through 16. The 2022 standards print those values, and so do the 2019 standards, which took effect on January 1, 2020.
Six years, and no movement.
The 2025 code, CEC-400-2025-010-F, applies to permit applications submitted on or after January 1, 2026, and for the nonresidential roofing sections it reprints its predecessor. The layer that actually moved sits one subchapter over, in Table 141.0-C, and it moved in the cycle before this one.
Aged 0.63, in Torrance and in Palm Springs
Section 140.3(a)1A, Table 140.3-C and Table 141.0-C, 2025 California Energy Code, CEC-400-2025-010-F; zone labels from Reference Appendix JA2.
The low-sloped row of that matrix runs flat across all eight Southern California columns. A commercial roof at a rise to run under 2:12 owes 0.63 aged reflectance and 0.75 emittance, or SRI 75, in Torrance in Climate Zone 6, in Palm Springs in 15 and in the six other Southern California columns.
Steep-sloped roofs, at 2:12 and above, carry the one reflectance value in the matrix that did move: Climate Zones 1 and 3 owe 0.20 and 0.75, or SRI 16, while Climate Zones 2 and 4 through 16 owe 0.25 and 0.80, or SRI 23, which puts every Southern California zone in the second band. The 2019 code had asked 0.20 and 0.75 of every zone in the state, and the 2022 cycle raised it.
Guest rooms of hotel and motel buildings get their own rows and their own zone lists: low-sloped at 0.55 and 0.75, or SRI 64, in Climate Zones 9, 10, 11, 13, 14 and 15, and steep-sloped at 0.20 and 0.75, or SRI 16, in Climate Zones 2 through 15. So a hotel in Torrance recovering a low-sloped guest-room roof has no prescriptive aged reflectance to hit at all, because Table 140.3-C prints NR in that cell, and NR is the code declining to require rather than the code forgetting. The insulation lands on that roof anyway, because Table 141.0-C carries no occupancy column.
A membrane rated 0.80, and the branch it gets tested on
Where a product carries no rating-council aged value, Section 110.8(i)2 supplies an equation instead of a measurement: aged reflectance equals 0.2 plus a soiling resistance term times the initial reflectance minus 0.2, with that term set at 0.65 for field-applied coatings and 0.70 for everything else.A membrane rated 0.80 initial runs 0.2 plus 0.70 times 0.60, which is 0.62. It misses by 0.01.
Then Section 140.3(a)1Aia offers a second way through, because the requirement is written as a choice, and the alternative to 0.63 with 0.75 is a minimum SRI of 75. Section 110.8(i)3 pins how that gets calculated, at ASTM E1980-11 approach I, equations 1 and 3 only, at a moderate wind velocity, and SRI reads thermal emittance as well as reflectance, so run at those settings the two branches disagree with each other. A product sitting exactly on the prescriptive 0.63 and 0.75 returns an SRI of 72, and fails the alternative the same sentence offers it. The 0.80 membrane, at 0.62, returns 74.8 at an emittance of 0.90 and 75.0 at 0.91.
Which branch the plan checker runs is what decides a borderline product, and the emittance printed on the label is what decides which way it breaks.
Polyiso, three inches or four
Table 141.0-C is the layer that moved, and it requires a low-sloped nonresidential or hotel and motel roof recover or replacement to carry R-23 continuous insulation, U-factor 0.037, in Climate Zones 1 through 5 and 9 through 16, and R-17 continuous, U-factor 0.047, in Climate Zones 6, 7 and 8, with at least R-10 of it above the deck either way. The 2022 standards print that table identically, and the 2019 standards did not: they asked R-8 in Climate Zones 1 and 3 through 9 and R-14 in Climate Zones 2 and 10 through 16, and they carried an exception letting any roof already holding R-7 insulation, or a U-factor below 0.089, skip the table entirely.That exception is gone. It was deleted in the 2022 cycle, effective January 1, 2023, and the recover language was broadened at the same time to the whole area of the recover or the replacement.
So a roof in Climate Zone 9 goes from R-8 to R-23 and one in Climate Zone 6 goes from R-8 to R-17, which at the R-5.7 per inch the supporting analysis assumed is four inches of above-deck insulation and three.
INSTALLED COST OF ABOVE DECK POLYISO, 2020 ANALYSIS DOLLARS PER SQ FT R-8, THE 2019 MINIMUM IN CLIMATE ZONES 1 AND 3 THROUGH 9 0.97 R-14, THE 2019 MINIMUM IN CLIMATE ZONES 2 AND 10 THROUGH 16 1.47 R-17, REQUIRED NOW IN CLIMATE ZONES 6, 7 AND 8 1.71 R-23, REQUIRED NOW IN EVERY OTHER ZONE 2.19
The Statewide CASE Team report prepared for the Energy Commission priced that material at $0.97 per square foot installed at R-8, $1.47 at R-14, $1.71 at R-17 and $2.19 at R-23. Those are 2020 dollars off RSMeans 2020 and contractor interviews, produced to justify a rulemaking, not a quote.
Base flashing at the height it was built to
Four inches of polyiso raises the membrane four inches, and every termination it runs into stays where the last crew left it. Base flashings, curbs, parapet caps, drains, scuppers, door thresholds.The code wrote an exception around the rooftop units, and the exception is what decides the crane. Exception 2 to Section 141.0(b)2Bii says that where existing mechanical equipment will not be disconnected and lifted, what gets added is the greater of R-10 or the maximum thickness that still keeps the distance from membrane surface to top of base flashing inside the manufacturer's instructions. Lifting is therefore a code decision before it is a cost decision, and leaving the units down drops a Climate Zone 9 roof from R-23 to whatever the flashing height allows, with R-10 as the floor. The CASE Team put $1,500 on lifting a five-ton unit and assumed one unit per 2,000 square feet of roof, which is $0.75 per square foot of roof area.
Recoat, recover, replacement
Three words, three prices, one building. Section 141.0(b)2B pulls the full requirement in when more than 50 percent of the roof area or more than 2,000 square feet is altered, whichever is less, which puts the 2,000 square foot figure in charge of any roof over 4,000 square feet; healthcare facilities are excepted from Section 141.0 altogether.A recoat isn't required to be insulated at all, under Exception 4, so its polyiso line is zero, and a recover that adds new R-10 above deck escapes Table 141.0-C under Exception 1. A full replacement carries the table, the thickness, the flashings and the crane, which in Climate Zone 9 is $2.19 a square foot of polyiso against the $0.97 the same roof would have cost under the 2019 minimum, plus $0.75 if the units come off.
None of that makes the prescriptive numbers unavoidable: Exception 1 to Section 141.0(b)2Bi sells a lower aged reflectance against a tighter assembly, and Section 141.0(b)3 is the other way out, an energy budget in place of a table. A darker roof is purchasable. What buys it is insulation.
An owner whose last reroof was permitted before 2023 has priced none of this; the contractor pricing the work has, on every commercial replacement that crossed the trigger since January 2023.
The meeting that set the number
It was not held on anybody's roof: it was the October 2020 Final CASE Report on nonresidential high performance envelope, 2022-NR-ENV1-F, where Table 56 records the Statewide CASE Team walking its own draft proposal back from R-29 and R-20 to R-23 and R-17 after stakeholders objected to the first cost and the complexity. The Energy Commission adopted the walked-back levels verbatim.Permits filed on or after January 1, 2023 have carried them, and the 2025 cycle reprinted the sections without changing a digit.