R Value vs U Value: What Each Measures, How to Convert, and When You Can't

What do the key R-value and U-value statistics show?

In this September 2026 R value vs U value document audit, 1 ÷ published R did not equal published U in any of 19 model records. These are comparisons of published labels, not 19 new laboratory tests; the findings are reproduced in Tables 2 and 3.

Source checks and calculations: September 14, 2026.

1. Across 19 commercial door models from three manufacturer names, dividing 1 by the published R-value produced the published U-factor in zero cases. The published U-factors ran 1.75 to 4.76 times the inverted R-value in consistent US units. Source: St. Louis Dock Door Repair Research compilation of Amarr, Overhead Door and Raynor documents; checked and calculated September 14, 2026.

2. Amarr's 2743 specification chart publishes section R=28.0 h·ft²·°F/Btu and assembly U=0.17 Btu/(h·ft²·°F). The inverse of 28.0 is 0.0357, not 0.17; the inverse of the published U-factor is equivalent assembly R≈5.88 h·ft²·°F/Btu. Sources: Amarr product page and brochure; checked and calculated September 14, 2026. 6 7

3. DASMA says a calculated garage-door section R-value and a tested door-assembly U-factor are not reciprocals of each other. This is a scope distinction, not an exception to the reciprocal relationship for matching boundaries. Source: Door & Access Systems Manufacturers Association, TDS-163, revised July 6, 2022; checked September 14, 2026. 1

4. Raynor lists ThermaSeal TM200C and Commercial Aspen AP200C at numerically equal R-values of 18 and 18.0 h·ft²·°F/Btu, but installed U-factors of 0.24 and 0.17 Btu/(h·ft²·°F). The first U-factor is 41.2 percent higher than the second, using 0.17 as the denominator; configurations were not matched. Source: Raynor CSI Section 08 36 13, V091025; checked and calculated September 14, 2026. 14

5. Published R-values across these 19 records span 9.83–28.0 h·ft²·°F/Btu, a 2.8-fold range; reciprocals of the published assembly U-factors span equivalent R≈4.17–10.00 h·ft²·°F/Btu. At two-decimal display precision, 16 of 19 equivalent assembly R-values fall between 4.17 and 6.67. Source: St. Louis Dock Door Repair Research calculations from the paired dataset, September 14, 2026.

6. Haas Door's commercial 2000, 600 and 700 Series pages publish headline “Tested U-Factor” figures of 0.094, 0.106 and 0.093, respectively. These are manufacturer-page observations, not a certificate-row extract or a verified within-series range; the headline values are transcribed as printed. Sources: Haas Door series pages; checked September 14, 2026. 4 5 15

7. One US customary U-factor unit equals approximately 5.678263 W/(m²·K), and one US customary R-value unit equals approximately 0.1761102 m²·K/W, using the international-table Btu convention. Source: NIST SP 811, Appendix B.9, updated August 18, 2025; checked September 14, 2026. 19

8. NIST's international-table and thermochemical Btu conversion factors for U-factor differ by approximately 0.067 percent, using the international-table factor as the denominator. The published factors are 5.678263 and 5.674466 W/(m²·K) per respective US customary U unit. Source: NIST SP 811, Appendix B.9; checked and calculated September 14, 2026. 19

9. The section-R method in DASMA TDS-163 adds R-0.85 h·ft²·°F/Btu from surface air films: 0.68 for still interior air and 0.17 for exterior air at 15 mph. This is the stated method, not a finding about every manufacturer's R label. Source: DASMA TDS-163, revised July 6, 2022; checked September 14, 2026. 1

10. The 2021 IECC commercial prescriptive provision permits assembly U≤0.440 Btu/(h·ft²·°F) in Climate Zones 0–6 and U≤0.360 in Zones 7–8 for horizontally hinged sectional doors with one row of glazing occupying 14–25 percent of door area. It is not a universal limit for every overhead door or jurisdiction. Source: ICC, 2021 IECC C402.4.5.2; issuer text checked September 14, 2026. 26

11. The City of St. Louis lists the 2018 IECC under Ordinance 70799. Its building-code table labels August 1, 2018 as “Date Adopted,” while the ordinance record labels July 6, 2018 as “Effective Date”; this reference preserves both official fields rather than selecting one. Sources: City Building Division and ordinance record; checked September 14, 2026. 22 23

12. DOE's Missouri profile lists “None Statewide” in both its commercial and residential energy-code entries. This does not mean a particular Missouri project has no energy requirements. Sources: DOE Building Energy Codes Program and Missouri DNR; checked September 14, 2026. 24 25

13. 16 CFR § 460.22 excludes fenestration-related products, including doors, from that section's testing requirement for certain R-value claims on non-insulation products. The exclusion is section-specific, not an exemption from all advertising law. Sources: eCFR § 460.22, added at 84 FR 20790 on May 13, 2019, and FTC Act summary; checked September 14, 2026. 20 21

14. DASMA's program-label rule puts an optional R-value after the U-factor and in smaller type; its participant page contained 11 named entries on September 14, 2026. That is a count of list entries, not independent corporate groups. Sources: DASMA TDS-196, program page and labeling guidelines; checked September 14, 2026. 2 3 30

R value vs U value comes down to one question the formula hides: do both numbers describe the same thing? R-value measures resistance to heat flow. U-value, also called U-factor, measures the heat-transfer rate per unit area per unit temperature difference. They are reciprocals, U = 1/R, when both describe the same physical scope under the same conditions in consistent units. Often the published labels don't. We collected paired ratings for 19 commercial door models from three manufacturer names on September 14, 2026. Dividing 1 by the published R-value never once produced the published U-factor in this selected dataset. Amarr's 2743 lists R-value 28.0 h·ft²·°F/Btu and U-factor 0.17 Btu/(h·ft²·°F) in the same specification chart. One divided by 28 is 0.0357. 6 7 28

That is not an error demonstrated in Amarr's figures. It is the whole point. The two numbers describe different rating boundaries, and this page shows exactly what.

By St. Louis Dock Door Repair Research
Last verified: September 14, 2026 · Dataset version 2026-09-14.2

On this page

• R value vs u value: what is the difference?
• How do you convert R-value to U-value?
• Why didn't 1 ÷ R match the published U-factor on any of these 19 doors?
• What does each published rating actually describe?
• What do these numbers show, and what don't they?
• How was this reference built?
• How is a door's R-value calculated?
• How is a door's U-factor tested?
• Which number do building codes require?
• Which rating applies to a window, a door, or a wall?
• What don't R-value and U-factor tell you?
• Where do Missouri and St. Louis requirements come from?
• Why does this distinction matter now?
• What are the limitations?
• Citation reference
• Other R-value and U-value questions
• Primary sources and update history

R value vs u value: what is the difference?

R-value measures thermal resistance and is reported in h·ft²·°F/Btu in US customary units — higher means greater resistance. U-value, also called U-factor, measures thermal transmittance in Btu/(h·ft²·°F) — lower means less heat transfer for the same area and temperature difference. The two are reciprocals when both describe the same physical scope under the same rating conditions in consistent units, and that condition is the part people skip. 28 29

The trouble starts when one number describes a slice of a product and the other describes the assembly. A calculated R-value through a door section and a tested U-factor for a specified door assembly can both be legitimate. They are not two views of the same measurement, and flipping one does not give you the other. 1

Here is the test to apply before you invert anything: do the R-value and the U-value describe the same physical boundary? Same materials, same edges, same conditions, consistent units. If yes, U = 1/R holds. If no, the arithmetic still works, but it answers a different question. The equivalent R calculated from an assembly U stays an assembly value; it does not become an insulation-core or section rating.

How do you convert R-value to U-value?

Divide 1 by the R-value when the scope, conditions and unit system match: U = 1/R, and R = 1/U. An R-value of 20 h·ft²·°F/Btu converts to U=0.0500 Btu/(h·ft²·°F), while U=0.30 Btu/(h·ft²·°F) converts to equivalent R≈3.33 h·ft²·°F/Btu. The relationship is exact; these displayed decimal answers are rounded, and the judgment is in whether the two figures describe the same thing. 28

The formulas

• US customary: U = 1 ÷ R, and R = 1 ÷ U
• R-value, US to SI: multiply by 0.1761102 to get m²·K/W
• U-factor, US to SI: multiply by 5.678263 to get W/(m²·K)

Both rounded conversion factors come from NIST Special Publication 811, Appendix B.9, and both use the international-table Btu. NIST publishes a second pair for the thermochemical Btu — 0.1762280 for R and 5.674466 for U. The U-factor conversion factors differ by approximately 0.067 percent using the international-table factor as the denominator. State the convention when reproducing an SI figure; convention, source precision and rounding can each affect the last displayed digit. 19

Two worked examples

R to U. For a material layer with R=13 h·ft²·°F/Btu, U = 1 ÷ 13 = 0.0769 Btu/(h·ft²·°F). In SI, R-13 × 0.1761102 = 2.2894 m²·K/W.

U to R. For a window with U=0.30 Btu/(h·ft²·°F), R = 1 ÷ 0.30 = 3.33 h·ft²·°F/Btu. In SI, 0.30 × 5.678263 = 1.7035 W/(m²·K).

Table 1 — R-value and U-value conversion chart, US and SI

Bold entries mark selected published R-values in the commercial-door audit below. These are reference inputs, not measured properties assigned to unspecified products.

Source: St. Louis Dock Door Repair Research calculations using the reciprocal relationship and NIST SP 811, Appendix B.9, international-table Btu factors; calculated September 14, 2026. All four-decimal table cells were recalculated from the unrounded input, not from another displayed column. 19

Dataset: Conversion chart — CSV. The 27 rows contain US R and U plus SI conversions under both the international-table and thermochemical Btu conventions, with calculation date and version.

This chart is valid only where the resistance and the transmittance describe the same physical scope. It does not assign these values to any particular material or product.

Why didn't 1 ÷ R match the published U-factor on any of these 19 doors?

Because the published labels are not an established same-scope reciprocal pair. We selected 19 commercial sectional-door model records across Amarr, Overhead Door and Raynor where one manufacturer publishes both figures, producing 14 distinct numerical R/U pairs. In all 19, the published U-factor was higher than the inverse of the published R-value by a factor of 1.75–4.76; this is a selected document audit, not an exhaustive model census. 7 8 9 10 11 12 14

That gap is not evidence of a bad product or a false claim. The section-versus-assembly explanation is explicit in the Amarr and Overhead Door references. Raynor publishes its R figures under insulation entries, but does not establish in that wording whether facings or surface films are excluded; the calculation cannot resolve that missing scope detail. 7 8 14

Two different levels of scope documentation appear in this data, so we have kept them in two tables. Mixing them into one performance ranking would be the exact error this page exists to document.

Doors where the manufacturer labels the R-value as a calculated door section

Overhead Door footnotes its R-value as a calculated door section value and its U-factor as independently tested and verified per ANSI/DASMA 105. Amarr's brochure ties its R-values to the DASMA calculation method and carries the DASMA verification-program badge on its U-factors. Those are the manufacturers' statements; this audit did not independently inspect their certificates. 7 8 9 10 11 12

Table 2 — Published section R-value against published assembly U-factor

Units: R in h·ft²·°F/Btu, U in Btu/(h·ft²·°F). Eleven model records, eight distinct numerical pairs. Repeated pairs are kept as separate model records and are not treated as independent tests.

Source: Amarr product pages and the Amarr Commercial Polyurethane brochure; Overhead Door model pages and their thermal-rating footnotes. All checked September 14, 2026. All three derived columns were computed by St. Louis Dock Door Repair Research and are not additional manufacturer ratings. Source values retain their published decimal precision, with leading zeros added where needed for readability; derived columns are rounded for display. 7 8 9 10 11 12

Doors where the R-value appears in an insulation entry without a complete scope definition

Raynor's architectural specification places its R-values in entries headed “Insulation,” alongside descriptions of polyurethane. The same document gives installed U-factors for the named models, but does not expressly state that the R-values exclude facings or air films. We therefore preserve the source's wording rather than upgrading it to an “insulation-core only” claim. 14

Table 3 — R-value reported in the insulation entry against published installed U-factor

Units: R in h·ft²·°F/Btu, U in Btu/(h·ft²·°F). Eight model records, six distinct numerical pairs.

Source: Raynor Garage Doors, CSI Section 08 36 13, Sectional Overhead Doors, version V091025, PDF pages 10–12 and 38–40; checked September 14, 2026. Derived columns calculated by St. Louis Dock Door Repair Research. 14

Source naming inconsistency: under the Commercial Aspen heading, Raynor’s installed-U lines refer to AP200C and AP138C as “ThermaSeal.” This table follows the model identifiers and enclosing Commercial Aspen heading. The naming inconsistency is retained in each affected download record, not silently erased.

Two doors, the same published R-value, different tested results

The cleanest illustration in this dataset comes from a single manufacturer, in a single document, with no cross-brand comparison involved.

Raynor's specification lists ThermaSeal TM200C at R=18 with installed U=0.24, and Commercial Aspen AP200C at R=18.0 with installed U=0.17, in the US units shown in Table 3. Numerically equal published R-values. The first installed U-factor is 41.2 percent higher than the second, using 0.17 as the denominator. This is a comparison of published numbers, not a controlled paired test. 14

In the same document, ThermaSeal TM175 carries an R-value of 16.4 and TM200 and TM220 carry 18.3 — and all three list an installed U-factor of 0.21. The higher R-value is approximately 11.6 percent above 16.4, while the published installed U-factor remains the same. That is a descriptive comparison, not proof that changing insulation has no effect. 14

We are not claiming one of these doors outperforms another. Configurations, glazing, dimensions and test bases were not matched or independently verified. What the document shows is narrower and more useful: the published R-value did not predict the published U-factor, even within one manufacturer's own product line.

What third-party verification listings can — and cannot — establish here

Some manufacturers emphasize U-factor without supplying a paired R-value in the inspected specification. Haas Door's thermal-performance explanation and commercial series pages are examples. Those observations are useful, but a manufacturer's page is not the same evidence as a row read from an ICC-ES listing. 18

ICC-ES administers DASMA's verification program. For this release, the supplied TPVP-100 and TPVP-101 report URLs could not be retrieved as readable primary listings during the verification pass. We therefore publish no certificate-derived within-series ranges, suffix interpretations, reissue dates or renewal dates from those reports. The separately checked manufacturer-page observations follow instead; they do not replace or purport to reconcile individual certificate configurations. 2

Table 4 — Haas Door manufacturer-page observations, not an ICC-ES certificate extract

Source: Haas Door commercial 2000, 600 and 700 Series pages, checked September 14, 2026. These are three series-page observations, not three laboratory tests or certification-listing rows. 4 5 15

The headline bullets do not print units beside those U-factor figures. They are transcribed as printed, without SI conversion or a computed spread. Nor do headline values establish that every optional size, window arrangement or configuration has that rating. A certificate comparison would require the certificate itself and its configuration fields; a matching series name is not enough.

Dataset: Paired door-rating audit — CSV. Nineteen model records across three manufacturer names, including published values, units, documented scope, source locations and versions, check dates, arithmetic columns, scope caveats and record IDs.

Supplementary data: Haas published series observations — CSV. Three manufacturer-page records with explicit evidence and unit-label limitations. This is not the unverified 34-row ICC-ES extract, which is not part of the published dataset.

Release reference: Attribution details and version.

Combined data: JSON includes the paired audit, conversion chart, supplementary observations, scope crosswalk, reference-route table, source register, formulas, exclusions and release version. The calculation script reproduces arithmetic from the included source-value snapshot; it does not re-check live sources.

What does each published rating actually describe?

There are four labels to separate here, but only two physical quantities: resistance and transmittance. Insulation-core R-value, calculated door-section R-value, tested assembly U-factor, and the broader term “U-value” can appear in the same conversation. The label does not establish the measurement boundary or test method; that has to come from the document behind it. 1 28

That last one matters for anyone searching this phrase. Wayne Dalton explains that DASMA program participants use “U-factor” to distinguish the program's verified rating from potentially ambiguous “U-value” listings. This is a sectional-door verification-program convention, not the retirement of “U-value” throughout building science. NFRC's glossary uses U-value as another term for U-factor. 17 28

Table 5 — The four labels, their boundaries and the documents behind them

Source: DASMA TDS-163 and TDS-196; ANSI/DASMA 105-2017; Wayne Dalton program explanation; NFRC glossary. Compiled and checked September 14, 2026. 1 2 17 28 29

The industry documents make the same scope distinction in different ways. DASMA TDS-163 separates section calculations from assembly ratings, and TDS-196 warns against treating tested U as the inverse of calculated section R. Clopay's current model table makes its basis explicit: section R is calculated under TDS-163, while door U is tested under DASMA 105. None of that changes the reciprocal relationship when the boundary and conditions genuinely match. 1 2 16

Reference data: Rating-scope crosswalk — CSV. Four labels, with source references and the distinction between a physical quantity and a rating boundary.

What do these numbers show, and what don't they?

This is a document audit, not a performance test. It shows what three manufacturers published, what each number describes, and what happens arithmetically when you invert one and compare it to the other. Across 19 records the inversion never landed on the published figure.

What it does not show: which door performs better, how any of these doors behave once installed, whether the test configurations were comparable, or what any of this saves on a utility bill. We did not test anything, we did not verify any certificate independently, and we did not match dimensions, glazing or configurations across brands.

One pattern is worth stating carefully because it is easy to over-read. Published R-values in this set span 9.83 to 28.0 — a 2.8-fold range. The equivalent assembly R implied by the published U-factors spans 4.17 to 10.00, and, after rounding equivalent R to two decimals, 16 of the 19 records land between 4.17 and 6.67. The ratio of the largest to the smallest published R is approximately 2.85, compared with 2.40 for the published U range; the displayed equivalent assembly R endpoints are rounded to two decimals. That is an observation about two sets of published numbers with different scopes. It is not a finding that all commercial doors perform alike.

How was this reference built?

We collected published thermal ratings from manufacturer documents on September 14, 2026, recorded each value with its stated scope, and calculated the reciprocals separately. A model was included only where one manufacturer published both an R-value and a U-factor for the same named model in material we read directly. Nothing was joined across brands, across documents of different vintage, or from a retailer, distributor or blog.

What we collected and from where

For each record we recorded: manufacturer, model, the figures at their published decimal precision, the units, the scope wording actually supplied, the source URL, the location within the document, the source version where stated, and the date we checked it. Missing scope detail stays missing: “R reported under Insulation” is not rewritten as “core only.” Source version and verification date are separate fields; a September 2026 check is not a claim that the product was released that month.

We read Amarr's 2743 product page and its Commercial Polyurethane brochure; Overhead Door's Thermacore 592 and 599, 525 WindStorm, 515 WindStorm and 470 model pages with their thermal-rating footnotes; and Raynor's CSI Section 08 36 13, specification version V091025. The supplied ICC-ES TPVP-100 and TPVP-101 links were not retrievable as readable primary reports in this pass, so their extracted rows and asserted certificate dates were withheld. For the separate Haas observations, we read its 2000, 600 and 700 Series manufacturer pages. For the standards we read DASMA TDS-163, TDS-196, ANSI/DASMA 105-2017 and the program's labeling guidelines; Clopay's current page supplies its own scope footnotes. For units we read NIST SP 811, Appendix B.9. For the federal rule we read 16 CFR § 460.22 on the eCFR. For the local layer we read the City of St. Louis Building Division's adopted-codes page and Ordinance 70799. Code-section observations also use issuer-published indexed text where ICC's interactive reader blocked direct retrieval; Table 6 distinguishes a verified section locator from a provision whose full conditions are not restated here. 1 2 4 5 7 14 15 19 20 22 23 29

How the figures were processed

Source numerical values and decimal precision were preserved, with leading zeros normalized for readability. We calculated three derived columns and labelled every one of them as a calculation:

• 1 ÷ published R. Arithmetic only. This is explicitly not a predicted assembly U-factor, and the table says so in the column heading.
• 1 ÷ published U — equivalent assembly R. A same-scope restatement of the published U-factor. It does not replace the manufacturer's separately calculated section R-value and does not establish an insulation requirement.
• Published U ÷ inverted R. The arithmetic ratio U × R in consistent US units. It describes the numerical mismatch, not the isolated physical effect of scope, framing, installation or a particular component.

Derived columns retain 12 decimal places in the downloads; the displayed table uses four for inverted R and two for equivalent assembly R and ratios. Calculations start from the published decimal inputs, use decimal arithmetic, and round half up only at the output precision. SI columns use NIST SP 811 international-table Btu factors; the conversion-chart download also includes the thermochemical alternatives. Repeated models with the same numerical pair remain separate model records, not independent tests. 19

Verification depth

We use two tiers.

★ means we read the primary document, the stated value and its stated scope directly. It does not mean we verified performance independently. The included manufacturer-page observations, DASMA documents, NIST factors, federal-rule text and City ordinance records meet that documentary standard. The inaccessible ICC-ES reports do not. A primary document can leave scope or configuration unspecified; ★ does not fill that gap.

● means we identified a primary reference route but downstream verification is incomplete. It is not permission to fill a cell with an unverified number. The St. Louis County energy-code edition sits here. A locator-only code row is identified as such and supplies no unverified numerical requirement.

Re-running the arithmetic does not re-check a source and does not earn a new verification date.

How is a door's R-value calculated?

Under the section method in DASMA TDS-163, by adding the specified layer resistances — it is a calculation, not a full-door test. The method includes air films, exterior surface, insulation and interior surface; the air films contribute R-0.85 h·ft²·°F/Btu. TDS-163 treats the resistance of metal facings as negligible, but its calculation is not a universal definition of every published door R-value. 1

The insulation term comes from a k-factor, the material's thermal conductivity, traced to testing under ASTM C177 or ASTM C518 at a 40 °F mean material temperature. Where a section has varying insulation thickness, TDS-163 combines the values proportionally across the section height.

What the calculation leaves out explains why section R is not an assembly rating. It does not account for the joints between sections, the steel stiles at the ends, the hardware attachment points, or the perimeter where the door meets the opening. DASMA expressly separates this section calculation from garage-door assemblies. 1

That R-0.85 of air film is worth sitting with. As an arithmetic illustration of this method, a section total of R-6.5 leaves R-5.65 for the material layers after subtracting the two surface films, in h·ft²·°F/Btu. The films would be 13.1 percent of that total, versus 3.0 percent of R-28.0. Neither share is literally a rounding error, and the example is not a newly measured product rating. 1

How is a door's U-factor tested?

A specified door specimen is mounted in a laboratory hot-box apparatus, and heat flow, area and temperature difference determine its U-factor under steady-state conditions. ANSI/DASMA 105-2017 covers sectional garage and rolling doors; the thermal test separates transmittance from air infiltration. The specimen boundary is broader than a section-layer calculation, but it is not a promise that every component of an operating installation is tested. 29

The standard includes defined specimen sizes and mounting arrangements. It expressly does not require a garage door's horizontal track and balancing hardware for the test. “Assembly U-factor” therefore means the assembly represented by that rating method and specimen, not every accessory, every field opening or every possible configuration. 29

Different rating routes also matter when comparing documents:

• Garage and rolling doors: ANSI/DASMA 105 is a thermal and air-infiltration test method. The 2021 IECC's product-rating provision also names NFRC 100 as an alternative for required garage- and rolling-door U-factors; ANSI/DASMA 105 is not the only route named there. 29 33
• NFRC-rated fenestration, including appropriate doors and windows: the product's U-factor basis follows the applicable NFRC rating procedure. Do not confuse glass-only data with a whole-product rating. 27 28
• Opaque-assembly laboratory methods: ASTM C1363 is a hot-box method referenced by ANSI/DASMA 105. A test-method citation alone does not establish that a specific local code accepts a particular proposed assembly. 29

The verification program

DASMA's Thermal Performance Verification Program is administered by ICC-ES. TDS-196 describes approved laboratory testing and independent program review, with oversight of manufacturing and rating claims. The program is not this publisher's test program, and manufacturer statements of participation are not a substitute for independently checking a listing. 2

The participant page contained 11 named entries when checked: Amarr, C.H.I. Overhead Doors, Clopay, Garaga, Garex Garage Doors, Haas Door, Hörmann LLC, Midland Garage Door, Overhead Door, Raynor and Wayne Dalton. This is a count of the page's named entries, not a count of independent parent companies. 3

The program's labeling rule is a clear signal of how its verified labels prioritize the numbers. A participant may include an R-value on the program label, but only after the U-factor and in smaller type. Its marketing guideline separately specifies a U-factor font at least 50 percent larger than the R-value font where both are presented in that format. 2 30

The program's limits matter as much as its contents. Its standard enrollment scope covers sectional doors with no more than 16 percent glazing; doors above that percentage may also be enrolled, but require separate testing and listing. Rolling steel and high-speed doors are outside this program's scope even though ANSI/DASMA 105 itself includes rolling doors. Air infiltration, solar heat gain and NFRC 100 simulation are not this program's verified U-factor scope. 2 17

Which number do building codes require?

The required quantity depends on the door category, compliance path and adopted code edition. In the 2021 IECC commercial prescriptive provision, a horizontally hinged sectional door with one row of glazing occupying 14–25 percent of door area may use assembly U≤0.440 Btu/(h·ft²·°F) in Climate Zones 0–6 or U≤0.360 in Zones 7–8. That specific allowance is expressed in U-factor; it is not a blanket “U-factor only, every time” rule for every door. 26

An R-value label alone does not establish compliance with an adopted energy code. The applicable door category, compliance path and locally amended edition have to be identified together; a later-edition allowance cannot simply be carried backward into a 2018 requirement. This release identifies the City’s adopted edition but does not restate a verified 2018 door subsection or opaque-door threshold. 22 23 31

The section number keeps moving

The door provisions use different section numbers across these editions. A section locator and a fully checked numeric requirement are different kinds of evidence, so the table separates them.

Table 6 — Where the door provision lives, by edition

Source: ICC issuer-published section text and the 2024 relocation table; ANSI/DASMA 105-2017; NFRC and ENERGY STAR definitions; eCFR § 460.22. Checked September 14, 2026. Scope labels identify exactly what was checked; a verified locator or definition is not a verified project requirement. ICC section text was available through its published search index where the interactive reader blocked full-page retrieval.

Reference data: Standards and code-reference crosswalk — CSV. Eight rows, each with its verified scope, source and check date.

The federal rule has a carve-out worth knowing

The FTC's R-value Rule governs how home insulation R-values are labelled and advertised. A 2019 addition, 16 CFR § 460.22, extends a testing requirement to R-value claims made for products that are not home insulation — and then excludes fenestration-related products, a category the section defines to include windows, doors and skylights.

Read that precisely. It does not mean R-value claims on doors are unregulated; the FTC Act's general prohibition on deceptive practices still applies. It means the specific testing requirement in that section does not reach them. The exclusion does not establish why the industry created its verification program, and we do not infer that causal history from the regulation. 20 21

Which rating applies to a window, a door, or a wall?

Read the rating boundary, not the letter. The common shorthand — R-value is for materials, U-factor is for whole products — is close enough to be useful and wrong often enough to cause errors. NFRC defines R-value for a material or a fenestration assembly, which is enough to retire the idea that R can only describe insulation. A letter on its own therefore cannot establish whether the number describes an insulation component or an assembly; the boundary still has to be read. 28

Whole-window against glass-only figures

Whole-window U-factors account for the window unit, while centre-of-glass figures describe a different boundary. Do not assume a centre-of-glass figure is always lower, or substitute it for a whole-window rating. 27 28 A centre-of-glass number and a whole-window number are the same kind of confusion as a section R-value and an assembly U-factor, wearing different clothes.

Section and complete-door ratings

This is the case documented in Tables 2 and 3 above. Check whether a published door R-value describes the insulation core, the door section, or something unlabelled. Amarr's 2743 product page, for example, lists R-value 28.0 and U-factor 0.17 in a specification chart with no scope footnote on either line; the scope explanation lives in the brochure, not on the page most people land on.

Insulation against a complete wall

R-20 cavity insulation alone does not establish a whole-wall U-factor of 0.0500 Btu/(h·ft²·°F). Framing paths and the other layers also enter the assembly calculation; the reciprocal of cavity R still describes that cavity layer, not the entire wall. The same boundary logic that separates a door section from a door assembly separates cavity insulation from a wall. 28

What don't R-value and U-factor tell you?

Neither number accounts for air moving through or around the product, and neither accounts for sunlight. Air infiltration and solar heat gain are separately measured and separately reported quantities. For sectional doors, air leakage is tested under the same standard as U-factor — ANSI/DASMA 105 — but it is a different number with a different limit.

Air leakage and solar heat gain

Air-leakage limits depend on the adopted code, applicable exceptions, door category and test pressure. This reference does not publish one air-leakage ceiling across IECC and ASHRAE editions, or a universal solar-heat-gain coefficient for windowless doors. ANSI/DASMA 105 separates leakage testing from the thermal test; ENERGY STAR explains air leakage and solar heat gain as separate quantities. 27 29

Worth stating plainly for a loading dock: none of these ratings describe an open door. A tested U-factor is a closed-door number. Door-open time and the gap around a trailer are separate operating conditions, not measurements supplied by a closed-door U-factor. The rating does not quantify those operational losses. 29

Energy bills and code compliance

A single rating does not produce a savings figure. Actual energy use depends on climate, hours of operation, the rest of the envelope, equipment efficiency, and how the building is run. We publish no savings percentages here because we have no basis to calculate one.

Nor does a rating establish compliance. Compliance is determined against the code edition a jurisdiction has actually adopted, with its local amendments, by that jurisdiction's building official.

Where do Missouri and St. Louis requirements come from?

Unit conversions do not change at a county line, but requirements do — and in Missouri they change a great deal. The US Department of Energy's state profile lists "None Statewide" for Missouri's commercial and residential energy-code entries. Local jurisdictions adopt their own, so the applicable requirement is a jurisdiction question before it is a code question.

Missouri's jurisdiction-based references

DOE’s profile lists no statewide commercial or residential energy-code entry; that is not a finding that every category of Missouri construction is exempt from energy requirements. The Missouri Department of Natural Resources maintains jurisdiction-based code references, which is the route to the applicable requirement for a given address. A "None Statewide" entry does not mean a particular project faces no requirements — it means you have to ask the jurisdiction.

St. Louis city is not St. Louis County

These are two separate jurisdictions. The City of St. Louis describes itself as an independent city and the County as a separate governmental entity. A City adoption is not a County adoption. 34

Table 7 — Where to find the applicable requirement

Source: DOE Building Energy Codes Program, Missouri profile; Missouri DNR, Energy Codes by Jurisdiction; City of St. Louis Building Division and Ordinance 70799. Checked September 14, 2026. The date discrepancy is preserved, not resolved by assumption. 22 23 24 25

The practical consequence for anyone specifying a door in this metro: the City’s official list names a 2018 edition with local amendments, while the qualified sectional-door allowance quoted above comes from the 2021 IECC. They are not interchangeable requirements, and this reference does not supply a verified 2018 door subsection or a project-level compliance determination. 22 23 26 Citing the wrong edition's section number is an easy mistake to make here, and Table 6 above exists partly because of it.

Why does this distinction matter now?

The relevant change is in how a published rating is identified, not in the reciprocal formula. DASMA's current verification-program documents prioritize U-factor on their labels, while manufacturers present scope information in different places. This September 2026 source check documents those differences; it is not a longitudinal study of industry adoption. 2 30

The inspected Haas series pages emphasize tested U-factor without a paired R-value in the headline specifications. Clopay's model-table footnotes distinguish calculated section R from tested door U. Overhead Door likewise footnotes which figure is calculated and which is tested, while Amarr's brochure provides the scope explanation needed to interpret its paired product figures. 4 5 15 16 8 7

That means a writer comparing two documents may be handed an assembly figure in one location and a section figure in another, both discussed as thermal performance. The conversion arithmetic will happily run on either. Knowing which number you have is the entire job.

What are the limitations of this reference?

This compilation is a purposively selected document audit, not a market census or laboratory study. It does not establish representative averages, independent performance verification, matched test configurations across brands, or any product ranking.

• Three manufacturers are not an industry. Nineteen model records are nineteen model records, selected because both numbers were published together, not sampled at random.
• The R-value scope is not equally explicit in every source. Amarr and Overhead Door identify calculated section values. Raynor places R under insulation entries without expressly resolving facings or air films; Tables 2 and 3 preserve that distinction. The ratio does not isolate how much of a difference is caused by scope or any physical component.
• Manufacturers publish figures for particular configurations. Listed values are not a random sample of what gets installed.
• Certificate-row claims are not verified in this release. The supplied TPVP-100 and TPVP-101 report links were inaccessible during this pass. Their 34-row extract, alleged within-series ranges, reissue dates and renewal dates are not published as verified data. Table 4 uses separate manufacturer-page observations instead.
• The verification program excludes rolling steel and high-speed doors. This audit supplies no estimate of their share of dock openings. The program’s coverage should not be confused with the broader scope of the ANSI/DASMA 105 test method. 2 29
• Nothing here is a field-installed performance measurement. A published laboratory U-factor describes its rating basis, not the seal condition, adjustment or installation quality at a particular building. This audit cannot quantify the effect of those site conditions. 29
• Equivalent assembly R is arithmetic, not a rating. It restates a published U-factor on the same scope. It does not replace a manufacturer's calculated section R-value, does not establish an insulation requirement, and is not a certified value.

Figures we did not publish

Honest gaps belong on the page.

Overhead Door's 850 was excluded from the paired tables. Its page carries two U-factor figures with different labels — 0.07 in one location and an installed U-factor of 0.14 elsewhere. Without reconciling which configuration or test basis each applies to, we did not silently select one. This is not an allegation of error. 13

Several Haas Door commercial series pages were excluded from the paired tables because they publish a U-factor without a matching R-value. We did not join an R-value from a different source or vintage to enlarge the sample. Three series appear only in the supplementary manufacturer-page table, where the U-factor headline and evidence limitations are preserved. No certificate range is inferred from those values.

We did not publish per-climate-zone opaque door U-factors from IECC Table C402.1.4. We could not read that table directly, and the 2021 sectional-door rule in C402.4.5.2 stands on its own.

We did not publish an explanation of the model-name suffixes attributed to ICC-ES TPVP-100. Without a readable primary listing and the applicable configuration definitions, a suffix interpretation or an “identical construction” conclusion would be unsupported.

We did not publish St. Louis County's energy-code edition or any County door U-factor threshold. The official lookup route is identified in Table 7; the edition itself is not verified here.

We did not claim to audit the program’s full certification directory. Its participant page had 11 named entries on the check date; none is counted as an independently verified certificate in this release merely because the manufacturer appears on that list. 3

How is this page identified in a citation?

The attribution details below identify this reference and the exact data release. Individual manufacturer specifications remain attributable to their original publishers.

Publication: St. Louis Dock Door Repair Research
Page: R Value vs U Value: What Each Measures, How to Convert, and When You Can't
URL: https://stlouisdockdoorrepair.com/research/r-value-vs-u-value/
Dataset version: 2026-09-14.2
Source checks and calculations: September 14, 2026

The versioned CSV and JSON files preserve the observations and calculations used on this page. The source register below identifies the primary publisher and document behind each external claim.

What other R-value and U-value questions come up?

Changing the rating boundary or mixing unit systems can invalidate a comparison even when the division is correct. These answers keep the unit and scope attached to the number.

Is U-value the same as U-factor?

In general usage they name the same quantity: thermal transmittance. Neither term alone establishes whether a figure describes glass, a section or a complete assembly. DASMA's verification program specifies “U-factor” for its verified labels to avoid ambiguity in this product category; that does not make “U-value” invalid elsewhere. Check the units, scope and method behind the label. 17 28

What R-value is a U-factor of 0.30?

An equivalent R of approximately 3.33 h·ft²·°F/Btu, from 1 ÷ 0.30, when U is 0.30 Btu/(h·ft²·°F). The result describes the same boundary as that U-factor: a whole-window U gives an equivalent whole-window R, not glass-only R. Using NIST's international-table Btu factor, that US U converts to approximately 1.7035 W/(m²·K). A U of 0.30 already expressed in SI would be a different input. 19 28

Can 1 ÷ U replace a garage door's published R-value?

Not when the published R describes a different boundary. Inverting an assembly U-factor produces an equivalent assembly R, not the manufacturer's separately calculated section value. In this audit, Amarr 2743 publishes section R=28.0 h·ft²·°F/Btu and assembly U=0.17 Btu/(h·ft²·°F); 1 ÷ 0.17 gives equivalent assembly R≈5.88 h·ft²·°F/Btu. The distinction is scope, not conflicting arithmetic. 6 7

Does U-factor include air leakage?

No. ANSI/DASMA 105 treats air infiltration separately from the thermal-transmittance test. A U-factor does not supply an air-leakage rate or quantify heat lost through an open door, and solar heat gain is another reported quantity. Applicable leakage limits require a specific code edition, door category, test pressure and any relevant exceptions; this reference does not assert one universal limit. 27 29

Is a higher R-value always a better comparison?

Only after confirming a comparable scope, unit system and rating conditions. Raynor's TM175 at published R=16.4 and TM200 at R=18.3 both list installed U=0.21 in the US units shown in Table 3. The different R figures did not distinguish those published U values, but the documents do not establish a controlled experiment showing that insulation changes have no effect. 14

Why do insulation products use R-value and doors use U-factor?

R is useful for describing a material layer's resistance, while a door-assembly U-factor can describe thermal transmittance across the rated assembly. But both quantities can describe assemblies when their boundaries match; there is no rule that R means material and U means whole product in every context. Product-label conventions and code provisions must be read separately. The FTC's § 460.22 fenestration exclusion is specific to that section, not a general advertising exemption. 20 21 28

What units do R-value and U-factor use?

R-value uses h·ft²·°F/Btu in US customary units and m²·K/W in SI. U-factor uses Btu/(h·ft²·°F) in US customary units and W/(m²·K) in SI. For the international-table Btu convention, multiply US R by approximately 0.1761102 or US U by approximately 5.678263 to obtain SI. These are NIST's rounded tabulated conversion factors; U=1/R still requires consistent units and matching scope. 19

Which primary sources support this reference?

Manufacturer observations come from the named manufacturers, definitions and methods from the identified standards bodies, and jurisdiction statements from the issuing agencies. Every entry records what was checked on September 14, 2026; a check date is not a publication date or a claim that every referenced standard is the newest edition.

1. Door & Access Systems Manufacturers Association — Technical Data Sheet 163: U-factor and R-value for Residential and Commercial Garage Doors. Revision 7/6/22; pages 1–4, section-R method and assembly-U distinction. Primary URL: https://www.dasma.com/wp-content/uploads/2022/09/TDS163..pdf. Checked September 14, 2026.

2. Door & Access Systems Manufacturers Association — Technical Data Sheet 196: U-factor on Garage Doors and the DASMA Thermal Performance Verification Program. Revision 9/24; program scope, testing, labeling and exclusions. Primary URL: https://www.dasma.com/wp-content/uploads/2025/01/TDS-196.pdf. Checked September 14, 2026.

3. Door & Access Systems Manufacturers Association — Thermal Performance Verification Program — participant list. Eleven named entries counted on the check date; not a corporate-ownership count. Primary URL: https://www.dasma.com/thermal/. Checked September 14, 2026.

4. Haas Door — Commercial Insulated Steel 2000 Series. Series introduction: 2-inch polyurethane and headline tested U-factor 0.094. Primary URL: https://www.haasdoor.com/commercial/2000/index.html. Checked September 14, 2026.

5. Haas Door — Commercial Insulated Steel 600 Series. Series introduction: 1⅜-inch polyurethane and headline tested U-factor 0.106. Primary URL: https://www.haasdoor.com/commercial/600/index.html. Checked September 14, 2026.

6. Amarr — Amarr 2743 Commercial Door. Specifications chart: R 28.0 and U 0.17. Primary URL: https://www.amarr.com/us/en/commercial-doors/explore-commercial-products/steel-sectional-overhead-doors/amarr-2743. Checked September 14, 2026.

7. Amarr — Commercial Polyurethane Doors brochure. PDF page 4: six audited model pairs and calculation footnote; imprint Form #6210825/PDF. Primary URL: https://gw-assets.assaabloy.com/is/content/assaabloy/Brochure_Amarr_Commercial_Polyurethane-B621pdf. Checked September 14, 2026.

8. Overhead Door — Thermacore Sectional Steel Door 592. Thermal figures and rating-scope footnotes. Primary URL: https://www.overheaddoor.com/commercial/commercial-details/thermacore-sectional-steel-door-592. Checked September 14, 2026.

9. Overhead Door — Thermacore Sectional Steel Door 599. Thermal figures and rating-scope footnotes. Primary URL: https://www.overheaddoor.com/commercial/commercial-details/thermacore-sectional-steel-door-599. Checked September 14, 2026.

10. Overhead Door — WindStorm Commercial Sectional Door 525. Thermal figures and rating-scope footnotes. Primary URL: https://www.overheaddoor.com/commercial/commercial-details/windstorm-commercial-sectional-door-525. Checked September 14, 2026.

11. Overhead Door — Insulated WindStorm Commercial Sectional Door 515. Thermal figures and rating-scope footnotes. Primary URL: https://www.overheaddoor.com/commercial/commercial-details/insulated-windstorm-commercial-sectional-door-515. Checked September 14, 2026.

12. Overhead Door — Insulated Sectional Steel Back Doors — Model 470. Thermal figures and rating-scope footnotes. Primary URL: https://www.overheaddoor.com/commercial/commercial-details/insulated-sectional-steel-back-doors. Checked September 14, 2026.

13. Overhead Door — Advanced Performance Sectional Steel Door 850. Excluded: page presents 0.07 and an installed U-factor of 0.14 without a reconciled pairing in this release. Primary URL: https://www.overheaddoor.com/commercial/commercial-details/advanced-performance-sectional-steel-door-850. Checked September 14, 2026.

14. Raynor Garage Doors — CSI Section 08 36 13 — Sectional Overhead Doors. Version V091025; PDF pages 10–12 and 38–40; family-name inconsistency disclosed. Primary URL: https://raynor.com/wp-content/uploads/specs/Sectional-Doors-Specifications-08-36-13.pdf. Checked September 14, 2026.

15. Haas Door — Commercial Insulated Steel 700 Series. Series introduction: 1¾-inch polyurethane and headline tested U-factor 0.093. Primary URL: https://www.haasdoor.com/commercial/700/index.html. Checked September 14, 2026.

16. Clopay — Energy Series with Intellicore — Insulated Polyurethane Overhead Doors. Model-table footnotes distinguish calculated section R under TDS-163 and tested door U under DASMA 105. Primary URL: https://www.clopaydoor.com/insulated-polyurethane-doors. Checked September 14, 2026.

17. Wayne Dalton — DASMA Thermal Performance Program. Program-specific terminology and separately tested glazed configurations. Primary URL: https://www.wayne-dalton.com/about/dasma-thermal-performance-program. Checked September 14, 2026.

18. Haas Door — Thermal Performance. Manufacturer explanation of assembly U-factor and the verification program. Primary URL: https://www.haasdoor.com/thermal-performance. Checked September 14, 2026.

19. National Institute of Standards and Technology — Special Publication 811, Appendix B.9 — conversion factors. Thermal insulance and coefficient of heat transfer; page updated August 18, 2025; factors are rounded. Primary URL: https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b9. Checked September 14, 2026.

20. Electronic Code of Federal Regulations / Federal Trade Commission — 16 CFR § 460.22 — R-value claims for non-insulation products. Section-specific fenestration exclusion; source note 84 FR 20790, May 13, 2019. Primary URL: https://www.ecfr.gov/current/title-16/chapter-I/subchapter-D/part-460/section-460.22. Checked September 14, 2026.

21. Federal Trade Commission — Federal Trade Commission Act. Agency explanation of its authority over unfair or deceptive acts or practices. Primary URL: https://www.ftc.gov/legal-library/browse/statutes/federal-trade-commission-act. Checked September 14, 2026.

22. City of St. Louis Building Division — Building Codes Adopted by the City. 2018 IECC, Ordinance 70799; table Date Adopted field 08-01-18. Primary URL: https://www.stlouis-mo.gov/government/departments/public-safety/building/building-codes.cfm. Checked September 14, 2026.

23. City of St. Louis — Ordinance 70799. 2018 IECC adoption with amendments; ordinance metadata Effective Date field 07/06/2018 differs from the building-code table date. Primary URL: https://www.stlouis-mo.gov/government/city-laws/ordinances/ordinance.cfm?ord=70799. Checked September 14, 2026.

24. US Department of Energy — Building Energy Codes Program — Missouri state profile. Commercial and residential entries both read None Statewide. Primary URL: https://www.energycodes.gov/status/states/missouri. Checked September 14, 2026.

25. Missouri Department of Natural Resources — Energy Codes by Jurisdiction. Official reference routes; jurisdiction confirmation and amendments still necessary. Primary URL: https://dnr.mo.gov/energy/efficiency/codes-jurisdiction. Checked September 14, 2026.

26. International Code Council — 2021 International Energy Conservation Code, Chapter 4 [CE]. Issuer-indexed section text for C402.4.5.2; the public reader blocked automated full-page retrieval. Primary URL: https://codes.iccsafe.org/content/IECC2021V3.0/chapter-4-ce-commercial-energy-efficiency. Checked September 14, 2026.

27. US Environmental Protection Agency — ENERGY STAR — Independently Tested and Certified Energy Performance. U-factor, solar heat gain and air leakage are distinct reported quantities. Primary URL: https://www.energystar.gov/independently-tested-and-certified-energy-performance. Checked September 14, 2026.

28. National Fenestration Rating Council — Consumer Guide to Windows — Glossary. R-value, U-factor, thermal resistance and rating-scope definitions. Primary URL: https://efficientwindows.org/glossary/. Checked September 14, 2026.

29. Door & Access Systems Manufacturers Association — ANSI/DASMA 105-2017 — Test Method for Thermal Transmittance and Air Infiltration of Garage Doors and Rolling Doors. Sections 1, 3, 4, 5 and 8.5; steady-state hot-box measurement, specimen scope and separate leakage test. Primary URL: https://www.dasma.com/wp-content/uploads/2022/03/ANSI-DASMA-105-2017-DASMA.pdf. Checked September 14, 2026.

30. Door & Access Systems Manufacturers Association — TPVP Labelling and Marketing Guidelines. Program label/marketing rules; based on procedural guide Rev. 4, 3/23. Primary URL: https://www.dasma.com/wp-content/uploads/2023/06/TPVP-Labelling-and-Marketing-Guidelines-4-23.pdf. Checked September 14, 2026.

31. International Code Council — 2018 International Energy Conservation Code (IECC) — edition reference. Edition reference only; a complete 2018 door provision was not verified for restatement here. Primary URL: https://codes.iccsafe.org/content/iecc2018. Checked September 14, 2026.

32. International Code Council — 2024 International Energy Conservation Code — Preface. Issuer relocation table: C402.5.5.2 corresponds to 2021 C402.4.5.2; not an assertion of unchanged numeric requirements. Primary URL: https://codes.iccsafe.org/content/IECC2024V1.0/preface. Checked September 14, 2026.

33. International Code Council — 2021 IECC, C303.1.3 — Fenestration product rating. Issuer-indexed garage/rolling-door method exception: NFRC 100 or ANSI/DASMA 105. Primary URL: https://codes.iccsafe.org/s/IECC2021P2/chapter-3-ce-general-requirements/IECC2021P2-CE-Ch03-SecC303.1.3. Checked September 14, 2026.

34. City of St. Louis — City Government Structure. City and County are separate governmental entities. Primary URL: https://www.stlouis-mo.gov/government/about/city-government-structure.cfm. Checked September 14, 2026.

Release and verification history

2026-09-14.2 — final verification release: retained all 19 paired model records; corrected Raynor scope labeling and source precision; recalculated derived values; replaced the unverified certificate-range table with three explicitly separate Haas manufacturer-page observations; preserved the City’s conflicting date fields; and synchronized the downloadable data and visible content.

The refresh targets are quarterly for manufacturer figures and jurisdiction references, with an additional check when their source documents change, and annually for definitions and conversion references. These are maintenance targets, not a claim that future checks have already occurred; the visible verification date changes only after the relevant sources are actually re-read.

Related commercial service: Commercial overhead door repair in St. Louis

St. Louis Dock Door Repair Research is the independent research and reference section of stlouisdockdoorrepair.com.

Last verified: September 14, 2026 · Dataset version 2026-09-14.2