Clopay's garage doors with their proprietary "Intellicore" polyurethane foam insulation claim R-values as high as 20.4 in a 2" thick door, or R-10.2 per inch.

State-of-the-art spray polyurethane insulation has an initial R-value up to 6.7 per inch, or about 65% of what Clopay claims (in a best-case scenario).

Clopay's technology is proprietary, but how is such a high R-value even technically possible for a polyurethane foam?


I realize that there are other elements besides foam in the door, but their cross section illustration (top of page) depicts polyurethane foam injected into a steel shell. The steel certainly does not increase the R-value, so the R-value apparently comes solely from the foam.


Some context for posterity: I'm considering building my own insulated garage door, and through some research I found that Clopay appears to lead the market in garage door R-values. Trying to see if (and how) I can get anywhere close to their R-values.

  • Because the door is not pure foam - there are other elements...
    – Solar Mike
    Mar 13, 2019 at 13:08
  • Interesting question but it is not a diy home improvement question. Perhaps the density of the foam is greater since it is produced under controlled factory conditions.
    – Kris
    Mar 13, 2019 at 13:10
  • the rvalue seems to be quoted for the whole door, not just the foam.
    – dandavis
    Mar 13, 2019 at 17:34
  • The source links in that section of the wikipedia article you linked are dead, so I'm not so sure it's "state-of-the-art"
    – Nate S.
    Mar 13, 2019 at 21:01
  • I'm going to go with the Wikipedia page is just out of date. Here's an example from a quick google search that claims 7.4 per inch: demilec.com/Products/Closed-Cell/…
    – Nate S.
    Mar 13, 2019 at 21:03

3 Answers 3


Note the fine print in the chart: "Calculated door R-Value is in accordance with DSAMA TDS-163". Here is DSAMA TDS-163.

From the PDF:

Refer to Figure 1. A typical insulated door has an exterior surface, interior surface, and an insulating core material. Also present is the insulating effect of air on a vertical surface, termed “air film”. Each of these elements has a unique R-value that added together create the door section R-Value. Rsection = Rair films + Routside surface + Rinsulation +Rinside surface

So the 20.4 value includes not only the 2" of foam, but the R values from the outside surface, inside surface, and some air films that are assumed not to be moving. I expect you're correct that the foam alone would provide a value more in line with the typical 6-7 R/inch you're used to.

  • Thanks, Nate! Somehow I missed that data sheet. I'm still skeptical, though, as the first equation on page 3 shows that the air films total R-0.85 and the steel surfaces total R-0, meaning they're still attributing R-19.55 to the foam interior. That's either ~R-9.8 per inch, or the R-20.4 door is more than 2" thick. This is probably the best we can figure it out, though. It's also good to confirm that their R-values are not measured installed values (I had assumed they weren't), but theoretical calculations that certainly won't match real-world conditions. Thanks again.
    – Bungle
    Mar 13, 2019 at 23:01
  • 1
    It appears that this company makes wood-faced doors as well, so I'm guessing the 0-R-value steel ones are probably not what they used for this calculation. Probably you'd have to ask them what part of the value is attributable to their foam, and what part is the (unspecified) cover material.
    – Nate S.
    Mar 13, 2019 at 23:05
  • Good point - although I'd be surprised if the thickness of wood they use counts for that much. Wood's R-value is only roughly R-1 per inch.
    – Bungle
    Mar 13, 2019 at 23:09

I contacted Clopay. They sent the attached general information regarding thermal testing of garage doors, however, they did not specifically address how they could achieve the 18.4 R value of my garage doors. I asked again for specific test data, either measured, or calculated, for their Thermacore insulation. Supposedly their engineers will provide the data. A follow-up response will be provided if they actually provide test data. See attached.

Follow-Up.... Clopay responded the next day with the following data.

“Thermal conductivity is how easily heat is transmitted thru something. Better insulation, lower conductivity.

The end result of this, the R-value, is the thermal resistance, which is a measure of how much it inhibits heat flow can be thought of as a measure of insulation.

Note that thermal conductivity can be represented as “k” or “c”. “k” is unitized; that is, it represents a per-inch valuation. You can unitize it by multiplying by the specimen thickness, but you’ll just take that back out in the TDS-163 equation.

The GR2LU is a 2” intellicore door; the 3720 is also a 2” intellicore door. For the purposes of TDS-163 analysis, they are equivalent.

The air film does help prevent heat transfer; the metal skins are near-perfect thermal conductors and that’s why those are valued at 0 in the R equation. If the door has vinyl or some other skin, the skin values could be different.

From the report, c = 0.055. The equivalent k value would be 0.055*2 = 0.11

Therefore the Rinsulation = 2/0.11 = 18.1. Note that the report also gives R = 18.1. (Rsi is just R in metric units.)

0.85 + 0 + 18.1 + 0 = 18.9”

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  • Hello, and welcome to Home Improvement. This is interesting, but doesn't answer the original question. Please take our tour so you'll know how best to contribute here. Nov 14, 2019 at 12:47

When manufactured, the initial R-value of polyurethane foam is about R-9 per inch. This value will get lower with time as the gas inside the insulation is replaced with air until it stabilizes at about R-7 per inch. Maybe Clopay manufactures their door so that the gas stays inside and the insulation remains at R-9 per inch over time. Maybe they achieve a bit more with proprietary gas mix?


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