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 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 at 13:10
  • the rvalue seems to be quoted for the whole door, not just the foam. – dandavis Mar 13 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 Strickland Mar 13 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  • I'm going to go with the Wikipedia page is just out of date.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 Strickland Mar 13 at 21:03

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 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 Strickland Mar 13 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 at 23:09

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