How are Clopay Intellicore garage door R-values so high?

Question

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?

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EDIT 1:

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.

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EDIT 2:

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.

Answer 1

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.

Answer 2

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”

Answer 3

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?