R-20 Kalwall Panel is Misleading

In Volume 11, No. 12, EBN included Kalwall® R-20 (RSI-3.1) with Nanogel in its list of ten best new green building products. Certainly the first commercial use of aerogel is a remarkable milestone. It is very worthy of an EBN award.

However, what is not worthy of the award is the R-20 claim. The R-20 claim is almost certainly only for the panel. And since every panel needs a frame, the claim is a bit misleading. Indeed a whole organization (the National Fenestration Rating Council, or NFRC) was formed to stop misleading thermal performance claims—claims that, for example, don’t include the effect of the frame.

For the record, a typical thermally broken aluminum frame would degrade the insulating value of a 50 ft

² (5 m

²) R-20 panel by 50–60%. Even one of our insulated fiberglass frames would degrade the same panel by 10–20%.

The first commercial use of aerogel is very cool indeed. But the questionability of the R-20 claim unnecessarily distracts from the achievement.

Stephen Thwaites P.Eng.

Thermotech Windows Ltd.

Ottawa, Ontario

Editor’s response:

Thank you for the important clarification, Stephen. We checked with Bruce Keller of Kalwall, and indeed the R-20 value represents the panel alone, although it does include the aluminum and fiberglass-reinforced polyester structure within the panel. According to Keller, this value is based on a combination of testing and simulation, as the NFRC-certified labs don’t have testing boxes that are insulated well enough to accurately test an R-20 panel. As you’ve noted, the R-value for an entire installation would be lower and would depend on the framing system used. Keller is hopeful that they can come up with a framing system, based on thermally broken composites with foam covering, that provides an overall R-value close to 20.