I found another comparison with cellular glass. Like in a previous post, I assume that the report is correct but I extend the benchmarking to get a better view.

I found the following description for this kind of foams on Wikipedia:

These are flexible, closed-cell, rubber foams based on NBR or EPDM rubber. Flexible elastomeric foams exhibit such a high resistance to the passage of water vapour that they do not generally require additional water-vapour barriers. Such high vapour resistance, combined with the high surface emissivity of rubber, allows flexible elastomeric foams to prevent surface condensation formation with comparatively small thicknesses. 

As a result, flexible elastomeric foams are widely used on refrigeration and air-conditioning pipework. Flexible elastomeric foams are also used on heating and hot-water systems.

More information was found in the following prints (Doc1 and Doc2) from the this website. I found there the following important facts:

The three main components used in the manufacturing of elastomeric closed cell foam insulation include the following:

• Synthetic rubber blend, typically nitrile butadiene rubber (NBR) and/or ethylene-propylene-diene monomer (EPDM)
• Polyvinyl chloride (PVC)
• A chemical foaming agent

The product will not absorb moisture, or trap dirt or debris that supports the growth of mold. It is a fiber-free, formaldehyde-free, low-VOC material, so it is a good candidate for those facilities that are especially concerned with IAQ.

Closed elastomeric foam is in fact closed cell rubber foam. Besides the remark of formaldehyde-free, low-VOC and fiber-free, the áuthor forgot to mention that working with rubber itself can be a risk. Occupational exposures in the rubber-manufacturing industry are carcinogenic to humans (Group 1).

I remember that closed cell elastomeric foam has a smaller thermal conductivity than cellular glass (can be compensated by thickness) and it is flexible. But cellular glass has a much larger temperature range ( from cryogenic to 430°C ), is absolutely vapour tight and does not absorb any water. GLAPOR cellular glass is foamed with materials, all belonging to the IARC classification group 3: Not classifiable as to its carcinogenicity to humans. Closed cell elastomeric foams are only necessary when a flexible substrate needs thermal insulation.