Frequently Asked Questions

Q: What is an R value?

R value is defined as a measure of the ability to retard heat flow rather than to transmit heat (BTU loss over a given area in a given time between a given temperature differential).  The higher the value, the better the insulating qualities of the product (the less the material will allow heat to flow through it).  The R value is directly related to the k factor and is sometimes expressed as: Insulation thickness (inches) / k value (BTU-in/hr-sq.ft – F).   Thus, where as the k value is the same for all thicknesses of a material, the R value is directly related to the thickness: greater thickness = greater R value.  Please reference Technical Bulletin TS 13 under Resources and Tools for more information.

Q: What are the national building code requirements for combustibility of insulation?

Building codes are dependent on adoption by local, state and national code jurisdictions.  National codes are established from various organizations such as ASHRAE (American Society of Heating, Refrigeration, Air Conditioning Engineers) and the ICC (International Code Council).  The NFPA (National Fire Prevention Association) specifically deals with combustibility requirements of materials used in Buildings.  The most common test method is a large scale test, also known as the tunnel test.  NFPA and UL have similar tests with their own specific designations.  There are 2 components to the test, a flame spread and smoke development component.  The requirement most often specified for building materials, including insulation regarding combustibility of materials, is:

• All materials (considered a permanent part of the structure) must meet a requirement of 25 flame spread and 250 smoke development value.
• Any material used in a plenum, air handling unit or duct must meet a requirement of 25 flame spread and 50 smoke development value.  Often, even though it is not specifically required by code, the insulation used in the entire building will be required to have a 25/50 rating to simplify the material requirements.

Q: How many square feet does a can of adhesive cover?

Most coatings and adhesives are listed as being able to cover 200 sq feet per gallon.  If both surfaces need to be covered, the actual coverage rate would be 100 sq feet per gallon.

Q: What temperature is the product rated for?

K-Flex USA standard elastomeric insulation products have a high temperature service rating of 220°F (K-Flex HT is 300°F).  Cross-linked elastomeric products will take high temperature spikes above their listed service temperature rating.  High temperatures cause elastomeric products to degrade gradually – they will not melt or burst into flames.  The degradation process results in a hardening / stiffening of the product, but little loss of thermal conductivity.  The product will insulate itself from the “hot side” and create a temperature gradient, so the ambient temperature side may remain soft and flexible even when the ID of the product has hardened.  The degradation process is a time / temperature function.  The longer the time or the higher the temperature, the farther the hardening of the product will progress.

Q: Is the product flexible?

All K-Flex USA elastomeric products are flexible.  This is one of the key properties of the product to allow it to be easily fabricated and installed in the field.  Certain applications, such as air conditioning line sets or refrigeration systems for supermarkets, require a product that is flexible to install.

Q: What is the difference between the K-Flex Duct® Liner Gray and Insul-Sheet®?

K-Flex Duct® Liner Gray was specifically designed for sheet metal duct lining applications.  K-Flex Duct® Liner Gray differs from Insul-Sheet® in several ways:

• Offered in a variety of widths from 46” to 60” so it can be used for the full range of duct sizes.  
• Offered in longer roll lengths (50’ to 100’ rolls) to reduce change-overs and improve efficiencies.
• Softer so it conforms to corners better when the sheet metal is bent.
• Better in acoustic reduction as it has a higher noise reduction coefficient (NRC) value closer to that of fiberglass.  It outperforms fiberglass in sound absorption coefficient values at low Hz frequencies (<500 Hz).
• A distinctive color (gray) for identification purposes.

Similarities between the two include: excellent thermal insulator, resistant to moisture penetration and mold / mildew growth, and GreenGuard® listed for low VOCs and mold resistance.  


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