Johns Manville Helps Ease LTTR Transition

Johns Manville (JM), a supplier of commercial roofing products, advises customers of revised LTTR (Long-Term Thermal Resistance) values for its polyisocyanurate insulation product line.

To help educate the industry and ease the transition to the new test method and change in LTTR values effective Jan. 1, 2014, JM has prepared a packet of information detailing the updated specifications.

As part of the current ASTM C1289 standard for polyiso, products must meet R-value requirements, presented as LTTR, pertaining to how foam ages over time. The LTTR test is a technically supported, more-descriptive measure of the foam’s in-service thermal performance.

“In the short term during this transition, there may be some confusion in the industry with regard to the planning, bidding and constructing of projects,” says JM’s M.J. Cusick, portfolio manager for Cover Boards and Insulation. “To get in front of this, we began notifying design professionals of the potential confusion in the third quarter of 2013, suggesting they specify polyiso insulation by its thickness rather than R-value during this transition.”

For jobs that will be permitted after Jan. 1, 2014, JM advises that projects should be designed and bid using the new LTTR standard. The test method change typically results in an extra 0.1 inch of thickness per board or 4 to 6 percent more material/thickness, depending upon desired R-value.

To further support customers, JM will modify its packaging to reflect LTTR values by both test methods, beginning in the fourth quarter of 2013. As an example, a 1-inch board label will now include information from LTTR-S770-03: 6.0 (the old test method) and LTTR-S770-09: 5.7 (the new test method).

To learn more about the LTTR values transition and access an informational booklet, please visit the JM roofing website and click on the LTTR banner, or contact a JM representative.

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