Important Changes of Polyisocyanurate R-Values

 To Take Effect January 1, 2014

The Polyisocyanurate Insulation Manufacturers Association (PIMA) recently reported changes in determining  the R-Value for polyiso. An update to ASTM C 1289-11 has revised the certification of Long Term Thermal Resistance (LTTR) values that will go into effect January 1, 2014.

These changes shouldn’t impact the 2010 Florida Energy Conservation Code since the code is based on prescribed performance requirements (resistance values) of the insulation. With that said, these changes may impact the cost of and the amount of material used to achieve the required thermal resistance.
In the case of existing roofs the 2010 Florida Existing Building Code is clear in section 601.2 Conformance. An existing building or portion thereof shall not be altered such that the building becomes less safe or energy efficient than its existing condition. Be aware that because the R-value per inch will be reduced by these changes, using the same thickness of existing insulation may not be code compliant.

In either new construction or reroofing, remember that, with the reduction of R-value per inch of polyiso, special attention should be given to perimeter attachment height, vent and chase attachment height, interior roof drains, wall scupper and emergency overflow height. Also there may be the occasional access door onto the roof that might need to be considered as well electrical, plumbing and mechanical equipment. It may be prudent to contact the insulation manufacturer and/or design professional of any estimated or contracted work that may be unfavorably changed to discuss possible options.

I’ve included the web link to the PIMA QualityMark/LTTR page that contains web links to PIMA manufacturer members where additional information can be found for their brand-named products.


Trenton H. Cotney
Florida Bar Certified Construction Lawyer
Trent Cotney, P.A.
1211 N Franklin St
Tampa, FL 33602


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