In June, the Polyisocyanurate Insulation Manufacturers Association (PIMA) announced its Quality Mark certified R-value program is being updated to incorporate a new test method for determining long-term thermal resistance (LTTR).   As you may know, R-value is a measure of thermal resistance used in the building and construction industry.  Under uniform conditions, it is the ratio of the temperature difference across an insulator and the heat flux.  The polyisocyanurate product is NOT changing any current chemical makeup.  What is changing, is the test method (LTTR) process of calculating R-values.  As a result, new LTTR values are going to decrease for roof insulations from their current values.  Please note that this change will not affect wall insulations. Even with these changes, polyisocyanurate is and will continue to be the greatest energy-efficient performance of any building insulation product on the market. To give you a couple of examples of these changes, the current R-Value of 2″ polyisocyanurate is currently 12.10.  Effective January 1, 2014, that same material will have an R-Value of 11.4.

The 2012 International Building Code (IBC) requires that R-25 be met during all roof replacement (tear-off) projects.  Fortunately, local municipalities still follow IBC 2009 or older guidelines.  We do not foresee local municipalities adopting IBC 2012 for at least another 2-3 years.  The combination of IBC 2012 and the lower R-values given to polyisocyanurate insulation effective January 1, 2014 will require at least another 1″ – 1.5″ of insulation be installed just to meet local code on future roof replacement project.  More material obviously results in an increase in roof replacement costs.  We recommend adjusting future roof replacement budgets to reflect these additional costs.

We hope you find this information beneficial.  Feel free to call or email if you have any questions about this issue.

Cale Prokopf
Project Consultant
(314) 687-5687