WHAT IS LONG-TERM THERMAL RESISTANCE (LTTR)?

LTTR is the most advanced, scientifically supported method (based on ASTM C 1303-95) of predicting the Long-Term Thermal Resistance of polyisocyanurate insulation products, such as the HCFC-Free, Green Zone Approved Atlas Products featuring ACUltra Technology. Long-Term Thermal Resistance (LTTR) provides specifiers, design professionals, and roofing contractors many advantages, including:

• A Long-Term Thermal Design Value (15 year time-weighted average)
• A better understanding of thermal performance of foam. Click Here for a detailed look at the Long Term Thermal Resistance of Pentane Blown Polyisocyanurate.
• An advanced test method, based upon consensus standards used by both US and Canada
• A technically supported, prescriptive method to measure the Long-Term Thermal Resistance (LTTR) of polyiso foam insulation
• Long-Term Thermal Resistance (LTTR) values are required in the mandatory annex of ASTM C 1289-02
• See the following Technical Bulletins for more information

The roofing industry now has a definitive standard for predicting Long-Term Thermal Resistance (LTTR) values. The new Long-Term Thermal Resistance (LTTR) values became effective July 1, 2002 in Canada and January 1, 2003 in the United States.

Atlas ACFoam® LTTR Calculator

How To Use The Calculator: Select the desired Long-Term Thermal Resistance (LTTR) value from the pull down menu below. The calculator will automatically determine the required thickness and the minimum number of layers needed to achieve the Long-Term Thermal Resistance (LTTR) value selected for each product listed. Additionally, the calculator will reveal the actual Long-Term Thermal Resistance (LTTR) value achieved:

Select Your Long-Term Thermal Design R-Value R-Values 3.0 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5 24.0 24.5 25.0 25.5 26.0 26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0

Roof Insulation: Thickness Inches   Minimum Layers   Actual LTTR ACFoam®-II     ACFoam®-III     ACFoam®-IV     ACFoam® Composite/FB     ACFoam® Composite/PB     ACFoam® Composite/GB     ACFoam® Supreme     ACFoam® Recover Board                 Nail Base Insulation:           ACFoam® Nail Base Insulation     ACFoam® CrossVent™ (1.0" Air Space)     ACFoam® CrossVent™ (1.5" Air Space)     ACFoam® CrossVent™ (2.0" Air Space)     NOTE: Higher LTTR values can be achieved by adding a second layer of ACFoam®-II or ACFoam®-III to any product listed above.