Ever since I saw my first bullt-up roof blister caused by off-gassing of Polyisocyanurate Insulation (1988), I have been analyzing and studying R-values in insulation. My major concern and conclusion was that R-value was not being stated correctly. This made predictive energy modeling and utility cost estimating not very reliable, not to mention over paying for overstated R-values. I believed that full disclosure through a method like LTTR (Long-Term Thermal Performance) would help with give a more accurate accounting. (LTTR - Read Article)
This October 2019, the US Federal Trade Commission will finally close a loophole in regard to Extruded Polystyrene (XPS) and their avoidance to “fully reflect the effect of aging” on their product. “The final rule, though not mandating a prescriptive LTTR method, requires that manufacturers publish R-values” that are more accurate.
The EPS Industry Alliance in a recently published paper, (Polystyrene Foam Insulation in Long-Term Building Applications, Effective R-Values) provided a method to estimate effective R-value for polystyrene insulation. This has started to address my two biggest issues with Effective R-values - 1) “Long-Term” and 2) testing temperature of 75ºF.
Long-term testing statements in insulation should not be 5-15 years (we don’t build building to last 5 years) but rather 50 years. So what is the average R-value over 50 years in a building? Fifty year testing is more reflective of homes and buildings insulation life cycles. Even though the Federal Trade Commission is mandating LTTR for XPS, they are still leaving a loophole by allowing “open” LTTR test methods and not requiring a 50 year prescriptive method. It will be interesting to see what the XPS industry comes up with for R-value. Will it be 4.3r/inch like the testing showed from the EPS Industry Alliance?
The issue of “Testing Temperature” has bothered me for years. Why test at 75ºF? Who needs R-value at 75º? In the Northern States, where heating is a concern, it is more realistic to look at R-value testing temperature at 40º, if not 25º in some states. The opposite is true in the South during summer where 90º may be a more reflective testing temperatures. Knowing the R-value performances of insulation, at various temperatures, is critical for designers to make important R-value decisions. They would have the ability, based on their climate, to select the most appropriate insulation. However, the current testing temperature approach of 75º is really a “one shoe fits all” approach and is not very helpful and leads to poor energy conservation decisions.
It has taken over 30 years to see a more accurate accounting of what the R-values of rigid insulation really is and I applaud the FTC for one more step forward. Just 2 more to go - 50 year LTTR and Variable Temperature Testing Disclosure. Accomplish that and we can finally focus on a really important issue — moisture in insulation and its effects.
John Calkins - JC Edison and Associates