By:  Kyle Staley, Sales Representative – Architectural Products


Are we being lied to or just looking the other way to get the job?  When a roof is designed and the roofing manufacture or product is selected do they take into account R-Value in the design? The answer is YES!  Problem – do they look at the long term thermal resistance (LTTR) R-Value and present the losses in R-Value over time to the building owner? The answer is NO!

It is common practice to ask for a NDL (No Dollar Limit) warranty for the roofing system from the manufacturer, which includes all products on the roof. However, in this warranty, the Polyiso insulation is not required to keep its as manufactured R-value, but would only be replaced if the membrane was to have a leak. In truth, the insulation is leaking R-Value.

The Polyiso Manufactures have a third party called PIMA Quality Mark (Certified LTTR-value) which they all belong to. PIMA uses techniques in ASTM C1303 that predicts an R-value that has been shown to be equivalent to the average performance of a permeably faced foam insulation product over 15 years. With this test, it is my opinion that they truly do not know what the R-value will be. It sounds as if they are coming up with an average over 15 years or just guessing. (POLYISO INSULATION LEAKING R-VALUE) So, my next question is, why would you need a third party Certification on your product if it can perform at a 100 percent of its specifications? I am sure most of us in the roofing industry are asking this same question.

The NRCA (National Roofing Contractors Association) has asked this same question. They have stepped up and suggested that in designing a roofing system, the R-Value is part of the design and that the LTTR-value not be included in the design. They choose to use the true R-value rather than the LTTR-value. NRCA has stated that ISO be rated at R-5.6 per inch in warm climates, and R-5 per inch in cold climates. At this time NRCA does not endorse or recommend the use of the LTTR method for determining the thermal resistance of polyisocyanurate foam board roof insulation.

In truth, it should be lower since the warranty is only good for 80 percent at 15 yrs? Please visit manufacturers websites for their ISO insulation warranties. Firestone, Johns Manville, Atlas, Hunter Panels, Rmax

Is there a better product which can keep 100 percent of its R-value? For more than 15 yrs? There is! It is Expanded Polystyrene (EPS) roof insulation. EPS doesn’t inflate their R-value numbers and provides 100 percent R-Value warranty for 20 yrs. My clear choice in design would be EPS. Cost Value per inch EPS is the best value.

If I was designing a roof system I would go with a 20 yr Materials Warranty and a 20 yr EPS  r-value warranty. Most contractors will take liability up to 10 yrs, but 2 to 5 yrs is standard. If the contractor is stable and does quality work, any roof manufacture membrane should last 20yrs.  Learn more about the EPS roof insulation 20 year warranty.

I hope in designing or looking at options for roof insulation that all the facts and options are presented to the owners. If you read this post and have any questions please contact me, Kyle Staley, at (801) 809-3301. I would love to provide you with an EPS presentation or provide a contact in your area. Thanks for reading.

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