Letters

I am writing in support of NRCA's position on polyisocyanurate insulation's thermal-resistance values as explained in "Comparing polyiso R-values," April issue, page 61.

For submittals, my current specifications require a sample of the insulation board being furnished to a project. This is not strictly done. The most recent submittal I received offered the material's label but was dated—in small print—1999.

I also require manufacturers to state the name or names of their products' principal blowing agents. I recently have received a manufacturer's letter indicating generic words of no meaningful value and have required three resubmittals with no improvement. It is clear the information never will arrive. I have advised the contractor to save representative samples with packaging labels and furnish them for reference if necessary. I recommend all purchasers of new products save all wrappers from every lot or truck with a matching material sample.

My conversations with people in the industry indicate the following:

• There are several blowing agents, and they have chemical names and numbers for identification.
  
  
• Pentanes have several molecular chain forms, including ring formation and straight molecular chains, formed of carbon and hydrogen groups.
  
  
• Pentanes burn. To mitigate this, higher quantities of fire retardants are needed.
  
  
• Shrinkage may be a problem.
  
  
• Conventional blowing agents are similar to those used during the past 10 years.

Based on my latest attempts to discover what currently is being marketed, I would add the following comments:

• We are in a new era of materials forced on us by the outcome of the Kyoto protocol with which we have little, if any, experience.
  
  
• Combinations and/or quantities of blowing agents and foam components need some form of identification if for no other reason than to improve quality over time. I suggest NRCA request such a system.
  
  
• I suggest NRCA conduct an in-depth study of what currently is being marketed and publish the results.
  
  
• Owners need to be aware of all their roof system components.
  
  
• It is my understanding that many—if not all—polyisocyanurate insulation manufacturers use a thickness tolerance of 0.1 inch (2.5 mm) for a specified thickness (for example, a 3-inch [76-mm] board could be furnished from 2.9 inches [73.7 mm] to 3.1 inches [78.7 mm]). I suggest this tolerence be reduced.

My congratulations to NRCA for holding the position it has taken. I agree architects should specify thickness, not R-values.

Toby Nadel
Toby Nadel, Architect
Dewitt, N.Y.