@PupnTaco: I am amused that you took more time to answer this with a googleit than to actually heed your own advice. Had you tried it yourself you would have found that there is not a readily available, obviously correct answer in the front page results for google. I know. I did try googling it. I got 4 different answers based on four different, not-entirely-apples-to-apples results, leaving me more confused than before.
I also tried: wikipedia, several engineering and chemistry related sites and my own library of engineering and building materials texts. How do you like them apples?
None of the sources I tried had a definitive answer. Trust me, if I post a question on fluther its because I want a fast answer…not to wait a day to get any answer. Obviously I tried googling it first.
If snarky, Ill-informed responses are going to become the norm here, I fear for the future of fluther as anything better than yahoo answers.
by the way… I eventually did track down what I think is the correct answer. I had to call a wholesale plastic supplier. He said he didn’t know the r-value, but gave me the thermal conductivity, k-value. A quick division into one for the inverse… 4.4/inch.
justeffinggoogleyourself.com