As of May 1, 2008, Icynene has ICC ESR-1826 describing the installation of Icynene with an approved ignition barrier. This allows it to be used in attics and crawl spaces which are accessed for servicing utilities. Previously, only Demilec's Sealection 500 (as far as I could ever find) had such an ESR.

I'm now considering using Icynene as the under roof insulation in my house instead of Sealection 500. Does anyone have any experience, or reasoned opinion, as to whether either insulation is better than the other? If so, how is it better? I need to decide in a few days which to go with. As of right now the Icynene cost will be less than the Sealection.

I am not familar with the Sealection product, having never even heard of it, much less used it.
However, we have used Icynene on several projects over the last dozen years. I am very happy with the results, and would recommend it to anyone needing such a product.

Just an opinion but I feel either is equal in performance. Both will accomplish the same goal. I believe it is the natural base versus the oil base that makes the difference and how it is applied. I have Icynene in my home, 5.5-6" under the roof. Buries the top cord of the truss and gives an R-25 performance at that depth at the roof deck. Keeps the non vented attic space at about 95 deg. this time of year in FL. I am satisfied. GR

I have used soy based ,Icynene and Demelac All three are basically the same product except for thecatalyst that is used to create the expansion - all three use dupont products as the base. the difference is closed cell versus open cell. Open cell will allow water to "drop" if there is a roof leak were as closed won't. The efficiency rating of closed cell is more dense R-7 per inch. In my opinion, the fear is that if there was an attic fire the foam could create toxic fumes. Why not put a smoke detector in the attic

From a performance POV half-pound foam is half-pound foam. The finished result chemically nearly-identical whether the feedstock is from fresher plant oils or gazillion-year-old plant-oils (aka "petroleum").

The "greenliness" arguments about using soybean vs. fossil oils gets complicated, without a simple & clear answer. (Is it really "greener" or more sustainable to cut down rainforest for soybean production?) In the end it's the actual performance of the house over time that overwhelms the rest of the arguments, and that performance will differ more by the relative skill of the installers than the source feedstock used for the material. (Get references- look at the installations if you can. All else being equal, buy on price.)