I've been told by HVAC people that Icynene or any similar product that is "open cell" can hold moisture where as a polyurethane type product that is "closed cell" will not. Also the closed cell type insulation has a much higher R-Factor which is important to me when I begin to build in Maine.
I've talked with manufactures about the products , either open/closed cell, being attractive to carpenter ants and termites. Some of them can treat it with borax but all suggest yearly treatments around the perimeter of your house.

Eric

Sealection does not "wick" moisture out of the air that is merely a statement the Icynene dealer is using to scare you into buying his product. The main differences between Icynene and Sealection 500 is that: A)Sealection's smoke rating is about 1/2 of Icynene B)Icynene will hold water longer (i.e. roof leak). Icynene is higher, because as stated below, they spend more money on marketing. If you spray open or closed cell in your roof, YOU DO NOT NEED TO VENT! A ridge vent is used to get hot air out. If you have foam on the roof deck, the air is substantially lower (about 40 degrees) making the ridge vent obsolete. Any area that is not foamed in the roof is a point of entry for moisture. So make sure you seal up the attic good. It is also very important that you bring in air by filtered means (fresh air exchanger) hooked to your return side with a manual damper.

I'm looking into this too for a crawl space basement of about 800 sq ft.
I understand that the close cell version of spray foam has a higher R value.
I wonder if anyone has a couple of manufacturers I could follow-up with.

Not to surface this thread again, but my understanding is that icynene is hydrophobic and therefore does not suck up water.

Not sure where this discussion is now. But as a building science consultant I can offer my 2 cents.

I have experience in numerous homes with Icynene, Sealection 500, Biobased, NCFI and Corbond. Spray foam is a chemical. The difference between different brands is the recipe used in the chemistry. Icynene, Sealection 500 and Biobased are referred to as open cell foams. (although Demilec, Biobased and NCFI manufacture closed cell foams as well). Open cell foams typically weigh between .4 to .6 lbs per ft3 fully cured. As opposed to closed cell foam which weighs 1.6 to 2.2+ lbs ft 3. Open cell foams use water as a blowing agent where as closed cell uses a zero depletion blowing agent, typically Enovate manufactured by Honeywell.

Open cell foams have an R rating of 3.5 to 4 per inch. Closed cell foams have R's ranging from 6 to 7.3 per inch. This means open cell foams usually have to be 2 x the depth to achieve comparable R value of closed cell. Most of the time, this requires open cell to completely fill a 2x4 or 2x6 wall cavity to yield R values comparable to 2 to 3 inches of close cell. The excess foam then must be shaved off to accomdodate drywall. Such activity adds labor cost and waste.

Neither product is particularily great at absorbing sound.

Moisture can move rather easily through open cell foam via diffusion as its permenace is 6 to 10. Whereas closed cell foam has a perm rating of less than 1.

Since open cell foam has a high open cell content (90%+/-), liquid water can enter the foam rather easily. Conversly, closed cell foam has greater than 90% closed cell content and resists liquid water quite nicely. Closed cell is used as a weather or rain barrier.

(If you want to do a neat science project, take a cup of water and add some food coloring. Then get a sample of both kinds of foam and pour water on them. Watch the spread pattern.)

As to which product (closed cell-open cell) is the best choice for your home -- the answer is ------It depends. A huge factor is your climate. Can you be assured of indoor humidity levels between 35% to 50%? Is there duct work in the attic. (if not, there is absolutely no good reason to spray a roof deck with foam.)What type of exterior sheathing will you be using? Do you possess the skills to air seal the envelope?

On the practical side, I have tested identical homes side by side with a blower door and found little to no difference in the air leakage rates between an Icynene insulated home and a home with cellulose in the walls and ceilings that was properly air sealed.

Open cell foams are also much more caustic than closed cell,(Corbond)during the installation process.

One of the biggest reasons, I believe there has been an increase in foams being used in homes is that a builder cannot go to the yellow pages and find a contractor that specializes in air sealing. After all, an insulation contractor knows little about caulks, foams and sealants. Since most builders now a days don't hammer nails and rarely get involved in the actual construction of a home, this is a huge headache for them. Foams allow the builder to delegate the air sealing task to the foam installer.

As far as the differences between Icynene and Sealection 500, it has been my experience that Icynene has little trouble stretching the truth, making unsupported claims about their product while being critical of their competition. I have not found that to be the case with Demilec, Corbond or Biobased. They seem to stick to the features and benefits of their product which tends to give them more credibility in my book.

I found this post very helpful when researching foam products for my new home. I got bids from multiple contractors for multiple foam products. I was looking for the open cell foam, so I did not get bids on the close cell product. I was told that the close cell product was not really meant for residentual homes in Texas.

After comparing them all and doing my research, I found then all to be pretty simular products. Icynene and Sealection 500 seem to be the leading products in the area.

Like the last post said, all of the contractors pretty much stuck to giving the features of thier product except for the Icynene guy. He mostly just talked about what was wrong with the other products. Maybe its in their training, but it really put me off.

I ended up going with the Sealection 500 product using ThermalShield Foam here in Austin. It was less than Icynene and I liked/trusted the contractor more. Its been great. I am very happy with my choice.

The great thing about open cell is that you KNOW if you have roof leak. With closed cell it could stay up there forever till it builds and comes out somewhere else.

I was very happy to have open cell (and not happy to have a metal roof leak) when we had a roof leak a few weeks ago in the monsoons here.

housedoc or anyone else with info,

what is your opinion of biobased (soybean) vs. sealection 500? we are building in south louisiana. also, do you know anything about apex? thoughts....

thanks

Has anyone spoken with any of the installers of these products? Seen any of the jobs the company has done?
Anyone tested these homes to determine the true air sealing of these products?

These companies spend days educating the salesmen on how to sell these products, and the installers get about half a day to learn to install the product.
Install is the key with all insulations.
Foam is not the miracle product it is sold to be, if it is not installed properly.

Before you spend 3x the cost of conventional insulation, check the install on homes in your area.
If wall cavities are not overfiled & shaved back for full insulation depth, it is a questionable install. In my hot humid climate where walls dry to the interior this gap between foam insulation & sheetrock is where mold growth starts. Insulation needs to be in FULL contact with sheetrock.
In attics if the roof rafters are visible & there are low spots, voids & missed areas, this is not a good install.
If spiderwebs are present this is a sign of air infiltration and is an unsealed area.

I really enjoyed your post housedoc. Glad to see you here!
BTW mega, in what part of south La are you building?
And what soy based foam are you looking at?
Sorry to hear of your roof leak dallasbill. Hope you got if repaired between monsoons!

I am looking into using Sealection and found this discussion helpful. In the last house we did in 2006, we used Icynene but the cost was higher on this bid. On that project, we did figure out that there is a good reason to spray to the roof deck on our cathedral ceilings, even though we had put vents in to allow for a vented roof and soffet area. We ended up ignoring those. We used recessed can lighting in the ceiling and even with the best of those they allow a lot of heat movement through them. Spraying the foam to the roof deck shut off this avenue of heat transfer.

Any advice for open vs. closed cell in the DC environment? I'm baffled by the discussion, and can't figure out in our transitional zone whether to use isonene open cell vs. the BASF closed cell product.

closed cell is always better if you can afford it.