Soy Based Foam Insulation: What It Is, and Why You Should Use It

by heather

There’s no doubt that green building is taking off in a big way (and hooray to that!). It’s getting easier, and cheaper, to build homes that are not only safe for the environment, but also safe for us.

When it comes to your home’s insulation, you’ve got some great choices to pick from. There’s regular spray foam insulation, cotton-based insulation (like those made from recycled jeans), and soy based insulation.

All have their perks and drawbacks, and I’m focusing today’s article on soy based insulation.

Important Addition: After this article originally posted on 2/23, I was contacted by James Morshead, a spray foam installer with SDI Insulation, Inc. out in California who pointed out some factual errors within the text. He generously took the time to clarify these and point me in the right direction. I have rectified those errors, and attempted to give a more balanced look at soy based foam insulation. My sincere thanks to him for separating the facts from the hype about this product!

Now, let’s jump into the fascinating world of insulation.

What Is Soy Based Insulation?

Sorry if I’m stating the obvious here, but soy based insulation is insulation that uses soy as an ingredient. It’s a spray-on foam, which means trained technicians come in with suits and tanks and spray it into the walls of your home. The insulation then expands up to 100 times its size, filling in every nook and cranny and making an incredibly tight seal

As you can probably imagine, there are many benefits to using it in your home. Let’s go.


First of all, using soy based insulation versus regular fiberglass means that you don’t have to worry about off-gassing. It’s sprayed on using water. So, it’s safe for our bodies. It also doesn’t off-gas as it ages like fiberglass might.

Contrary to some rumors out there soy based insulation does resist moisture, so you don’t have to worry about mold and fungus growth like you would with wet fiberglass insulation.

And, rodents won’t eat it, so you don’t have to worry about providing an “all you can eat” buffet for your neighborhood’s rat population.

What’s it made of?

Well, all spray foam insulation is made up of an “A Side”, which is the catalyst, and a “B Side”, which is the resin. Much like epoxy glue, the two sides are mixed together as they come out of the tank, which causes a chemical reaction and creates the “spray foam”.

Well, every brand is different, and they don’t all break down what’s in their insulation. From my research online it seems as if almost all companies use the same “A Side”. So already half of the soy based foam insulation is petroleum or chemical based.

I did uncover the material and safety data sheets (msds) put out by Urethane Soy Systems.

Urethane Soy Systems give a complete breakdown of both the “A-Side” and “B-Side” of their spray foam insulation. It’s a downloadable .pdf that you can find here.

Here’s what each side of Urethane Soy Systems soy based insulation is made from:

Side A:

Polymeric Diphenylmethane Diiosocyanate 100%

Side B:

Component CAS# %Composition
Polyol 68152-81-8 0-50%
Halogenated Phosphate Ester 13674-84-5 0-50%
Polyether Polyol Trade Secret 0-25%
Water 7732-18-5 0-20%
Amine Catalyst 3030-47-5 0-5%
Silicone Surfactant Trade Secret 0-5%


Soy-based insulation a green alternative to traditional fiberglass insulation.

First of all, most companies use American grown soybeans, so this helps support the more than 600,000 farmers that grow them. And considering I come from a family who’s still growing soybeans in north Louisiana, I’m pretty enthused about this part!

Important point here: many companies make it sound as if soy based foam insulation is largely made up of soybeans. This is one claim I fell for myself, and only after my “insider help” was I aware that this is part of the hype of this product.

All spray foam insulations are petroleum based. Including soy based foam insulation. The difference is that soy based foam replaces a portion of that petroleum with soy.

How much soy is actually in the finished product? Well, James at SDI Insulation said that the maximum for any spray foam is 15% soy. I dug through my resources I used, and even some I didn’t, to verify this, and could find nothing, anywhere, that actually said how much soy these companies use in their insulation.

I did find an enlightening article from The graph below shows the breakdown in ingredients in regular spray foam insulation, and below is a quote from the article itself on the sometimes “misleading” claims of high soy content.

courtesy of

courtesy of

From the article: Jennifer Wilson of Biobased® Insulation, a soy-based SPF product, claims that its exclusive Agrol® polyol is 96% pure making it one of the purest bio-polyols on the market. Jeff Soto, Apex Foam, states that their Earth Seal Foam System offers a unique sucrose-based polyol that contributes to a B side that consists of 30% to 40% of a renewable resource, the highest renewable resource content in SPF.

Biobased® Insulation and Apex Foam are both very reputable companies with fantastic customer and third party “bio-testing” credentials and endorsements. We are proud of their efforts and do not discount any of their claims. However, one of the key objectives of this article is to educate our readers and therefore we will offer some more clarifying insight to the layman interested in using, or choosing green insulation products such as spray polyurethane foam.

Ninety six percent (96%) pure bio content – What does this claim mean? What are the “impurities”? We would suspect the answer is that the soy polyols are 96% soybean oil, modified with 4% of other (petro-chemicals) to make the oil a reactive polyol. The misconception that comes from this statement, since the word “polyol” is meaningless to most consumers, is that Biobased’s® foam is 96% Soybean based. Look at the chart above and notice that the polyol side is only 50%, or half, of the entire foam system.

There is a popular misconception that the bio-containing foams (whether soy or sugar) are more substantially green, when, in fact the final polymers are still mostly petroleum based. However, the USDA has offered the criteria that if a material is at least 9% renewable content, the claim of being “bio-based” is valid.

So while all spray foam systems have some degree of “green bio-content” in their composition, it comes down to the level of bio-based and renewable materials in their polyol mixture that distinguishes which SPF product is truly greener than the other.


Soy based insulation is just as good at insulating your home as traditional insulation. With soy based insulation you don’t have to worry about sacrificing quality in order to be more eco-friendly. You can get a high R-value in less space than bat insulation, which means in new construction this can help decrease the amount of building materials used.

Most soy based insulation companies claim their insulation will help reduce monthly energy bills by 50% or more. Soy based insulation is more expensive than regular fiberglass, but the investment will pay for itself over time.

How much more expensive? Well, I couldn’t find an exact number from the companies I researched (they all say to call for a quote…figures!).

I did find one couple who installed soy based installation in their Arts and Crafts style home, and they said the cost was three times that of regular insulation. Their blog, Humphrey House, details their insulation project and has some great pictures. They also say why they love their soybean insulation, so you should check it out.

Open Cell or Closed Cell Soy Based Insulation?

Soy based foam insulation comes in two forms: open cell and closed cell.

Open cell insulation is like broken bubbles. The walls are soft, and air gets trapped in the insulation, working like a down sleeping bag. Open cell insulation has a value of R-3.6 per inch, but is usually less expensive. It’s also very lightweight, which means you can often use less building materials when you use it.

Closed cell insulation is much harder. It’s densely packed foam, and its bubbles are not broken. This means it’s hard enough to walk on, and will even help improve your structure’s strength in high winds. Closed cell insulation is the more expensive of the two because it requires more materials to support its weight. Closed cell insulation gives an R-6.8 per inch in standard walls.

How do you know which to pick?

Well, if you live in a very cold climate, or you’re concerned with structural strength, you’ll probably want to go with closed cell.


Soy Based Insulation Resources

Check out some of these soy based insulation companies if you’re interested in using this in your home.

Last Word…

I must admit I was a bit floored by all the hype surrounding soy based foam insulation once my eyes were opened to it. It’s a great product, but I now realize that many companies try to make it sound much greener than it actually is.

All spray foam insulation, including soy based, is green in the sense that they can help you dramatically reduce your energy bills. And, that’s a good thing.

If you’re knowledgeable about spray foam insulation (either regular or soy-based) and you notice any errors in this post, please let me know! It’s not my intention at all to publish false or misleading information. I’ve done my best to pull information from reliable sources, but there’s a lot of mis-information out there, as I learned the hard way!

Again, my sincere thanks goes out to James Morshead with SDI Insulation, who really took time to make sure that I better understood this complicated subject.

Republishing Policy:

Like this post? Great! You’re welcome to reprint anything that’s posted on, as long as you link back to the original article. Please see my Republishing Policy for more information.

{ 3 trackbacks }

Where To Buy Insulation and Plasterboard Insulation |
February 26, 2009 at 4:34 pm
A Carnival of Everything Home | My DIY Home Tips
February 27, 2009 at 6:45 am
Soy based insulation
August 22, 2009 at 8:33 am

{ 32 comments… read them below or add one }

Green Bear Innovations February 23, 2009 at 6:10 pm

This was an awesome post!

You are right on. We have used polyurethane spray foam in the past but have recently invested in a new rig setup for the soy-based foam and will only be offering soy-based.

One thing that is incorrect is that you stated near the bottom that they have not developed a way to fill existing wall cavities. I want to update that and let you know that soy-based spray foam can be injected into existing wall cavities with special spray gun attachments through a very small entry hole. A small patch job over the hole and some paint makes it unnoticable. What people will notice is a huge difference in their energy bills each year.

Another thing I should mention is that our company is offering the same r-value of spray foam at $.10 per square foot over fiberglass.

heather February 23, 2009 at 7:12 pm

Green Bear,

Thanks so much for clarifying! I’ll remedy the post to reflect your new information. All the sites I checked stated it was only for new construction, but that’s awesome you guys have an attachment that can do existing homes.

Thanks so much for writing in!

Jason February 25, 2009 at 9:48 am

This is a great analysis. One thing I’d like to add… During a recent visit to Home Depot, I recently stumbled across Soy Seal – which is BioBased spray foam in a can. I was amazed that it was sitting on the shelf next to Great Stuff giving consumers a new choice by providing soy foam in a can. I did a bit of a write-up at my blog.

heather February 25, 2009 at 10:03 am


Thanks for writing in, and especially for sending that link to your analysis! It’s nice to know we can get this in smaller cans for tiny fixes.

I loved your blog; it really was the only one I found online that showed people actually installing soy based foam in a renovation project. Thanks so much for giving people an idea of what that’s like!

Mark March 2, 2009 at 11:08 am

Thanks for writing in, and especially for sending that link to your analysis! It’s nice to know we can get this in smaller cans for tiny fixes.

Dave April 28, 2009 at 10:26 am

This means it’s hard enough to walk on, and will even help improve your structure’s strength in high winds. Closed cell insulation is the more expensive of the two because it requires more materials to support its weight.

Gail May 14, 2009 at 5:18 pm

Wow, this is really informative. My husband and I are building a new home and are seriously considering using soy based foam insulation. In my reseach, I found a great website to help you find spray foam contractors in your area If anyone else is looking to find local spray foam contractors check it out!

Dinda May 26, 2009 at 11:02 pm

It’s a spray-on foam, which means trained technicians come in with suits and tanks and spray it into the walls of your home. The insulation then expands up to 100 times its size, filling in every nook and cranny and making an incredibly tight seal

ashoka July 6, 2009 at 10:11 am

this info is really good, in order to make our home with stronger barricade between our walls and outer world, we have to always see the benefits of California spray foam as the resister between the walls rather than using traditional and risky material like a harmful fiberglass.

Ashoka July 6, 2009 at 11:11 am

Talking about foam insulation, the first thing that comes to my mind is the prevention of moisture and pathogens. Now this blog was really very informative and helped me a lot in understanding what it really is.

Satish July 29, 2009 at 1:23 pm

It’s a spray-on foam, which means trained technicians come in with suits and tanks and spray it into the walls of your home…I like it..thank you..

Vicror August 7, 2009 at 11:02 pm

Does anyone have any information about using Bio-based insolation as a radiant barrier?

john r desmaretz November 4, 2009 at 3:03 pm

I am trying to find the raw materials to produce polyethylene foam insulation. Does any one know where I can get products which are component A and Component B from the raw manufacturer? I don’t want to buy a finished product from a middle man I want to go directly to the manufacturers of the polyethylene glycol s and the polymeric isocyanate. Does anyone have a better formula. any information would be helpful

Randy Miyan January 9, 2010 at 4:45 pm

Excellent resource! I will be re-visiting this site for sure. Thank you for the work and update. I am a green builder who specializes in remodel and renovation. Currently researching soy based spray foam in a consideration to \expand\ my business. DIRRRP!

The research has been eye opening. I think soy based foam has its place. But I would warn against homeowners being hypnotized by Greenwash. Even when blown with water, soy based still has chemicals and petroleum in it.

As a matter if fact, the A side of all spray foam (50%) in made out of isocyanate. This fact is downplayed a bit. Long term isocyanate exposures are linked to a myriad of health problems. Short term exposures are problematic as well. The MSDS sheets claim that once the foam is fully cured (approx 2 days), the foam no longer offgasses. But during application, and up to the curing threshold, isocyanate offgasses. The installers are the ones that take the brunt. But I have read testimonies from homeowners who have been adversely affected by offgassing from all spray foam, including soy based. If you are chemically sensitive, I would warn against Soy based spray foam as well.

I am also looking into Air Krete, cementitious foam, which has its trade-offs, but is essentially made from Sea water minerals, insulates well, and is fully non-toxic. Claim is that you can take the waste from the job and enrich your soil with it.

I saw a guy on Renovation Nation dip his hand in the stuff and eat it like cake icing. LOL! I’m sure he was displaying a major lack of intelligence. But it was a ringing endorsement!

If anyone has any Air Krete horror stories, let me know.


Scott January 25, 2010 at 10:37 am

We’re looking into getting a new house. The builder uses the Soy based foam so I’ve been looking into it.

As far as gassing….our builder makes the walls off site and brings them to the site to assemble. Other than spraying the gaps where the walls meet and respraying areas where electricians and such run their lines through the walls there isn’t much done after the walls are up. So I’m hoping gassing won’t be a problem.

We live in Edmonton Alberta….so we get temperature extreams here. (+30 to -30 C…give or take 10 C)
Apparently closed cell foam can crack when a house shifts, or expands or contracts due to temperature changes like these. Cracks = poor insulation
Open cell foam won’t crack and so is supposedly better overall….I’ve also read that it breathes a little which closed cell does not. This is supposed to help with the air quality in the house.
Closed cell therefore relies more heavily on the HVAC system to keep the air quality good….which is fine as long as it’s working properly.

I haven’t heard yet if our builder uses the open or closed cell foam. I’d be partial to the open due to the cracking problem of the closed cell….either way hopefully all will be well.

Randy Miyan January 25, 2010 at 2:25 pm


It sounds like your contractor creates his own form of SIPS (Structurally Insulated Panels), where a layer of cured foam insulation is sandwiched in between two layers of Plywood. I think SIPS are a superior approach to building, and the fact that the foam is cured before it makes it to your structure is a big plus. I still have a concern with SIPS. Some of the plywoods still have nasties in the glue that is used. This is an offgassing hazard as well.

Andrea Johanssen February 5, 2010 at 12:49 am

thank you for pointing me in the right direction this November i went with Green Bear Innovations to insulate my new addition with a closed cell soy-based foam. I was very pleased with how i was treated and with the results. the new addition is now the warmest room in the house…thanks Heather for being a nuetral resource.

Andrea Johanssen, Amhesrt, MA

Tom Spoler February 10, 2010 at 6:35 pm

Can anyone talk about the differences between Air Krete and the soy based products discussed here?

Russell G. Namie February 22, 2010 at 3:16 pm

I am checking into removing the attic’s fiberglass and having open-cell foam sprayed. We are in a ” heating ” climate ( PA ) and I am still undecided about doing the attic floor or the roof rafters. No HVAC equipment is in the attic. Does anyone know if Demilac is better than Lapolla? Is Lapolla better than Bayer, or Icynene? Any advice would be appreciated. Thanks, RgN

Jordi May 31, 2010 at 8:16 am

I had a soy-based insulation blown into my attic, front wall and some basement joints about two years ago. The attic is totally sealed and my contractor said it was necessary to make a thermal envelope. The house is old- 1796. I live in PA, no central AC, oil-fueled radiator heat. Now it seems there is a lot of humidity in the attic. I am not sure if it is closed or open cell.

Anyone know if high levels of humidity is a problem? Does the attic really have to be sealed off?

Chris Bolton June 4, 2010 at 1:28 am

I very much enjoyed your article and will refer back to it as a launching off point.

One issue though in which there is some debate is the production of the soybean themselves as being truly “green”. Many American farmers are now growing GMO soy products, and “RoundUp Ready” soybeans. The use of these technologies does come at a cost, both to the farmer as well as the environmental impact of a monoculture crop production reducing biodiversity. Although roundup ready soy reduces pesticide use, ironically it does increase herbicide use.
Although a better alternative to using a petrochemical product, and using spray foam insulation quite a bit, as a timberframer, I’m not 100% sold on the idea of raw materials coming from an outfit like Monsanto as being truly a Green Product. Greener, yes, but Green … I’m not entirely sure.
But thank you for taking the time to write the article.


Gary Schumacher June 18, 2010 at 1:00 pm

Great bunch of info.One thing that is seldom mentioned is the actual thickness that one can use.It is suggested to have R 20 in walls and R 40 in ceilings–even R 50.
From what I have read,it should not be used over 5-6 inches thick.Therefore you cant get the high R value for the ceiling.
R 20 in the walls would allow you to use 2 x 4 as opposed to 2 x 6.
Part of the efficientcy of spray foam is the sealing from air leaks.Is it possible to use 2 inches of spray foam and then use batts to finish it off?
If that could be done,it would help with the cost.
I did have an industrial building built in the 70`s.I had 20 in the walls and 40 in the ceiling.It was 5400 sq ft.The heat bill was 1/4 of the amount of a similar building with less insulation.I also used high efficient outside air furnace.The other company used unit heaters.
2 things that stand out was,my building increased in value 300% in 20 years.Yes there was inflation,but the insulation also was a great part of that.
The other thing was,the cost to heat.The last year I had the building the cost for the year to heat was 1400.00 and the other company was 4800.00 .These are CDN dollars.The first year mine was 678.00 and his was 1800.00.
I spent about 3500.00 extra dollars to insulate.I paid back well.

Dan July 22, 2010 at 3:09 pm

I’ve read about rodent problems with soy-based insulation on automotive wiring. I have one friend that experienced more than $5000.00 damage to their Toyota. I’m wondering if there is any experience with rodents eating soy-based home insulation. Having had a terrible rodent problem when I first bought my house, I wouldn’t even consider installing something that might bring that problem back!

Dennis August 20, 2010 at 9:35 am

Your article only covers one side of using spray foam insulation. To be fair to your readers, there are other considerations that need to be considered before spray foam is used in the attic.

First, if the spray foam is used on the uderside of the roof sheathing there is the concern of trapped moisture in the roofing system’s structural components. The spray foam insulations do not allow detection of roof leaks that occur often in roofing systems. These undetected leaks can lead to structural failure of roofing members. Second, most asphalt roofing shingle manufacturers will not warranty their product (or reduce their warranty) if spray foam insulation is used without proper ventilation of the roofing deck. Special construction of the roof deck (additional cost) is needed to provide ventilation to the roof deck. Lastly, a dedicated mechanical ventilation system and ducting are recommended to exchange the “stale” inside air with “fresh” outside air since spray foam construction leads to a tighter building envelope. Only a dedicated mechanical ventilation system can provide adequate protection from the negative effects of indoor humidity, pollutants, microorganisms, combustion appliances and odors.

Your article was informative about the soy-based spray foam product. But, it is also important that potential users understand all factors so informed decisions can be made.

gail September 7, 2010 at 10:48 am

First thank you for the informative article.
I have a question about the off gassing, if the soy based product contains petroleum based products how is it that it doesn’t off gas?


John October 7, 2010 at 5:27 am

It is true that “soy”-based foam is mostly petroleum-based. But so is nearly everything that houses are made from today, from the basement concrete, which requires HUGE amounts of fossil energy for its production, to the asphalt shingles. Ditto for glass in windows and fiberglass insulation, which require much energy for manufacture.
But here is my main point. You should report on the blowing agents that are used in foam insulation, because these are usually HFCs or pentane, which are bad greenhouse gases. The HFCs are especially bad (see Great Stuff in the handy spray can). If either is listed in the MDA, it should be boycotted. You can find spray foams that use water as the blowing agent. Only such foams can be called green. You sacrifice a little convenience and a lower initial R value, though the long-term R value is the same (once the greenhouse gas has escaped into your home and the atmosphere.) By the way, gasses other than CO2 are becoming a huge part of anthropogenic greenhouse warming, so this is a real issue. If you need help with research or documentation of any of the above, contact me.

Drew March 31, 2011 at 7:00 am

“I’m wondering if there is any experience with rodents eating soy-based home insulation.” I haven’t seen that problem. Heatlok Soy and some of the other soy-based brands aren’t food for critters or insects. The most you have to really worry about is having termites burrow into it. It’s not a food source, but it happens in areas with bad termite infestations.

Mike May 6, 2011 at 7:49 pm

Can anyone tell me where I can buy the aerosol cans of Soy Seal?
Thanks kindly

Jen May 14, 2012 at 10:58 pm

You mention that rodents won’t eat soy based insulation, but I can actually hear something munching away in at least two spots in my home. I tried putting a natural deturrant near where I can hear them and so far tonight, he seems to me happily munching away. It is driving me crazy!! Up until now, we have been so pleased with our spray in insulation but am at a loss as to what to do to keep them out.

Taylor Parker August 27, 2012 at 10:31 am

My husband and I recently finished building our home, and we used the soy based spray foam insulation . We had a friend recommend it to us, because it was safer for our bodies. We decided that it was worth doing some research on, and it turned out that there were so many health and safety benefits to it, that we decided to go head on with it. We have yet to regret our decision. I feel so great, knowing that it’s safe to breathe in my house! We don’t ever have to worry about breathing in glass shards from the regular insulation. I have hated insulation ever since I was little. My parents bought a house when I was in elementary school, with an unfinished bedroom and bathroom. It turned out to be the most gorgeous bed and bath in the entire house when it was actually finished, but I remember when my Dad was putting in the insulation, I decided to “play” with it. I found a pair of scissors, and cut up the scrap pieces of insulation. It was horrible! Glass shards got in my hands, legs and clothes. The itching was awful! I have stayed away from that stuff ever since. It was especially nice when we were building, to know that I wouldn’t ever have to worry about that being in our home.

John T. January 10, 2016 at 1:53 am

Thanks for this informative post. But there’s one thing that I really want to know about that was not mentioned: VOCs. Outgassing of volatile organic compounds is one downside of conventional polyurethane spray foam, and I want to know whether that also occurs with the soy spray foam, since it’s also loaded with petro-chemicals. I’m a big skeptic of all forms of foam insulation, as well as fiberglass (formaldehyde in its binders), because of this. I seriously don’t want any level of VOC contaminants, no matter how “safe” they are said to be.

peg August 31, 2016 at 4:01 pm

I have chemical sensitivity particularly with solvents. Are you aware of problems like that with soya based product? Mostly breathing issues with me and it can worsen with prolonged contact> I need my crawl space done.


Leave a Comment