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Open and Closed Cell Soy-Based Insulation

Lower Utility Bills all Year Long by Giving Your Home a Tighter Envelope

© 2010 by all rights reserved; content may not be copied, rewritten, or republished without author’s written permission

Freshly picked soy beans. Photo courtesy Pennylayn

Just-picked soybeans before being processed into insulation

This article was last revised on 10/23/20.

When most people first hear of soy-based insulation, they react like this, “Hey, wait a minute, soy is food! If I put that stuff in my home, critters will eat my walls.” But it’s really not like that. Soy, along with some other biopolymers, are classified as inert materials. This means that they don’t allow mold propagation and won’t attract insects or critters.

What is Open-Cell and Closed-Cell Foam Insulation?

These are the 2 basic classifications of spray insulation which is becoming more popular in exterior residential walls. Here’s the difference:

  • Closed-cell spray foam is recommended on exterior applications. It’s characterized by a low-vapor penetration. The reason for this is its dense cell structure. When sprayed on to a certain thickness, it can provide a vapor retarder although not a vapor barrier.
  • Open-cell spray foam, on the other hand, is only applied in home interiors. This is because it doesn’t provide any structural support although it does give more ROI (return on investment) with respect to insulation R-value than the closed-cell variety.

Soy Insulation is Energy-Efficient and Effective

There are 2 basic reasons for this. First, the manner in which it’s applied and secondly, the way it cures. Since it’s sprayed-on foam, it’s delivered as a liquid, water-blown and free of chemicals. This means that the coverage is very efficient. It starts to harden right away, and as it does it expands up to roughly 100 times the original volume. A little goes a long way.

During this expansion process, it just stands to reason that it forces itself into all available space. This provides a tighter envelope on the home than fiberglass batts or loose-fill rockwool. And once it is set up, soy will be there over the long haul because it won’t degrade or settle as time passes.

It sticks to all surfaces with ease, whether it’s drywall, structural wood framing, or even commercial steel studs.

Downside: It’s More Expensive than Fiberglass

Why? For one thing, because people that are really into the save-the-earth camp will pay more for it. But that's just given as a marketing reason. The primary reason is that fiberglass products are mass-produced which brings down costs.

Is it worth the extra financial investment? Yes, and this is why. It really saves money over the long term. Assume your new home’s construction is being financed by the bank. Further assume that the additional cost of soy insulation will up your monthly mortgage payment by $20.

However, since soy is so energy efficient, the thermal mass gain and loss to your home will be lowered resulting in lowered air conditioning and heating usage. It's reasonable to assume that your cost from electricity and/or natural gas bills will be reduced much more than the additional $20. Other cost-reducing strategies, like radiant barrier foil in the attic will reap further reductions.

It’s also effective because of its R-Value. When it’s sprayed in a wall cavity of 3.5 inches (8.89 centimeters) deep, it yields an R-Value of 13 to 18, depending on the formulation the insulation contractor uses.

Many homeowner's insurance policy premiums may be changed because soy insulation sports a fire rating of Class 1. This means that building materials with a Class 1 fire rating will become charred but won’t sustain a flame.

What Kind of Buildings are Good Candidates for Soy?

Both residential and commercial buildings can benefit from open and closed-cell soy-based insulation. One trend in the residential construction market is to use wider exterior walls, i.e. framing them with 2” X 6”s rather than 2” X 4”s. This allows a bigger cavity for insulation, therefore, an enhanced thermal barrier. Commercial buildings can really benefit as much since they tend to lose efficiency from constantly opening doors and some method of conservation must be found.

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About the Author:

Photo of Kelly R. SmithKelly R. Smith was a commercial carpenter for 20 years before returning to night school at the University of Houston where he earned a Bachelor’s Degree in Computer Science. After working at NASA for a few years, he went on to develop software for the transportation and financial and energy trading industries. He has been writing, in one capacity or another, since he could hold a pencil. As a freelance writer now, he specializes in producing articles and blog content for a variety of clients. His personal blog is at I Can Fix Up My Home Blog where he muses on many different topics.

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© 2010 all rights reserved; content may not be copied, rewritten, or republished without author’s written permission.