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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

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 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.

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 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 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 a marketing reason. Realistically, 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.

Since soy is so energy efficient, the thermal 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 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 homeowners insurance policy premiums may be reduced 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 use soy. 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, thermal barrier. Commercial buildings can really benefit since they tend to lose efficiency from constantly opening doors and some method of conservation must be found.


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