From Old Duvets to Corn Stalks, a Look at Bio-Based Insulations

CC BY 2.0. Cellulose insulation in a prefabbed passivhaus wall/ Lloyd Alter

Blaine Brownell of Architect finds finds some new and interesting all-natural insulating ideas.

This TreeHugger has often written about how we should be building out of sunshine, using natural materials with low upfront carbon emissions in their manufacture. Now Blaine Brownell of Architect Magazine explores bio-based materials for insulation. He notes, as we have, that insulation "is drawing scrutiny and disagreement within sustainable design circles."

Generally speaking, the higher the R-value, the more energy saved (depending on the climate). However, increased focus on material performance—referring here to the intrinsic environmental properties of materials—points to two concerns in the most common insulation types: embodied energy and toxicity.
He notes the toxicity of the ingredients going into foams, and doesn't even mention the dangers from flame retardants that leach out or the products of combustion when they burn. But he does conclude that "although strong support will undoubtedly continue for all of these materials, we should seek the highest environmental performance in both embodied and operating phases (or more holistically, all phases) of the material lif
Rock Wool

Rock wool on my house, where I needed a noncombustible insulation/ Lloyd Alter/CC BY 2.0

There are insulations that are not made from fossil fuels, but still take a lot of energy to make, like rock wool and fiberglass. That's one reason Brownell pitches the benefits of cellulose, including some interesting statistics:

“Based on our calculations of the most recent statistics from the American Forest and Paper Association, approximately 1,126,330 pounds of paper become waste about every 10 minutes in the United States,” said Dan Lea, executive director of the Cellulose Insulation Manufacturers Association, in a press release. “Recycled as cellulose insulation, that’s enough paper to insulate 220 energy-efficient new homes every 10 minutes.”

It certainly makes a lot more sense to recycle newspaper than it does to convert fossil fuels into foam. Brownell also likes recycled denim insulation. I am not so crazy about it; it is often installed poorly and they show little children playing on it when it is full of borax and the MSDS forms say you should be wearing masks. I have heard of people with chemical sensitivities reacting to chemicals from dryer sheets that left residues in the denim.

Straw Bale Cafe wall detail

© Paul Young/ Hewitt Studios

But he also describes new and interesting research into other insulations:

According to the researchers, nearly 62,000 metric tons of duvets and pillows are discarded annually, particularly from hospitals. In the United Kingdom, the production of wheat flour results in about 7 million metric tons of straw, half of which is thrown away. “It is estimated this 'leftover' 3.8 million tons of straw could be used to build over 500,000 new homes, solving the U.K. housing shortage within five years,” the scientists claim in a University of Bath press release. Corn stalks may also be utilized more effectively, with a quantity of 420,000 metric tons of corn pith—the internal portion of the stalk—produced annually.

I am not so sure about old hospital pillows and duvets, and think that they might be the first waste-to-energy fuels that I approve of. Straw, cellulose and corn stalks, however, certainly meet our criteria for building out of sunshine. As Brownell concludes, "When considering material health and embodied carbon in combination with insulating value, repurposed biobased materials can’t be beat." I concur.