Aerogel: Emerging Eco-Friendly Insulation

Green Architect

Okay, let's backup, emerging may be a little misleading, because aerogels were invented decades ago! Primarily used in NASA applications, Aerogels, which are the world's lightest solid materials, has been very difficult for people to grasp both literally and figuratively until recently. Aerogels are incredibly lightweight (only three times heavier than air!), strong and highly insulating and are now being used as real-life insulators.

What Are Aerogels?
The easiest way to explain aerogels is by comparing them to Jell-O. When jello is left out it dries out, shrinks and where liquids once were are thousands of tiny pores. Aerogels are created essentially this same way, except through a process called 'supercritical drying' aerogels are made to not shrink when the liquid is extracted, and they typically maintain 90-99% of their original volume. While it's mostly comprised of air at this point, it can also hold 500-4,000 times its weight. It's because of this composition that aerogels have very low thermal conductivity, can withstand very high heat and are water resistant, unlike most other insulations that must be chemically treated to have these properties.

Types of Aerogels
Aerogel refers not to a particular substance, but the geometry of the substance. Unless noted otherwise, Aerogels are most commonly made of silica, or otherwise carbon, but they can really be made of several types of raw materials. Silica aerogels are generally transparent and may have a blue cast of color.

Aerogels as Insulators
Aerogels' incredibly low density and high surface area makes it both a great lightweight structural material as well as a super insulator. Aerogels provide the highest R-value per inch than any other insulation on the market &mdash they have an rating of over 10 per inch compared to R-6 for closed cell insulation and R-3 for fiberglass. However, aerogel in its raw state is very brittle and inflexible, so it must be combined with other materials to be used in real life applications.

Because of their translucent nature, silica aerogels work well when sandwiched between layers of glass. This type of application is where aerogels insulating potential is really exciting, because windows and glass are some of the weakest points in a building. Filling the windows with aerogel would increase their insulation value while maintaining their transparent quality. This type of application was seen in the most recent Solar Decathalon competition.

The other common type of aerogel insulation is using them in blanket form. In this application aerogels are woven with a fiber to make them flexible. These batts can be wrapped around pipes, placed on curved walls and installed in cavities. On frame built buildings, thin strips of aerogel can be applied to studs to prevent thermal bridging. Because the aerogels in this format are woven with fibers they are opaque, usually white or gray in appearance.

Aerogel Products
Because of the high costs, aerogel has been primarily used in high-end industrial applications, such as insulating oil and gas pipelines, insulating NASA spacecrafts and used as a spacedust collector.
However, with technology advances and some drop in prices, several companies are ofference a variety of aerogel products that can be used in even residential applications:
Cabot: Cabot's Nanogel is being used to insulate window units, wrap oil and gas pipes, is woven in outdoor apparel, and as granules and blankets for building applications.
Aspen Aerogels: Aspen Aerogels Spaceloft product is available as batts to replace traditional fiberglass and cellulose insulation. It offers the highest R-value, at 10.3, than any other product on the market.
ThermaBlok: Thermablok makes a self-adhesive strip of aerogel insulation that can be applied directly to studs to prevent 'thermal bridging,' which is heat conduction through the studs.

For more information on Aerogels, we highly recommend checking out these websites:
Aerogel.org
Ceramic Tech Today

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(Images: 1. Aspen Aerogels, 2 & 3. Aerogel.org, 4. ThermaBlok)