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Insulation is the great “split-personality” building material from an environmental perspective. On one hand, insulation’s role in conserving building energy by minimizing thermal transfer is critically important. On the other hand, many typical insulating materials are derived from fossil fuels, require significant power to produce, and incorporate ingredients that are harmful to human health. In such instances, the result is a conflicted material that reduces operational carbon yet increases other environmental hazards. As life cycle accounting methods become more holistic, incorporating all these factors, the benefits of such a material appear to cancel out.

For example, extruded polystyrene, a common insulation material, exhibits a global warming potential of 1,430, which translates to the equivalent of 1,430 tons of CO2 for one ton of emitted gas. A typical spray foam insulation might have a GWP of 700 to 1,000, depending on the blowing agent used. Meanwhile, the material composition of insulation is increasingly under scrutiny. For example, benzene and styrene are fundamental ingredients of expanded polystyrene. Both chemicals, which are released in small amounts during manufacture, are highly toxic. Even an “eco-friendly” foam like polymeric flame retardant has raised concerns with its harmful ingredients of butadiene, styrene, and bromine.

As a result, scientists and product manufacturers are focusing on developing fossil fuel alternatives that deliver thermal performance without high emissions or negative health effects. Similar to established green options like cellulose, wool, and recycled denim insulation, the following emerging technologies—which include novel bio-based products and materials recaptured from waste streams—suggest a more promising future for this challenged building material.

Aerogels represent an area of particular interest for insulation. Some of the lightest known materials, aerogels exhibit impressive thermal insulation capabilities, with thermal conductivities from 0.012 to 0.020 W m−1 K−1. By comparison, conventional insulation thermal conductivities are 0.030 to 0.040 W m−1 K−1. Therefore, a thin layer of aerogel can perform as well as a thick layer of a common insulation product. However, aerogel is still largely fossil fuel-based, and it remains too delicate on its own for broad commercial use.

Researchers at the Wallenberg Wood Science Center in Sweden are developing a more robust, biobased aerogel in combination with wood. The team has developed a process to remove wood’s lignin structure and fill the remaining voids with nanopores from the material’s surrounding cell walls. The result is a superlight substance that insulates as well or better than fossil fuel-derived aerogels and does not involve the use of harmful blowing agents like typical foam insulation. Employing this material one day in construction, it’s easy to imagine mono-material wood structures in which the various components—such as framing and insulation—perform differently based on internal chemistry rather than material type.

The material composition of insulation is increasingly under scrutiny.

Scientists at Tennessee’s Oak Ridge National Laboratory have proposed another alternative to fossil fuel aerogels in the form of hollow silica particles, which may be combined with cellulose fibers to create a novel thermal composite. Exhibiting a thermal conductivity of 0.02 to 0.03 W m−1 K−1, HSPs outperform conventional insulation, and the new composite is more robust, inexpensive, and scalable than aerogels. Furthermore, given the substance’s inherent hydrophobicity, the material remains stable in the presence of moisture. Although hollow silica structures require a measurable amount of energy to produce, methods are being developed to limit the embodied energy necessary for their manufacture.

Another innovation relies on a much more familiar household product. Scientists in the Faculty of Forest Sciences and Forest Ecology at the University of Göttingen in Germany have developed a method to produce insulation boards from granulated popcorn. The process delivers a product with good thermal insulation, fire resistance, and water-repellent properties. Additionally, the team claims that the manufacture of popcorn insulation, which they call Abocorn, will easily scaleto an industrial level cost-effectively. “Especially in the field of insulation in construction, this ensures that natural insulation materials are no longer just niche products,” said Dr. Alireza Kharazipour, head of the research group, in a university press release.

Another low-tech solution is a novel composite made of wool, sulfur, and discarded cooking oil. Researchers at Australia’s Flinders and Deakin Universities and England’s University of Liverpool developed the new material to utilize waste products that offer mutually supporting properties, which may be commercialized as safe products for human health. The new substance is created by hot-pressing wool off-cuts in combination with a binder made from canola oil and sulfur. The resulting composite exhibits good thermal insulation and fire resistance and has the potential to biodegrade safely at the end of its useful life.

A curious waste-related development is the use of industrial byproducts to create insulating materials. A team at the Hönggerberg campus of ETH Zurich in Switzerland has devised a method to produce lightweight porous foams from a variety of industrial waste. The researchers, who have since launched the company FenX, first experimented with fly ash—a byproduct of coal-fired power plants—blended and aerated into a meringue-like state. The team is considering at least 10 different byproducts from other industrial processes, including building construction. Energy-wise, the new insulation has a minimal carbon footprint, as no heat and very little power are required for its manufacture. The product is also financially attractive as the feedstocks can be obtained for little or no money. However, on the human health side, more research is required to determine the potentially harmful effects of using various types of industrial waste. In the case of fly ash, the EPA determined that the material is safe for use in concrete and wallboard; however, other applications must also be evaluated for potential harm.

More testing is a given for these materials to determine their full ecological, health, and economic impacts, but—as a departure from petroleum dependence—they represent a fascinating future for insulation. “Making buildings more energy-efficient is a key part of tackling the climate crisis," said Arlene Blum, executive director of the Berkeley, Calif.–based Green Science Policy Institute, in a cautionary review of PolyFR foam. "But we need to be careful not to create new health and environmental problems along the way. A 'green building' with potentially hazardous insulation isn't a green building at all.”

The views and conclusions from this author are not necessarily those of ARCHITECT magazine or of The American Institute of Architects.

Read more: The latest from columnist Blaine Brownell, FAIA, includes a look at illegal timber harvesting, the rise of holistic interior greening, user experience design in architecture, and what we can learn from India about confronting a warming climate.