Best green insulation materials: Savings, sustainability or safety?

Iris Price | Improvement Center Columnist | June 15, 2015

Who wants to read about insulation materital? Once your drywall is up, insulation's out of sight, out of mind, right? Unless…

You are building a new house, remodeling your present home, repairing serious home damage, or you just need more of it. Then, you might want to think about it. It's usually that pink stuffing in the walls and attic that vaguely resembles cotton candy.

That's traditional fiberglass insulation, and instead of spun sugar, it's made from spun fibers of glass that can get under your skin. Not in a good way, either; it makes you itchy. According to the National Association of Certified Home Inspectors (NACHI), despite fiberglass insulation's sustainability, fire-resistance, and widespread use for decades, it can pose more serious health hazards than just skin irritation -- potential lung diseases and cancer, for example.

You can, however, find a green alternative insulation to fiberglass that goes beyond increasing your home's energy-efficiency, which, by its very purpose, every type of insulation does to one degree or another.

Why look at green insulation options?

Besides improving energy-efficiency, green insulation fulfills any one or more of these additional criteria:

  • Sustainable. Sourced from recycled materials, industrial waste or easy-to-replenish natural resources
  • Safe. Resistant to fire, molds, mildew, insects; free from toxins, carcinogens, allergens and other health hazards
  • Recyclable/compostable. Cradle to cradle life cycle instead of cradle to grave
  • Resource conservation. Reduces the product's carbon footprint and/or conserves water during its life cycle

Choosing green insulation options depends on which criteria you value the most. One of the following green insulation materials may offer the right combination of green characteristics you care about.

Natural materials for best green insulation

If you favor natural content for your insulation, these are the prime contenders:


  • Energy-efficiency. R-value ranges from 3.6 - 3.8 per inch
  • Sustainability. Originally made from natural materials with low thermal conductivity such as straw, hemp or sawdust. Now made from shredded recycled newspaper; generally around 85 percent recycled content
  • Safety. Treated with sodium borate, boric acid, or ammonium sulfate (all considered non-toxic to humans) for fire, fungus and pest-resistance. Outgassing from the newsprint ink may irritate sensitive individuals.

Cellulose is blown in as loose fill or can be packed. For new construction it may be applied slightly moistened, either behind netting or directly into the building's wall cavities. The moisture releases starches in the cellulose, which when it dries, allows the insulation to adhere to the insides of the walls. Cellulose is widely considered the best green alternative insulation to fiberglass. Straw is attracting renewed interest, not only as bales but as pre-fab panels, and hemp, though not used much in the U.S., is popular abroad for its R-value of 3.5, which is similar to cotton fiber insulation.


  • Energy-efficiency. R-value ranges from 3.4 - 3.7 per inch
  • Sustainability. Made from recycled cotton and denim; 85 percent cotton and 15 percent plastic fibers from unused manufacturing scraps and post-consumer recycled clothing
  • Safety. Like cellulose, treated for pest, fungus and fire-resistance with borate. Considered non-toxic. May be installed without the need for skin or respiratory protection.

Cotton insulation comes in batts and is easy to install, especially since no protective gear is required. When installed, it provides you with R19 per 2 feet-by-6 feet section of wall. For those who want to give back what they get from their denim insulation, you can donate your used denim garments for recycling. Blue Jeans Go Green, as an example, takes used denim made from all or partial cotton content in any condition and recycles it into UltraTouch™ manufactured by BondedLogic, Inc. Cotton/denim insulation costs about 15 to 20 percent more than fiberglass.

Sheep's wool

  • Energy-efficiency. R-value is about 3.5 per inch
  • Sustainability. Sheep's wool replenishes itself with every shearing.
  • Safety. Borates, as with other natural insulation, safely inhibits mold, insect pests and fire. No protective gear is required for installation.

Sheep's wool insulation comes in batts or as loose fill that can be blown in behind netting. Sheep's wool expands rather than settles over time, making it unnecessary to blow in more fill to top it off. Wool also can absorb and retain a great deal of water, which can be a big benefit for some parts of your house; however, after repeated wetting the borate may leach out. Cost can be more than other natural insulation types.

Other types of insulation material

Insulation does not have to be from natural, recycled materials to be sustainable. Fiberglass, for example, is made from sand and recycled glass (which is made essentially from sand). Some spray-in foam products, because they mold themselves to all surfaces, are exceptionally good insulators compared to other choices. When all things seem equal as far as energy conservation is concerned, deciding on insulation may come down to safety and price.

If you don't need insulation just yet, you may want to wait and see what's new on the horizon. From panels made of cattail plants to those made of water, the best green insulation choices may be yet to come.

Photo credit to Myryah Shea

About the Author

Iris Price is a single Baby Boomer whose antidote to a lack of retirement funds was to launch a long-delayed career as a writer. While others her age concoct bucket lists and travel the world, she bought a new-construction home and obsessively creates lists of must-have home improvements and personal realization goals. She specializes in writing about home services and self-motivation.