• Fiberglass batts are readily available but are very harmful to work with, have low R-value, and require a vapor barrier from moisture.
• Concrete-and-foam forms are energy efficient when insulated but can only be used in new construction.
• Rigid foam boards use hydrochlorofluorocarbons (HCFCs) in production, which is harmful to the environment.
• Blown in cellulose is environmentally friendly but is also susceptible to mold among many other issues.
• Spray polystyrene foam of a closed-cell type is very expensive while open cell absorbs moisture.
It's not hard to see that there's a real industry gap for what many would consider the perfect insulating material. If a product could be affordable, environmentally friendly, convenient to work with, and offer an unprecedented R-Value then it could corner the insulation market – almost easily.
• Cotton – leading the way in the alternative insulation market is cotton. Interestingly enough cotton insulation is considered a green building product because it is largely made out of recycled blue jeans. Cotton is much safer and more convenient to work with than fiberglass, and it is formaldehyde free. Another big benefit is that cotton provides great acoustical qualities.
Made from all natural fibers – recycled denim – cotton batt insulation contains no irritating fiberglass and no formaldehyde (courtesy Menards). In fact, it contains no chemical irritants and no volatile organic compounds (VOCs) and requires no warning labels compared with other traditional products. Yet is has identical thermal performance to fiberglass and as good or better sound isolation – albeit at a 3x higher price.
• Wool – the reason sheep are able to live in any climate is because their wool is constructed of tightly packed fibers that trap air. These properties are what makes wool insulation such a viable option for home insulation. Wool insulation is renewable and sustainable, and it uses a fraction of the energy to produce compared with foam boards. Wool fibers are also breathable, which allows them to release moisture, and as a bonus wool is also non-combustible.
Wool fiber is natually "crimped," and when it is firmly packed together, it forms millions of tiny pockets that trap air, resulting in great insulating performance – keeping heat inside the insulated envelope during winter and out during summer (courtesy Oregon Shepard). Although wool is naturally fire resistant, as a home insulating material it is treated with an all-natural solution that provides extremely high fire and vermin resistance. Cost is about twice that of traditiional fiberglass insulation.
• Cork – a 100% natural product that can be harvested from the same tree every 18 years or so (using only the bark of the tree). Cork insulation sheets are moisture resistant and offer great thermal and acoustical characteristics.
Expanded cork insulation is a natural material that nevertheless requires sophisticated processing to be an effective insulating material. It is naturally moisture resistant and more fire resistant than polyisocyanurate and polystyrene foam board insulation. The cost to achieve R-19 would be 3 to 5 times the cost of polyiscyanurate and 2.5 to 2.75 that of extruded polystyrene boards (courtesy The Future Build).
• Soy-Based Spray Foam – one of the problems with cork boards or even wool or cotton batts is that they don't always cover the tiniest crevices in a wall or around pipes, which is why many homeowners prefer a spray foam. Soy-based spray foam is a much more eco-friendly material than traditional types of spray foam, and it is mold and moisture resistant as well as non-flammable.
If you want to use a spray foam insulation in your home but are concerned about off-gassing and hydorfluorcarbons, you might consider a spray foam that is soy-based, Though not 100% soy, it reduces the amount of petroleum products used and is applied using water, so it is less toxic. The materials costs approximately 3 times more than traditional spray insulation (courtesy International Association of Certified Home Inspectors).
With so many alternative options available (not to mention others such as recycled plastic bottles and more) it may seem dumbfounding that polystyrene foam and fiberglass are still the most common insulating options today.
The two main factors holding down alternative insulation materials from cornering the market are cost and availability. Approximately 9 out of 10 building contractors would prefer using wool or cotton over itchy and irritating fiberglass batts, but it's hard to pass on a price markup of two to three times to the homeowner. Using cork boards compared with polyisocyanurate foam sheets will come at a price differential that is five times higher. In addition, unfortunately, there aren't any significant increases in R-value when using one product compared with the other.
These alternative insulation types are also harder to come by than fiberglass batts, foam boards, or even blown-in cellulose, which all can be obtained at your local hardware store.
Homeowners who are striving to build their house as green as possible have been driving the market for these alternative insulation materials. For the majority, however, the cost advantages of traditional materials are too much to overcome.
It won't be like that forever, however, so don't be sad when those old jeans don't fit anymore – they may insulate your house someday.
Footnote: the photograph at the bottom right of the lead image is of cellulose being blown into an attic space. For more information, click here.