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Thermacork Boardstock Insulation

Thermacork is a 100% natural, rigid-insulation material produced from natural cork… Read more
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  • Some materials provide a better alternative in an application dominated by products for which there are concerns about toxic constituents, intermediaries, or by-products. With the panoply of products made with polyvinyl chloride (PVC) and brominated flame retardants, some products are green simply because they provide an alternative. Examples of this are natural wall coverings, drain and vent piping, and roofing membranes. Some green products are free of hazards common to the product category; for example, LED lighting is inherently free of the mercury found in fluorescent lighting sources.

    However, it’s worth noting that without transparency about actual ingredients, there’s no guarantee that a product won’t have less common or less well-known hazards that the manufacturer isn’t talking about. We use Pharos’s Chemical and Material Library to assess less well-known hazards, and we encourage manufacturers to review the hazardous properties of all chemicals they use and seek out safer materials.

  • Growing and harvesting our building materials would be a great way to move toward a closed-loop system rather than a linear path from extraction to disposal. Doing so holds the promise of true sustainability and regeneration of ecosystems instead of damage to them.

    Unfortunately, biobased materials today can be at least as problematic as any other material. Intensive land use, chemical use, fuel use, nutrient runoff, and other pollution are among the impacts of agriculture; add to that competition between food crops and those used for building materials or fuel. We would like to see sustainable use of biobased materials, but improving practices and figuring out how to assess and document more sustainable practices will take a long time. There is no ready equivalent to FSC for biobased materials that aren’t wood, although certification to “organic” standards or other sustainable agriculture standards can provide guidance in some cases.

    At the same time, we don’t want to exclude biobased products that are typically responsibly sourced just because they don’t have a certification—particularly where they replace more problematic materials. GreenSpec continues to give preference to rapidly renewable alternatives to materials that present greater concerns. Examples of rapidly renewable materials in GreenSpec include linoleum, cork, and textiles such as wool, sisal, and organic cotton.

  • Third-party forest certification based on standards developed by the Forest Stewardship Council (FSC) is the best way to ensure that wood products come from well-managed forests. Wood products must go through a chain-of-custody certification process to carry an FSC stamp.

    Manufactured wood products can meet the FSC certification requirements with less than 100% certified wood content through percentage-based claims (30% certified content is required if only virgin wood fiber is used; certified-wood content as low as 17.5% is allowable if the rest of the fiber content is from recycled sources).

    With a few special-case exceptions, FSC-based certification is a requirement for GreenSpec inclusion of any nonsalvaged solid-wood product and most other wood products. A few manufactured wood products, including engineered lumber and particleboard/MDF, can be included if they have other environmental advantages--such as absence of formaldehyde binders. Engineered wood products in GreenSpec do not qualify by virtue of their resource efficiency benefits alone (for more on this, see EBN, Vol. 8, No. 11).

  • These products are environmentally attractive because they need to be replaced less frequently or their maintenance has very low impact, both of which can reduce costs as well as environmental impact.
    Robust answers on typical service life of products can be hard to come by, however. In GreenSpec we reserve this criterion for products where the material is clearly more durable than alternatives, such as an exceptionally traffic-resistant polyurethane floor finish. We refer to standardized tests for durability when they are available and appropriate.
    We also consider “appropriate durability”: long life is more important in a building envelope than in interior finish materials that will be replaced for aesthetic reasons. Here, reduced maintenance can be particularly important. An example is resilient flooring that doesn’t require regular waxing: an unnecessary use of resources and a health hazard.

  • Better information alone doesn’t make a product green, but it does make it a lot easier to see just how green that product actually is. We can make more informed purchasing decisions when we know what’s in a product, not just manufacturer’s claims about what it’s “free-of”; and when we know the actual environmental impacts of manufacturing the product relative to alternatives, not just a trade association’s claim that it’s “green.” Making information public can also help manufacturers get greener. It’s often the manufacturers that are already greener that are willing to share more information in the first place, but in the process of doing so they see where they still need to improve. Products with Environmental Product Declarations are included here, along with products with other forms of disclosure, such as products from companies that participate in the Global Reporting Initiative, or provide full disclosure of ingredients, potentially via the Health Product Declaration format. GreenSpec also lists products that help track buildings' energy and water performance, especially when those tracking tools can be used to publicly display or report energy and water usage.

  • Before specifying efficient heating and cooling equipment, it’s important to do what we can to reduce heating and cooling loads. Insulation is one of the key products to consider here, but because there are so many insulation products on the market, we look for additional benefits. Examples include cellulose insulation with recycled content, mineral wool insulation with no flame retardants, and fiberglass insulation with no formaldehyde binders. Other products in this area are high-performance windows and glazings, products that contribute to building airtight envelopes, products that reduce thermal bridging, and window-retrofit products.

    With products in this area under constant development, we are always refining our approach. For example, as we have learned about insulation products with hazardous flame retardants and blowing agents that have high global warming potential, we have removed those products from GreenSpec, pending manufacturing changes. We encourage building professionals to pressure manufacturers for those changes through specification language and purchasing decisions.

Tristan Roberts
Editorial Director

Thermacork is a 100% natural, rigid-insulation material produced from natural cork. The cork forests are FSC-certified, and the Amorim facilities are FSC chain of custody certified. To produce rigid boardstock insulation, cork granules are steam-heated in an autoclave, which expands the cork and activates a natural binder, suberin, that is in the cork; additional binders or other chemicals are not used in production. Large billets are then cut into slabs as insulation. The material insulates to R-3.6 per inch, offers excellent acoustic control, is highly durable, has high vapor permeability, and meets fire-safety requirements (Euro Class E, based on EN 13501) without flame retardants. It is labeled Red List Free for use in Living Building Challenge projects.

Rigid board insulation, usually made from plastic foam, glass fibers, or mineral wool, is a critical component in many new or retrofit energy-efficient buildings. Rigid board insulation typically provides high R-value for a given thickness and can be applied across the surface of walls, roofs, or foundations to reduce thermal bridging through framing, foundations, and other structural components.

Foam board insulation is petroleum-derived and uses a blowing agent for expansion. Polyisocyanurate—or “polyiso”—foam board typically has foil facing and has the highest R-value of any common insulation material. Polyiso boards are made with hydrocarbon blowing agents that are non-ozone-depleting and have negligible global warming potential (GWP).

Extruded polystyrene (XPS) is non-ozone-depleting, although XPS in North America is produced today with a blowing agent (HFC-134a) that has high GWP. (Most European manufacturers have converted to very-low-GWP hydrocarbon blowing agents, while North American manufacturers have been unwilling to have the R-value per inch drop as a result of a similar change.)

XPS and expanded polystyrene (EPS) are manufactured using a number of hazardous chemicals, including benzene and the brominated flame retardant HBCD—which is a persistent, bioaccumulative toxin that is slated for elimination in Europe. Because of the health and environmental concerns surrounding these materials, GreenSpec does not list rigid polystyrene insulation as a stand-alone product. However, because energy performance is a high priority with any building, use of XPS or EPS may be appropriate when those are the only options available.

Alternatives to rigid foam include rigid mineral wool, rigid fiberglass, and foamed cellular glass. It may also be possible to redesign building enclosure systems to utilize spray polyurethane foam (SPF) or minimize thermal bridging in other ways so that cellulose or other fiber insulation products can be used without an energy penalty.

Mineral wool board is a versatile insulation made from molten slag (a waste product of steel production) or natural rock (such as basalt or diabase), held together with a phenol formaldehyde binder. Mineral wool has a higher density than fiberglass, is more resistant to fire, and is better at blocking sound. It is appropriate for foundation wall insulation and, in highest-density form, may be considered for use under concrete slabs (although such applications may need special approval by building officials).

While expensive, cellular glass (Foamglas) is another option. Its high compressive strength and moisture properties make it appropriate for below-grade applications, especially sub-slab applications where XPS currently dominates the market.

Rigid fiberglass is made similar to fiberglass batts, but formed into denser boardstock. A shift to a non-formaldehyde binders has not been as rapid with rigid insulation products as it has with batts, but some manufacturers are making that transition. Concentration of the binder is higher in rigid boardstock than in batt insulation.

Note that board insulation products vary widely not only in R-value but also in permeability, moisture resistance, insect resistance, fire resistance (and need for flame retardant additives), and end-use applications. Selection of these products can be complex and confusing. More detail is offered in the BuildingGreen Guide to Insulation Products and Practices.

Products listed here have at least one of the following attributes: post- and/or pre-consumer recycled-content, reduced off-gassing, avoidance common hazardous ingredients, high durability, and blowing agents with little or no global warming potential.

LEED Credits

EAp2: Minimum Energy Performance

MRc6: Rapidly Renewable Materials

MRc6: Certified Wood

MRc7: Certified Wood

Ratings and Commentary

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Manufacturer Information

Amorim Isolamentos, S.A.
Rua da Corticeira 66 4535-173


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Declare is a voluntary self-disclosure program aiming to transform the building materials industry towards healthier and more ecological products through ingredient transparency. Living Building Challenge Red List Free means this product does not contain any ingredients on the Living Building Challenge’s Red List.