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Foamglas Sheet Insulation

Foamglas® cellular glass insulation from Pittsburgh Corning is 100% glass, made with sand (60%), limestone (20%), soda (15%), and trace minerals (5%)… 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.

  • 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.

  • Just how low the VOC level needs to be for a given product to qualify for inclusion in GreenSpec depends on the product category. For most products, we require certification to California’s health-based emissions standard, CDPH Std Method v1.1 standard (also referred to as California Section 01350), which tests a product’s resultant VOC concentrations in the space after a given period of time. For wet-applied products like paints, caulks, and adhesives, we still also look for VOC content instead of, or in addition to, verified low emissions; this is because emissions testing doesn’t adequately test initial offgassing, and VOC content is currently the only widely available proxy.

  • Periodic pesticide treatment around buildings can be a significant health and environmental hazard. Green alternatives obviate the need for pesticide treatments. Examples include physical termite barriers and bait systems that apply toxins in a much more targeted way than broad-based pesticide application.

Tristan Roberts
Editorial Director

Foamglas® cellular glass insulation from Pittsburgh Corning is 100% glass, made with sand (60%), limestone (20%), soda (15%), and trace minerals (5%). It contains no HCFCs and can be used for insulating roofs, walls, and below-grade applications, including beneath slabs. Foamglas is impervious to moisture, inert, resistant to insects and vermin, strong, and has an R-value of R-3.44 per inch. The high compressive strength makes it particularly appropriate for roof decks, green roofs, and parking decks. Unfaced Foamglas is produced in 18" x 24" dimensions in thicknesses from 1-1/2" to 6" in 1/2" increments. A bitumen-faced product (Readyboard) is available in 2' x 4' dimensions with the same thickness options.

Read more on this product in "BuildingGreen's Product of the Week"

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

EAc1: Optimize Energy Performance

EAp2: Minimum Energy Performance

Ratings and Commentary

UL Ratings

Also non-combustible!

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Manufacturer Information

Pittsburgh Corning
800 Presque Isle Dr.
Pittsburgh, PA
Toll-Free: 800-545-5001


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