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MillenniumBlok ICFs are unitary blocks consisting of 85% pre-consumer expanded polystyrene (EPS) from other ICF manufacturers, cement, and other additives… Read more
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  • 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.

Brent Ehrlich
Products Editor

MillenniumBlok ICFs are unitary blocks consisting of 85% pre-consumer expanded polystyrene (EPS) from other ICF manufacturers, cement, and other additives. According to the company, the unitary, octagonal cell design provides increased stability and protects against blow-outs. Blocks are available in 10", 12", or 14" depths, 4' or 8' lengths, and are 16" tall. The blocks have 4" exterior walls and 2" interior walls, which brings the thermal mass of the poured concrete closer to the interior of the building. The steady state R-values for the 10", 12", and 14" MillenniumBlok are 24, 32, and 38, respectively.

Insulating concrete forms (ICFs) provide a labor-efficient means of making insulated poured-concrete walls. ICFs are permanent forms—they aren’t disassembled after the concrete has cured. Most of these products are made from expanded polystyrene (EPS) foam, which has a very low global warming potential (GWP); several are made from extruded polystyrene (XPS), which is currently blown using a high-GWP HFC blowing agent, and a few are a composite of wood waste or EPS beads and portland cement.

Both EPS and XPS are produced from benzene, a known carcinogen) and both currently contain the brominated flame retardant HBCD, which is a persistent, bioaccumulative toxin. To protect against potential damage from wood-boring insects, some EPS foam used in ICFs contains low-toxicity borates.

Due to their high GWP, GreenSpec does not list XPS-based ICFs. GreenSpec does list some EPS-based ICFs, despite our concerns, because of their energy performance and other environmental attributes, such as the reduced portland cement use compared to conventionally formed concrete walls.

Be aware that the R-values claimed by ICF manufacturers are not always arrived at in a consistent manner and may be misleading. We recommend only using “steady-state” R-values for comparing products, when that information is available.

Mass-enhanced or “effective” R-values are only relevant in certain climates or under certain conditions, but they’re often listed in product literature in a way that fails to distinguish them clearly from steady-state R-values. In general, claims about the benefit of the thermal mass in ICFs may be exaggerated; the insulation interior to the concrete core of some or most ICFs dampens the ability of the concrete thermal mass to transfer heat to and from the interior environment of the building—and it’s this heat transfer that is key to effective use of thermal mass. Due to these issues, some ICF products may be excluded from GreenSpec because of misleading energy performance information from manufacturers.

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