As explained in the first post about the Hudson Valley River build GBA is following, minimizing carbon emissions is a primary objective. Therefore, limiting the amount of concrete used is key. For this reason, the BPC Green Builders–Trillium Architects team spec’d an insulating composite concrete form (ICCF) foundation, specifically The Perfect Block from Eco Building Systems.

Project Manager Ben Bogie found The Perfect Block through Steve Baczek, who is a fan of the product. Manufactured in Arizona (and soon Virginia), it is made with ground recycled EPS foam that is mixed with binding agents and cement; the resulting block is roughly 87% insulation.

The difference between ICFs and ICCFs is that the latter is integral to the foundation system (vs. a way to contain concrete), meaning it forms part of the structure. Also, whereas ICFs are concrete cores sandwiched between two pieces of rigid foam, The Perfect Block ICCF is more like what Ben describes as “honeycomb cells.” In the case of this project, the foundation is a grid of 6-in. by 6-in. columns 12 in. on center, and 6-in. by 6-in. beams 12 in. on center—together, the vertical and horizontal structure create a latticework of support, or a screen grid. It provides continuous insulation and has an R-value of 28. Ben says the cost comes in just below that of a conventional concrete foundation wall. For this project, there was an increase because of current shipping costs; the material alone was $29K.

Installation is straightforward. The 4-ft.-wide by 10-in.-deep by 12-in.-tall blocks come palletized, are lightweight (about 40 lb. each), and are easily hand-lifted; they can be cut with a cordless Sawzall (or even a handsaw) and stacked directly on top of one another and secured with a foam adhesive—no running bond necessary.

Here, the bulk of the foundation is 6-ft. tall—that’s six blocks high. The crew installed #5 rebar on 24-in. centers (the rebar falls on the center of every other core) up to the height of the first three blocks (3 ft.). Then they tied in another piece with a 12-in. lap and stacked the final three blocks. Staggering the rebar in lifts meant they weren’t reaching up over 6-ft.-tall rebar to stack the blocks.

Getting the first course level and plumb is critical. The focus on consecutive courses is on being plumb; shims are used as the blocks get stacked to keep them on course. They are glued together with a continuous bead of adhesive expanding foam running the entire length of the wall on both sides and at the joints. The three-member crew stacked the entire foundation in two weeks. In addition to the speed at which it goes in, Ben notes another benefit: Due to the product’s coating, debris from cutting doesn’t  blow around the job site, which happens with standard EPS forms.

The one pitfall, according to Ben, is an engineer’s comfort level working with the product. In this case, the engineer’s plans called for #4 rebar 12 in. on center both vertically and horizontally. Instead the team went with #5 on 24-in. centers, which cut the schedule nearly in half. The engineer also spec’d a 1/2 in. of cement board on the exterior of the blocks because the ICCF manufacturer doesn’t have any test results to show the product’s performance in this environment. (Notably, they have a 23-year track record with no failures). The design-build team pushed back, feeling the precaution was unnecessary. Instead, they opted to use Rockwool Comfortboard on the exterior because they are confident it has enough compressive strength to distribute the soil-pressure load across the foundation wall.

Asked what he thinks about the system, Ben responds, “It earns its name, in my experience. We are looking at integrating it as a standard foundation for our future projects.”

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Kiley Jacques is senior editor at Green Building Advisor. Illustration by Patrick Welsh. Photos by Brian McAward.