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Opinions or experience with APEX block?

Searching for wall assembly options, weighing cost, thermal performance, durability and so forth, below and above grade, SIPs, ICF, SCIPs, brought me to APEX block. Cementious mix with EPS type of ICF, the EPS form creates a tubular-type grid of concrete with rebar. Supposedly uses something like 25% less concrete than standard ICF, while claiming R-38, and uses recycled EPS at a lower cost than ICF. Anyone have any opinions/experience with the product?

Asked by Sal Lombardo
Posted Jun 5, 2013 2:17 PM ET


3 Answers

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I have no experience with the product. However, I would be leery of any R-value claims.

According to one of the company's web pages, there is no information provided for "Thermal resistance - ASTM C1363 / ASTM C518." Instead, the page notes, "Results pending."

The company also makes exaggerated energy savings claims, which immediately makes me suspicious. One web page claims, "APEX Block structures are proven to save up to 50% on heating and cooling bills."

Answered by Martin Holladay
Posted Jun 5, 2013 4:37 PM ET
Edited Jun 5, 2013 4:40 PM ET.


Here is a link to a file that I read some time ago on the ORNL Whole Wall site. www.ornl.gov/sci/roofs+walls/research/detailed_papers/whole_bldg/pdf_fil... The simple answer is that the Apex block appears to be a variant form of Rastra/Cempo block. It appears that the whole wall value is likely about R7.6.

I believe that grid poured ICFs have a common issue; the functional R value of the whole wall is limited by the thinnest section of insulation provided by the form. I would have to dig into my old files to see the exact difference, but I think the forms that use the grid poured format for the structural concrete, seem to be relatively thin where the concrete grid attains maximum core dimension. The inherently more stressed full wall pour ICFs forms have thicker EPS walls as minimums, with some newer versions offering thicker integrated EPS on the exterior side (Logix for one). Many discussions on GBA cover thermal bridging as present in framed construction and how it reduces whole wall R values. Much like the R19 2x6 wall that will perform at a lower whole wall value, the somewhat thinly insulated waffle grid of (thermally massive and conductive) concrete degrades the insulation value of the thicker parts of the EPS form.

In any case, the mix of polystyrene beads and cement to create an ICF may offer advantages in stacking, stabilizing, pouring and stuccoing, but from the reported steady state R value for at least one of these types of forms (R1.1/inch), it clearly degrades the useful insulation function of the polystyrene beads. A similar style of grid pour ICF composed of EPS only, tested out at R16. Aside from decreasing the insulation value, I was advised not to use this type of block for foundation forms due to the porous nature of the EPS/cement mix. Sealing them can be quite the pain. Being damp also decreases the thermal value of the material.

They do appear to be very fire resistant, as I personally used the intense flame from a plumbers torch to test that aspect on a unfinished block sample. A final note, if you do select this style of ICF, be sure to follow the manufacturers specifications for the concrete/aggregate mix. One TV show about the trials and travails of building a dream house covered an incident of bad mix choice which resulted in later discovering that the grid had numerous gaps where flow did not occur.

Answered by Roger Berry
Posted Jun 9, 2013 4:04 PM ET


Roger thanks, I was thinking along the same lines. The block are 10" wide, they create a 6" tubular grid pattern of concrete. Thus at the thickest concrete dimension, your getting 2" of EPS/cement insulation on each side of the structural member, total of 4" EPS/cement. Averaging out these thinner areas with the thicker internal areas (where there is EPS/cement block only) not sure how they were getting R-35 or R-38. As Martin pointed out, and a phone call to Apex block confirmed, they do not have certified testing to make these claims, so far. The supposed mid R-30 values are expected. I am awaiting more info from Apex. I also appreciate the wicking effect of a cementitious product in creating possible issues with keeping the wall dry. For above grade applications, continuous application with an overlying stucco, as per my plans, could create an undesired result. Thanks for the link and both your input.

Answered by Sal Lombardo
Posted Jun 10, 2013 10:05 AM ET

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