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Opinions or experience with APEX block?

Sal Lombardo | Posted in Energy Efficiency and Durability on

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?

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  1. GBA Editor
    Martin Holladay | | #1

    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."

  2. Roger Berry | | #2

    Here is a link to a file that I read some time ago on the ORNL Whole Wall site. 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.

  3. Sal Lombardo | | #3

    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.

  4. 1piper | | #4

    My house is built with Apex Blocks and I love it! I live in NM and my heating and AC bills are less than half my neighbors with wood frame houses. Very energy efficient.

  5. DC33 | | #5

    I have used both Apex and Rastra type ICCF blocks. Some manufacturers offer various wall thickness, so I will only compare the 10” wide block. Most of my outlying landscape walls use the Apex while the main structure was constructed with the Rastra or similar. The basic mix of each is quite similar and the post (vertical) and beam (horizontal) holes are approximately 6” diameter. Both use rebar and concrete according to the SE specifications. Therefore I will first give the main differences.

    The Apex is roughly 10”W, 15”H, 48”L with a weight of approximately 50 lbs. The 3 post holes are 15” on centers (one being in the center) with the beam hole running through the center length. The block ends, top and bottom are contoured with an interlocking design to assist alignment.

    Apex pros:
    Easy to handle, stack and align.
    Plenty of surface area for glue.

    Apex cons:
    Requires rebar to be placed during assembly (beam hole only accessed from ends).
    Corners must be planned well ahead of assembly.

    The Rastra block is roughly 10”W, 15”H, 120”L with an approximate weight of 145 lbs. The post holes are on 15” centers with half diameter on each end (butting two blocks creates a 6” post hole at the joint). The 6” diameter beams are achieved when one block is placed on top of another (the top and bottom of the block have a 3” radius running the full length to create the 6” diameter beam).The ends, top and bottom are not interlocking. (There are other manufacturers using this design, but in shorter length.)

    Rastra pros:
    Blocks are heavy and cumbersome, but can be easily cut.
    Rebar can be shaped and simply dropped into the radius after each block course is in place, even in curved walls.
    Special vertical corner blocks are available.
    Flat panels can be used in place of blocks if a concrete roof is desired.

    Rastra cons:
    Blocks are heavy and cumbersome.
    Care in block alignment is a must (just like a cinder block wall).
    Additional care should be taken when gluing the blocks together.

    Now for the good part: Although, pure foam has a greater R value, ICCF has a fire rating of 4+ (only because the ICBO didn’t like issuing a “5” rating … my opinion). I have thrown some of this block into a fire pit and also held an oxy-acetylene torch on the block for 10 seconds with NO effect. I heated a protruding anchor bolt red hot to bend it at the wall surface … again, no problem. I have seen plenty of foam go up in smoke … not something to breathe in!
    Termites do not even nest in ICCF (they will chew out 100% foam). So, my main purposes for choosing ICCF products were fire and termites. I built in the SW desert where typical utilities for a 2,000 sqf house run $300 to well over $500 / mo during the summer heat (April thru October). My total utilities for last July and August 2019 (the really HOT months) were $125 and $132 respectively. That is with a two-year old 3.5T LP gas-pack AC. My previous AC unit was only 2.5T, but ran 24-7 during the two week stretches of 115 degrees. During the winter I use two or three portable oil-filled radiators for heating. As electric is currently cheaper, the LP only gets used as secondary. Total winter LPG use including BBQ is less than 200 gallons. Currently, my windows have no special tint or shading. That will be changing.

    I have approximately 2,200 sqf, 10’ ceilings and a 250,000+ lb concrete and rebar roof (no attic or crawl space). This puts a different perspective on who’s ICCF you use. Rastra is one of the very few that offers flat panels for solid concrete walls (most likely required for concrete roofs). My roof is currently covered with DuraLast and is fully walkable. I can take my shirt off, lay on that roof in 112 degree high noon and not burn … sweat, yes, but no burn! There is an additional expense for a concrete roof in two ways. You will need a bit more concrete in your floor plus rebar to support the shoring material which will need to be in place for a month till the roof cures. The shoring material may cost you more than you expect, check your local resources. 20 years ago it cost me $10,000 for the shoring material, setup and tear-down. But, I estimate it has saved me $500 a year in cooling and heating costs vs a conventional roof. Choosing a concrete roof does restrict the room size due to span limitations. All of my exterior door frames (and some interior) are commercial steel … no wood. This in no way makes my house a bunker (I have designed those), it is mainly for fire and termite protection. I also use metal frame windows, SW desert UV eats vinyl for lunch. Also, all of my ventilation is underground, below the concrete slab (no basement). That is a plus during the summer as that air stays cool and can be accessed by using only the circulating fan on the AC unit. An additional system that works well is an economizer which allows outside cool air to be brought in vs running the AC compressor. My AC unit is ground mounted.

    Things I would do to improve would be use 3/4” conduit as a minimum for all electrical (I used 1/2” in many runs). I do NOT suggest stuffing your wiring into the ICCF! Go ahead, try to pull that wire out!


  6. DC33 | | #6

    Regarding the R value of ICCF material: ICCF may only have a R value of 6.5 / 2” of thickness.

    Do some research, trial and whatever. R value is for the specified material only. When the rated material is applied to different applications, the combined true value is subject to that specific application. A 2x4 stud wall with 100% foam insulation coated with stucco is a good insulator and the interior of the structure will heat or cool quickly. A poured-in-place concrete wall with the same 100% foam and stucco exterior will take a while to get to the desired temperature. But, the concrete wall will hold the temperature much, much longer requiring less HVAC run time in the long run. The point is that it may only take a small amount of R value to get the desired results. The application of reflective paints can also make a huge difference. Of course, all of these factors depend on the environment and application of the structure.


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