Concrete masonry units (CMU) and insulated concrete form (ICF) walls have several features in common: energy-efficiency, durability, and good indoor environmental quality (IEQ). However, ICF is quicker and easier to install compared to CMU, which saves time and money.

CMU and ICF are mass wall systems used in energy-efficient commercial and residential construction. Mass walls provide energy efficiency through mass, rather than insulative values. The mass of the wall system stores energy during the day and releases it throughout the night, which makes mass walls, like CMU and ICF, an excellent choice in hot and humid conditions.

Both CMU and ICF wall systems strive to create durable structures that are resistant to wind, moisture, fire, rot, and mold. CMU and ICF wall systems also aim for suburb indoor environmental quality (IEQ). IEQ includes the air quality, lighting, thermal conditions, and ergonomics inside a building. Excellent IEQ protects human health, improves quality of life, and reduces stress and potential injuries.

The Simple Advantage of ICF over CMU Construction

There is one significant difference between ICF and CMU construction. Building with insulated concrete forms, like theFox Blocks, is faster and simpler than CMU construction. Therefore, ICF wall systems save money, reduce labor, and lessen construction risks over CMU wall systems and include interior and exterior continuous insulation and 8” on center full height furring for drywall and exterior finish attachment..

What is Concrete Masonry Units (CMU) Construction?

The first use of the modern-day concrete block was in 1830. However, in the United States, it was not commonly used until the first half of the 20th century. Three situations promoted the increase in CMU construction: the 1904 St. Louis Louisiana Purchase Exposition (St. Louis World’s Fair) that advocated concrete block construction, the development of concrete block machinery, and the formation of a domestic Portland cement industry. Over the decades, the basic design of CMU has not changed. CMU is concrete block made from Portland cement, aggregates like stone and quartz, and water. The blocks come in an assortment of shapes and are hollow or solid, with two or three cores or voids.

Advantages of CMU Construction

There are several advantages of CMU construction, including:

• CMUs are resistant to moisture, rot, and mold and are durable.
• CMUs are fireproof and can act as a firewall between rooms or structures.
• CMUs are pest-resistant.
• CMUs are a good sound-proofing material.
• Insulated CMUs provide an R-value compliant with climate zones 1-5, according to the ASHRAE 90.1, which reduces energy use, saves money, and is good for the environment. Concrete block walls have R-values ranging from 2 to 3, and insulated CMUs have R-values ranging from 4 to 14, depending on the block density and thickness.

Disadvantages of CMU Construction

Despite its advantages, CMU construction has some drawbacks, as well. Unfortunately, the design of CMU has not kept up with the increase in demands on wall systems. For the past 50 years, architects and builders have aimed to improve the durability, energy-efficiency, and fire and wind resilience of wall systems. Modern wall systems must also give the occupants a high level of IEQ.

Instead of improving the specific design of CMUs to accommodate these demands, builders and designers opted to add new components, extra layers, and more steps to CMU construction. These steps have complicated the building process and result in more time and money, and a greater chance for errors during the constructing of a CMU wall assembly.

CMU appearance is another problem. CMUs have an industrial look unless a facing, like stucco, is applied over them.

What is Insulated Concrete Forms (ICF) Construction?

Insulated concrete forms were first developed in Belgium in 1937 by Swiss nationals August Schnell and Alsex Bosshard. The initial purpose of ICFs was to produce a fast, cost-effective, and solid construction method using mainly unskilled labor. Registration of the first modern patent application ICF, however, didn’t occur until the late 1960s.

Today’s ICFs are cast-in-place concrete walls, inserted between two layers of insulation. The R-values for ICF construction vary with the kind of ICF and thickness of the foam. Fox Blocks exceed ASHRAE/ANSI 90.1 energy code requirements and are an example of an excellent energy-efficient ICF product.

Insulated concrete form walls are constructed by dry-stacking expanded polystyrene foam panels or interlocking hollow extruded polystyrene foam to a wall’s length. The forms are reinforced and braced. Then concrete is placed into the EPS forms.

The Advantages of ICF over CMU Construction

The goals of both ICF and CMU wall systems are to produce durable, energy-efficient, storm- and fire-resilient wall assemblies. The two wall assemblies also aim to create a comfortable and healthy environment for the occupants of the building or home.

However, similarities between ICU and CMU part ways in the ease and efficiency of the two building methods. Insulated concrete form takes half the time to build over concrete masonry unit walls. There are a few reasons why CMU walls take longer to construct than ICF walls.

1. CMU walls require the placement of mortar between all horizontal and vertical joints and then need to be finished. ICF walls are put together like a lego. No mortar, extra tools needed.
2. Sizing and handling, 1 ICF block is equal to 6 CMU blocks at a fraction of the weight.
3. Unlike ICF walls, a CMU wall needs an application of insulation. Applying insulation over the concrete masonry wall involves a second trade to the project site. The second trade adds one more day of costly labor to the wall construction project.
4. A concrete masonry wall often requires the installation of an air and moisture barrier, which adds another trade and more labor to the wall construction project.

In the video below, a team of 9 first time ICF installers puts up more wall than established masonry crew averaging over 20 guys on this 100,000 sq ft school. That's a 50% reduction in man hours ICF VS CMU.

The Fox Block Series Insulated Concrete Forms

The Fox Block Series concrete form wall system includes two pieces of 1.5 pcf density modified two ⅝ inches expanded polystyrene (EPS) foam panels. The panels are locked six to eight inches apart with molded plastic ties made of polypropylene (PP) regrind resin.

Utilizing the Fox Block Series creates an energy-efficient, moisture-,disaster-, and pest-resistant wall system. Fox Blocks also ensure excellent indoor environmental quality in the following ways:

• The Fox Block wall system includes a vapor retarder which ensures a moisture-resistant wall.
• Fox Blocks, with steel reinforced concrete, are disaster-resistant and can withstand tornado and hurricane winds of over 200 MPH and projectile debris traveling over 100 MPH.
• Fox Blocks are durable and resistant to termites and rot.
• Fox Blocks create a quiet and healthy environment for the occupants of the building.

Importantly, the Fox Block Series is quick and easy to install, compared to CMU construction, which saves builders time and money. The Fox Block is an all in one wall assembly.

Select Fox Blocks ICF Over the CMU Alternative

Fox Block Wall systems combine five construction steps into one, including structure, insulation, air barrier, vapor retarder, and attachment. This feature significantly accelerates project delivery by eliminating the need to coordinate multiple trades, while achieving all of the wall systems objectives.