News Article

ICF vs CMU: Understanding Your Options

Concrete masonry units (CMU) and insulated concrete forms (ICF) are two choices for wall systems in both com­mer­cial and res­i­den­tial con­struc­tion. The goals of CMU and ICF wall systems are to create durable struc­tures that are resistant to fire, rot, mold, and moisture. Both also strive for excellent indoor envi­ron­men­tal quality (IEQ). There is one sig­nif­i­cant dif­fer­ence between ICF and CMU con­struc­tion. Insulated concrete forms, like the Bautex Wall Systems, are quicker and easier to build than CMU; therefore, ICF saves money, reduces labor, and lowers con­struc­tion risks over CMU wall systems.

Insulation Requirements for CMU and ICF

Since 1999, the ASHRAE 90.1 (the U.S. energy standard) has ref­er­enced pre­scrip­tive R‑value rec­om­men­da­tions for con­tin­u­ous insu­la­tion, for all com­mer­cial and res­i­den­tial single or multi‐​family struc­tures greater than three stories in height above grade. The quantity of insu­la­tion required (as indicated by the R‑value) by the standard depends upon the climate zone, the wall type, and whether the structure is res­i­den­tial or non-res­i­den­tial. Wall types include wood, steel framed, metal building, and mass walls.

Both CMU and ICF are mass walls. Mass walls provide energy effi­cien­cy through mass rather than insu­la­tive values. The mass allows the wall system to store energy during the day and release it through­out the night, which makes mass walls a good choice in hot and humid climates where the tem­per­a­ture varies sig­nif­i­cant­ly through­out the day. The R‑value require­ments for mass walls range from 5.7 to 25 depending on the climate zone and whether the structure is res­i­den­tial or non-residential.

Concrete Masonry Units (CMU)

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

R‑Values of CMU

Concrete block walls have very low R‑values ranging from 2 to 3, and insulated CMU have R‑values ranging from 4 to 14, depending on the blocks thickness and density. Insulated CMU is not widely used in the U.S. which, in many cases, requires CMU walls to be insulated with addi­tion­al materials and systems.

Advantages of CMU

CMU are durable and resistant to moisture, fire, rot, and mold. CMU are also pest-resistant and a good sound-proofing material. Insulated CMU provide an R‑value compliant with zones 1 – 5, according to the ASHRAE 90.1, which reduces energy use and is good for the environment.

Disadvantages of CMU

Unfor­tu­nate­ly, the design of the CMU has not kept up with the rise in demands on wall systems. For the past 50 years, builders and archi­tects have strived to improve on the energy-effi­cien­cy, dura­bil­i­ty, and fire and wind resilience of wall systems. Modern wall systems must also provide occupants with a high level of indoor envi­ron­men­tal quality.

Instead of improving the design of CMUs, designers and builders have added new com­po­nents, extra layers, and addi­tion­al steps to CMU con­struc­tion. These steps have com­pli­cat­ed the process and resulted in more money and time spent and increased oppor­tu­ni­ties for errors during the building of a CMU wall system.

CMU appear­ance is another dis­ad­van­tage. CMU have an indus­tri­al look unless a facing, like stucco, is applied over it.

Insulated Concrete Forms (ICF)

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

Today, ICF are cast-in-place concrete walls, inserted between two layers of insu­la­tion. Insulated concrete form walls are made by dry-stacking expanded poly­styrene foam panels or inter­lock­ing hollow extruded poly­styrene foam, to a wall’s length. The forms are braced and rein­forced. Industry pro­fes­sion­als then pour concrete into the hollow form panels.

R‑Values of ICF

R‑values for ICF con­struc­tion vary with the type of ICF and thickness of the foam. An example of an ICF product is the Bautex Wall Assembly. Bautex Blocks are made from 90 percent foam plastic insu­la­tion encap­su­lat­ed in a cement matrix. Bautex Blocks achieve an R‑value of R‑14. The Bautex Wall System exceeds by three times the 2018 Inter­na­tion­al Res­i­den­tial Code (IRC) insu­la­tion require­ments of mass walls in climate zones 1 and 2.

There are several benefits to insulated concrete form wall systems.

  • ICFs are disaster‑, fire‑, and pest-resistant.
  • ICFs are also noise-reducing, healthy, easy to maintain, and energy-efficient.
  • ICF struc­tures are aes­thet­i­cal­ly pleasing and provide design flex­i­bil­i­ty, such as complex archi­tec­tur­al contours and curves.
  • Impor­tant­ly, ICFs are easy and quick to install.

ICF vs. CMU

ICF and CMU wall systems both strive to create energy-efficient, durable, storm and fire resilient wall systems. The wall systems must also create a healthy and com­fort­able envi­ron­ment for the occupants of the building or home. Where the two methods part ways are the ease and effi­cien­cy of the building process. Insulated concrete foam takes half the time to construct over concrete masonry unit walls. For example:

  • A concrete masonry wall needs an appli­ca­tion of insu­la­tion. Applying insu­la­tion over the concrete masonry wall involves a second trade to the job site. The second trade adds one more day of costly labor to the wall con­struc­tion project.
  • A concrete masonry wall often needs instal­la­tion of an air and moisture barrier, further adding another trade and more labor to the wall con­struc­tion project.
  • The light­weight nature of ICF speeds con­struc­tion time over CMU.

Building a wall system with ICF sim­pli­fies con­struc­tion, shortens the schedule, reduces cost and lessens con­struc­tion problems over CMU construction.