In our recent post “Climate Change Resilient Building Materials for California Homes,” we identified ICF as a durable, energy-efficient and disaster-resilient material ideal for homes in the Golden State. Invented in the 1940s and patented by Werner Gregori in 1967, ICFs are better known as “insulated concrete forms.” First termed “foam forms” by Gregori in the late twentieth century, insulated concrete forms differ significantly from traditional concrete building. When used in construction, concrete is usually poured into a mold, which is later removed once the concrete has hardened or cured. Insulated concrete forms, on the other hand, are a complete structure in and of themselves. After concrete is poured into the foam forms, the mold serves as insulation for the finished building. Though ICFs were initially slow to permeate the US housing market, they are fairly popular in residential construction today. As homeowner priorities changed -- with disaster resilience and energy efficiency topping their lists -- ICFs became more mainstream. California homeowners are especially well-served by ICF construction, as these forms are exceptionally strong and contribute to a tight thermal envelope. In fact, the US Department of Energy National Renewable Energy Laboratory (NREL) identifies ICF construction as one of the best building methods for energy-efficient homes and those in disaster-prone regions. Throughout this post, we will outline the pros and cons of building an ICF home in California. We will also discuss the costs of building an ICF in 2021 and what the building process is like for homeowners. To learn about all of this and more, follow below.
For those unfamiliar with insulated concrete forms, ICFs are lightweight insulation forms that are hollow inside. The hollows within ICFs are filled with concrete once the forms have been laid. These forms are commonly used in foundations and exterior walls of both residential and commercial buildings. Common configurations of ICF walls and foundations are flat wall, waffle-grid and screen grid. Interestingly, ICF patent-holder Werner Gregori did not foresee the use of insulated concrete forms in residential construction. He initially believed that ICF construction would be too expensive for home builders. However, the cost of lumber and skilled labor rose precipitously in the years following Gregori’s patent application. Today, ICF construction is fairly competitive and can be very affordable, especially when one considers energy savings over time.
The type of foam used in insulated concrete forms varies from project to project. While the majority of ICF manufacturers use molded EPS or expanded polystyrene foam, four others are also used. Another common polystyrene foam used in ICF construction is extruded polystyrene -- also referred to as XPS. According to ICF Builder, all but one type of foam used in ICF construction are derived from polystyrene. The final type -- a rigid foam that can be sprayed -- is an expanded polyurethane foam. Most ICF builders consider this spray foam to be ill-suited to insulated concrete form construction.
Material costs involved in building an ICF home are typically greater than those involved in building a wood-framed or traditional concrete home. However, homeowners often enjoy cost savings in labor and post-construction operation. Because insulated concrete forms are more modular and lightweight than other residential building materials, labor costs may be lower. According to the HomeAdvisor Cost Guide “How Much Does It Cost To Build A Concrete House?,” because ICF forms are never removed, “ICF takes less time to install and as such, usually costs less than poured concrete.” Similarly, because ICFs create a tight thermal envelope -- preventing undesired air from escaping or entering the home -- energy savings are usually quite significant over the structure’s lifetime.
The HomeAdvisor Cost Guide “How Much Does It Cost To Build A Concrete House?” outlines exactly how much homeowners should expect to pay for ICF construction. According to HomeAdvisor, “ICF house construction typically costs between $150 and $160 per square foot [which is] comparable to the cost of a concrete house, if not identical.” Unlike other building methods, insulating concrete forms construction construction is usually priced per square foot rather than linear foot. While ICF commonly costs $150 per square foot -- as mentioned above -- “prices could span between $103 to $205 per square foot” depending on current availability.
Because contractors skilled in ICF construction are still relatively rare in the United States, it might be difficult to find a local team willing to pour an ICF foundation or build ICF walls. Thankfully, California builders Element Homes are experienced in insulated concrete form construction -- across both Northern California and Southern California. Installation of the ICF blocks usually tacks on an additional "$7 per square foot,” though this is actually less than traditional concrete construction. All in all, homeowners can expect ICF construction to cost “at least $3 more per square foot than traditional wood construction,” but should be prepared for costs as much as “$8 more per square foot.” HomeAdvisor’s Cost Guide recommends that homeowners explicitly ask their construction crew if true ICFs are being used because “some builders use ICF interchangeably with poured, removable forms.”
Most homeowners consider the higher cost and limited availability of skilled laborers to be the two most significant cons involved in building an ICF home in California. However, these two cons are typically mitigated by lower operating costs and cheaper installation. On the other hand, the pros of building an ICF home in California are myriad. These benefits range from impressive energy savings to incredible disaster resilience. If you are a prospective California homeowner interested in ICF construction, follow below to learn more.
Benefits of building ICF homes include fast construction, low energy bills, limited maintenance, disaster-resilience and superior sound insulation. In her 2019 article “The Advantages Of Insulated Concrete Form Foundations” for Forbes, Downsize: Living Large In a Small House author Sheri Koones writes that all in all, “ICF is used internationally because it reduces labor costs, is lighter to install, provides superior waterproofing and can be installed in any climate.” California homeowners pursue ICF homes because their “steel-reinforced concrete core protects the home against fire, hurricanes, and earthquakes…[while] it also reduces noise infiltration.” The July 2020 article “Benefits of Living in an ICF Home” from ICF Builder supports this latter claim. According to ICF Builder, most insulating concrete forms “with a six-inch concrete core have STC ratings of 50 to 55.”
This means that “only about one-quarter to one-eighth as much sound penetrates an ICF wall when compared to a wood frame.” Because of this sound absorption capability, ICF has become popular in multifamily housing complexes and in the commercial sector. ICF Builder notes that developers today are “using ICF to eliminate sound transmission between theaters in multiplex cinemas and between units in apartment buildings.” As mentioned above, the priorities of California homeowners appear to be reduced energy costs and reliable disaster resilience, both of which are offered by ICF homes. We discuss these two characteristics in detail below.
Insulated concrete forms are often chosen for the exterior walls and foundations of homes and commercial buildings in areas prone to hurricanes, tornados, high winds and wildfires. Builders will opt for ICF rather than conventional wood-frame buildings in these climates. The resource “Costs and Benefits of Insulating Concrete Forms for Residential Construction” prepared for the U.S. Department of Housing and Urban Development Office of Policy Development and Research and PATH by the NAHB Research Center explains why. According to this resource, “ICF wall construction provides 5 to 10 times the racking resistance of conventional wood-frame walls.” Conventional wood-frame homes usually begin to sustain damage from hurricane speed winds, suffering “major structural damage including collapse.” ICF walls, however, can be expected to “withstand Category 5 hurricane winds and even a moderate to severe tornado with minimal damage.”
Retrofitting a conventional wood-frame building to match this level of resistance would be incredibly inexpensive and would be nearly infeasible with “light frame wood construction.” HUD and the NAHB note that “similar benefits are found in the resistance of ICFs to forces that may be experienced by buildings located in velocity flood zones of coastal or riverine flood plains.” Perhaps most significant for California homeowners, the NAHB resource writes that ICF walls “have superior fire resistance in comparison to most other building materials.” Walls made from solid concrete ICF rather than wood framing “can generally sustain as much as four hours of extreme fire exposure, whereas typical wood-frame walls in houses generally do not exceed a one-hour fire rating.” Other structures built from wood and similar traditional materials would be completely consumed after four hours of exposure to intense heat. All in all, HUD and the NAHB note that “the individual performance attribute which has greatest technical significance to ICF construction is structural safety.”
One of the most publicized examples of ICF homes surviving disaster in California dates to 2007, when a series of suburban homes survived a San Diego wildfire. Though the San Diego wildfire of 2007 razed over two thousand other residences, three ICF homes were still standing after the disaster. According to ICF Builder, both the concrete and foam in insulated concrete forms are fire resistant. The post notes that though ICF foam “will melt if exposed to high heat, it will not contribute any fuel to the fire” because the flame retardant added by ICF manufacturers to EPS foam is “virtually ‘self-extinguishing.’”
Writing for CBS Local SF Bay Area in their 2018 article “Homeowners Rebuild With Concrete Construction Following Wine Country Wildfires,” Emily Turner and Whitney Gould note that homeowners turned to ICF after the Napa and Sonoma County wildfires several months prior. Speaking with Rene Latosa -- a Santa Rosa resident who lost his home in the Tubbs Fire --, Turner and Gould explain why California homeowners have adopted ICF. Quoting Latosa, they write that “‘the fire safety [of ICF homes] is almost 100%, the durability is 1,000 years.’” Because of this, homeowners have turned to ICF in the rebuilding process. Of course, ICF homes are not fireproof. If a fire is started within the home, the fire-resistant concrete and foam of exterior walls will not prevent the spread of flames or smoke indoors. Similarly, if there are openings between exterior walls and windows, the roof or the foundation, embers could enter the home.
In their brief “Elements of an Energy-Efficient House,” the DOE explains that ICF homes are more energy efficient than other types of homes because ICFs contribute to “a well-constructed and tightly sealed thermal envelope.” The thermal envelope of ICF walls limits heat transfer from the exterior of the home into the interior while also minimizing the escape of desired warm or cool air from the interior to the exterior. Because the exterior of ICF homes is well-sealed, passive home builders have recently turned to insulated concrete forms as a method of reducing energy consumption.
California homeowners who choose ICF construction can expect impressive cost savings -- even during the summer and winter when external temperatures are extreme. Writing for Green Home Guide in his article “How Insulated Concrete Form Works,” Zach Williams notes that “it’s common to see a reduction in energy expenditure of between 25 and 50 percent.” As part of our upcoming post “5 Surprising Energy Efficient House Designs,” we explain in greater detail how ICF homes lower energy bills over time. Stay tuned to learn more.
Common problems with ICF homes may include pest infestations, higher cost of construction, obstruction of available interior space and difficulty remodeling. Most of these negatives are incurred when an inexperienced builder pours concrete during installation, compromising the stability of ICF walls or foundations. As such, most of these issues are easily mitigated or wholly avoided when the homeowner chooses an experienced design-build team that understands how to install ICF blocks and pick the proper supportive materials. In his article “Problems With Insulated Concrete Form Walls” for SF Gate, Mike Matthews supports this, noting that “experienced construction professionals have likely learned how to overcome these challenges.”
As mentioned above in the cost breakdown of ICF home construction, ICF blocks are more expensive than some traditional building materials. While ICF homes could cost as much as five or ten percent more than traditionally built homes, they save homeowners money on energy expenditure and labor.
Writing for SF Gate in the article “Problems With Insulated Concrete Form Walls,” Mike Matthews notes that insect infestation can be an issue with ICF homes. According to Matthews, “subterranean termites have repeatedly demonstrated the ability to burrow through the panels, find hairline cracks within the concrete, and begin damaging wood flooring and joists before being detected.” Thankfully, Matthews notes that there “are a variety of preventative measures for warding off termites, including chemical treatment of the polystyrene panels, waterproof barrier membranes, and the use of metal shielding.”
Another potential con of building an ICF system is one homeowners might not anticipate. According to Jennifer Blair in her article for Hunker, ICF homes can be difficult to remodel. With ICF home building, Blair writes that homeowners “must think carefully about their home's design and anticipate changes that they might want to make in the future.” This is because major changes like “adding a window or door will require cutting into solid concrete walls, which can be complicated and time-consuming.” Homeowners must also “account for all of the electrical and plumbing chases that they require, because adding them after construction may also require cutting into concrete.”
Writing for Hunker in her article Jennifer Blair also identifies limited interior space as another con of living in an ICF home. According to Blair, “if you are building a smaller home, you may have an issue with the amount of valuable indoor floor space that must be devoted to the insulated concrete forms.” This is because “ICF walls consist of several inches of rigid foam insulation and reinforced concrete.” As such, insulated concrete form walls “take up more space than traditional wood frame walls” and could limit interior space.
In the article “ICF Construction - What You Need to Know About an ICF Home” for Common Sense Home, Laurie Neverman explains that building an ICF home is a bit different from building a traditional concrete or wood-frame house. Neverman notes that initially, builders assemble the insulated concrete forms. Afterwards, these forms are “laced with rebar and then filled with concrete.” Walls are built in layers, with three levels of insulated concrete forms filled at a time. Once three levels have been filled, builders must wait for these to set before increasing the height of the wall. After the foundation is laid and the walls are mostly finished, plumbing and electrical are added. Neverman writes that “plumbing and electrical must be done a little differently [in an ICF home] than with a stick built home.”
Most ICF builders will “plan any wall perforations [for plumbing and electrical] in advance” to avoid cutting through solid concrete after the walls are complete. Once the ductwork, framing and structural construction is completely finished, Neverman writes that “drywall is screwed into plastic strips in the ICF forms, allowing the home to be plastered and finished like a conventional home.” In the end, the only ways homeowners would know their home is an ICF construction rather than “standard construction are the deep window wells and doorways.”
As mentioned above, finding a professional ICF builder can be difficult because insulated concrete form construction is still unusual in some parts of the US. Thankfully, both California homeowners and the California government are known for demanding innovation and advancement in the residential construction industry. Because of this, it is possible for California homeowners to find builders with ICF construction experience. As one of California’s premier design-build firms, Element is one such resource.
We noted in previous posts that the Element Homes team has years of experience working with California homeowners to protect their properties from earthquakes, floods and wildfires. Our staff not only understands the ins and outs of ICF construction, but is also well-educated in all California building codes -- even the newest energy standards. Schedule a consultation with our design-build team or learn more about our process by filling in the form here.
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