What is ICF? What are the Advantages and Disadvantages, and Why Would You Choose It?
What is ICF…And Why Would You Choose It? Find out what ICF is, the benefits and disadvantages of use, its history, and more.
What Is ICF and How Does it Work?
The forms are hollow foam blocks that look like toy building blocks. The foam provides a high level of insulation. ICF forms are typically 48” long, although some brands make up to 96” long. They have a variety of core widths, from four to twelve inches, with eight-inch width blocks commonly used for residential construction. There are specialized shapes for different house sections and types of construction: for instance, both straight and corner blocks are commonly used in general residential construction, but other projects may utilize 45-degree angle blocks, brick-ledge blocks, or radius blocks for curved walls.
To form the walls, blocks are stacked together and rebar is inserted in the hollow spaces between foam, both vertically and horizontally. Then concrete is poured into the forms. Together, the rebar and concrete create exceptionally strong walls.
How Long Has ICF Been Around?
The first ICF form was patented by Werner Gregori in 1967.
Click here to find out how he drew inspiration from the beach! Interest in the form decreased in the ’80s, then rose again in the ’90s, where growth increased rapidly.
Advantages of ICF: Why Would I Choose it?
ICF has a host of benefits: in short, it’s durable, safe, and energy-efficient.
Rebar and concrete provide strong structural support. One measure of this is increased racking strength (lateral/side pressure) created by wind and earthquakes. This means an ICF home is more likely to survive natural disasters such as earthquakes, fires, hurricanes, etc. In general, ICF wall construction provides 5 to 10 times the racking resistance of conventional wood-frame walls. Read about an ICF home that survived a hurricane here.
ICF homes resist mold, rot, mildew, and insects because there are no wall cavities. The layers of foam and concrete mean that finished ICF walls are roughly twelve inches thick, which is slightly thicker than traditional stick framed houses. Because of this, the walls block sound, and the house is much quieter. Another benefit of ICF is fire resistance: concrete has a much higher fire resistance than most other building materials. Generally, solid concrete ICF walls can sustain as much as four hours of fire exposure.
The continuous thick walls and high insulative value also mean that ICF homes are extremely energy efficient and airtight. There are no hot or cold spots in the walls, and the houses have a high airtightness rating, which is measured by air changes per hour (ACH). For comparison, older stick frame homes typically have a rating between 5 and 12 ACH, newer stick frame homes are typically 3 and 5 ACH, and ICF homes are typically between .15 and 1.5 ACH. This high level of airtightness means lower expenses for heating and cooling.
Cost comparison: ICF construction is more expensive to build than traditional stick frame houses, and costs about 4-9% more upfront. However, through energy savings, the actual cost difference over the lifespan of the house is less.
Disadvantages of ICF:
Future Remodeling: ICF houses are much harder to remodel and renovate than traditional stick frame houses, because of the concrete walls. However, this does not mean it is impossible. Furthermore, if you work with an architect and have a clear vision, you are unlikely to need to remodel.
How long will ICF houses last?
ICF homes will, barring extreme circumstances, last over 100 years.
The foam insulation will not degrade and there are no wooden walls that will rot. Due to their structural soundness, they are much more likely to survive extreme weather than stick and frame houses.
How are things like siding and sheetrock attached to ICF walls?
ICF blocks have internally embedded hard polypropylene plastic strips that can be drilled into and used for fastening exterior components. These strips provide strength similar to that of a wooden frame. Siding and other exterior materials are attached similarly to traditional stick frame homes.
ICF construction creates a safe, durable, energy-efficient home that will last generations without the risk of insects, mold, or mildew. Although it incurs a higher cost upfront, these high-quality, high-performance homes contribute to significant energy savings and will be a quiet, secure space for years to come.
Want more details? Click here for our ICF page with specifics such as how thick ICF walls are, and what impact this has on homeowners!
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