Insulated Concrete Forms

Insulated concrete forms are prefab building components made from blocks of rigid insulation, most often from different types of polystyrene foam. The blocks are subsequently linked together and include an empty cavity in the middle for pouring a concrete filler.

ICFs were originally developed for use as foundation walls, as they incorporate water resistance and insulation properties. More recently, some builders have been using ICFs for above-ground walls as well, connecting foundation and walls into one solid structure.

A home with the walls and foundation built with poured concrete can’t, however, be towed or moved. Many people interested in the tiny home movement are young folks looking for an economical pathway to homeownership, but who aren’t ready to settle down long-term in a specific place.

ICFs: Pros and Cons

Some other advantages associated with tiny homes built from ICFs include:

Durability: When constructed correctly, ICF construction can last hundreds of years. Poured concrete walls offer strength and robustness not usually associated with lightweight tiny homes on wheels. One manufacturer of ICF blocks states that its products “are disaster-resistant… (and) can withstand severe winds exceeding 200 MPH and projectile debris moving over 100 MPH.” Tiny homes located in areas prone to severe weather can, if built with ICFs, be more resilient. ICFs also offer an increased level of resistance to fire and earthquake damage.

Built-In Insulation: ICFs are incorporate insulation directly into the foundation and wall components. In most cases, ICFs are pre-manufactured to have an insulation rating between R-20 and R-22. This insulation rating might not be enough insulation for tiny homes located in areas with cold, long winters. Still, it will offer more than enough insulation for regions with more moderate climates. Additional insulation can be added to the outside of the walls to increase the thermal performance of the home.

Tight Building Envelope for Energy Efficiency: Because ICFs are prefabricated, they can efficiently be designed to create an airtight building envelope. Tiny homes that use ICFs, then, can often be built to passive house standards. Because of reduced interior space, many airtight, highly insulated ICF homes might be able to eliminate the need for mechanical heating and cooling.

Easy to Incorporate Sustainable Wall Alternatives: Most homeowners may not want polystyrene forms visible on the interior or exterior of their home. Fortunately, the foam blocks or “casing” of ICFs can easily be covered up with sustainable cladding or interior wall coverings. For interiors, natural earthen and mineral plasters work great with ICFs. For exteriors, wood cladding sourced from salvaged or reclaimed barn boards is an attractive option.

Quick Build: ICF homes are relatively quick to build. According to homeowner Luke Edwards, who is constructing a new, but not tiny, home for his family in Trinidad, “the speed of ICF construction was really a deciding factor for us as we considered how to build our new home.”

Insulated concrete forms also come with some sustainability drawbacks that homeowners should consider. Some studies suggest that the concrete industry might be responsible for upwards of 8 percent of total greenhouse gas emissions. The foam used in ICFs is often sourced from petrochemicals like polystyrene. Not only is this a non-renewable resource, but some of the foam options might also lead to VOCs leaching into a tiny home.

Considering ICF construction for your future tiny home? Consider using concrete with fly ash content, a recycled material that will lower the cement’s carbon footprint. Also, these green cement options would reduce the carbon footprint of an ICF home.