ICFs provide monolithic concrete which satisfies the air barrier code requirement minimum. However, seeking to build to a higher standard, many architects are adding a vapor permeable fluid applied membrane to fully seal the envelope. Impermeable membranes are also sometimes used on coastal installations.
Ultimately, code requires the ICF foam surface to be covered and not exposed to the elements requiring the addition of brick, stone, or stucco facade.
The polypropylene webs that hold the panels together and rebar in place within the core also extend within the foam to almost the face of the wall on both sides (15.8 mm [0.625 in.] away). They have approximately one-and-a-half times the axial pullout of a 2×4 and are used to directly attach sheet rock and minor cabinetry. For heavy items, such as cabinetry or steel embed connections, the concrete can be allowed to flow to the face of the form.
For storm shelters, rough openings for windows and doors are typically framed with lumber, which is removed after the pour to provide direct anchorage to the concrete. Steel integrated framing assemblies are also available on the market which encase the rough opening in thermally broken steel for attachment of windows and doors. Electrical and plumbing is also cut into or routed in the foam post-concrete pour. Sheetrock is attached directly to the foam via the 38 mm (1.5 in.) wide furring strips that run floor to ceiling every 203 mm (8 in.).
Brick ties are available to attach to the external webs; however, for most storm shelters, brick ties are usually embedded in concrete prior to pouring.
The endurance and energy-saving benefits of ICFs can apply to any type of structure, from storm shelters and single-family homes to apartment buildings and schools.6 ICFs are especially useful for building critical infrastructure, such as hospitals and fire stations, to ensure consistent services during an emergency.
ICFs offer continuous exterior insulation, which virtually eliminates thermal bridging so, in a power outage, ICF buildings maintain interior temperatures for much longer than those using insulation installed within the stud cavities of wood- or steel-framed construction. Thus, they are less reliant on HVAC systems to keep occupants safe and comfortable.
To assess the durability of ICF construction, ABC Domes and Wind Science & Engineering Research Center Debris Impact Test Facility at Texas Tech University conducted debris impact testing, in accordance with ICC 500 and FEMA criteria. A 6.8 kg (15 lb) 2×4 was shot at an ICF wall at 161 km/h (100 mph) to simulate airborne debris hitting a structure at 402 km/h (250 mph), equivalent to an F4 tornado. The results indicated that while the wood penetrated the foam, the concrete core stopped the projectile, keeping the structural elements of the wall intact.7
In real-world hurricanes and tornadoes, ICFs have proven themselves stronger than wood-frame construction. In 2018, when Hurricane Michael struck Mexico Beach, Florida, hundreds of oceanfront properties were demolished or severely damaged; except for one. An ICF home, known as the Mexico Beach “Sand Palace,” stood alone and unscathed among the wreckage.8
