Insulated Concrete Forms
ICF Walls are Durable and Energy Efficient
Stay-in-place foam forms are well insulated, airtight, and strong
Most brands of insulated concrete forms (ICFs) consist of two parallel panels of foam held apart by rigid plastic spacers. Builders stack ICFs like Lego blocks, brace the forms, and fill the forms with concrete delivered by a pumper truck. The ICFs are left in place as a permanent part of the building.
ICFs are becoming increasingly common. Among their advantages over conventional wood-frame construction are low air infiltration, high thermal massHeavy, high-heat-capacity material that can absorb and store a significant amount of heat; used in passive solar heating to keep the house warm at night. , high strength and fire resistance, good sound-deadening qualities, and much higher insulating values than standard masonry construction. They can be used to form basement walls alone or for an entire wall system, including above-grade walls. According to the Portland Cement Association, using ICFs adds about 3% to overall construction costs compared with a conventional wood-frame building.
Types of ICFs
A variety of shapes and sizes
Most ICFs are made from expanded polystyrene (EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest.), although some manufacturers used different types of foam.
A common type of ICF is a hollow block with 2-inch-thick foam on each side, typically 16 inches high and 48 inches long. Concrete thickness can vary, depending on the application, from 4 inches to 12 inches. ICFs also are available as planks, usually 1x8s, and panels as large as 4x8s.
Internally, ICFs can form concrete in one of several ways: as a flat wall, as a grid, or in a post-and-beam pattern.
Good ICFs are adaptable and easy to erect
Besides being a system that goes together quickly and easily, ICFs give designers more flexibility than conventional concrete forms. Most ICF systems can be manipulated into curves and angles that require only minor on-site trimming and bending. Many form manufacturers will even create custom blocks or panels to execute your designs with no modifications, saving time and reducing construction waste.
ICF assembly is easy if you know what you're doing
In practice, it’s relatively simple to stack ICFs into walls, although bracing and leveling before the pour are critical. Each system goes together a little differently, so the manufacturer's instructions are a must-read before you start. Just like bricks or concrete masonry units, the first course sets the tone for the rest of the installation, so extra attention at the beginning will pay off. Cuts in the forms can make the concrete pour more shaky; avoid cutting corner blocks, use plenty of bracing, and secure large joints with scabs of plywood.
How do I attach an ICF wall to the rest of the house?
Steel channels secure the forms to a poured concrete footing; anchor bolts penetrate the top of the concrete as in a typical poured wall. Window and door openings that are framed with dimensional lumber go in before the concrete is poured. It may not always be necessary, but using spray foam to seal the forms to existing foundation walls will probably keep the pour a little neater.
Requirements for Insulating Concrete Form (ICFInsulated concrete form. Hollow insulated forms, usually made from expanded polystyrene (EPS), used for building walls (foundation and above-ground); after stacking and stabilizing the forms, the aligned cores are filled with concrete, which provides the wall structure.) wall construction can be found in Section 611 of the IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code.. Almost 30 pages in length, Section 611 includes numerous detail drawings and tables that help explain the code-approved use of ICFs.
If the building’s design follows the prescriptive guidelines outlined in the code book, plans don’t require the seal of an engineer or architect. Reinforcement specifications can be found in Tables 611.3 through 611.7. Standard floor and roof connection details are identified in Figure 611.7(1). Window and door opening details can be found Figure 611.7(2).
Plates that connect roof framing to ICF walls must be secured with 1/2-inch anchor bolts embedded a minimum of 7 in. and placed a maximum of 6 ft. on-center (611.9).