Flex Formation

Insulated concrete forms, developed in the mid-1960s as a method for forming more energy-efficient concrete foundation walls for the residential market, are gaining acceptance as a viable alternative to light-gauge steel frame, wood frame, brick masonry, and precast concrete construction in the nonresidential market.

ICFs are 4- to 10-inch-thick concrete walls poured between expanded polystyrene (EPS) forms that stay in place permanently as an insulation barrier. A growing number of Building Teams are turning to ICFs to build load-bearing and infill walls for schools, theaters, warehouses, churches, banks, hotels, multifamily buildings, and college dorms, says Joseph E. Lyman, executive director of the Insulating Concrete Form Association, Glenview, Ill. He says the nonresidential market, especially light commercial and industrial construction, represents about 20% of all ICF business.

"It's not just about energy efficiency any more," says Lyman. Building Teams are taking advantage of the technology's inherent qualities in design flexibility, acoustic and thermal control, jobsite safety, cost efficiencies, and ease of installation. The Department of Defense has even begun to probe ICF technology for its resistance to blasts.

"We've found through blast demonstrations that ICFs lessen the impact of air pressure placed on the lateral face of a wall," says Lyman. "When an air blast hits the wall, it compresses the EPS foam against the concrete."

The DoD and other government agencies are planning to perform full-scale blast tests of ICF building systems later this year. Clearly, the military sees potential in the concrete forming system.

A case in point is the new 140,000-sf Florida Armed Forces Reserve Center currently under construction in Pinellas Park. The three-building multi-use facility is one of the first ICF applications for force resistance. The project consists of 6- and 8-inch-thick concrete walls sandwiched by 21/2-inch-thick EPS foam panels. Rising 44 feet high in certain portions, it is one of the tallest wall structures to be constructed using ICFs.

According to William Murray, project manager with architect of record URS Corp., San Francisco, ICF construction was a "cost-effective way" to meet the military's force protection requirements. He says traditional masonry construction would have been "prohibitively costly" (about 25% more than ICF), requiring nearly every course of block to be reinforced with tie beams and vertical reinforcing.

A three-building, 140,000-sf Army Reserve training facility under construction in Pinellas Park, Fla., near Tampa, is the first military project to employ insulated concrete form construction for its resistance to blasts.

Murray estimates that using ICFs also cut at least one month off the wall construction schedule. For instance, it allowed the team to use gypsum board as the interior wall surface throughout the building, even in warehouse locations. For the exterior cladding, the team applied a synthetic stucco coating directly to the insulated form.
 

"Ordinarily, gypboard would not be an acceptable interior finish for a warehouse, because it is too easy to punch holes through when it is fastened to steel joists," he says. "With ICF, every square inch of the board is solidly backed, making it far more durable."

The R-value and thermal mass of the wall system should result in lower energy usage, another key requirement for Defense Department projects.

"The thermal mass seeks an average temperature and just stays there," says Murray. By holding a steady temperature, there's less reliance on conditioned air. This is especially important for reserve facilities, which are usually occupied only a few weekends each month.

Contractors working in colder climates have found the forming system beneficial because the insulating effect allows for concrete pours in temperatures as low as -5 F, according to research conducted by Skokie, Ill.-based consulting engineer and testing laboratory Construction Technology Laboratories Inc.

The latest ICF systems enable Building Teams to construct walls up to 50 feet high by incorporating thicker wall designs and bracing/scaffolding systems.

"I know plenty of crews that have poured in temperatures as low as -15 F," adds Lyman. He explains that the heat created when the cement, aggregate, water, and sand are mixed is "trapped" between the insulation panels. "Concrete can potentially freeze at 29 F, so it's a huge difference."
 

An ICF primer

Lyman says there are three basic varieties of ICF systems:

• Block systems are factory-molded with special interlocking edges that allow them to fit together. They have the smallest individual units, ranging from 8 x 16 inches to 16 x 48 inches.

• Panel systems have flat foam edges that are interconnected using ties. They are assembled into units — either on site or by a local distributor prior to delivery — before being set in place. Panel systems range in size from 1 x 8 feet to 4 x 12 feet.

• Plank systems are similar to panel systems, except that they generally use smaller sizes (8-12 inches high and 4-8 feet wide) and are outfitted with ties as part of the setting sequence, rather than being preassembled into units.

Lyman says one potential growth area for ICFs is infill walls for mid- and high-rise multifamily projects. He points to a recently completed 11-story condominium near Fort Myers, Fla., where the Building Team substituted concrete block construction with ICFs, cutting more than a month off the wall construction schedule.