Commercial construction using insulated concrete forms (ICF) is an option available to building designers in certain situations. But there are important considerations to weigh when comparing ICF construction to competing concepts.
What are Insulated Concrete Forms?
ICF walls are created by pouring reinforced concrete into hollow panels, typically made of either extruded polystyrene foam or expanded polystyrene. Before the concrete is poured, the interlocking units are dry-stacked, which is a bit like building with Lego bricks.
Once the concrete is poured and cured, the ICF panels form a permanent exterior framework that can be used in structure up to five stories high. The inner and outer polystyrene panels remain permanently in place, usually separated by 6 – 8 inches of concrete reinforced with rebar. These panels allow the installation of plumbing and electrical conduits later on in the process. Drywall can be affixed to the inside panels, and exterior cladding can be attached to the outside panels.
ICF construction initially gained momentum in part because it provided greater wind resistance and energy efficiency than wood-frame residential construction. Insulated concrete forms have also been used in commercial structures that are only a few stories high.
The Disadvantages of ICF
Although there are advantages to ICF construction, it has its share of problems:
Construction Issues — During construction, the process of filling an ICF wall with concrete sometimes causes problems. Experienced contractors know how many feet of concrete can be poured at a time without risking so-called “blowouts.” When concrete is poured at too rapid a rate, it can burst through the polystyrene panels, which can result in a costly cleanup and construction delays.
As it is poured, the wet concrete must also be sufficiently vibrated to eliminate all air pockets and voids (a tendency often referred to as “honeycombing”). Hollow areas can reduce the strength of an ICF wall, decreasing its wind resistance. In extreme cases, an ICF wall containing voids may even be unstable.
Groundwater and Insects — Designers and architects must account for the fact that regular ICF panels are vulnerable to groundwater intrusion. Drainage tiles and drainage sheeting are often required to minimize the adverse effects of the resulting moisture. These components add to overall costs.
Although termites are usually associated with wood consumption, they have, on occasion, also burrowed through ICF polystyrene panels and tiny cracks in the concrete. Once they get through an ICF wall, they may go on to feast on joists, flooring and other wood components. Although the termite problem can be addressed proactively through a variety of means, these all represent additional steps to the exterior wall construction process.
R-values and Energy Efficiency — It used to be easy to demonstrate that the insulating value of ICF panels is higher than that of traditional wood stud walls containing fiberglass insulation. But since codes now require continuous insulation, ICF has now lost that advantage.
With the arrival of the 2015 International Energy Conservation Code (IEEC) updates, the energy efficiency of exterior wall systems has become more important than ever. While companies want to accumulate LEED points for energy efficiency, they also want an ideal balance between R-values and wall system costs.
Polystyrene Panels and Recycled Content – The concrete poured into the ICF panels may contain fly ash or other recycled material, and the rebar may include recycled steel, but post-consumer waste cannot be used in the polystyrene panels because of the potential for contamination.
Bautex Block wall systems are a cost-effective, energy-efficient alternative to ICF walls. To learn more about using Bautex Block for your next project, please contact us.