Insulating concrete forms (ICFs), also known as insulated concrete forms, are used in many developed countries to create highly durable and efficient structures. Developed in Europe after World War II, the forms are typically rigid foam blocks made of polystyrene or polyurethane. Sometimes they’re made from polystyrene beads bonded with cement, cement-bonded wood fibre, or cellular concrete.
The forms interlock to create a stable wall system and are filled with concrete. The forms can be made as sheets to which plastic or metal fasteners attach to create two walls with a central void, or they can be formed as complete blocks with central voids. The forms remain in place to provide insulation value and an air barrier.
As with any other building method, ICFs have their pros and cons. Benefits of the system, proponents claim, far outweigh the drawbacks. Concrete is certainly durable, with the ability to withstand rot, pests, fire, and extreme weather such as cyclones, tornadoes and earthquakes. A home in Mississippi that employed ICFs is reputed to be the only home in the area to withstand Hurricane Katrina in 2005.
Homeowner and builder, Scott Sundberg, a structural engineer, designed and built the structure to withstand the area’s hurricanes, and the structure held up remarkably well to the storm’s seven-metre storm surge and winds of 200 kilometres per hour, while neighbouring homes were swept away. As for cost, Sundberg noted that “using concrete adds about 10 to 15 per cent above the cost of conventional construction.”
Critics point to the carbon footprint of concrete, as cement manufacturing is estimated to contribute about five per cent of global CO2 emissions. Cost may also be higher than other building methods, though that can be hard to judge, depending on the methods chosen for other systems in the house. In addition, in areas without extreme weather events, there may be no reason to exceed the minimum code standards to build a stronger structure.
So far, ICFs are not much used in Australia, but the adoption of a particular building system may actually have little to do with its cost/benefit ratio. Dr. Paul Downton, architect and writer, author of Ecopolis: Architecture and Cities for a Changing Climate, noted that “construction systems that are new to the market have to contend with the inertia of established systems.”
Brick veneer building techniques, for example, may be the favoured method in Australia because of history, business, or economic considerations, not because they’re the “best” methods.
“The domestic construction industry has developed to favour brick veneer building techniques and the entire supply chain reflects that,” wrote Downton. “The entire system favours a particular kind of construction that has, in turn, refined its costings and the inter-relationships of component suppliers over time.”
Building codes can also play an outsized role in the ubiquity of different building systems.
“There would be a level playing field for double-glazing, for instance, in Australia if the National Building Code required insulated glazing units like the codes do in many other countries, such as the UK,” Downton said.
One of the most common dings against concrete buildings is the carbon footprint of the structures. According to Downton, ICF structures may be acceptable if the structures save energy compared to conventional buildings.
“If it can be demonstrated that the ‘carbon investment’ required to build with ICF pays off in energy-saving over the anticipated life of the building it may yet become a construction system of choice for the increasingly climatically challenged environment that global warming is promising to deliver,” he noted.