This type of exterior wall system is becoming more popular due to the surge in green building construction. The first patent for the application of an ICF was registered in the 1960's. Insulating concrete forms or molds have built-in insulation for accepting reinforced concrete. ICF's are stay-in-place polystyrene forms that have proven to be energy efficient, cast in place reinforced concrete walls. This wall system can be used to create residential or commercial structures. Unlike conventional concrete forms, these stay-in-place after the concrete is placed in the wall cavity of the forms and serve as form, insulation, exterior wall sheathing, and in some cases wall studding. ICF wall systems allow for flexible design, and a wide array of architectural styles and treatments. The wall becomes a high performing wall that is structurally sound, insulated, has a vapor barrier, and is ready to accept final exterior and interior wall finishes.
There are many manufacturer's of this type of stay in place wall system. The wall systems can be grouped into three different systems:
o Panel Systems are the largest units, as big as 4 feet by 8 feet. The panels typically have flat edges and are connected to one another with extra wall fasteners.
o Plank Systems include units of long narrow planks of foam held a constant distance apart by steel or plastic ties. Typically, these planks are 8 foot long and 8 or 12 inches high. The planks have notched, cut, or drilled edges that they tie into. Additionally, the ties connect each course of planks to one above and below.
o Block Systems include units varying in size from standard concrete block sizes and up to much larger 16 inches high by 4 feet long. Along the edges are teeth or grooves and tongues for interlocking. They are able to stack without separate fasteners, in the same manner as children's lego blocks.
The various wall systems types have different cavity shapes – flat, grid, or post and beam. There are structural and architectural advantages for each type cavity.
There are many benefits and advantages of using these wall systems that promote greater comfort and lower energy bills. ICF's have a high R-value. Four inches of ASTM C578 polystyrene foam insulation combined with a five inch concrete wall would typically be rated a R-17. Nothing blows through the reinforced concrete, eliminating drafts, thereby have a very minimal air infiltration into the building envelope. The thermal mass of the exterior wall envelope eliminates temperature peaks and valleys. Energy savings have been estimated to be 25% to 50% for an ICF building versus wood framed or steel framed buildings.
Safety and health benefits include no CFCs, HCFC's, or formaldehydes, and also no wood to rot and mold. Typically the structures provide a two hour fire rating and highly termite and pest resistant. Concrete homes have proven track record to withstand the ravages of nature – hurricanes, tornados, and fires. This safety facet typically refers to reduced insurance premiums. The structures can also eliminate outside noises due to their high sound absorption qualities.
Disadvantages including adding or moving doors, window, or utilities after the building is complete. Concrete cutting tools are needed to perform these tasks. Typically, initial construction costs be anywhere from 55 to 15% more than conventional wood built structures.
Look for a future increase in the use of the ICF wall systems. The durability of the system coupled with the push for a green environment and greater energy efficiency will lead the way. Additionally, there are federal energy tax credits for this type of building system that many times stir the interest for utilization.