The ICF building block has been an innovative addition to the green-building phenomenon and one that has remained largely unchanged since its inception. ICFs may have improved their R-values and increased competition has seen changes in pricing, but the basic structures have remained the same. The ICF structure consists of an EPS shell bolstered by plastic braces. The ICF blocks are stacked, rebar is fitted into the braces to provide tensile strength and the hollow core is filled with concrete. The finished product provides improved resilience to fire, floods, earthquakes and severe storms while creating an effective building envelope that drastically reduces quantities of energy required to heat and cool the building.
ICF Block Characteristics
Most ICF systems are manufactured from two 2.5 inch-thick (65mm) EPS boards. Combined with the insulating effect of the concrete core and the exterior and interior finishes, the building owner can expect an R-value of around R-22, although these figures vary from one manufacturer to the next.
The thickness of the concrete core differs from build to build, depending on the wall’s structural requirements. The concrete core can vary in thickness from 100mm (4 inches) to 300mm (12 inches) with a commensurate variation in thermal mass of up to 300%.
Technological advances in ICF design: Graphite-impregnated blocks
As green-building techniques gain traction and building codes demand improved performance, ICFs have undergone several technological advances designed to improve R-values without changing the basic structure due to the prohibitive costs of creating new block molds.
One method is to coat EPS beads with graphite prior to expansion which gives the EPS blocks a slightly grey or metallic colour. Graphite-impregnated ICFs are said to have an R-value that is 20% higher than non-coated EPS systems. However, the functional R-value is far lower with an R-Value closer to R-24.15, rather than the R-26.5 claimed by the manufacturers.
Thanks to their darker colour, some builds have been hampered by melting in the corners of the EPS when exposed to sunshine. It’s thought that radiant heat from the sun caused the blocks to melt.
Technological advances in ICF design: Thicker Insulation
Another way to improve ICF R-values is to increase the thickness of the EPS layer. This can be achieved by adding additional sheets of EPS to the inside of the blocks. This is a labour-intensive process that delays construction and is prone to damage or displacement when the walls are vibrated. A better solution is the Amvic 3.30 which simply extends the wall of the existing EPS design. The ICF walls are thicker and are molded as one unit, thereby avoiding the problems of displacement and damage while adding incredible R-value.
The engineering of the blocks remain the same. The new ICF blocks are 3.25 inches thick (an increase of 30%) on each side for a combined thickness of 6.5 inches which increases the R-value from R-22 to an impressive R-30.
The added width provides advantages beyond the improved R-values. Plastic braces are spaced every 8 inches on center and have proven to be the strongest block on the market.*
The blocks also feature deep 1-inch grooves that make up the Amvic FormLock™ systems for easy alignment and a recess on the interlock for drainage. The corner cross ties also sport a 6 inch-by-1 inch attachment area every 16 inches for exterior siding and finishes.
The new improved Amvic 3.30 is also the largest corner block available at 7.78 sq. ft. of wall area and is the strongest corner block in the industry. They also boast the largest 45 degree corner in the industry at 6.22 sq. ft. of surface area.
* According to Canadian Construction Material Center forming capacity tests.