Insulated concrete forms (ICF) are an appealing method of construction because they offer a good combination of strength and energy performance. For foundations, they offer a far more insulated wall than conventional CMU or poured concrete. There are those who don’t like the plastics in ICFs, but not all ICFs are made with petroleum products. Durisol has been making ICF blocks using only wood fiber and cement, and these blocks offer a number of advantages that make them an appealing construction material.
Durisol is not a new product, though it may be unfamiliar to some. The company has been around for more than 70 years, and the material has been in production in North America since 1953. Recently, we came across a Passivhaus project choosing to use Durisol for the exterior structure for a 4-story, 7-unit apartment building.
Durisol blocks are large (typically 24″ to 36″ long by 12″ tall) which, like most ICF systems, allow for fast construction. The blocks are stacked to create the wall and then filled with concrete to tie them together and provide the final strength of the wall. Typically, this means that less concrete is needed than with typical poured concrete. The blocks can be finished with stucco applied directly to the surface.
The basic Durisol block offers R-8 insulation. Thicker Durisol units are available up to 14″ thick which allows them to be used for taller construction, and many mid- and high-rise apartments have been built with this material. The thicker units are also available with added insulation inside the core which increases the R-value (to as much as R-28 with 4.5 inches of rockwool mineral fiber insulation. By putting all the insulation to the outside face of the block, Durisol ICFs can have better performance than ICFs where the insulation is evenly divided between the inside and outside faces.
Durisol walls are also good for controlling noise, which is another factor that makes them a good choice for multi-family housing projects. Durisol is also fireproof and offers a 4-hour fire rating. The material will not burn or offgas toxic smoke in a fire, and since the material is naturally fireproof, there is no need to use brominated fire retardants or other chemicals of concern.
Photo credits: Durisol.