What is Durisol?
Thoughts on an Insulated Concrete Form.
Durisol is an insulated concrete form (ICF) wall forming system. The Durisol wall form material is made from shredded (often recycled) wood material steeped in a proprietary solution to essentially petrify or denature the wood material. This is then combined into a cementitious slurry and molded into the ICF wall forms and mineral wool insulation plugs inserted taking up part of the hollow interior core space.
Wallform blocks are dry stacked to form walls proceeding in a similar manner to the many systems using polystyrene ICFs. The stacked wall form assembly has steel reinforcing rods horizontally and vertically and the cores are filled with concrete (usually pumped) producing a structurally strong, non-combustible, non-biodegradable, acoustically absorbent, well insulated wall.
Durisol is produced in Canada (southern Ontario) and has seen extensive use in recent years in that region as well as the Detroit region of the U.S. There is an exactly similar product named 'Faswall' produced in South Carolina
Over the past five years, Coldham & Hartman Architects has designed and documented a number of projects using this material and exploiting its unusual properties:
- A reliably well insulated masonry wall — (Type 3 construction under the BOCA code).
- A completely non-combustible wall assembly — the wall form material, as well as the mineral wool insulation and concrete core.
- Air and vapor permeable – both the wall form material and the mineral wool insulation
- No capacity whatever to "lift" moisture through capillary action (though the same is not true of the concrete core). In fact, both materials can act essentially as a drainage medium.
- Completely non-biodegradable wall system that can be deployed equally well for below or above-grade construction.
- Noise reduction coefficient (NRC) of greater than .75
- A suitable substrate for all forms of stucco and plaster applications.
- The wall form material accepts mechanical fastening of wood and other furring materials using screw fasteners. (Nails fall out too easily.)
- The wall form seems appropriate use of the mixed hardwood forest produce of the US northeast, which otherwise has limited use in building.
Coldham & Hartman Architects has employed the use of Durisol in the following projects - each for a specific set of reasons, which are described as follows:
Camp Alice Rich Northrop
Before the Durisol was proposed for the replacement of the principle building at the camp in southwestern Massachusetts (after its predecessor was destroyed by fire), the non-combustibility of this material as the principle load-bearing structure was a suitable choice for a building with this history.
Northrop hosts children from the New York City area. The sound attenuation properties in conjunction with the large interior multi-use space were attractive. We proposed extending the stucco finish only to 6' and leaving the unfinished Durisol material above that height - allowing the sound attenuation properties to work to their greatest advantage.
Our client's design requirements included a single-floor dwelling with continuous on-grade indoor-outdoor connections, as well as a building that could accept plants growing up and over the exterior walls. Here, Durisol's complete non-biodegradability was its key virtue. With the capability of extending the wall unbroken from foundation to roof we can achieve an almost unbroken extension of the interior floor plane to the exterior. We can also proceed with some confidence that the building can be engulfed with planting without constructional detriment.
Our client also came to appreciate the "breathability" of the wall system, particularly with a lime-based plaster applied to the interior walls, which maintains the wall's moisture permeability. The exterior wall acts as something of a humidity reservoir with excess humidity taking up by the exterior walls and released back to the interior as interior RH levels diminish.
Vipassana Meditation Center
The Center is a large campus in a small New England Town with a volunteer fire department, and VMC requested additional buildings that would endure for hundreds of years. For this project, therefore, both the non-combustibility and non-biodegradability were Durisol's primary attractions.
VMC had constructed approximately 50,000 square feet of predominantly wood-framed buildings prior to our office's involvement. Adding more combustible building was , and sought material combinations (Durisol, metal roofs, finished concrete interior floor, etc.) that would reverse this trend.
There was an opportunity to downsize the heating system equipment in this new 30,000 S.F. institutional residential building, which provides 100 accommodation suites, each with its own bathroom. Domestic hot water accounted for approximately half of the total heating load, with space heating and ventilation air tempering accounting for the remainder. The well-insulated high-mass wall provides a relatively long-time constant for the interior space (i.e. the interior space heats or cools slowly in response extreme exterior temperature changes). This property, which is primarily a function of the high-mass Durisol Wall, allowed us to dedicate all of the heating capacity to serve their hot water heating for short periods, abandoning the space heating altogether during that time without an adverse affect on interior comfort. The capability of alternating the heating between the two major loads rather than size boilers to handle both loads simultaneously allowed a considerable reduction in the size and expense of the boiler capacity on this project. The high-mass Durisol Wall System was a key element in the building's performing in this regard.
Download PDF:Link to PDF
What is Durisol?