EPS Sandwich Walls

We are developing wall systems that use reconstituted Styrofoam (aka EPS or expanded polystyrene) as the middle insulation layer of Structural Insulated Panels - SIP’s. There are several companies that are currently offering Concrete SIP products and services with panels made with new EPS. (see links below) We are exploring the possibility of replacing the new EPS with recycled material.

Some of the challenges:

Full Cost Effectiveness: Concrete SIPs using new EPS are cost competitive with standard wood stud and plywood wall systems with many long term advantages in reduced energy and maintenance costs, increased strength and durability, and greater resistance to fire, insect damage and sound transmission.
The challenge is to keep the cost of using local recycled EPS competitive with new material including the cost of shipping. Each step in the process will need to be carefully designed for efficiency and minimal environmental impact.

Collecting: There seems to be no shortage of Styrofoam to be recycled or desire in many people to save it to be reused in some way. With flyers, samples and bags available at the Bayside post office we were able to collect about 35 cubic yards of large EPS chunks in two months. With the material accumulating quickly we took down the flyer and were able to reduce the flow dramatically.

Storage at Collection Site:

Shredding: The Shredder is coming soon.

Cubing: We now have a 20" x 20" hot wire grid cutter with an eight foot in feed chute. The chunks advance in 1" steps on a conveyer belt while the grid cutter at the end of the chute goes up and down intermittently in 1" steps cutting the chunks into 1" cubes. It sounds simple but it has been a fun challenge to get all the components working together properly. The cubes could actually be used as they are for package filler like the Styrofoam peanuts. I will get some pictures and perhaps a video of the cutter in action.

Transporting

Storage at Job Site or Panel Assembling Plant

Reconstituting Recipe: A combination of cubes, bits and beads, portland cement, acrylic adhesive and water. Any input on this (other additives) would be greatly appreciated.

Mixing: At this time I am mixing in plastic garbage cans with a mixing rod in a large electric drill. Ultimately we will want to mix in a mortar style mixer with modified paddles and a bottom auger/pump to a hose for placing.

Placing: We may be able to place the shredded material between floor joists and in walls between studs with a wet blow in process similar to the way cellulose insulation is placed. For the sandwich walls, we will dump it into wall forms from the garbage cans until the pumping system is developed.

Cleanup: It is important in all phases of working with EPS to keep the little bits of the stuff contained and out of the environment. With cleanup after mixing the extra step is to run the wash water through a fine screen.

Links:

http://www.sipcrete.com/index.htm

http://www.tridipanel.org/index.htm This one has a fair amount of Technical Specs and engineering available online.

http://www.solarcrete.com/

http://www.greensandwichtech.com/

http://www.dur-o-wal.com/prod/singlewythe.html This company sells a wire truss reinforcement that will be used to tie the inside and outside layers together.

http://www.helixfiber.com/ This steal fiber reinforcement is very promising and would greatly reduce labor. It is also possible that we may be able to eventually shred tin cans and use them in the same way.