By: Jim Nugent, Sales Representative - Architectural Products
Most people connected to the construction industry have some awareness of EPS Geofoam. Often the awareness is of high profile road and bridge projects or a green roof where the material is easily seen by the passer-by. The volume associated with these types of projects at times can be mind boggling. Some bridge approaches have been constructed of EPS Geofoam that are over 30 feet tall!
As the use of EPS Geofoam evolved it moved inside buildings to create stadium seating risers for movie theaters and auditoriums. Today EPS Geofoam in being used in countless applications for infills to create elevation changes inside a building. For example; ADA ramps, or to fill voids for truck docks or swimming pools that are being taken of service, or converting school auditoriums to level floor areas, or creating new elevations or filling low areas in upper stories of a multi story building where excessive weight can be a concern. The new applications continue to grow.
With the growth of new applications some confusion has surfaced about when is EPS Geofoam and when is EPS a perimeter or sub slab thermal insulation and when is it both? The confusion can be enhanced by the fact that there are two ASTM standards for EPS; The Geofoam standard which is D-6817 and the thermal insulation standard which is C-578. Within both D-6817 and C-578 there are 7 different EPS material types and yes, (to keep things simple) the 7 material types are the same in both standards.
So why do we need two ASTM standards for the same 7 material types? To those of us in the EPS industry who deal with this on a daily basis the answer is really simple, but I can not lie, when I first explain in detail the differences in the two EPS standards you can start to get a “glazed look” in the eye of your audience. Even as I am typing I can sense the reader drifting away……..
So why do we need the two standards? Measuring compressive resistance!
We are used to hearing compressive strengths of EPS insulation measured at 15 psi, 25 psi, 40 psi and 60 psi. Those compressive resistance parameters are found in the insulation standard C-578, and allows for 10% deformation of the material. That may be fine for a foundation wall but for a structural or civil engineers who are designing the EPS to support a load, that percentage of deformation is not acceptable. In the EPS Geofoam standard D-6817 compressive resistance is measured at 1% deformation being acceptable.
When EPS is being used as a thermal insulation for a roof, a perimeter wall, or as an under-slab insulation C-578 is correct design standard and typically will be in division 7 of the specification. When EPS is used to support a load or reduce force, then D-6817 is the correct design standard and you should find it referenced in Division 3, 17, 31 or the general conditions.
So when is EPS both Geofoam AND a thermal insulation? Typically when it is placed under a concrete slab over unstable soil or on a deep foundation to reduce lateral pressure. In both cases the excellent thermal performance and strength characteristics of the EPS are both beneficial to the structure.
EPS has long been valued for its versatility. From the frost line to the roof line there is not a better material for thermally insulating the building envelope and for solving load reduction problems as strong yet lightweight Geofoam fill.
I was wondering if you know of any projects or case studies where Geo foam has been used as under and around gunnite in ground pools as insulation for radiant heated swimming pools?
Most of the pool applications Geofoam is used to lighten the load of the pool on the structure below. However, being that EPS is also used as a below-grade insulation it’s quite possible that it would do well in this kind of application. Here is an example of Geofoam in a pool engineering application: http://www.achfoam.com/media/docs/Projects/High%20Adventure%20Recreation.pdf.