I need to show that 4″ of EPS is weather resistant
I am working with a product from South Africa called Imison.
Web page: http://imison.com/
The core is 4″ thick type 1 EPS panels that meet ESR1946/ASTM C578. I understand that 4″ wide EPS is waterproof/weather resistant due to it’s permeability rating and should satisfy the IBC in regards to being a water resistant barrier however I do not know how to prove it.
I need to prove that the 4″ of EPS resist water, however if water does get in it can diffuse out.
When EPS covers conventional wood construction such as with EIFS there are issues with mold and rot however with Imison there is no wood the EPS is the solid core of the wall panel.
The EPS is joined with 3-5/8″ metal studs, covered with metal lath, and sprayed with 1′ of stucco/plaster on the interior and exterior.
Imison has built many structures in South Africa and has its full Agrement Certification. Currently we are working on receiving our approvals from ICBO and ICC in the US.
The product boast nearly twice the R-values, great STC ratings, will not mold, rot or mildew, and can be erected in half the time for less then conventional wood systems
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Replies
Daniel,
The International Code Council has established procedures for manufacturers of materials who propose that their materials are equivalent in performance to the code mandated material for use as a water-resistive barrier (WRB), which is asphalt felt.
Manufacturers must submit proof to the International Code Council Evaluation Service (ICC-ES). In the case of rigid foam products aiming to be accepted as a WRB, the relevant acceptance criteria document is AC71, “Acceptance Criteria for Foam Plastic Sheathing Panels Used As Water-Resistive Barriers.”
For more information on this topic, see Using Rigid Foam As a Water-Resistive Barrier.
Must all EPS be tested using AC 71 to be considered a water-resistive barrier "WRB"?
I was told in the IBC there is a section referring to water permeability. Where it specifically says items with a perm rating <1 can be considered a weather resistant barrier. are you familiar with this?
I was also told the perm rating on 4" of EPS is <1, therefore the 4" of EPS should be consider a WRB.
There are references in the tables of ASTMC578 however I don't know how to read then nor do I have a copy of the IBC to look into the permeability claim.
Daniel,
As far as I know, the situation is as I described in my first answer. If a manufacturer wants a rigid foam product to be approved as a water-resistive barrier (WRB), the product has to comply with AC71. That's why AC71 was developed.