Something has Changed! But EPS itself Has NOT!

By:  Dale Mullikin, Sales Representative – Architectural Products

Water Absorpotion of EPS XPS ISO

Over the last five years I have done over 300 Lunch & Learns with architects and engineers. There seems to be a common occurrence each time I do a presentation. Architects and engineers either don’t know what is in their Thermal Insulation specification or they have not looked at it for years. Most ask, “What has changed?”

I say, “A lot has changed, yet nothing about EPS itself has changed!” Fourteen years ago when I started selling Expanded Polystyrene, I was told that you can’t use EPS (Expanded Polystyrene) below grade. Why? I was told to do a test and find out why. I took a piece of EPS and a piece XPS and put them in a bucket of water for 24 hours. Then I weighed them and learned the XPS took on less water. I was then informed this water absorption test, ASTM C272, is part of ASTM C578. Bummer!  When architects and engineers look at these test results it seems logical to choose XPS for their Thermal Insulation specification.

Well it is time to look at some NEW test results because SOMETHING has CHANGED! There is some new information from a test that lasted 15 years not just 24 hours. The water absorption test was performed by an independent third-party testing firm, Stork Laboratories, that compared EPS and XPS side by side below grade for 15 years. Not 24 hours but 15 years! That is a real-world test! When I tell architects and engineers about this test they realize something has changed and it is time to rethink their Thermal Insulation specification. EPS itself has not changed, but this real world test has changed everything.

The test results are shown in Technical bulletin 1016. I also carry a letter from Stork Laboratories that states this information is correct. So lets talk about water absorption facts. After 15 years EPS had 94 percent r-value retention and XPS had 52 percent r-value retention. What an amazing difference. I have always known that that EPS r-value warranty is better than the XPS r-value warranty. Basically the warranties make the r-values similar with EPS being a little better than XPS. When water is introduced to rigid insulation it will impact r-value. What is amazing is that XPS took on almost four times the water as EPS in that 15-year test.

Architects and engineers always want to know what has changed in the EPS. The answer is, nothing has changed with EPS other than all EPS used for below grade applications is UL certified and stamped. EPS has always been permeable; water goes in and water goes out. Table two in Tech Bulletin 1016 shows that after four weeks EPS lost almost all the water it had absorbed. Table one shows that when water leaves the board r-value returns. XPS does not have the same results with the water it absorbs’ therefore the r-value does not return.

Architects and engineers are hearing this information and starting to change their specifications. Using EPS for below grade insulation seems to be a new trend. Last fall EPS was used for the below grade insulation at Carver Hawkeye Arena in Iowa City, Iowa.

Something has changed, but it is not EPS. Architects and engineers are changing their thermal insulation specifications to include Expanded Polystyrene for their below grade insulation.

About Dale Mullikin

Dale Mullikin has been in the EPS business for 14 years. He has done hundreds of educational Lunch & Learns for architects and engineers all over the midwest.
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