Atlas ThermalStar X-Grade Reviews?
Does anyone have experience using Atlas’s ThermalStar Product — X-Grade?
I am looking for an alternative to XPS in a below grade product. It will be used beneath the thickened edge (essentially a footer) of a monolithic slab on grade. The 25 psi version of this product seems like it could be a winner for me but I wonder if others have tried it out? What is your opinion of it?
I recently spoke with Bob Murphy of Universal Forest Products about this EPS foam board and it sounds like it has a lot of promise.
It is an EPS Foamboard available in 4′ x 8′ sheets in varying thicknesses. The X-Grade line is designed for use below grade and includes beeswax and a termiticide in it’s mix. The R-value rating is warranted to remain consistent over time (where the R-Value of XPS is known to decrease in correlation to water saturation as well as with it’s expiration of blowing agents). X-Grade is also somewhat breathable with a perm rating of 2.5.
Specs for X-Grade can be found here
http://atlaseps.com/products/thermalstar/below-grade
One lumberyard in my vicinity priced it for me at $42/ sheet at 2 â…œ” thick.
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Thought it prudent to add that I have no ties to Atlas - financial or other. Just looking for a good product.
The short sheet product spec contains a thumb on the R-value scale, listing only the 25F mean temp performance without specifying it's 40F mean temp or the 75F mean temp performance required for labeling. Unless your subsoil is permafrost the 25F mean temp is completely irrelevant.
http://atlaseps.com/wordpressfiles/wp-content/uploads/2015/10/LIT-1004-X-Grade-PIS-100215.pdf
That's great if you live above the Arctic circle and all, but to compare with other products you'd need to know it's performance at more reasonable mean temps. Under a 60F slab with 40F subsoil would have a mean temp of 50F, and would be a US climate zone 7 or 8 type of climate, so even the 40F performance wouldn't be relevant for slabs, but might be for walls.
The ICC-ES evaluation report for Atlas EPS products gives the R-values at the usual temperatures for testing and comparison purposes (75F mean). I've reproduced the table below. Here is the link to the evaluation report: Atlas EPS evaluation report from ICC-ES.
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