And just what if you put it over or under 1-1/2" R- Control EPS with termiticide in it?
You have no idea what kind of bubblewrap I used. It had the itty bitty tiny bubbles and was designed specifically to go under concrete.
I would do it the exact same way again. And will if I get time and money to do the shed. Except #5 bar and thicker floor. And probably put the vapor barrier under the foam.
6 bag mix with fiber, 10 ga wire mats. Pex clipped to the wire mats. #4 Rebar on 3 foot centers.
People use blue and pink board without realizing it ***** up water and is worthless when wet.
Most plastics will transmit air and water vs osmosis. The rate depends greatly on thickness and type of plastic but it happens.
Bubble wraps eventually will not have air in them no matter what sizes bubbles or thickness of plastic. Bubble wraps with weight on them will do it faster.
Bubble wrap will provide a barrier, but other cheaper products will to, why put it over foam?
As for xps vs eps, there is ONE(and only ONE) study, where in Minnesota they burred foam at 6 feet depth. Unfortunately I have never been able to find the conditions it was installed in. IE the brand, gravel and drainage underneath, and soil types.
XPS is usually used as EPS is hard to find high psi ratings to use under foundations and slabs. I can not find it at any of my local yards.
Second, as your post alluded to, EPS has low damage resistance and termites can burrow in it much easier, hence your uses of termicides with long term ones are not available anymore.
Third, The conditions were not scientific, nor do they make sense. Both types of foams transmit water (as they are plastics) but XPS according to ASTM 272 test transmits much less. XPS is .1 percent vs 4 percent for eps. This makes sense as the perm rating of XPS is much lower than EPS So why did one example act this way? XPS is specifically used for life boats for its resistance to water absorption, and I have seen many docks floating on xps foam for years without sinking.
Fourth. Unlike bubble insulations that will loose 100 percent of their overstated R value insulation, if we are to believe that every install will perform like that single 15 year test, then the foam absorbed 18 percent h2o. 18 percent water absorption is hardly worthless. There is still a large value of insulation retained. Conversely the xps starts off with high insulation value to start with(5 R value). It does loose about 0.5 R Value over time if blown with Freon as it is replaced with air. EPS on the other hand is rather stable as its blown with air but the looser wall structure means most of it even after XPS has lost its freon(most isn't blown with freon now) its still about 0.5 R value higher than EPS. This is about a 11 percent greater R value per inch with XPS vs EPS. XPS R value is 5 new to 4.5 old with freon. EPS is 3.85-4. Only the graphite eps is 4.5-4.7 which I have not seen available yet.
Now the big "IF" is exactly how much did in just the one Minnesota results did the R value drop due to the 18 percent water absorption. I find it glaring that the EPS industry uses this specific water gain results of both but does not retest the R value itself.
Note, I don't have a problem with EPS, Its still a good foam and has a good ROI. I have a large amount of it on my ICF house. I probably would have used it under my slab as well if a higher psi version was available as well at a cost savings over XPS. I just find that the one 15 year results are dubious at best. Was it a bad batch of XPS foam? There is an idiot working in every factory. Was it location specific, ie where they pulled the EPS was well drained and the xps was setting in a clay lined hole???? I would love to see more long term test in controlled conditions but alas it will take another decade or so probably to get them.
