# xps vs eps as a thermal break?????



## Windows on Wash (Aug 30, 2011)

Seems to work pretty good in coffee cups.


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## 1985gt (Jan 8, 2011)

EPS will absorb more moisture then XPS.

XPS has a slightly higher R-value.

Depends on what you are thermally breaking.


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## Windows on Wash (Aug 30, 2011)

+1

Need to know application.


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## concretemasonry (Oct 10, 2006)

The difference in water absorption can make a considerable difference in insulation since moisture can reduce the insulation (as it does for all materials) in the real world.

"R" value tests are short term tested on dry materials in pristine condition for advertising claims, so the moisture reduces the insulation more for EPS than XPS that will not absorb as much moisture in the real world. - Still not as bad as fiberglass that just holds moisture for almost forever.

Dick


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## wantboost (Nov 1, 2011)

is it necessary to waterproof paint on the cinder blocks before installing the xps?


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## Windows on Wash (Aug 30, 2011)

Inside surface? No and actually not recommended.


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## 1985gt (Jan 8, 2011)

+1 the exterior needs to be waterproof.


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## wantboost (Nov 1, 2011)

Windows on Wash said:


> Inside surface? No and actually not recommended.


Yes interior and why not?


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## 1985gt (Jan 8, 2011)

wantboost said:


> Yes interior and why not?


Do you have moisture coming inside the walls currently?


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## stick\shift (Mar 23, 2015)

Water infiltration needs to be addressed on the outside with gutters, grading and downspout extensions.


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## Windows on Wash (Aug 30, 2011)

wantboost said:


> Yes interior and why not?


It will form a vapor trap and there is nothing about that waterproofing paint that works, so why use it?

As stated directly above me, the water infiltration must be addressed from the exterior (ideally) or interior via drainage board and interior sump.


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## wantboost (Nov 1, 2011)

1985gt said:


> Do you have moisture coming inside the walls currently?


Only at one spot. And slight amount of water. Due to a crack on the outside parging


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## 1985gt (Jan 8, 2011)

wantboost said:


> Only at one spot. And slight amount of water. Due to a crack on the outside parging


That should be fixed first before any interior finishes. The paint ect doesn't work, and if it does happen to work in this case will trap moisture in the foundation, not a great place for it to be.


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## wantboost (Nov 1, 2011)

Yes obv. I will fix that first. Ok i wont use the paint. Thx!


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