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under slab insulation
- Thread starter stealman
- Start date
Kevin C
Well-known member
Dow does as well. http://building.dow.com/na/en/products/insulation/highload40.htm
ScaldedDog
Well-known member
That's what I used.
Mark
Sent from my cm_tenderloin using Tapatalk
Mark
Sent from my cm_tenderloin using Tapatalk
I found some factoy seconds for a good price. Its 4.5" thick. Does this thickness create any problems for under the slab and around the perimiter?
R-max has a Product called Thermasheath-3 its polyisocyanurate. They say it is 25psi and approved for under slab. Ive never heard of anyone using it. Can any one see any potential problems with using it? I beileive the polyisocyanurate is a different material from the foamular and highload.
R-max has a Product called Thermasheath-3 its polyisocyanurate. They say it is 25psi and approved for under slab. Ive never heard of anyone using it. Can any one see any potential problems with using it? I beileive the polyisocyanurate is a different material from the foamular and highload.
Last edited:
Highbeam
Well-known member
I used Insulfoam brand EPS foam. The white stuff. I bought the 25 psi rated foam for under slabs. Since 25 psi is much stronger than all but the strongest soils, it doesn't matter how thick you install. Be sure that your subgrade is very flat when using the thick stuff. 2"would conform to slight irregularities.
There is a misconception that you must use XPS (pink or blue) under slabs. Consult the manufacturer.
There is a misconception that you must use XPS (pink or blue) under slabs. Consult the manufacturer.
Can anyone else comment on using Thermasheath-3 polyisocyanurate inder a slab on grade. The manufacturer insists that it is fine, but all the searching on the Internet says no. Its is closed cell and rmax says it can hold up to 1% moisture. It is 20psi unless it is ordered special at 25psi. I am looking at factory seconds so it will probably be the 20psi
Any foam can hold moisture. The moisture will knock down the R value but 4.5 inches is R-30 or so, depending on where you live thats a healthy R value under a slab. In my case my slab is slightly elevated above grade with lots of gravel underneath, my foam might get wet in spring but should dry out over the summer. I Think its ok I used some leftover Urethane foam under my sidewalk, its worked ok, no cracks, no heaves
BadgerBoilerMN
Well-known member
The spec. depends on the application.
How much moisture can a radiated slab hold...?
How much moisture can a radiated slab hold...?
The spec. depends on the application.
How much moisture can a radiated slab hold...?
Im guessing very little?
pstnbly
Well-known member
Can anyone else comment on using Thermasheath-3 polyisocyanurate inder a slab on grade. The manufacturer insists that it is fine, but all the searching on the Internet says no. Its is closed cell and rmax says it can hold up to 1% moisture. It is 20psi unless it is ordered special at 25psi. I am looking at factory seconds so it will probably be the 20psi
I believe that you will find the polyisocyanurate is open cell, thus not a good choice for ground contact or underslab.
sneezer41
Well-known member
iso foam is not intended for ground contact, it can absorb moisture. You want EPS or XPS