Has anyone done this?

[sixty4]

Interesting use of spray foam.

 

[homebuilt burner]

I had heard of this. When I had my house spray foamed in November I asked the spray foam guy and he indeed had done this already. Then some times they attach the pex for in floor heat to the foam.

 

[Streetbu]

No vapor barrier? That surprises me...

 

[FANTM58]

The vapor barrier should go on top of the foam, I think.

 

[Lwel9226]

The foam is the vapor barrier.....

LW

 

[ddawg16]

looks like an expensive way to duplicate rigid foam.

rigid foam has been used for years under slabs.

 

[PhysicsDude]

Looks pretty cool, but probably quite a bit more expensive than other options..

 

[EOC_Jason]

According to the video:

Compared to blue Dow foam board it carries a 40% higher r-value for the same thickness.

That seems quite significant.

looks like an expensive way to duplicate rigid foam.

rigid foam has been used for years under slabs.

 

[Voi]

It has been done by at least one GJ member. I don't have the thread bookmarked and it's been a few years at least. I'll see if I can find it.

 

[Showkey]

looks like an expensive way to duplicate rigid foam.

rigid foam has been used for years under slabs.

Agree......seems like a very very expensive way to insulate when foam board would function perfectly at a fraction of the cost. 40% increase in R value at 4 times the cost ???????

 

[iagsxr]

When I built my shop one of the heating contractors I had bid it suggested we insulate under the slab that way.

I don't remember the exact numbers but it was significantly more than rigid foam.

 

[K'ledgeBldr]

Agree......seems like a very very expensive way to insulate when foam board would function perfectly at a fraction of the cost. 40% increase in R value at 4 times the cost ???????

Yep- not exactly hard math!
Plus TIME! And the spray foam was not going very fast compared to 32s/f every 10-15sec.

 

[small&rusty]

Company I work for build a house last year and used spray foam under the slab. It was the first and last slab they will ever use spray foam under. After the floor was poured it cracked everywhere, one spot even had the in floor heat tubes showing due to the foam thickness varying so much under the concrete.

 

[Firstram]

Company I work for build a house last year and used spray foam under the slab. It was the first and last slab they will ever use spray foam under. After the floor was poured it cracked everywhere, one spot even had the in floor heat tubes showing due to the foam thickness varying so much under the concrete.

Did they use foam with enough density? Spray foam can be as hard as a Brick Bat or as soft as Angel Food Cake, depending on the product applied. Proper installation is VERY important to avoid holidays and excessive buildup.

 

[MikeF2316]

Did they use foam with enough density? Spray foam can be as hard as a Brick Bat or as soft as Angel Food Cake, depending on the product applied. Proper installation is VERY important to avoid holidays and excessive buildup.

Yes, sounds like they shouldn't have even poured the concrete in the first place. But that's the trouble today - there's too many people passing themselves off as skilled doing a half-*** job.

 

[930dreamer]

Would the foam be a radon barrier?

 

[69gp]

Company I work for build a house last year and used spray foam under the slab. It was the first and last slab they will ever use spray foam under. After the floor was poured it cracked everywhere, one spot even had the in floor heat tubes showing due to the foam thickness varying so much under the concrete.

Closed cell foam is extremely strong, I weigh in at 260lbs. On a commercial project i was working on the roof was framed with trusses on 24" centers. attached to the bottom was hat channel and 5/8 rock. Rock was all taped. Insulation company came in and sprayed 2" of closed cell across the whole ceiling. Next day you could walk wherever you wanted on that insulation without any fear of falling through. That stuff is tuff

 

[LS6 Tommy]

Company I work for build a house last year and used spray foam under the slab. It was the first and last slab they will ever use spray foam under. After the floor was poured it cracked everywhere, one spot even had the in floor heat tubes showing due to the foam thickness varying so much under the concrete.

Those types of issues caused by uneven material thickness & density was the first thing that popped into my head...

Tommy

 

[LS6 Tommy]

Would the foam be a radon barrier?

Probably, but you'll most likely get cancer from the foam off gassing...

Tommy

 

[JRC3]

^LOL.

Not that radon should be a problem on an above grade slab. Many opinions on that sort of thing.

 

[ynned]

As stated a couple times already, keeping the top of the foam on grade seems really hard to do. The slab could vary in thickness by a couple inches or more.

 

[dfiler2]

It seems to me it would be a really slow tedious process, maybe not? The only thing worse than working over your head all day is working bent over like that

 

[bwringer]

Yeah, I was also wondering why the hell the nozzle couldn't be two feet longer so the guy doesn't have to be all hunched over like that.

 

[nelstomlinson]

Rigid foam under concrete is cheap, especially if you can buy it used. Who cares about R-values per inch? Just dig a few inches deeper and use enough used, cheap rigid foam to get the R-value you want.