slab radiant, comercial garage

HEATON

installing 3/4 pex, about 4800ft in a 60x80 garage. The slab will be 8in thick. Recommend an insulation and installation procedure you think is best.Thanks for guidence and opinion in the past.

Gordy

How will it be poured? What is the reinforcement detail for the slab?

Rich_49

As far as insulation goes , check out barrier X5 . Good stuff , easy install , price is good .

Zman

I am not much of a barrier x5 fan.
They take serious liberties with their r value. They include gravel in the calc. Reminiscent of double bubble.
The compression rating of 10 psi is not appropriate for commercial slabs.

kcopp

A 2" layer of high density (250psi) XPS foam would be my vote. Make sure to get the edges to stop heat from getting out laterally.

Gordy

Right now I'm most curious of the rebar schedule. If there is one with an 8" slab. Keeping the tubing where it should be could be a challenge. 8" of concrete is also a huge amount of mass.

Rich_49

Zman said:

I am not much of a barrier x5 fan.
They take serious liberties with their r value. They include gravel in the calc. Reminiscent of double bubble.
The compression rating of 10 psi is not appropriate for commercial slabs.

They give specs at different assemblies . Material only of the X5 is R5 . What's the problem . Most situations we face is in an assembly where there is gravel below , usually 4 " , I use R 8 for that . There is no nefariousness in their ratings . Here is a fact , less seems , less downward loss . Sealed seems , vapor barrier . Roll of material that is 256 sq ft , less labor . What's the problem ,? They list the different values , it's your job to look at them .

Zman

In my opinion, listing any R value that that involves gravel is BS. Sure you and I can quickly sort out what they mean, but folks making a quick comparison to blue board will likely get it wrong. I believe it is intentional.

I also think they should publish the R value after it has been driven over by a truck a couple hundred times and is compressed to 1/2". 10 PSI is very week for any slab, especially with vehicle traffic. The 8" concrete slab will apply 8.25 psi all by itself.

Note:
I stand corrected. 150 * .67/144 = .70 psi.
Thank you for you attention to the math....



I've been burned by double bubble and insultarp. You can install what you want, I stand by my opinion that it is an inferior product.

Rich_49

Why would we be mentioning Double bubble or insultarp ? I have never used them nor have I ever recommended them .

Never have seen 1 1/4" thick EPS compressed down to 1/2 inch .

So , how heavy is an 8" thick slab per sq ft ? A cubic foot ( 12" x 12" x 12") weighs 143 pounds . Correct me if I am wrong but that is a wee tiny bit less than 1 PSI ( a square foot is 144 sq inches) , so please tell me how you arrived @ 8.25 PSI all by itself ?


The other reason I prefer EPS insulations over PolyIso or XPS is the R value does not decline over time . What good is a listed R value when at some point it goes to trash ? This is a known fact throughout the building Science Community .

http://www.epsindustry.org/sites/default/files/LTTR_33116.pdf

Weights and measures are very important as are many details when you do what we do .

Zman

I stand corrected. 150 * .67/144 = .70 psi.
Thank you for you attention to the math....

Gordy

To put things in perspective. Xps 150 is 15 psi, xps 250 25 psi. eps can be between 10 to 60 psi. However in question is 10 psi.

It does not make any sense to use any type of foam board insulation that has a stronger psi rating than the actual sub grade that lies below it. Value engineering comes to mind.

Concrete slabs designed to proposed loads of proper thickness, and reinforcement will bridge far beyond the actual point loading of the weight distribution.

A 10000 pound pickup has around 17.5 psi, a 80,000 pound loaded semi has a 30psi load, yet a manitowac 10000, 100 ton capacity crane of 178000 gross weight has 47 psi. This is point loading. Those weights are more distributed through the properly designed concrete slab than the point loading figure.

The slab, and subgrade need to be designed around the potential loads, and eps, or xps to that rating.

Just so we are clear on when what ever is used is enough, and when it's not. I give you a link to a calculator for how point loading is distributed, and all the variables. http://www.buildingsguide.com/calculators/structural/FCSGSG/

Zman

I am not sure I am following the conversation. A very conservative design bearing pressure for foundation design is 2,500 PSF. That works out to 17.33 PSI. Most soils are capable of supporting more than that.

Highway bridge rules are based around 18,000lb axle loads or point loads of about 9,000 lbs. Concrete slabs spread this load over an area based on thickness and reinforcement.

I guess my point is that most soil can support much more than 10 psi and loads in excess of 10 PSI are fairly common.
25PSI has become the standard for a reason. I would only consider a 10 PSI product for interior residential application.

Gordy

Value engineering is all.

To the OP we need to know more about the slab construction to better guide you on your endeavor.

One can spec tubing layouts, installation procedures, etc,etc. however one needs to know what is the design/ build of the slab, the heat loss of the building, what it will be used for.

HEATON

Very helpfull input. Thanks, Owner says he is going with 6in. slab and using the insulation board with the snap in tracks and is rated for r10. pricey board but labor saver.

superdave

I have always had good luck with Crete Heat. both inside and out.

CreathermTyler

Might want to consider Creatherm. I'm with the company but we've done many commercial jobs and our standard panel is R10, 36 PSI. We have it in several projects with semi truck traffic (80,000 lbs), AG projects with loaded grain trailers in excess of 100,000 lbs, military tank shops, and others. Call us for information. I've seen competitors products at 25 psi that have knobs and are completely flat after trade shows just from foot traffic - doesn't happen with Creatherm with the higher PSI ratings.