We are planning to run pex in our basement and garage slab for in-floor heating. Before we pour the slab, we had planned to install a 10 mil vapor barrier, 6" up on the inside ICF wall.  Then, insulation, the pex, and finally concrete.

What is the best underslab insulation to use? What R-value should we be providing? Has anyone heard of "Energy Shield"? We had an energt consultant recommend it but we haven't seen it anywhere. He claimed it was R9.6 at 1.5" thick.

What about placing steel mesh? Is it just there to attach the pex or is there a structural reason to have it?

Is there a "best practice" available that documents how to properly insulate the slab for in-floor heating?

Thanks.

Brian.

2" of XPS/EPS foam for an R10. vapor barrier under.

either plain jane foam or one of the attachment-combo items like crete-heat or others.

structural requirements are between you and the structural guy ;) rebar is real structural help. mesh just keeps chunks from falling off.

We're using insul-slab for our insulation and vapor barrier.

I received this email in response to my posting. Are these types of products really effective? What will the building inspector say about it?

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Subject: concrete insulation
Received From: radiantbarrier
On: Tue, 15 April 2008 02:43 PM
Please read about the Barrier, has 10 mil poly and is one of the best insulation for under concrete radiant slabs.www greeninsulationproducts.com
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WE use the BARRIER all in 1 product. it is the under concrete insulation

the Barrier is foam and will work, but it is only equivalent to an equal thickness of rigid foam.

it's not "these types" of products.. the other tarp/roll products are total junk. That one is just thinner than i would normally spec for a heated slab. It is sometimes usable, but definitely not "one of the best".

If you have an energy code that requires a slab insulation of a certain R-value, that will answer your question as well.

The first question should be; where is your building?

North Bay, Ontario. We have a fairly cold winter and a reasonably hot summer. Right now (April 15, 6 pm) it is 9 degrees C and sunny.

Photos of our lot and footings is here: http://www.greenbuildingtalk.com/Forums/tabid/53/forumid/13/postid/34983/view/topic/Default.aspx

Brian.

For a residential floor or a garage with only cars, steel mesh isn't necessary (assuming proper compaction).  It does provide an inexpensive tie base and, of course, it will strengthen the slab beyond what you need.  I recently used a fiber additive with no steel in a slab (not hydronic) and was very happy with zero small cracks, only expansion cracks right on the "zip strip" as planned.  The finisher grumbled a little about the fibers sticking up, but they soon disappeared.  I'm planning on using the fibers in an upcoming hydronic project, but still with mesh as a tie base.

Hard to beat 2" EPS foam and a vapor barrier for a belt and suspenders.  Until somebody comes up with legitimate numbers to prove that a new-fangled mylar bubble teflon whizding barrier is somehow better AND cheaper, I'd stay with what works.

Mark

Has anyone used XPS instead of EPS? What is the difference and is there any advantage to one over the other?

Thanks.

Brian.

In the 3000 sf custom home I am building spring outside of Philadelphia I will be using 2" of closed cell urethane foam sprayed directly to level stone then will overlap bottom footer of Superior Wall Xi foundation. No need for taping seams or vapor barrier. Will then lay wire directly on foam and attach PEX tubing for radiant. I have seen several installations in my area and it works out very well. John

My dad went to houseneeds.com and his sytem is near perfect...

The Barrier X5 at 1.25" will do a great job.see underconcreteinsulation.com

there is a new one out? Now we're starting to get to thicknesses I can live with if so. I see nothing on it on that website though.

Sorry put the cart ahead of the horse! it is available in rolls 4 x 60 and hopefully will be up on the website soon!

I plan on using XPS instead of EPS.  My state's energy code requires R10, which is more than 2 inches of EPS, so it isn't available at the home stores.  XPS meets the R value, has higher load bearing and perm ratings, and is only a $220 difference on my house.  The sheets are 2x8 instead of 4x8, so it will involve more fiddling.

Mark