I know I'm doubling up on topics here, feel free to answer one or both.  I've been getting great advice from the ICF forum, wondered i any of you have experience using spray foam under a basement slab.

I'm having the rim joist, cantilever's, and underside of roof deck sprayed, and he mentioned in his bid he could spray 2" under my slab for $1800 (it's a 28'x30' slab)  He said it seals up better around plumbing pipes and stops radon from entering my basement.  It's also a vapor barrier that doesn't  rely on tapes and caulks at the seams because there are no seams.    

It's a closed cell polyurethane so I don't think there's issues of crushing, though I don't know that for sure.

I'll be placing radiant tubes every 16".  I had a heat loss calc done that came in at 24,800 Btu/hr.  I live in Southeast Iowa, I think it's zone 5.

Originally I'd planned on  using a water heater, but have been encouraged to use an electric boiler because of it's faster recovery and higher efficiency.  The home is a 2 story with full basement and attic trusses.  I didn't think I'd put anything in the attic, but wanted to run radiant in the basement slab, and staple up to the main floor and second floor subfloor. 

Any thoughts?

Ben

that $1800 is twice rigid foam and vapor barrier, isn't it? not sure i'd pioneer like that, but I can't say I know much about it.

16" o.c. is too wide for residential. You'll have heat striping, especially during startup conditions. do 12" o.c. and don't waste your money on large diameter pipe, use 1/2" with reasonable loop lengths.

I would question the economy of using electric for primary heat at all, but if you're in one of those areas where it makes sense, so be it. electric boilers are fine.

Rob,
It's either electric, propane, wood, or corn around here.   I believe when propane hits $1.50/gallon,  my 6 cents/kw rate is the break even point.  I also get a few hundred dollars back from  the power co. on the boiler purchase,  and there's no venting.  But I really don't know that much about any of this, just what I can glean from asking lots of questions.

I didn't realize spray foam under the slab was pioneering.  Foam dude let on like it was common practice.  I did like the fact that it was a seamless vapor barrier and insulation in one.  I'll post a few pics of the process, should be towards the end of next week.

Ben

Ben,
I'm in a similar sittuation fuel wise... so I'm also leaning toward electric also... sounds like a much simpler installation as well as less moving parts to malfunction... (there's long term savings right there...) would you mind sharing some brands of electric boilers that you're considering?
Thanks
George

Hello Ben,

I would like to offer some advice. Please contact me [email protected]

All-in-one subsurface barrier
The Barrier acts as a thermal barrier, vapor barrier, moisture barrier, and radon barrier, all in one. It is made with recycled, extruded polystyrene and heavy-duty black polyethylene film (less than an inch thick), laminated on both sides and with patented seamless self-taping edges. It can be used under slabs, basements, foundations, crawl spaces, pools, hot tubs, and mobile or modular homes. It also deters carpenter ants, termites and other insects. Many who use radiant use a small Wood Doctor outdoor furnace also from Barrett Enterprises Inc. website

.06/kwh is a good price, makes sense to use electricity there. I've had clients use seisco and argo and say good things about both, but none are long term enough to comment on long term lifespan.

... and to once again offer full disclosure on the barrier, the r value is equivalent to an equivalent thickness of XPS (which it is). at 1/2" to 3/4" in thickness, it is not the rvalue of a typical 2" of rigid foam.

NRT Rob: With the most respect to your post I would like to question your thinking on the Barrier type products. Even though I
don't sell Barrier I do sell compatible type products like Insul-Tarp and Bubble foil products. To say an 1/2 foam in Barrier is equivalent
to a 1/2 of polystyrene seems irrelevant. To me that would be saying 10" of fiberglass (approximately r-40) is equivalent to 10" of
EPS (approx r-40). We all know there is no comparison between those two items. Many mechanical professionals have told us that
there thermostat comes up to heat just as quick if not quicker with a radiant under slab product. Has your experience been different?

Also, unless I'm imagining it my hand is warmer next to a radiant reflective product than lets say a bed sheet. One would think you would freeze with a sheet over you in frigid weather than a space (survival) blanket.

Am I missing something?

Respectively.

Dave

P.S. I don't generally follow this forum but I will check back soon!

Hi Dave,

First, Insul-tarp and Bubble foil products are not "compatible" products. The barrier is actually insulation, with an R-value, though it's thin. The insul-tarp and bubble foil products have been proven in many studies at this point to perform at only a 1.65 R-value or so, plus or minus a few fractions of an R. If you want more complete explanations, here is a page that collects info on such studies: http://www.healthyheating.com/Page%2055/Page_55_o_bldg_sys.htm

the fact is, there is NO RADIANT HEAT TRANSFER UNDER A SLAB. It is purely conductive. foil stinks at blocking conduction. You get a basic thermal break which may help response time, but response time is not why you insulate; you insulate to reduce heat loss. Your only real insulation there is in the small amount of trapped air in the assembly.

You comment about irrelevency makes no sense at all. "The Barrier" IS extruded polystyrene, not a reflective product. 1/2" thick polystyrene, in fact. The reason I say it is equivalent is because it is not only equivalent, it is actually exactly the same in all respects except installation procedure. However, the Barrier often marketed itself to make itself seem superior to rigid foam in insulative qualities (mostly by using fake K-value calculations to confuse the issue), and it is not. Likewise, the products you sell have lied to customers for more than a decade claiming that they are equivalent to 2" of rigid foam under a slab or making even more outlandish claims, and those are flat out lies (that most such companies are not making in writing anymore, I've noticed). And if you sell those products, you should be careful, because the FTC has been enforcing the R-value rule lately, which basically states if you sell something as insulation, it better have a tested R value stamped on the product.

Radiant barrier insulation works in certain situations. Walls, and attics for example, or downward facing ceilings, all if installed with a proper air space.. In a blanket, again with an air space, when you're out in the cold it works wonders, reflecting enough heat that the paltry R-value it gives can still keep you warm.

Under slabs though (and in my more controversial opinion, in joists facing up), it's a bad idea and a waste of money. It's better than nothing, absolutely, but it's a poor choice in any real heating climate and it's cost effectiveness isn't worth the cost in any climate where slab insulation is required.

Sorry, I thought Barrier was reflective. I will take under advisement and do my own test this winter.

Dave

Rob : I've lurked about over here for some time and appreciate your comments on foil faced bubble crap.
Why do the counter guys, continue to promote it for underfloor ? I'm kidding, let's not go there.

As floor and wall contractors, we've seen every kind of tube, laid every different way, on every different type of material.

You're totally on.

Rigid foamboard, type 2 minimum, is a sound investment. Heavier board for higher loads.

One of the first floors we poured had Wirsbo tube on mesh, over foil , face up.
We all know, don't we ???? that aluminum in any form, when in contact with concrete dissolves.

This guy pumps alot of heat into the ground and melts a lot of snow around his house. Can't figger out why he burns so much oil.
That was 15 years ago, and he is still there burning 2 x's as much oil as he should. Sad really.

And products without CCMC stamps ( in Canada) means that the product is untested or has no validation, and is money out the window.

A simple one loop pic for you. Cheers.
http://s83.photobucket.com/albums/j295/ericicf/Warm%20Concrete/?action=view¤t=June5016.jpg

Dave: test whatever you like. That link I posted has links to several studies that all confirm the same results. I would encourage you not to waste your time. This is not theoretical any longer, it's established fact. Now, you can make the case that an R10 is not always needed under a slab. And in some areas, below grade, or huge slabs, with dry sandy soil you might have a case. But even water tables change and so I generally consider insulation a sound investment even if current conditions are not worrisome. If you get it wrong, as the previous poster notes, you can waste a whole lot of energy.