hey guys first post so take it easy : )  were trying to get permits right now so we can add an addtion/replace our foundation with a basement...i want to put in the radiant floor heat and found this web www.pexsupply.com that seems to have everything i need (im an avid diy'er)
they have a product for insulation and i was wondering if anyone has any thoughts on it...appears to be slightly less R value then the 2" dow foam, as well as slightly more money, but the ease of installation (by me by myself) might make it worth it. heres the stuf http://www.pexsupply.com/NOFP-BAR46...-x-60-Roll
our existing house is 800 sq ft...addition of 400 plus 400ish for a garage that i also want to heat. 
ive talked with a few people about there systems and some are quiet extensive and fancy, but some are just a tanked water heater, pump and tubes.
currently i have an on demand heater, and was thinking about jsut getting another one for each system (house basement and garage) but im not sure how you vent them from a basement, my current one has a 10" stainless collar going thru the wall (between studs)  i put it in myself, even ran the gas line to it that wasn't originally there, and its been great for 5 years now, its a small unit, but have never ran out of hot water during shower even with  a sink going and dish washer...
i guess my other question is, should i just get 2 cheap tanked heaters just for ease of venting and low cost?  ive read that the on demand can run for a long time and makes it not quite worth it...my other concern is that my heater turns on with flow, but a tanked heater only turns on with temp, and i was wondering if the water returning to the heater would continue to climb higher, could it get too high? 
sorry for rambling
any suggestions or advise would be awesome

Blanket are for beds, foil for cooking and tankless water heaters...guess.

Professional use XPS and condensing boilers for multi-zone radiant slabs. If you have a very small zone, say a modest basement, a tank/type condensing water heater with a sub-system isolating potable from space heating water would be more appropriate.

Simple is not necessarily easy, safe or wise.

ok, so xps is the blue dow foam right? just wondering what you meant by your first line, because its a poly foam, just more maliable for ease of installation, not sure what you meant about foil? what foil? and im not sure what to guess about the tankless water heater comment???
the entire basement will only be 1200 sq foot so only 4 runs of 300' pex, i dont think i need a monster boiler to run that, ill still have my central forced air heater to heat the upstairs and main floor, so its only for the basement...
thanks for taking it easy though hahahaha yikes

yeah, this is actual insulation, not foil, but don't skimp. you want at least 2" under that slab. if you want ease of install, interlocking panels like (advertising alert!) "crete-heat" allow for installation of insulation, vapor retarder, and tubing attachment all in one step with no taping required. the cheapest way to go is 2" foam and wire mesh, but the panel products are so fast it's hard to explain...

if you're only doing 1200 sq ft of properly insulated basement, a tank heater would probably be fine. tankless would be a waste of money in this application... in fact, they are kind of a waste of money in almost any application. but you do not want to drink your heating water, if you are doing double duty from the source I completely agree with badger about isolating with a heat exchanger.

nope i want to keep them seperate,
our plan is icf basement walls, so should be nice and tight, im still not overly sold ont the rigid insulation as its only 13 or so R value (much less at each seam) compared to around 10 or 11 from the foam product with the tapeing strips...but so far havent heard any one suggest it other then the site that sells it haha
so the tank heater is the way to go then eh? i just figured the on demand would be most efficient, thats what i have for my potable water heating right now, i installed it about 5 years ago, might have cost 1000 all in, but i think it was less, and it was a small unit, but it works great for us...but just the venting alone seems annoying since its going to be in the basement.
thanks for the reply NRT

you linked to an R5 product. they have one that 1-1/4" thick but that is still nowhere near an R10 or 11. the interlocking foam panels are not "much less at each seam" and even if they were, the seams are very small on regular EPS/XPS. that's why the entire industry uses XPS/EPS rigid.

on demands are not really that much more efficient in space heat applications, unless you sink money into a condensing unit, and then you might as well get the real thing (mod/con boiler). tank heaters run about 80% efficient for space heat typically. you can spend more and get more efficient ones in that style as well.

oh oops, ya i meant the thicker stuff, it says in the product the r value is 5 - 10.5 but the 5 is at the seams i guess...but im not going to argue, ive never used the stuff and if no one else does, then why would I...just asking i guess
now what would be better for the water heater, a 40000 btu 50 gal, or a 60000 btu 30 gal? ive never really looked into tank heaters so i dont know too much about them.

my bad, you did link to 1-1/4" stuff. Of course, it is not possible to make a foam that is an R4-5 per inch hit R10 in 1.25". that would break the laws of physics.

gallons don't matter in this case. output only. and either of those is likely to be larger than you need, so, whatever you like. If you're doing domestic too, then more math woudl be advised.

i see from their brochure when they claim R10 they are included 6" of gravel in that number. when they claim R7 they are claiming 1" of sand and 3" of gravel in the number.

Man. those roll/blanket MFGs will worm their way around anything. how many times do they have to be sued??

The insulation blanket-under-slab guys bank on the R-value of the ground, which is considerable in some areas (around R-10 per foot) but just like in the old days when we didn't know any better, heating up a couple of feet of dirt may take a week or more. That's a lot of cash up front, like heating a pull first time in spring. For commercial buildings the ROI and operating costs may work out, but this is never the case in residential light-commercial construction and especially unwise if the building is set back or turned down for any length of time.

The blanket are for the lazy and the stingy and perhaps for the misinformed - to be kind.

I know, New Years resolution...trying to be nice. yuk

ok, now were getting somewhere, No offence badger but your first post just sounded like your typical pro who wants everything done so by the book it costs a fortune to get a song.
anyways thanks guys...there will be muc more to come.but one thread and ive changed my mind on 2 decisions haha
oh just a question about the hard foam, what do you do at teh seams if you dont have toung n groove? do people tape them? also are you supposed to use a vapor barrior with it?

yes and yes.

k so vapor barrior under or on top of the insulation? also what kind of tape

no and yes
If you provide a 6 mil barrier under foam, place your 2 inch foam on top tight, proper perimeter use of foam what function does the tape provide? added expense for what gain. The block of moisture/air is completed with the vapor barrier.
For the record as well 2 inch foam is the right way to do your system, and the added advantage if steel is not required of stapling 1/2 pex to the foam will save time as well.
I am curious about the added value of tape, seems over the top for under the slab.
Dan

I just thought the tape would help keep the seams tight together, but i guess if the foams shoved right up against the icf then there wont be any space for the foam to move...good call, thanks (ps i get free tape from work so it wasn't an added expense, but certainly added time)
I'm not sure if in our area calls for rebar or wire mesh to be put down for added strength of the concrete, but ya stapling would be super quick...where do you get the staples?

We distribute staples and have rental tools as well, here is a link http://www.blueridgecompany.com/radiant/hydronic/501/rht-foam-stapler-and-staples
you will need about 1 staple per foot on 5/8 pex, 1 per 16" on 1/2 pex
Dan

I am never offended and glad you have the good sense to ask. We make a nice living following around behind folks - professional and layman - who think short cuts in radiant floor heating installations save money. God bless them, one and each. :-).

ya its comments like that which make diy people not take forums like this serious. i've done countless jobs at home that I was told the only way to go is the 10 G way...then found real people, who have already done it successfully and actually wants you to save some money and be able to do expensive type projects affordably, I dont want to cut corners and never have, but sometimes more money isn't always better. I started a similar thread in another chat room and a guy wanted me to use this stuff ..http://www.crete-heat.com/ super expensive and really does nothing except maybe save some time...then i get decent people like the blueridge company guy and pushes cheaper staples, might take a bit more time but instead of 5G , might cost 500. big difference for not so rich people like myself. but you keep on making money off peoples mistakes, I personally would have a hard time blessing people for there mistakes so i could make a buck..just me i guess.

DIY people are no different than "pros/experts"...there are good ones and bad ones... Bottom line, do a proper analysis/design and proper installation...either DIY if you are up to it or hire a good pro. We have DIY analysis/design calculators on our website. Please read the instructions carefully before using the calculators.

Borst Calculators

cool thanks salla, ill check it out