300 mm 80-100 kpa eps is pretty much standard for shallow foundations

Ha Ha. That's 12". A foot of EPS under the slab and 4-8" under the footings.

yes 300 mm or a fot under the slab and 100-200 mm under the footings nothing strange here in sweden.  97%  for single family houses , rowhouses, townhouses etc  the foundations here are frost protected shallow foundations. Basements are very rare
on new builds here so we probably insulate way more under the slab than u guys . How muh insulation do u put under your slabs if its a shallow foundation?

How muh insulation do u put under your slabs if its a shallow foundation?

Let's just say it's not the first thing people think of. Typically, 2" is used, hopefully more if it is a radiantly heated slab. Maybe more to the North and into Canada. All that insulation is probably why you can get away with putting the tubing at the bottom of the slab. I recently built a sunroom on a new home and put insulation under both the slab and the thickened edge. No one had seen that before.

Wow..... only 50 mm ?  we had that in the 1970s...   they must have more than than that in the cold parts of North America, Alaska and Canada?

Yeah, in general they do, but not a lot more. Canada has been better about it, but, of course, they are colder, too. There isn't too much oversight in Alaska. Things like this always change quickly when the price of energy goes up.

To determine minimum insulation R-value under heated slabs, we use the equation: Minimum R-Value = 0.125 (Ti – To), where Ti is the design indoor temp in F and To is the design outdoor temp in F (this difference often called the design delta T). Using this minimum R-value is intended to result in a heated floor having about a 10% downward/side-ward heat loss (or 90% upward heat gain) of the total heat BTUs supplied to the slab. So 12” of EPS would have an R-value of about R50 and meet this minimum requirement up to a design delta T of 400F. 10% is often considered a reasonable trade-off between economics and performance for many design considerations. 12” is not uncommon in northern Canada and Alaska today where a 10% downward heat loss can be very expensive.

"We use prefabricated eps elements as a form for footings "


https://www.google.se/search?q=kantelement&client=firefox-a&hs=PXW&rls=org.mozilla:sv-SE:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=d2oTU4TiLJOShgf1ioFA&ved=0CCwQsAQ&biw=1920&bih=919

not sure if u guys checked that link ... what do u think ? would there be a market for those eps elements for footings in Usa and Canada ?

12” is not uncommon in northern Canada and Alaska today where a 10% downward heat loss can be very expensive.

The presence of permafrost changes everything.

would there be a market for those eps elements for footings in Usa and Canada ?

Yes, but really only towards the north. Although, I do have to point out the product also addresses the issues of moisture wicking and footing forms, in addition to the thermal issues.

Yes, great construction photos and another good illustration that Europe is way ahead of the US with regard to green, long-lasting residential construction. Not too surprising as Europe adopted ICF and HR heating about 50 years before the US did. Given that the US has had relatively low energy rates and plenty of relatively cheap wood, there hasn't been much of an incentive to build green, long-lasting buildings. 95% of US residential construction is designed to be bulldozed after only a 40 year life-span. It is nice to see modest, well-constructed residences located in nice residential settings again. The trend in the US these days is to build over-sized, poorly-constructed single family residences on very small lots. Americans tend to equate their success in life with the size of their houses. I reckon that when you have too much wealth for too long, your greed increases and your intelligence decreases.

Yes, permafrost must be addressed. You can dig and place your footings below the permafrost or you can place highly insulated footings in the permafrost. Presumably, economics and intended building life-span dictate which approach to use.

Posted By sailawayrb on 02 Mar 2014 02:40 PM
You can dig and place your footings below the permafrost or you can place highly insulated footings in the permafrost.

Please elaborate.

Posted By FBBP on 24 Feb 2014 09:58 PM
••••This allows the PEX to stretch over this 24” as opposed to only the control break dimension.••••
Pex stretch is never restricted to "just the control break dimension." As soon as there is any tension, pex de-bonds from the concrete as its outer dimension shrinks marginally. In essence, all pex in concrete is "sleeved" once it goes through a few heat cycles.
If you ever break up a floor that had pex embedded in it you will find that the pex falls free from the concrete as you break it, unlike deformed bar, which must be broken free bit by bit so it can be recycled.

A voice of reason and experience, well done.

Posted By sailawayrb on 25 Feb 2014 11:08 AM
We use 6" x 6" WWF. I don't think 12" x 12" would provide adequate reinforcement. That's the fundamental problem when using WWF...you pretty much have to walk on it! So we just walk on it (wearing shoes that won't damage the PEX) and we lift it into the center of slab immediately after the concrete has been poured a section at a time. The WWF and PEX will stay exactly at the level you raise it. What you do NOT want to do is raise it any higher than it needs to be because there is no way you are going to be able to lower it. This likely sounds much more difficult to do than it really is. However, this is easy to accomplish for a good HR concrete team.

Really? In what universe?

Posted By CairoBoy on 25 Feb 2014 11:30 AM
I like the idea of setting the PEX exactly where it needs to be. Chairs of some type are the best way to go, technically.

Is there a best practice that would allow these guys to survive this 12" x 12" pattern? Like a type of chair that works better than others?

Can I do 12" x 18"?

This is super valuable insights and very helpful to me.

"the idea of setting the PEX exactly where it needs to be" is a matter of legitimate debate and should be determined by an experienced designer and not presumed on any level as gospel. The misleading phrasing refers to a "theoretical" model published by the estimable "Ziggy" and in practice is rarely necessary and always costs more to accomplish, in residential application.

Posted By FBBP on 25 Feb 2014 12:19 PM
OP - you are getting yourself all worked up because some people get tied up with the last degree of effiency with no regard to practicality. If you search back through the radiant forum, you will come to a multi page document discussing exactly where the pex should set in a slab. It is interesting to note that ALL the radiant professionals who do it for a living (and have for many years) put the pex on the bottom.
While most agree that there is a statistical advantage to center to top placement, it would appear that the advantage works out to about thirty cents a month for each month of the heating season. That is for an average residential slab. Sailor - did you ever WAG at what that cost was??

Save yourself a lot of grief. Install the pex on a product like smartwall mentions (and there is lots of variations of the theme, just go to your local eps manufacturer and they probably have something similair) or just staple it to the eps.
Use 3/8 to 1/2" bar, 18 to 24 inches on center each way, set it on chairs and have it done with.

If you are going to wheel the concrete in place, put down 2x10 runways but you would be better using a line pump.

Bravo!

Posted By warimoto on 01 Mar 2014 02:57 AM
We put the pex tubes under the mesh here in sweden works fine imho

here a pic  http://wellmax.se/files/grunder30.jpg

Now that is crazy talk! Nearly everyone here, most especially the officious "professionals" KNOW that the PEX pipe is to be PRECISELY place in the center, or exactly 2" below the surface of any given radiant floor slab regardless of application, floor covering, climate or any other circumstances that might mitigate the dictates of good conscience and sound engineering practice. Besides it is direct conflict with "The Book". HERETIC! Please explain how the Swedes, (with more than 50 years of real-world experience with slab-on-ground FPSF and "deeply" embedded PEX tubing, dare I say; attached directly to the foam) sleep at night? And the wire is placed ON TOP of the PEX tubing? Say it isn't so! http://www.badgerboilerservice.com/hrf.html

If we use a vapor retarder at all, it is under the insulation. All due respect to the incomparable Dana.

Posted By warimoto on 02 Mar 2014 05:50 AM
Wow..... only 50 mm ?  we had that in the 1970s...   they must have more than than that in the cold parts of North America, Alaska and Canada?

How much do you pay per kW?

Posted By ICFHybrid on 02 Mar 2014 01:25 AM

How muh insulation do u put under your slabs if its a shallow foundation?

Let's just say it's not the first thing people think of. Typically, 2" is used, hopefully more if it is a radiantly heated slab. Maybe more to the North and into Canada. All that insulation is probably why you can get away with putting the tubing at the bottom of the slab. I recently built a sunroom on a new home and put insulation under both the slab and the thickened edge. No one had seen that before.

They probably have had the benefit of reading "The Book". As for "No one had seen that before." Maybe since 1973. http://web.ornl.gov/sci/buildings/2012/2004%20B9%20papers/151_Roots.pdf Yet another glaring example of the pitfalls of Radiant Floor Design by Internet.

Wow. Nine posts in a row. Is that a new GBT record?

As for "No one had seen that before." Maybe since 1973

You seem to be worked up over something. When I laid my slab recently, there were two concrete contractors present, a pump truck operator and a ready mix driver with about 20 years in the business, as well as a number of construction laborers and a radiant specialist. None of them had seen foam insulation put under the thickened (footing) portion of the slab, before. A couple of them had heard about it, but none had actually seen it. I have no idea what you are reading into this or why you are so threatened by it. Chalk it up to luck of the draw, standard practices, or better yet, regional differences, but I don't see the need for you to be so snarky. It has nothing to do with you and I don't know what it has to do with "Radiant Floor Design by Internet".

I know it has history in Sweden, so don't see what the purpose of your article is, either.

Really? In what universe?

It's hard to know what portion of that you are referring to, since you weren't specific, but I've seen you whining about concrete placement before, so I'll take a stab at it and guess that it has to do with lifting mesh. I'm not a fan of mesh in radiant slabs and I've never used 12" mesh before, because I don't see what the point is, but on the occasions I have used it I don't see any problem with lifting it and having it stay in place. My favorite is #3 bar tied in a grid and that seems to stay in place even better. Have you been having problems with your concrete crews?