no need to apologize, but it's just not possible that 90 degree water is making your finish floor surface 80 degrees with naked staple up pipe, or even with heavy plates for that matter, without something else going on. That's at least twice as much heat as should be possible in that configuration.

I suspect your thermal gun settings are not accurate for the surface you are shooting, or you have some pretty heavy stacking in your water heater so the outgoing water temp is much, much higher than you think.

NRT

The floor temp of 78-80 is in my sunroom with the gypcrete floors insulated with R25 over a crawlspace. The 'pex in the joists' kitchen floor is 75 -78 over a heated bsmt. I do not use any plates with the pex tubing, too expensive vs. my 2" hot air method.

 Both floors use the same water heater as their htg source. Sunroom 2 zones, kitchen 1 zone, and bsmt family room 20' baseboard 1 zone.

My nearby tiled laundry room floor over the bsmt is 70 degrees with no radiant heating system, so the pex in the joists heats the kitchen floor 5-8 degrees vs. no floor htg stsyem.

The heat gun is very accurate and the water heater is a closed system. I call it my 47,000 Btu mini boiler.
Smosky

75 I might believe, but again, it's simply not possible to get 20 BTUs/sq ft out of 90 degree water with any joist system, plated or not. if your floor surface were truly 80 degrees you would be putting 20 BTUs/sq ft into a 70 degree room. If that heat were wicking throughout the house maybe that would explain why you're not sweating to death in there when it's 30 degrees out, but it would not explain how you are breaking the laws of conduction and physics and pushing 3x more heat through your floor than it should be able to do.

However, you do say something interesting. if the floor is 70 degrees in an unheated situation... how warm are your rooms?

NRT

I keep the house at 70 with an 8 hour setback at night to 68. The circ pump is always providing heat to the floors ( 83 min - 98 max). The avg floor temp of 78-80 in the gypcrete sunroom almost remains constant due to the 24/7 circ pump.
This type of htg is what I found in Europe. Low temps with lots of radiation potential, unlike the USA where we have high temp (180) and few radiators or baseboards. Thats OK with a steam radiator, but not when the temp can be controlled. It was never fun to sit near a steam rad when it was cooking, I mean htg !
I installed a 50 gal water heater with a similar circ pump in a 900 sq ft house and that was the heating system for wall to wall radiation. Lots of radiation but low water temp(120- 140).  When it did get to 20 below zero the back up electric baseboard kicked in.
Smosky

ok then. your thermal shooter is definitely not providing accurate readings. an unheated floor should not be 70 degrees in a 70 degree room unless the basement is warm, and there is no way your floor is really 80 degree surface with 90 degree water.

I don't really like thermal guns because they are very hard to get good readings out of unless you know how to do the correct adjustments for different surface emissivities and/or correct to a known emissivity (like black hockey tape) and use that on all the surfaces you want to read for this reason.

"Unless you really loved those terrazzo floors, I would think a radiant installation above the slab would be less expensive and more responsive that going below a 6 inch slab."

One job, not quite finished, and I have wasted 25 years! Who'ld a thunk?

"An extreme radiant barrier would need to be installed to move this energy upward through the slab."

What is an "extreme radiant barrier". I have an extensive radiant library and can find no reference?

"This type of htg is what I found in Europe. Low temps with lots of radiation potential, unlike the USA where we have high temp (180) and few radiators or baseboards."

I designed Ag steel buildings (animal husbandry) using condensing boilers and PB tubing in slab-on-grade construction starting in 1990, non of these systems ever ran above body temperature. One would not hit 90°F in the 30°F N.Dakota winters. My residential radiant designs even in retrofit are well below 140°F design water temperature.

Maybe you are in the wrong neighborhood.

"One job, not quite finished, and I have wasted 25 years! Who'ld a thunk?"

Some folks can't stand the fact that despite not having 25 years of specific experience, but a good brain and sound mechanical abilities, someone can figure things out that will work. The job is finished and the proof is in the pudding.

Given a 6 inch thick suspended concrete slab - that is a lot of concrete to get the heat completely through to the upper surface. Once that concrete was warm though it would probably be relatively easy to keep warm, given its thermal mass.

-Rosalinda

I would advice the novice to save the useless extra reinforced concrete (which may have necessitated the costly and equally useless suspended tube), as the cost extra cost would have paid for a professional design and installation. These are just a couple of many mistakes 'smart' people make. I am glad you are happy with your work and if you can't afford professional help, it is understandable, but the blind leading the blind is too hard to watch.

The fact is, radiant floor heating is quite forgiving, to a point.

The whole string reminds me a lot of the old solar days of the late 70's.

I think Rob deserves most of the credit as he imparts knowledge in hopes of selling some goods, but as in this case, he made things possible without credit or profit.

What is a lot of concrete?

I generally find the people who are going to cowboy it on their own are going to do it whether they have good info or not. and good info is not enough to make most of those systems great... too many ways to get it wrong.

the existence of info and knowledge accessibility may or may not help on any particular project. But I can certainly say having good info out there makes it easier for a good professional to demonstrate their value in a sea of hacks.

obviously my activity on forums attracts some attention and some business. but you can take your characterization of my involvement here and your lamentation of its result, and stuff it.

Much love regardless, you crusty old fogie.

heheheee

back at ya

Heating with tubing from underneath, and not suspended in the slab, I think 6 inches is a lot of concrete.

I have thanked Rob several times for his assistance, and appreciate it greatly. I have even thanked Morgan when he deigned to reach down to us silly little DIYers and helped.

My 6 inch slab (with 12 inch thick perimeter and additional thickness pads down the center for the center modular supports) was built the way it was, because that is how the contractor I hired does ALL his slabs, though he does not usually have someone add radiant tubing or the amount of insulation I did. This seems to be the industry standard for those contractors who work with modular homes. The slab cost approximately $7500. and that included the finished floor surface. This was well in line with the prices I researched. The contractor who did my slab also stick built the ground floor to the unfinished sheetrock inside and finished siding outside, did all the plumbing and electrical including the septic system and new 220 electric service, and all the ground prep and grading, in addition to making sure the modular was properly placed on the ground floor. This at a price all told of under $47/ft2 did not seem unreasonable to me.

Am I wrong in my understanding that radiant tubing is best placed suspended in the center of a slab? Everything I read said this was the way to do it. In my case it was the easiest way to do it as my contractor suspends his rebar and wire mesh in the center of the slab regardless of what I was going to do, he prefers NOT to pull up on the wire as some contractors do as they pour, but to have it all fixed in position for the pour. So I am not sure why Morgan considers it to be " costly and equally useless suspended tube".

As to the blind leading the blind, none of the advice or opinions here are guaranteed, just hopefully suggests possibilities that an individual can think about, research and pursue or not as suits them. This IS a board for Pros, DIYers and beginners, so we are all entitled to add our 2cents worth.

-Rosalinda

Since your floor heats, it looks like your suspended tubes aren't "useless". There are all kinds of ways to design concrete slabs, but there isn't any such thing as "extra reinforced concrete" if a particular design matches the load and soil characteristics at the best price. That might be post-tensioned, waffle slab or a uniform thickness.