gypsum has a great place. but the lightweight FBBP is referring to has, by several of my clients, been used as a finish floor and radiant layer all in one with some success. the small difference in conductivity between those two products is blown away by the elimination of a finish floor in overall conductivity.

FBBP, I have never heard of the 30 lbs per cubic foot concrete being used for flower pots and planters. Like Gypsum concrete, I would think a wet environment would quickly break it down. And like Gypsum concrete, the 30 lbs per cubic foot concrete is normally covered with a durable floor surface such as tile. Both products can be used to good advantage, but you do NOT want to use the 30 lbs per cubic foot concrete for hydronic radiant floor heating. At 150 lbs per cubic foot, the R-value is about 0.1. At 120 lbs per cubic foot, the R-value is 0.2. Once you get below about 120 lbs per cubic foot, the R-value quickly increases and heat transfer efficiency quickly decreases. We will soon be testing a new high density Helix slab design for heat transfer efficiency and we expect to see an R-value below 0.01.

I suppose how much you work heat transfer efficiency really depends on your design objective. We no longer do any 1.5” thin slab hydronic radiant floor heating which is typically done when dealing with remodel situations. These days we are 100% new construction and our focus is on integrating passive solar and hydronic radiant floor heating. I think Badger does a considerable amount of 1.5” thin slab hydronic radiant floor heating remodel work.

keep it simple
Concrete for topping floors should be referred to as such. It is marginally heavier than gypcrete. Perhaps it would be use full to loose the term light weight when referring to in-floor heating. 7 1/2 sack mix with pea gravel. Anything else in the mix is seasoning.
Understand the mix is called out by the persons you hire that will Pump the mud and do the placing and finish (they work as a team and bill as one in my experience).
The cement plant follows what they ask for.
Gyp crete is great for some applications, it pours like pan cake batter and will for the most part self level once placed at desired thickness. Is in most times not used for finish floors. You are unwise to tile direct to gypcrete product even with sealer.
Concrete for topping pours can be tiled directly on however your Tile tradesman may prefer a slip mat under the tile.
At the time of pour when adjusting slump, water, air (foam) and soap are added to the mix as well to assist with flow and handling characteristics of the mud.
Dan

Posted By sailawayrb on 23 May 2013 10:57 AM
FBBP, I have never heard of the 30 lbs per cubic foot concrete being used for flower pots and planters. Like Gypsum concrete, I would think a wet environment would quickly break it down.

Then today you get to learn something new (;=)) http://www.all-about-planters.com/articles/hypertufa_pots.php

I would advise against using styrofoam peanuts as a radiant media as well. I can quote R-values if necessary.

Posted By Blueridgecompany.com on 23 May 2013 11:13 AM

keep it simple
Concrete for topping floors should be referred to as such. It is marginally heavier than gypcrete. Perhaps it would be use full to loose the term light weight when referring to in-floor heating. 7 1/2 sack mix with pea gravel. Anything else in the mix is seasoning.
Understand the mix is called out by the persons you hire that will Pump the mud and do the placing and finish (they work as a team and bill as one in my experience).
The cement plant follows what they ask for.
Gyp crete is great for some applications, it pours like pan cake batter and will for the most part self level once placed at desired thickness. Is in most times not used for finish floors. You are unwise to tile direct to gypcrete product even with sealer.
Concrete for topping pours can be tiled directly on however your Tile tradesman may prefer a slip mat under the tile.
At the time of pour when adjusting slump, water, air (foam) and soap are added to the mix as well to assist with flow and handling characteristics of the mud.
Dan

It is not that simple! If your floor designer has design the joist and support system for light weight concrete and you decide to use normal weight concrete you will ruin his calc's in a hurry. It may not effect the actual floor joists to quickly but it will sure effect the beam and column loading.

Just like glycol is not water, so light weight concrete is not "topping" It is about the same weight as gypcrete, much strong but somewhat harder to work with.

Correct,
When you design the joist system, you need to understand the loads. That said tell your architect what you will use and the weight. Is that not simple. This gets back to the first line in my post (concrete topping pour) call it what it is. Get rid of the light weight words unless you really intend to use some light weight product.
Dan

Posted By Blueridgecompany.com on 23 May 2013 11:45 AM
Correct,
When you design the joist system, you need to understand the loads. That said tell your architect what you will use and the weight. Is that not simple. This gets back to the first line in my post (concrete topping pour) call it what it is. Get rid of the light weight words unless you really intend to use some light weight product.
Dan

Like calling all heat transfer fluids "water." It simple and doesn't really make a difference anyway, right? Not!

When we say "light weight" assume that it is light weight and not anything else. The cost of the flooring system can go up exponentially on long spans if we just upsize the structure so that people don't have to understand the difference between materials!

When I design, I specify (am required to) the weight (loads ) on the roof, floor, foundation and on. SIMPLE
Weight of product, then you understand the load on a joist system.
The building departments I have worked with are looking for a number in pounds not a product name.
Engineered joist manufactures when providing the joist lay out and span designs are looking for per square foot load numbers, not a product name.
So call it what you want, but understand the pounds per square foot.
In hind sight, I should have skipped this particular blog as I have been not referring to Light weight topping pour, in fact I know nothing of the Light weight product.
I have been speaking about more to what is common among the cement trades with 2 inch line pumps and what I have used for the last 3 decades in new construction. It never has been light weight concrete, alas simply 7 1/2 sack/pea gravel topping pour.
Sorry for the confusion.
Dan

the confusion isn't yours dan. There is just a massive butchery of terminology going on in this thread. http://www.norliteagg.com/structuralconcrete/insulation.asp ok? everyone take a good look and a deep breath.

What we use in radiant systems, almost everywhere, when asking for "lightweight" concrete, is the 110-120 lb/cu3 style shown here... it may not be this exact product, but it would be similar. this company calls it "structural lightweight". I am not a concrete guy but even I know to look for about 14 lbs/sq ft in a 1.5" overpour as a target for "lightweight" concrete. NO ONE I have ever met is using anything like what this thread is calling lightweight concrete in a radiant slab, which this link would call "insulative lightweight". I sincerely doubt, if anyone has used it in a radiant slab, that they would ever do it twice. Underperformance would be very nearly guaranteed.

The 0.05 to 0.1 increase in R-value of 1" of the heavier "structural lightweight" concrete over the pipe does *technically* make a difference. But we are again in the world of fairly esoteric differences that, in the real world, is completely lost in the natural variation of noise inherent in our design estimations of even the best of us, even with blower door testing and post-installation verification.

so YET AGAIN, we are in an incredibly overly detailed conversation about stuff that doesn't, in the end, matter at all. Seems like these conversations are all that happen around here lately. I wonder why that is.

Correct again Rob!!
I am not actually confused.....
Have a good holiday,
Dan

I would advise against using styrofoam peanuts as a radiant media as well. I can quote R-values if necessary.

No, no, let's rethink this. Foam solves all the problems...

1) Lightweight, so it doesn't stress the structure.
2) Can get it in nearly any thickness.
3) Easy to transport and install
4) Strong in compression
5) A slab of foam isn't going to crack......
6) It's flat as a board. No difficult screeding...
7) Not the best in conductivity, but you could find worse....

Thanks a lot guys. It is now clear to me which direction to go;(back to my lumber yard and check the lbs/sq ft of my floor truss design)!! Although I clearly told them that I was using concrete and not "Gypcrete". BTW - I am due to buy a new work truck, should I get a chevy, dodge, ford, Toyota ? Clearly the responses to this question will be similar, everyone will will agree I am to buy a Ford! Thanks Hank!

Not to worry. Cellular, or low density, concrete is impossible to pour without considerable experience and expensive equipment. It's usually shipped as finished blocks or panels. It would not hold up to traffic without covering. It's used outdoors right along. Gaze left and right on the Interstate in suburban stretches. Those noise barriers are typically are autoclaved aerated concrete (31lb/cf)