Heat Transfer Plates vs Climate Panel/Quick Trak etc.

Chris Maderia

This is a follow up to the post last week on transfer plates. Now ME if we are selling on efficiency can you really in figures tell me what the system efficiency is between the two applications. Let's see what is the governing factor, water temp right. So, what factors determine our water temp? Required BTU's and MOST IMPORTANTLY Floor R-Value. What is the difference in Floor R-Value between the two applications? Between a .5 and .7. What's our delta-t for an above floor system? 20 Degrees. What's our Delta-t for transfer plates? 15 Degrees. My whole point to this is that you are really not gaining that much in system efficiency as far as water temp required goes. What you do gain by going above the subfloor is system response time and ease of installation. I don't buy the argument that it is more efficent. Later on this week, I'll post the radiant design for house that I'm working on right now and I will do it both ways and you will see that there will not be much of a difference in water temps that would make a significant difference.

Troy_3

Above floor advantage?

Having done a considerable number of both, I prefer above the floor for ease of installation and ease of zoning. While it can be done under the floor, it is certainly easier and in my opinion more effective on the surface. My drill gets hot when drilling all those floor joist also. The key is either method works when done correctly. There are definite reasons that I do both. No one system fits all jobs. The big issue under floor in my design conditions is the need to use extruded aluminum plates. On that I will not compromise!

John Felciano

Radiant

I have to agree with Troy.The systems we do on top of the floor just seem to work better than below the floor.I don't have any hard facts to back up that statement all I can go buy is real life working jobs.

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John Jr

I agree

with both Troy and John! well said!

John Jr

Chris Maderia

Follow-Up

Now I will agree that climate panel/quick trak, thermal board etc. is easier to install and will give you a better response time but the question is system efficiency. Which system is more efficient?

Let's take 1 Room. This is a 900 sqft room with a heat loss of 12,774 btu's. First let's look at it with Quik Trak. It would require a water temp of 91.5 degrees @ 0 to heat this space. It would also require us to use 1,680ft of tubing this includes leader lengths. Now, with transfer plates it would require 115.3 degree water @ 0 and we would need 1,470 ft of tubing.

This gives us a water temp difference of 23.8 degrees between the two at our design temp of 0 degrees. So, does this make the above floor more efficient than below the floor? They both end up with the same result, a 74.3 degree surface temp. I would say NO. Why? Because the system isn't finished. All we have done is determined our method of delivery and what water temp we need to have to heat the room on our coldest day. The point to all of this is that the method of delivery while important is in no means what controls our system efficiency. It's our next step control strategy, and this means everything to our system efficiency.

What if installer #1 uses the above floor method and controls it with a thermostatic mixing valve with bang/bang operation and installer #2 uses the below floor method with an injection pump and outdoor reset. Wouldn't installer #2's system be more efficient than installer #1's? Why yes it would. It would also be more comfortable for his customer.

What if installer #1 used a Burnham, Weil McClain, Utica or any other American Boiler and installer #2 used a Buderus or better yet a Viessmann. Whose system would be more efficient? We all know the anwser to that. See, this is why I never try to sell a job on efficiency with Radiant. The method of installation means squat. It's just a tool that we use to deliver the btu's we need and in no way is a measurement of system efficiency. I could do joist heating with no plates and have a more efficient system than half the radiant systems I've seen out there. Why, because anybody can install tubing and call it a radiant system. But start asking them about boilers and control strategy, and their lost. This my friends is the most important part of radiant and it doesn't matter which method you use as long as you do it right.

ScottMP

Chris

From what I am reading your question is the efficiency of the system using either under floor or over floor systems.

Let look at your numbers and assume both boilers are the same and both are usiong injection with reset.

Above floor is using 91.5 deggre water, below floor is using 115.3.

As I see it theres the effeciency difference right there. Lower water, less fuel used. Gotta more efficient right !

Scott

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ScottMP

heatboy

I also do both............

and working on top of the floor is usually advantageous. It takes more planning to do a non-cementious system on top of the floor, though. I usually use Thermo Fin U when it comes to working on top of the floor. Never saw the sense in paying to have plywood shipped around the country. With U Fin, there is a greater amount of transfer compared to the plywood/flashing type of systems. Another drawback which is often overlooked is the fact that I can design my own plated system around 300' loops and use a 30 to 60 Watt circulator with a 10° to 15° Delta T as opposed to a 200+ watt pump at a 20° Delta T with the other products. If you shorten the tube lengths to a managable length where you can utilize a smaller pump, the number of loops involved is problamatic and expensive. That is not to say the plywood/flashing products don't have there place. For small areas, radiant walls, etc., it is an excellent choice.

I would rather just staple the tube down and have Troy come pour gyp. But we aren't discussing this option.

Warm Regards,

heatboy

"Expert in Silent Warmth"™

610.250.9885

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heatboy

Both work well.

Having done a fair amount of both, working on top of the floor is advantageous, for the most part. I use extruded plates above and below the floor, so heat transfer is roughly the same and immensely greater than the plywood/flashing type products. There doesn’t seem be any sense in paying to have plywood shipped all over the country when there is a dozen places locally to buy it. I can have the builder rip plywood for $20 per/hr. instead of having someone else do it, creating a greater cost to my client.

As far as efficiency concerns, which sounds more energy frugal? Designing your system around 300’ loops of ½” with a Delta T of 10° to 15° and using a 50 watt circulating pump or, designing around 250’ loops of 5/16” with a Delta T of 20° or greater and having to use a 200 watt pump? Remember, we are talking long term here. How much would it cost to have a 150 watt light on 24/7 from October through April? If you shorten the loop length of the small tube where you can use a 50 watt pump, you are going to increase the amount of loops and manifolds, leader pipe, etc. Leading still, to higher cost for your client.

That being said, there are some excellent applications for the plywood/flashing products. Small rooms, radiant walls are a couple of places. If you absolutely, positively can not alter floor height more than ½”, than you have little choice but to use these products. How often does that happen?

My favorite floor, would be to staple down the tube and have Troy come down and pour it for me.

Warm Regards,

heatboy

"Expert in Silent Warmth"™

610.250.9885

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radiant

above floor

I have read posts on the wall from time to time but have never responded. My company installs radiant floor systems exclusively and that is all we have done for the past nine years. Our boiler of choice and the only equipment we install is Viessmann.
It seems this topic always comes up and I find it very confusing as to why. After you install enough complete homes with radiant floor it is very obvious that on top installations are far more efficient. Most of our projects are installed on top of the subfloor in a gyp-crete pour with 1/2" pex tubing with very tight tube spacing 6"-9" except for interior spaces which may get 12" on a very low water temp. All tubing runs are short 250' or under and this system will always out perform the calculations and have a very low delta T about 8 deg F.We always find the heating curve can be turned down from where it was designed at in the first place. We have used panel systems which perform adequately but we find the high delta-T across the floor and the very poor flow rate with higher head to be unacceptable, and the heating curve typically has to be turned up one or two clicks above design. Although in retro-fit or any height restricted place it is a far better choice than going under which is reserved for when there is an existing floor only! AND never will a system be installed without heat transfer plates.
Now, the difference between being on top or underneath is not just one of water temp (which of course is huge) it is also the fact that the heat is directly transferred to the finish floor, this is always the goal to transfer the heat directly to the finish floor keeping the R down and letting conduction work as simply and quickly as possible. That extra R that was mentioned as being only 5-7 meaning I guess that the under install only has to fight through that small extra R which is negligible in the authors mind. However, on top not only does not have to fight through the extra R but it now has that extra R below it which is now R as insulation. I do realize that it is also absorbing heat downward but being a solid surface it helps drive the energy up, as well as keeping the temperature under the floor lower that the fiberglass or whatever insulation is exposed to.
After all that run on (Sorry), we have just completed a few installs of a panel system that we find not only acceptable but is the best radiant floor I have seen. Rehau has a new panel out, the Raupanel which is made of extruded aluminum only (no wood). The only wood in this panel system is small 2" nailing strips (sleepers)and the return bends but the panel itself is all aluminum. It stands 5/8" tall uses 3/8" tubing and we have found the water temperatures extrmely low. The panel is extruded with legs (like an aluminum threshold) and this air gap it creates retards the heat transfer from going down into the subfloor. Resulting in much less downward loss and greater transfer to the finish floor and unbeleivable response time (ramping up and down). I think any of you that design and install radiant systems to be as efficient as possible will be as impressed as I am by this product.

hr

As hb stated

There are several "efficiencies at work here. The electrical efficiency is one. The amount of electrical energy consumed to distribute the heat. Compare a small wet rotor power consumption to a fan in a forced air unit. 1/12 hp to 1/2 hp or more. More importantly the amount of heat that each can move while consuming electricity. Pumps moving hot water win hands down over fans in boxes in this area!

Also heat transfer efficiency. Hard to beat transfer plates here. A step further would be copper in transfer plates, in my opinion.

Next comes fuel efficiency. The amount of gas or oil consumed to heat the fluid to a given temperature. I'm still not convinced the Germans are that much more efficient when comparing cast to cast, although the do seem to have an edge in insulation thickness and quality Condensing equipment would have a small lead here, in my opinion.

But lets not forget the building envelop efficiency. This is what ultimately drives the fuel costs. Windows, insulation, construction, fireplaces, can lights, owners useage, etc. All the best equipment and transfer devises mean little if the building leaks or is inefficient, from a fuel cost point of view.

hot rod

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Chris Maderia

Rheau

I saw a sample of this plate a few months ago. Was very impressed for it's thermal mass alone. You are the first person I have run in to that has used this plate. What was the difference in water temp between using this plate vs quik trak/climate panel. How do you think the response time differs? Was the ease of installation quicker? How about cost comparison? Since it has legs how is it attached to the subfloor. Any noise complaints? Would you continue to use this plate vs quik trak/climate panel?

Matt Connolly

A quick note to HR

First - your comment about copper vs. aluminum plates. In the world of heat transfer, copper is 4th, after aluminum, gold and silver. Aluminum wiring is better than copper, however it has problems with expansion which looses and leaves the fixture, usually shorting out and causaing a fire. Cast iron is about 10th, incidentally.

You comment about condensing boilers being more advatageous is right on - but they make a HUGE difference - they can be reset down to room temperature. I live in a well insulated 2700 sf home with radiant in gypcrete with an MZ25C (94,000 BTUH) and I have yet to break $100 a month in natural gas. Thats at least 50% less than if I had a conventional boiler.

Matt

radiant

Raupanel

Rauhau does not have any data available for us yet but from what I see the water temperatures are at least 20 degrees lower. The response time is amazing the panels get warm right to the edge in a matter of seconds. The installation of the panels was about the same as the others however, the tubing basically walked in with only some light tapping here and there with a rubber mallet which is nice for the forearms. We had no noise on start up. The panels heat so well you could really feel the heat right away with 120 degree water and no insulation in the building or under the floor yet and it was 18 deg day. We put different types of wood over small areas and they warm very quickly, aluminum readily gives up it's heat as you well know. I believe we will be restricted to about 110 degrees max temp on a design day because of the greater heat transfer. Anything over that will probably result in heating the wood flooring past the 85 degree max.

Yes, I will use these panels we always poured our projects except where we had to use panels(if we could not elevate the floor heigt or weight) I was never a panel fan the 5/16 tube is to small, the heat transfer is on the bottom, and the tubing doesn't have great contact with the "thin"aluminum sheet. THe Raupanel addresses all of this with 3/8" tubing direct heat transfer to the finish floor and less transfer to the subfloor. I also believe it is the lowest possible water temp system you could find which is what we look for and we now get the advantage of very quick response time.

radiant

Raupanel

Rauhau does not have any data available for us yet but from what I see the water temperatures are at least 20 degrees lower. The response time is amazing the panels get warm right to the edge in a matter of seconds. The installation of the panels was about the same as the others however, the tubing basically walked in with only some light tapping here and there with a rubber mallet which is nice for the forearms. We had no noise on start up. The panels heat so well you could really feel the heat right away with 120 degree water and no insulation in the building or under the floor yet and it was 18 deg day. We put different types of wood over small areas and they warm very quickly, aluminum readily gives up it's heat as you well know. I believe we will be restricted to about 110 degrees max temp on a design day because of the greater heat transfer. Anything over that will probably result in heating the wood flooring past the 85 degree max.

Yes, I will use these panels we always poured our projects except where we had to use panels(if we could not elevate the floor heigt or weight) I was never a panel fan the 5/16 tube is to small, the heat transfer is on the bottom, and the tubing doesn't have great contact with the "thin"aluminum sheet. THe Raupanel addresses all of this with 3/8" tubing direct heat transfer to the finish floor and less transfer to the subfloor. I also believe it is the lowest possible water temp system you could find which is what we look for and we now get the advantage of very quick response time.

radiant

radiant