In our new home we will have radiant in slab in the basement. I've decided not to do gypcrete on the main floor, but will do either Warmboard or the aluminum plates under the subfloor.

Here's my perception, if you have anything to add please let me know:

Warmboard: High initial cost ($14,000 just for the Warmboard on our first floor). Must be installed now, I already have paid for the design which is refundable if I purchase the Warmboard. A little more difficulty installing flooring, must be really careful and make templates when fastening cement board for tile. Hardwood will be fairly easy because you can see the tubing while your installing. We'll have some of both in our house. Difficulty making engineered wood flooring and tile have the same "height" (possibly shim underneath the areas that will get engineered lumber with plywood) OR use solid hardwood which probably isn't the best choice for radiant. More even heat with better response time to changes than the plates.

Metal plates under subfloor: Don't have to install now, can do it after we move in which could be nice since we're already pushing the budget a bit. Cost wise, I haven't priced it but I'm guessing MUCH cheaper than $14,000. Will probably require more tubing, but tubing is cheap. Would also likely require higher water temp since it's under the sub floor.

Thoughts?

Staple up form under the joist system is an effective alternative but if using a condensing boiler will be less efficient than a surface mounted system due to the higher operation temperatures of the water in the pipe to push through the sub floor.
We provide an alternate surface mounted system, RHT Floor panel system.
This typically runs about $3.00 per sq ft (pipe, turns, plates, manifold and 3/4 ply as needed.
If you would like a quote I will be happy to have our guys look at your plans.
Contact Blueridgecompany.com look for Radiant design on the left hand side bar.
Dan

What Dan said, above floor will be more efficient with lower water temps. IMO staple-up is better suited to retrofit installations. Because you are running much lower temps in an above sub-floor system, hardwood should be fine over it. What does your heat loss say you need for a floor temp to deliver the required heat? In an above floor system, the water temp wil not be much above that floor surface temp...

I splurged on WB as I thought it would save me some time, and I guess in the end it will. I sent them a CAD floorplan to provide a design, but wound up sending them my own design and tube routing which they approved. But since the design fee was refunded in the purchase price, it didn't cost me anything to try it(would have if I had used their design). Their plan had nearly 7 panels of waste, which was unacceptable to me in general, and at $250 a panel in particular. My plan had 1/10 of one panel waste, with only a few compromises from my original layout and zoning.

In general I was not pleased with the quality of plywood they used to bond the aluminum to. You would think for $8 a SF they would use high quality T&G subfloor. It says it is rated for one year exposure but it reacts horribly to moisture compared to the T&G subfloor I sourced locally for the areas I wasn't using WB. And of course we have had more snow here in the past 2 months than we have had in the past 2 decades, so I am a little frustrated by that fact right now.

It was also pretty warped upward at the ends of the panels. This is I believe from the type of glue they used(hot) to bind the aluminum to the ply. As the glue cooled, the aluminum shrunk pulling the panel ends up. Not a horrible big deal but it made getting T&G engagement a PITA for my wife and me to install. Really needed a 3rd person to hold the corners down to get the tounge started into the groove, and required a lot of force with sledge and block to seat them fully.

In the end I think it will work great, but if I ever do it again, I will spend a little more time putting together my own above floor system like RHT, and save a bunch of money. The good thing is that you can use the layout/design you got from WB and assemble it using something like RHT, so not a total loss in your case.

Good Luck.

Lots of red flags as I quickly read the site specs verified above. I first questioned the need for that much aluminum and associated cost and whether all of it conducted. Looks like hydropressed or drawn aluminum sheets which allows them to bang them out fast and cheap.

Next one was using an elastomeric glue to bond AL to plywood/OSB I think it was and how long the glue would sustain heat cycles and possible moisture cycles or what the warranty is? This heat, moisture, and glue food source could develop fungi that emits to IAQ under pressure. I didn't see any mold test in the specs. Also, what grade of AL and how is it treated for corrosion? What is the warranty on corrosion since a chem treat (CLAD, Alodine, Passivate, etc) is sacrificial and eventually wears off adding to the glue mold to IAQ.

AL is vapor barrier and I think I seen in the install spec they call out an underlayment retarder for whatever reason. If you have a vapor barrier under slab too it is now vapor locked at the bond, not good! Not as much of an issues in wood floor depending on design. I would not add more glue lines and use hard wood. It should conduct better and see less mold.

These plate systems look better. I have not look close at them. I'd avoid emitting heat/moisture through glue bond lines especially where dissimilar materials are bonded together.

http://www.radiantheatproducts.com/Heat_Transfer_Plates.php

Or just buy some .063" 2024-T3  ALCLAD plates and add them to the design. Or if you can some cheap pure AL 1000 series use it, highly anti-corrosive and conductive including electrical so watch out. Form-able too may be able to DIY form in routed wood. Thats another thing to consider EMF/I. 

I'd b looking at pay back periods is too. Yes AL is a good conductor but wood can too there has to be some loss to storage and I wonder how much faster the reaction time is.. I'm sure that depends on some variables.

Ronmar, where are you at in your build? We would be using the warmboard R since our main subfloor is already built and the house is closed in, so I don't think that we'd have toe tongue and groove to deal with.

Posted By ronmar on 11 Feb 2017 10:10 PM

In general I was not pleased with the quality of plywood they used to bond the aluminum to. You would think for $8 a SF they would use high quality T&G subfloor. It says it is rated for one year exposure but it reacts horribly to moisture compared to the T&G subfloor I sourced locally for the areas I wasn't using WB. And of course we have had more snow here in the past 2 months than we have had in the past 2 decades, so I am a little frustrated by that fact right now.

It was also pretty warped upward at the ends of the panels. This is I believe from the type of glue they used(hot) to bind the aluminum to the ply. As the glue cooled, the aluminum shrunk pulling the panel ends up. Not a horrible big deal but it made getting T&G engagement a PITA for my wife and me to install. Really needed a 3rd person to hold the corners down to get the tounge started into the groove, and required a lot of force with sledge and block to seat them fully.

In the end I think it will work great, but if I ever do it again, I will spend a little more time putting together my own above floor system like RHT, and save a bunch of money. The good thing is that you can use the layout/design you got from WB and assemble it using something like RHT, so not a total loss in our case.

Good Luck.

If they did their job right they should have bonded in temp and pressure controlled. AL would need alot of variance to go into bending and it would have delaminated. More than likely the wood edge seal is allowing moisture in swelling and that can happen with both series more so OSB.

I agree RHT looks like a much better product then this over priced junk! DIY pure AL plates in a HD mortar be good @ a fraction of the $$$. 

Another comparative low cost option may be to use pure AL tubing. We use it on aircraft to mock up fuel & hydraulic lines before going to production stainless steel. Unless I'm forgetting something. It be more efficient at heat transfer & lag time than PEX-AL-MASS. It can be formed by hand easily, and IIRC .5 depending on wall thk would not be a problem making the 1' radii.

I am curious why gypcrete was dismissed so quickly for this build? While not an option here, I will nevertheless also say that we always try to avoid multi-level home designs like the plague. However, even multi-level homes can be built using concrete floor decks. If you are doing a new build and know you want hydronic radiant floor heating, I think you should be thinking concrete floors and using an integrated design philosophy that accomplishes all the design goals at minimal cost.

Posted By PARAHOMES on 12 Feb 2017 09:33 AM
If they did their job right they should have bonded in temp and pressure controlled. AL would need alot of variance to go into bending and it would have delaminated. More than likely the wood edge seal is allowing moisture in swelling and that can happen with both series more so OSB.

It is ply, not OSB. I don't think the bonded AL plate would have to shrink very much to curl the ply, a little bit of shrink spread across all the bonded surface would get you the curl I experienced. It is a little more curl than you would get when holding a piece of ply by the ends. Just enough to make installation a pain. But knowing the temps involved, they could probably pre-stress the board to wind up with a flat product after it cools...

It is experiencing swelling at the ends. They of course knew this as well, as the edges were coated with a sealant from them, but it has not been too effective. In fact the sealant may actually be contributing to the problem by trapping moisture as my cut edges are not swelling nearly as bad as their sealed edges. Hopefully it will retract when I can get the floor dry. I am sure it will, it is just a little anoying looking at it and the regular 1 1/8" subfloor right alongside it that has had the same exposure but shows no apparent ill effects from the moisture...

We just poured the upper wall last week and I am instaling the brackets to hang the roof trusses so maybe another month to get roof sheathing on and windows in(I am pretty slow). I am able to keep rain off of it pretty well, but wind disturbes my catch system, and snow just flat crushes it:)

Ronmar, I think you will be very happy with the performance of the Warm board. However, this product is clearly susceptible to moisture issues given that it is essentially milled plywood and laminated aluminum skin. We always get a roof on our buildings before starting on anything susceptible to moisture or sun UV issues.

I think I could find MUCH better ways to spend $8/SF. Lets look at some numbers starting with the KING!

Material                                 Thermal Conductivity (TC) (BTU/HR F/FT)        Specific Heat Capacity(SHC) (BTU/LB-F)             Density (LB/FT3)

Pure AL (1100-0):                                        118                                                            .22                                                           .1

Plywood:                                                    .049                                                            .5                                                             40.5

OSB:                                                          .053                                                            .5                                                              29.3

Concrete:                                                    .042                                                            .2                                                             25

Gypsum (pure)                                            .250                                                            .2                                                              77

Type S Lime Mortar                                      .30                                                              .2                                                            120
(OPC portland cement close
to the same)

Solid SPF                                                     .070                                                            .5                                                                31

1. Dry thermal properties OSB series is 10 lb/ft3 less dense, less weight. If it stays together depending on OEM it has a little better wet properties too.

2. Gypsum has high TC & VERY low max water content(MMC) but, add a binder and aggregates knocks its TC down for a high weight penalty. Lime/OPC worse. You can get recycled gypsum and fly ash probably free at a local utility, bind it with lime it will get hard as a rock over time @ .150 TC, perhaps some OPC (lime/FA should reduce the need for it). Both OSB & PW have over twice as much SPC as Gypsum BUT will react at a fraction of the speed as Gypsum IF it were pure that is not feasible in this app.

3. Dry SPF has tad bit better TC than plywood/OSB and wet properties including much better TC due to higher max water content. I'd route what I could (.25-.375) out of it (.75) with a 5/8 ball nose, use 1100-0 AL tubing or PEX/plate in a bed of aerated lime Type SA (higher MMC) or gypsum (VERY low MMC usually used as a cheap filler to cut cost)-Crete w/a density no greater than concrete and thickness no greater than .5, composed mainly or pure inert materials that will outlast and out perform glues/OSB/PW, by far to include one fast acting floor. No need for sleepers & should take well to tile especially if you float the upper surface with more high strength OPC screed. My guess < $3/SF.

I have to say that our RHT Floor panel system is actually a fairly easy system to install for the cost and effort.
2 carpenters can run about 500 square feet a day, as I said earlier combined materials (pipe, manifolds, plates, turns plywood fill strips) $3.00 or less sq ft.
We provide a loop layout with purchase.
Works fine with any 1/2 pex pipe.
That's not to say I do not like warm board, it to is a great product and has a strong place in the radiant market.
Same is true of many of the "sandwich" systems on the market. There are quite a few.
I appreciate topping pours as well, have installed many. The ease of a pipe install combined with heat mass, win win.
But RHT system goes easy on the budget, can be installed slowly, area at a time over months if need be. Can be applied during framing or after finish sheet rock. It is a great choice if you can spare 3/4" on top of the sub floor, and does not require additional structure to gain then needed 16 lbs sq ft for a topping pour.
I don't think I would be thinking so much so much about sourcing fly ash or other things for a topping pour, a simple budget topper is 7 1/2 sack Portland cement, pea gravel, sand, fiber mesh and a 2" line pump. That usually can be sourced here in the Seattle area for about $1.75 sq ft placed (labor, material, pumper).
Weight is 16lbs 1 1/2" square foot. Not sure about cost elsewhere.
Dan

Posted By sailawayrb on 12 Feb 2017 01:05 PM
I am curious why gypcrete was dismissed so quickly for this build? While not an option here, I will nevertheless also say that we always try to avoid multi-level home designs like the plague. However, even multi-level homes can be built using concrete floor decks. If you are doing a new build and know you want hydronic radiant floor heating, I think you should be thinking concrete floors and using an integrated design philosophy that accomplishes all the design goals at minimal cost.

I am curious why you avoid multi level home designs? The price for gypcrete on our main level was over $6000. Yes, that's $8000 less than Warmboard, I agree. But when you start adding engineering, additional lumber, treated lumber, more tubing etc to support gypcrete, the costs quickly approach each other. Another real benefit for us was the ability to quickly adjust room temperatures. Yet another benefit was the fact that we could staple solid 3/4" hardwood flooring to it. We did think about gypcrete pretty hard but in the end I felt like either WB or something between the joists from underneath would be a better fit so we moved forward with the framing.

And I'm definitely interested in the RHT system. From an initial look, it seems like it could be 90% of the benefits and 35% of the cost of warmboard.

Posted By ronmar on 12 Feb 2017 02:51 PM

Posted By PARAHOMES on 12 Feb 2017 09:33 AM
If they did their job right they should have bonded in temp and pressure controlled. AL would need alot of variance to go into bending and it would have delaminated. More than likely the wood edge seal is allowing moisture in swelling and that can happen with both series more so OSB.

It is ply, not OSB. I don't think the bonded AL plate would have to shrink very much to curl the ply, a little bit of shrink spread across all the bonded surface would get you the curl I experienced. It is a little more curl than you would get when holding a piece of ply by the ends. Just enough to make installation a pain. But knowing the temps involved, they could probably pre-stress the board to wind up with a flat product after it cools...

It is experiencing swelling at the ends. They of course knew this as well, as the edges were coated with a sealant from them, but it has not been too effective. In fact the sealant may actually be contributing to the problem by trapping moisture as my cut edges are not swelling nearly as bad as their sealed edges. Hopefully it will retract when I can get the floor dry. I am sure it will, it is just a little anoying looking at it and the regular 1 1/8" subfloor right alongside it that has had the same exposure but shows no apparent ill effects from the moisture...

We just poured the upper wall last week and I am instaling the brackets to hang the roof trusses so maybe another month to get roof sheathing on and windows in(I am pretty slow). I am able to keep rain off of it pretty well, but wind disturbes my catch system, and snow just flat crushes it:)

"But knowing the temps involved, they could probably pre-stress the board to wind up with a flat product after it cools... "

It's probably a 250 F cure film adhesive w/ plate pressure. Makes me think they are using Pure AL in the "O" condition non-heat treated non stress relieved so it bonded to the irrregular OSB/Plywood better but they could not go into the chem tank with the wood to take the AL up to T3. Just guessing. 

Once 1100-0 tube/plate is formed one can take it to a local chem tank and they can HT it to T3 or T4. Shouldn't cost much at all.

Posted By Blueridgecompany.com on 12 Feb 2017 07:51 PM

I don't think I would be thinking so much so much about sourcing fly ash or other things for a topping pour, a simple budget topper is 7 1/2 sack Portland cement, pea gravel, sand, fiber mesh and a 2" line pump. That usually can be sourced here in the Seattle area for about $1.75 sq ft placed (labor, material, pumper).
Weight is 16lbs 1 1/2" square foot. Not sure about cost elsewhere.
Dan

This is a bad mix, low TC/SHC per unit weight. The reason they use "Gypcrete: is due to it's high TC. Fly Ash & Type S or N Lime too & OPC at high weights. I guess you didn't understand the properties I posted. It takes Engineering to produce a high (TC ) U-value, low weight (D), High SHC dry/wet and it can be done with no added structure to IRC IF you know what you are doing.

Yea, I could have done it for less myself, but unfortunately working mostly alone, time has value. Routing 2000' and fitting plates, or piecing together ply and plates all have a time cost..

sailaway, Yes, would have been nice to have the envelope closed before the WB was installed, but this is a single over full daylight basement. Had to have the floor diaphragm in and basement wall backfilled before we could pour the main floor wall...

Rgonyer, we favor single-level homes to avoid having any stairs. We only design/build ICF homes with passive solar and hydronic radiant heating. Keeping the overall design simple and integrated reduces overall construction cost and results in a highly energy efficient envelope that is lifetime livable for multiple generations. You do need to have adequate land to make this work, so this often isn't a viable option in some areas.

Ronmar, that makes sense and I feel your pain. Seeing new wood construction get wet always troubles me even though it is commonly done.

Posted By ronmar on 12 Feb 2017 09:45 PM
Yea, I could have done it for less myself, but unfortunately working mostly alone, time has value. Routing 2000' and fitting plates, or piecing together ply and plates all have a time cost..

sailaway, Yes, would have been nice to have the envelope closed before the WB was installed, but this is a single over full daylight basement. Had to have the floor diaphragm in and basement wall backfilled before we could pour the main floor wall...

For $12,000 or $8/SF you could hire out all your labor & have a much higher performance fast acting floor. PEX has the TC (Thermal Conductivity) of ~ Gypsum ~ 500x < Al 1000x < copper so they create a market using costly gadgets and it still never gets even close in COP not even PEX_AL_PEX. It's cheap & flexible that's where it ends.

Warmboard design uses highly conductive AL bonded to OSB/PW with about the same low TC as concrete but twice the SHC (Specific Heat Storage) meaning it may take a while but the wood TC is still there & will eventually store more heat over time meaning less gets conducted out to living space over time. RHT is the same only they use a less effective cheap plywood and in time the heat/moisture cycles will eventually fatigue the bonds lines like you are already seeing.

Al or better copper tubing in properly designed hygro-thermal mass (certain hardwoods or cretes) will have a much higher COP/sustainability @ lower cost.  

I don't think some are understanding your frustration with Warmboard, for such high outright ridiculous cost of low performance one would expect an APA Exposure 2 rating that protects the bond line during wet construction delays which is very common but they probably used CDX or APA won't rate the metal bond due to delams/voids which is common with high contours. Nobody should "feel your pain" or early bond line failures and it makes NO "sense" at all at the price you paid.   

"Al or better copper tubing in properly designed hygro-thermal mass (certain hardwoods or cretes) will have a much higher COP/sustainability @ lower cost. "

So your saying we should be putting copper pipe in a radiant floor? Come on now!