Radiant Floor Heat Transfer Film?

archibald tuttle

Hot Rod,

Thanks for your in situ photos. I don't want to throw any cold water on an other wise beautiful hot water job, but it looks like you don't get quite the 'wrap' on the pipe that they did in the demo section john pictured which was probably assembled upside down with gravity in their favor.

Is there any adhesive involved or does is the film just stiff enough to stay up next to the floor with what looks like stapling? Does the material have any shape memory such that if you had some kind of a 'die', e.g., maybe a piece of the aluminum product being supplanted, to push the film around the pipe before stapling, do you think there might be any benefit to that?

Thanks,

Brian

archibald tuttle

Radiant Floor Heat Transfer Film

Recall a post perhaps 2 months back in with a FLIR picture of some miracle glad wrap approach to heat transfer where floor radiant is accomplished by attaching pex tubing directly under wood floor in joist spacings in which aluminum pans would commonly be used.

At the time, this was hush, hush beta not much more available. I have tried several searches to bring the thread back up but haven't been able to find it to query the waller who was following this. Just wondering if there are any developments here. If not, thinking maybe aluminum foil and spray adhesive for my next job might be a reasonable approximation or ... suggestions???

Thanks,

Brian

John Schober

flexible graphite for heat transfer

John Schober

flexible graphite for heat transfer

John Schober

\"glad wrap\" for heat transfer

You can see the "glad wrap" approach to heat transfer that Brian is referring to in the attachment. The material is flexible graphite and its use in hydronic radiant flooring is still in development. The heat transfer improvement that we've seen thus far has been very encouraging, and we've received some positive feedback thus far on ease of installation.

Though we're not ready to "go to market," we're at the point where we might welcome a few inquiries to use it in a small under floor (joist) installation (100-200 sq-ft). One type of installation that might be particularly attractive is a retro-fit, i.e. an installation where no aluminum was used and the heat output could be improved. The ease of installation offered by the flexbile graphite could really help in this case.

Please contact me directly via email if you are interested. We hope to be rolling out more info at Wetstock 2008 (if not sooner), including feedback from any of these installations.

hot_rod

Here is an actual install

I did for a master bathroom. Some extruded plates, some Graftech SpreaderShield.

I went back with the IR camera but, alas, the floors were too shiney, tile and new hardwood, for the camera to read. The owner wouldn't let me spray paint his new hardwood or tile, so...

I suspect the result would look similar to this pic of Advantech from above.

We need some more installers willing to try some out and help us come up with some attachment method options.

hot rod

archibald tuttle

the old graphite eh...

John,

Thanks for that update, I'm in for a trial if I'm local enough although this is a retrofit in terms of no tubes at the moment. I'm getting ready to put underfloor radiant into about 330 foot single room studio apt. space. 1890s building in rural RI. Most of the house is steam but I have some floor radiant running on a 3rd floor renovation portion of the house. The area slated to get floor radiant is first floor area as the north west end of cellar and away from the boiler that gets 'cold floor' disease and has reasonably easy access, cellar ceiling is about 7.5'and open. Flooring is 3/4" + pine or spruce subfloor and 3/4" fir finish.

Don't know if this would be suitable for your testing purposes, but didn't see a link for your e-mail so I replied on the thread.

Insofar as 'easy install' are we talking spraying the graphite film with adhesive or is it pre pasted in some way? How critical/difficult -- and this may not be fully known until the more testing -- is making the film contact the pipe.

If this isn't a suitable test project and the stuff isn't really available yet, am I crazy to think about trying something similar with aluminum foil. The pans are on the borderline of affordable for what is essentially a footwarmer. I have known folks who used 3 runs of pipe per bay with no pans and seem to getting enough effect that they aren't getting constant callbacks. But I thougt maybe picking up a food service box of aluminum foil and applying it in maybe 4 or 6 foot lengths where I spray adhesive down the center between two pipes already installed and on the pipes thus getting the foil to stick up and then more carefully molding the foil around the pipes and then spray outside the two pipes, or maybe I can just spray the whole thing and be careful to start from the middle and work out so I get it hung, and get decent contact with the pex.

I suppose after I try one bay and see how long that takes me, I can always give up and go with pans or no pans and just put up the insulation, but I wanted to give something a try.

I'd also be glad to try two different treatments on two sides of the room if that would be a helpful test and that would bring the area for the graphite down to like 150 square feet if that is more commensurate with currently avilable preproduction availability of the material.


Brian

ALH_4

Attachment

How about shipping the material in rolls and forming a channel for the desired tube diameter immediately prior to installation, similar to rain gutters? Packaging and shipping is not a minor issue.

Also, this might not help the heat transfer spread, but you could attach all but 3" of the width of a flat sheet, install the tube a few inches in from the unfastened edge, then fold the sheet over the tube and fasten it to itself. The superior conductivity of the graphite might still allow it to perform well even though the tube would be at one side. Folding the sheet over the tube would probably improve the contact between them and would capture the tube within the sheet.

hot_rod

Exactly, Brian

that's the challange the tube to graphite connection. My samples have peel and stick on one side. It grabs the pex very well but not so well to the bottom of the subfloor, even brand new stuff.

I did preform mine with a copper pipe and some old Roth panels.

It doesn't hold it shape as well as aluminum, but it may not need to. The way it spreads heat it appears a thin contact point to the tube gets the job done.

We are trying various aluminum extrusions to aid that connection, but also trying to keep the price reasonable, as well as the installation requirements.

Mine was stapled along with the tube, then I used a swing stapler to help the peel and stick connection.

John wants to get some more in installer hands to get more installation ideas.

hot rod

Gordy

Ya mean like this Poor mans Plates

It does work. I did the other half of the kitchen with no heavy gauge foil. There is a noticable but anal difference.

I filled the tube groove with thinset, then back buttered my backer board with thinset before laying in place. I'm going to be tiling the dining room next 15 x 12.

This time I will do the foil like Andrew is saying by wrapping the tube. I was going to use this method before.

My plan is to do sleeper RFH in each room as I redo the floor coverings. I have ceiling radiant now 56 years old still going. At least this way I will be covered if it ever craps out. Until then I will enjoy a radiant sandwich, or I can set it up as two systems to run independent or together.

Sure would like to use that graphite wrap for the rest of the house but until then.....

Gordy

Ron Gillen

A work of art

I don't believe that the foil would help much but I gotta say that for those of us in this business that copper is some kinda nice work. With backer and tile heat spread should be real good anyway.

John Schober

I guess my email didn't show up in the last post...here it is: john.schober@graftech.com

Regarding pre-grooving vs grooving it on site, that is one of our remaining issues that we'd like to help address through these trials. We could send sheets pre-grooved. It would cost extra, and the question for us (really, for contractors) is whether the extra cost would be worth it. For the trials, we're hoping to try both options and get feedback. We're hoping that we can get some people to experiment with different installation methods - Andrew's suggestion would be an example of just such an experiment.

Regarding stiffness, the appropriate amount of stiffness, to some extent, can be designed in. We think we have it about right, but again, we'd like some broad feedback through trials.

Regarding adhesive, we think that no adhesive will be the best option (i.e. relying on staples to hold it up). Installation with adhesive could get tricky, and we're not sure the extra cost would be worth it. If we do go without adhesive, the key will be ensuring as good of contact between tubing and graphite as possible. Trials will help determine how easy/difficult that is to control.

Gordy

Thanks Ron

It was an Idea to try. Cost was next to nothing. This was done before copper went through the roof.

Gordy

archibald tuttle

adhesive etc.

John,

Now I'm thinking that a third possibility is adhesive that is not preapplied to the graphite sheet, some kind of spray flooring or general purpose contact adhesive spray. It seems to me that while the material physics of the adhesive itself might not be the best heat transfer medium, especially if you use one that has a thicker body and so is more likely to have an easy high tack without a lot of burnishing which is sometimes acheived but generally I have observed to have a more frothy, e.g. less dense more airy consistency, but I think it is still likely better than stapling and the minute air gap virtually everywhere. That is seat of the pants logic so take it for what it is worth.

Obviously spraying adhesives overhead has its own downsides, although possibly one could have a plywood form positive and negative to put the pipe form into the material on site in say 4 or 6 foot length and then spray the adhesive on the film rather than upwards into the joist cavity.

With some experience, might even be able to spray outside and then carry in.

The other idea I have had for this conundrum is to see if I can get a set of rollers made for my Van Mark sheet metal slitter that could take flat 8" aluminum flashing(or maybe graphite film) and use extrusion technique to put the pipe shape in on the job. Or even in the shop (currently I have the Van Mark mounted on a shop bench) prior to the days work. This means we're dealing with a commodity that can ship in a roll and possibly has multiple uses and we're looking just at the cost of the basic material more so than the investment in forming these pieces in a factory setting and shipping them.

Not to put too fine a point on this, but since you are looking at price point, just in a inputs cost model, how does the material cost for the graphite film stack up against the material cost for aluminum -- in whatever seem to be the rationally applicable comparable thickenesses, e.g. if aluminum is 14 gauge but the graphite is 16 or 12 or whathaveyou, I'm looking at performance equivalent rather than absolute equivalent in terms of cubic volume or weight of material.

Of course you may not have absolutely standardized these metrics yet but I assume that you have some aim or thoughts in this arena.

I guess I'm interested in whether the idea is that this will cost less than aluminum, cost the same or more but perform better, cost less when installations is considered, etc. All of these are valid pursuits. Being the seat of the pants guy, I am trying to find a product that maybe strikes a performance/installations/cost balance between doing it myself with aluminum foil and the current expense of aluminum pans.

Thanks

Brian

archibald tuttle

rich man poor man

When you say the difference is noticeable but anal do you mean it is not much or ???

I can definitely see, given the materials involved as some other astute commentor has pointed out, you are going to get pretty good transfer even without the foil. But I'm looking at plastic pipe under two layers of wood floor. I've had success employing aluminum pans on a job like this before, but it is defintely pushing the envelope of whether the wood floor is the primary or sole heating element, or this is a comfort add while some other radiant or less passive source tops off the heating needs of the space.

Brian

Gordy

The whole point

For this product to be successful is.

1. Have better heat transfer than what is out there at present from the pipe to the product, and the product to the floor.

2. Be cheaper than what is offered at present, both in product cost, and labor to install.

I believe it was said that this graphite has a much better heat transfer capability than aluminum. But I believe it was the heat spread and not transfer to the surface.

Sucking the heat off the pipe is one thing, getting to the floor where it is needed is another. I think any time you are trying to push heat through the underside of the floor you are at a disadvantage to begin with. Sure it can work but with some sacrifice to output, or efficiency, or both.

The difference with foil was noticable on start up, but after the floor was up, and running there is no difference.


Gordy