5/8\" Pex between floor joists \"No Radiant Plates\"

GH

RADIANT HEAT HAS BEEN ON THE PLANET FOR OVER 500 YEARS.
HISTORY TEACHES PROPER RADIANT INSTALLATION AND RELATED
METHODS FOR PROPER INSTALLATION OF PROVEN PERFORMANCE.
STAPLE UP IS NOT ONE OF THEM.



























staple up is noy

vhlaundry

5/8\" Pex between floor joists \"No Radiant Plates\"

I have met with a local specialist who suggested instead of using single run 3/8" pex between floor joists with aluminum radiant panels, they would hang 5/8" pex about an inch or so below underside with a double run between each 16" OC floor joist and no radiant panels. Then they said insulate under the the 5/8" pex. They said this may require running slightly higher water temps but works better that the 3/8" with radiant panels.

But if you look at this link with infrared pics that may not be the most efficient way to do it. Does this sound right?

http://www.pmmag.com/CDA/ArticleInformation/coverstory/BNPCoverStoryItem/0,2372,123092,00.html

Unknown

First off, who the heck suggested running a single run of 3/8" per joist bay, even with plates? You want a double run there as well.

If they are both double runs, the hanging 5/8" will not work better, and they are working harder than they have to. They could hang double runs of 3/8" without plates and get very similar performance (but shorter loops) to their 5/8".

Has anyone done a heat load calc on this space? That tells you what the differrences are and whether either of those applications are good enough. You might need heavy extruded plates. You might not need any plates. It all depends!



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John Jr

local specialist?

local specialist? I hope it is by his stanards. I'd check around to see what others guy's would say about that. If he wants to run 5/8 pex staple up it has to be his first time, because if he did it before he wouldn't do it again.

SVDW

I retro-fitted my house with a staple-up install using 1/2" pex dual runs in the joists. I installed reflective bubble r-foil 1" below the pex I then insulated w/R-13 fiberglass. I do have to run a higher temp. (up to 130deg) to heat the space effectively. The install was much easier using dual runs as you can just pull down the joist space from the end. Hindsight is 20/20 but I should have used the transfer plates to run lower temps & have less floor creaking when the system is coming up to temp. Hope this helps. Good Luck.

Unknown

floor creaking?

That is most likely some sort of tubing expansion, caused by either not letting the pipe expand properly or a simple control strategy.

If your runs are not too long in each joist bay, and you have decent size joist penetrations, and the loop heads can move (i.e., they weren't clipped to the subfloor).. then you might be able to make that creaking go away with a change in control strategy.. maybe even just better thermostats.

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Jed_2

Rob

How do we get a handle on this butchery? DYI'ers and "I was told to do it this way" sources. I heard of a local contractor who is now "exclusively" using Ultra-Fin for his installs, and reports absolute satisfaction from clients(third party source). This is the Bangor area. I admit he is not a customer of mine, and cannot easily discuss this with him. I believe many DYI'ers are just not being informed properly. What do yoy think?

Jed

vhlaundry

Getting it Right

It is doubtful I personally will be a DIY in this application/home improvement project, but if I am not informed correctly, then I cannot judge whether what I am being told is correct or not.

From what has been posted, would it be correct to assume that 3/8" or 1/2" PEX doubled up between joists with aluminum plates, then backed with "what kind of insultation" is the right approach?

Also, are there different quality heavy gauge aluminum extruded heat dissipation plates?

Sorry to belabor this point.

ALH_3

Misconceptions

It's a common misconception that more flow through the pipe means more heat to the space. More fluid at the same temperature contains more heat, but that doesnt mean the heat makes it to the room. Suspended tube has many issues with respect to being able to release the heat contained in the fluid.

What you want is conduction. Hanging tube gives you none of that. Hanging tube will not perform or respond to a call for heat nearly as well as plates will.

There are a lot of different plates out there. I recommend using extruded plates. The tight fit of the tubing and plate and the good contact of the plate to the subfloor will maximize conductive heat transfer.

It's not necessarily an issue of efficiency. It's much more an issue of performance and effectiveness. Hanging tube can work if you heat load is low and you are not particularly demanding of your heating system. I know of few people who will pay for a radiant floor and then not be demanding of their heating system.

I recommend using extruded plates 8" on center. If possible use 1/2" tubing and keep your loop lengths under 300'. Staple the plates under the floor with a pneumatic stapler and 5/8"leg, 7/16"(or1/2")width, 16ga staples. Paslode, Hitachi, Senco, Spotnails and others make acceptable staplers for this purpose.

Plates sound like more work than they are. It just takes the right installation techniques to speed up the job. The stapler makes installation many times easier and faster than using self-drilling screws or pre-drilled plates. It can pay for itself easily in one job. Make it easier by cutting a couple of blocks to space the plate off of the side of the joist.

Pre-drilled plates are of no advantage. In fact I think they encourage the use of inferior screws. Drywall screws should never be used to install under-floor fin.

I'm getting a little off-topic here, but look at extruded plates more closely. They're the superior "dry" system.

-Andrew

Tom_35

Listen to the pro's here

I very rarely have seen anyone on The Wall recommend suspended pex for heating. If the guy you talked to recommended the 5/8" suspended because of nails protruding through the floor, you might consider the Onix product from Watts, as it is very flexible. But, if you have room to manuever around, nails not a problem, go with the plates and pex.

We just finished using plates provided by Watts, but designed via Radiant Engineering Co and there is an abolute difference between these plates and the very lightweight plates that we have used in the past. Not to say that all others are that inferior, but HR recommended them, I tried them, and will continue to use them.

Pex-Plates-Lower water temps= better efficiency.

Tom A

vhlaundry

Thanks

This is exactly what I am looking for.

Unknown

You're definitely right, but there are good reasons for it. There are a lot of ways to do radiant, and they can all work. But what's good for one project isn't always what's good for another. Sure, you can do every job in warmboard, or thermofin, and know it's top of the line. But if the client has a 10 BTU/sq ft heat loss, you haven't done him any favors that way.

I think the problem is just rooted in time. Most people don't have the time to get up to speed on a variety of solutions and to really get proficient in learning how to use each one. They want a one-size fits all solution, and there are only two ways to do that. One, you adopt a cheap and weak solution, save the clients money, and hope that the client isn't one of the few that the solution won't work well for... and don't think too much about efficiency or actual fuel usage savings. Or, you adopt an expensive solution, and price yourself out of a lot of work, especially if you can't really explain why it's better than Low Joe across town.

I can't think of any way to get more "tools for the toolbox" than to put the time in though, and it can be hard to find that time. All I do is radiant, and it's still a struggle to stay on top of everything, new research, new products, new techniques, new heat sources... for a contractor doing radiant, general heating, plumbing... I can imagine it must be damn near impossible to stay on top of it all.

Tough situation really!



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vhlaundry

Please explain

Rob,
You said: "But if the client has a 10 BTU/sq ft heat loss, you haven't done him any favors that way."

Are you implying that if my house is not that energy efficient this particular approach may not be the efficient? B/C my house is "old" and though I have replace most all windows it is still built with 2X4 walls and poor insulation at best.

If my home does have "high" BTU/sq ft heat loss, would my existing baseboard and or refitting with euro wall mounted panels be more effective?

bigugh_4

Thas what he said!

Carefull & knowledgeable engineering is needed! and it tough to do it without spending a lot of TIME. reading here and the other resources there are many ways to skin this radiant cat. And each one has its own advantages and DIS'S. $$$ is one side. another is (How many do you want to go into). Steam, Gas, electrical, oil, solar, scheese how do you do it all. Pick a point and go fore it!

Unknown

No, I was saying the opposite (that's a low heat loss number I used as an example). If you're in a situation where your losses are very low, you don't need high-end output to achieve low water temperatures, so the value of dumping money into high-end panel systems diminishes with the load. In fact if your load is low enough, I question the value of doing floor at all, as at some point it won't even really feel warm.. might as well do ceiling and really save some $$$$.

The higher your loss, the more it makes sense to use higher-output panels to drop your water temps; up to a point. Of course it's best to invest in the envelope first, then work on the heating system to meet the load you end up with.

There is an upper limit to what floors can do comfortably though. This is why heat loss calculations are necessary; imagine the dissapointment if even after dumping a ton of money on a top-end radiant system, it can't keep you warm, or it's too hot for you to walk on comfortably, or it wrecks those wood floors.. or.. or.. or....

But there are two big steps to a heat load calc; first is figuring the load. Second is interpeting those numbers and what it means for different types of radiant installations in terms of output, efficiency, heat source selection, flooring choices, possible supplemental needs, etc. If you're working with someone on radiant, ask to see the room-by-room heat load numbers. If they can't be produced.. you're being "ballparked" into a system, instead of having a system designed for you.

This isn't to say that everyone out there that uses one method of installation is wrong or their systems don't work. It's just the one-size-fits-all solution is not necessarily the BEST choice for everyone. Any system that can be done in radiant can be done with warmboard, for example. But do you need it on every project? no.

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jerry scharf_3

a hard topic to solve

Jed,

The problem I see is that the people out there offering these pearls of wisdom have two things going for them. They shout really loudly (advertisements, major internet presence...)

More important, they tell people what they want to hear. "You don't need to pay expensive people to do this. We can help you save lots of money and still get all the benefits." At some level, who doesn't want to hear this? So they stoop to the level of promising the stars and delivering whatever.

Many/most people who we see at this site are "stretching budgets" to include radiant heat into the project. It's hard to tell them that it will cost more than they imagined.

So we need to give them concentrated information and then use the wall for more detailed discussions. See my next post for some thoughts.

jerry

jerry scharf_3

Dan, an idea for the site

Dan,

I had been playing with the idea of wriing up some kind of introduction on controls, but didn't come up with a form I liked. When reading Jed's post of what can we do about it, it got me thinking (always dangerous.)

Maybe change the name from "Heating Q&A' to "Heating FAQ" and put together some kind of consensus of wall opinion on subject like radiant heat would be are real win. Many internet people understand the idea of FAQ and being pointed to it to cover basics. There was a great discussion about picking an installer with a list of questions to ask. Capturing that into an FAQ and putting it out there would be a great thing.It could also help people find their way to other things on the site with links that are easy to find. The only thing to add to this is you would want to turn off the google ads on this section, it could cause some difficulties otherwise. I think this could be a great draw for the site.

I would be happy to edit one for controls. I'm sure Mark would do one for CO poisoning. Steve Ebels did a bunch of stuff on choosing contractors already. Steamhead has the common steam questions and answers memorized. I could imagine a couple more on radiant heat and "I want to heat my house...". My thought is things stay on the wall until someine decdes "we've answered this question enoug times, let's put it in an FAQ we can point to." The only requirements I would have for being an editor is that the person have the ability to capture consensus and the understanding that you either need to keep it updated or pass the torch on (find the next victim.)

That way we can have more time to discuss flat rate pricing and energy policy.

jerry

Paul Pollets

Plates & 3/8\" PEX

We install our "suspended" systems using 3/8" Wirsbo hePEX and double groove aluminum transfer plates or single plates, as required. The nails protruding through the subfloor must be cut and ground before application. Any mechanicals (plumbing or wiring) needs to be rerouted a min. of 2-3" from the subfloor. After we commsion the application, R19 insulation (or rockwool)is placed in the bays, with a 1-2" air space between the plates and the insulation. Rockwool is sound-deadening insulation, which greatly reduces sound transfer,and costs more than R19 batts. All suspended systems use a mixing valve with motor actuator, controlled by the boiler computer. This assures no "ticking" or expansion sounds, and provides accurate setpoint temperatures. Plates do have various dissipation rates, which has been posted on The Wall before. Hot Rod has a handle on the latest tech data. I've used both types of plates (dbl grooved alum and "Joist Trac". Both work well. The better plates grip the tubing for better transfer.

If the residence has a high heat loss (min insulation, single pane windows) consider using wall panel radiators...Warm floors are the best, but cranking up the temps in a "suspended" application may exceed design temps. I'd be using a radiant heatloss program to verify the required temps and play "what if?"

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