radiant tube attached to joist?????

GMcD

I'm not sure what parts of the laws of physics you don't understand. The above quote of mine you took is not an assumption, it's a statement of fact. Conduction transfers heat at a rate many hundreds of times greater than by radiation and convection, and in a closed joist bay, there is very little convection if it's been insulated and left with a very small air cavity. The heating fluid in the tubing in a joist bay heating application generally has to run at very high temperatures to get heat to transfer by radiation from the tubing to the subfloor, and then overcome the insulating factor for the wood subbfloor and the finished floor on top of that.

At least with staple-up systems, the tubing is in direct contact to the flooring, especially using plates, so the heat transfer to the floor assembly is much greater, allowing the heating fluid to run at lower temperatures, and it wastes less energy compared to the heat transfer by radiant in a joist bay.

Bob Holohan

radiant tubing on joist

Is it exceptable to attach tubing to the sides of joist rather than to the under floor. I have a client who has been searching the NET and now he is an expert..

EXPERT=
Ex is a has been
Spurt is a drip under pressure

John Barba_2

Bob --

It's not in our book, and as far as we are concerned, it's not acceptable.

JMB

Leo G_99

Bob,

> Is it exceptable to attach tubing to the sides of

> joist rather than to the under floor. I have a

> client who has been searching the NET and now he

> is an expert..

>

> EXPERT= Ex is a has

> been Spurt is a drip under pressure



it really depends were you are located. In the more temperate zones of this world, with proper insulation it does work, though of course at a higher temp. Basically you are heating the joist cavity air to heat the floor above. I wouldn't want to do it in the more colder climes though.

Leo G

Leo G_99

Bob,

it really depends were you are located. In the more temperate zones of this world, with proper insulation it does work, though of course at a higher temp. Basically you are heating the joist cavity air to heat the floor above. I wouldn't want to do it in the more colder climes though.

Leo G

GMcD

Horribly inefficient

While staple up radiant under a wood subfloor is inefficient at best, doing the old "heated joist bay" method is just a sheer waste of energy and resources. To properly conduct heat from the hot fluid to the floor above, conductance is King. Get the tube fixed to the underside of the floor, and use heat distribution plates, the heavier gauge the better, with some kind of good paste or heat transfer material to get heat from the warm water in the tube out to the floor via good conduction. Sure it costs more $$ than the simple inefficient methods, but you know the saying, you save a bit of money now, but you'll pay and pay and pay for the gas bills for the life of the house.

J.C.A._3

I'm with Geoff,

Air isn't the best heating medium...BY FAR, and it's what you'll be heating by doing this. Even in a "mild" climate...wouldn't YOU want the heat transfer to be to THE FLOOR, where it can work?

I also like the heavy gauge trac panels for doing any sort of staple up/underfloor heating. It just makes sense.Put the heat where it belongs and spread it as wide about the joist bay as possible,not to mention the lower temperatures that will be needed.

If the "expert" insists on doing his job this way, at least point him to Thermo-Fin products. At least...he'll get MORE heat to the air that way. (I don't know why either..but it may be just what he needs) Chris

Mike T., Swampeast MO

Of every method of bare tube radiant floor heating, that is the WORST way. It takes nothing more than basic understanding of heat transfer to see why:

1) What little conduction is available has to pass through the joists before it meets the floor.

2) Such an installation retards natural convection as air cannot flow freely around the tube.

3) Radiant transfer to the floor is extremely oblique. The object with the best "view" of the tube is the opposite joist!

Jed_2

Not to mention

any striping that may occur, given the extreme temps required. I can't see any value to "joist stapling" as an acceptable method, other than a "low bid, you have radiant" lie.

Jed

Jimmy K

Just the facts, no bs

Mcdonell wrote:
"While staple up radiant under a wood subfloor is inefficient at best, doing the old "heated joist bay" method is just a sheer waste of energy and resources. "

Oh Mr. Wise radiant please show us the studies to proves this assumption.

Timco

Good paste or heat transfer material? Would good silicone work, or is there a specific paste for this?

Tim

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Weezbo

i dont want to read too much into your question...

however it occurs to me...i have no problem stapling radiant tube to a floor joist. about the only time you would want to fix it to the floor is if you wanted to heat the floor or warm the floor. the btus will go to the mass of the floor joist and wont be distributing the btus to the floor unless it is cooler. then , the insulation if any further slows the escape of heat. i would be inclined to say that stapling it to the floor dosent do much to a gypcrete radiant slab above it...the reason being heat goes to cold. so, if you are worried that the path for the radiant supply and return run outs have to be attached to the bottom of the floor or it will not get the heat to the sub panel trust me i never staple them up under the floor. mostly i travel along a beam or along the floor joist..away from nails and staples and insulated away from the space below ....*~/:)

hows that for an equal opportunity observation?

GMcD

Heat transfer material

There was a discussion a while back on the RPA forum at:

http://radnet.groupee.net/eve/forums/a/tpc/f/1041029701/m/5451042801

And the suspended radiant panel folks (Airtex, Twa) used to use a paste in the saddles where the copper tube was pressed, but I think the bean-counters have ruled and they don't use it much anymore. There is a slight improvement in the heat transfer rate, but when one is working with higher intensity heat sources over 125F, which s typical for most staple-up and suspended radiant panel systems, the added benefit was deemed negligible compared to the cost/benefit comparison.

hydronx_3

plateless reflections

For what it is worth I just got done fixing a job which was previously done as your client proposes. They were able to heat the place but where going through a gob of propane. It will be interesting to see how it changes the amount of fuel this winter.
The installers motto is "When Quality Matters" and I am sure his intentions were good. He did sell them on a high efficiency condensing boiler, but with it set to 172 degree target temperature it isn't being fully utilized.

by the way it is easier to add the plates now than after the wiring, plumbing, and HRV ducting is in -see pics

not to mention you have to share the crawlspace with the spiders who have had time to set up shop as well!

Glen Kauffman

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Dave H_2

Suspended Joist Systems

Of course the most important thing to do (or have performed) is the heat loss. Make sure that the underfloor system is going to perform to expectations.
Sure, plate systems are the best way to get the heat transfer from pex to the flooring system, but if the math works for the heat transfer, then the math works.

As for nailing the tubing on the sides of th joists, I wouldn't do it. You need the air to transfer the heat from the pex to the flooring system. However, I have seen it done some pretty creative ways. Attached is a picture of a system installed via pulling the subfloor since the ceiling below was already finished.

ALH_4

But

Stapling the tube to the joist is a lot easier. ;-)

In my opinion, if the customer can only afford this type of installation, it is time to start thinking of other options (radiators). It is for the same reason that I would never recommend anyone use Ultra Fin or any method with the words "staple-up" in the name.

I agree completely with Geoff, except that plates aren't staple-up. ;-)

-Andrew

ALH_4

Nice

Nice work. I am very curious how much fuel that will save them. What kind of boiler is it?

-Andrew

hydronx_3

space ship

Andrew,
It is a weil mclean Ultra.
I was trying to turn the temp down on it, which is easy enough, but the way I understand the outdoor reset on it is that it after every ten minutes of a continual call for heat it starts boosting the supply temp by 18 degrees until it hits your max target. 10 minutes ain't much when the whole idea of outdoor reset is continuous circ.
I couldn't find anything in the manual that let me override it or to also change the reset curve to be any good below 32 degrees outdoor temp either.

hope things are going well for you Andrew.

Glen

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

ALH_4

Reset

That sounds like a "cover your butt" approach to reset. Are Ultra's not designed for constant circulation?

Life is good. Hope the same is true there.

-Andrew

Jim\"Rocky\"Kelleher

? Still BS.

What law of physics ?
Let's talk facts ! Two houses side by side both have radiant one has onix staple up, one has what ever radiant you want. Show me the study that will tell me that staple up is grossly inefficient compared to whatever floats your radiant boat. Back it up .

GMcD

Studies

There aren't any studies. I know from contacts and my own European investigations that staple-up under wood floors is "not acceptable" by their energy codes for residential construction. All their installations are generally panel radiators and topping (PEX in concrete) installations, as well as extremely tight envelopes as the primary energy efficiency system.

Given two identical houses with identical envelopes (heat losses are equal), the PEX in concrete topping or slab radiant floor system will show less energy use over time due to the higher heat transfer efficiency of the heat from the tubing into the concrete- direct conductance and thermal spread in the concrete, thermal storage of the concrete, less cycling of the boiler, etc... The PEX in concrete systems will require lower fluid temperatures to achieve the same floor surface temperature to heat the home compared to staple-up systems, allowing the boiler to run at more efficient condensing modulation temperatures.

This is all nickel and dime efficiency comparisons anyway, since the primary, biggest bang for the buck energy efficiency "system" in a house is a good, well designed envelope and window system. The rest is just trimming. HVAC designers MUST learn building envelope thermal performance and become more tuned to designing proper envelopes first, before they apply HVAC systems to buildings.

Dave Belisle

stapling to the side of the joist

Bottom Line, Stapling to the side of the joist will work well in many cases.
We have done many jobs like that for quite a few years and have had great success and many happy customers and not one bad radiant system...

When a starter home cost over a quarter of a Million dollars, the cost of everything becomes a factor.

We stay in the top three inches of the joist ( not like the picture in a previous post ) and there is at least 6 inches of insulation in the bottom and at the box sills. The floor heat will be even with no hot spots, ...

I don't have to baby-sit carpenters, carpet layers with there tack strips , flooring guys with there underlayment, or anyone else on the jobsite who might damage my tubing.

Bottom line a BTU is a BTU is a BTU !!! It doesn't get lost in the system. If it isn't radiated it comes back to the boiler to go out and try again ! it is staying in the heated envelope of the house !

Yes, You will run that circulator more and that does cost electricity for the 1/25 HP motor.

( Oh ya , that's what makes radiant feel good when it is has long run times ) .

This system has its limitations but if the heat loss calculations work. it does allow people to have radiant over baseboard for a few thousand more.


I did it years ago in my family room to see how well it would work and was pleasantly surprised.

There is no question there are better systems.
But like it or not it will work and work well in the right application and you won't break the bank.

I live in New Hampshire so 20 below for a week is not all that uncommon.


Dave in NH

Bob Sweet

hydronx

The Ultra boost can be adjusted based on ODT curves or deactivated all together. You can find it in the control addendum interface supplement.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Jim\"Rocky\"Kelleher

Geoff wrote:
I know from contacts and my own European investigations that staple-up under wood floors is "not acceptable" by their energy codes for residential construction.

Show me the European Energy Codes, send me the link.

GMcD

Some references

There is no "specific" wording that "bans" staple-up systems, but the energy standards for new residential construction are so stringent that staple-up radiant floor systems are virtually ruled out as a viable system.

Here's a link to purchase the applicable German Heating Systems Standard on-line:

http://webstore.ansi.org/ansidocstore/product.asp?sku=DIN+EN+1264-2:1997

And here is another link for further reading:
www.eu-ray.com/technics/CEN-Standards-Heating-CLIMA-2000-Napoli.pdf

Additional background:
http://www.worldenergy.org/wec-geis/publications/reports/eepi/a1_newbuildings/eudata.asp

http://www.worldenergy.org/wec-geis/publications/reports/eepi/policy_evaluation/standards.asp

Excerpts from recent studies:

"Germany, Switzerland and some other continental countries have a legal requirement that new buildings, from detached homes to office blocks, meet a certain energy budget. With rare exceptions, actual energy consumption in those countries is consistent with the insulation and draughtproofing measures which are specified.
Germany’s first four Passive Houses were calculated to use 31 kWh/m2yr - gas plus electricity - under standard occupancy conditions and average German weather. They actually used 32 kWh/m2yr over the period 1992-97. So there was perhaps a 3% error." From: AECB ENERGY STANDARD‘PRESCRIPTIVE’ VERSION David Olivier 20.02.05

"Minergie was introduced as a voluntary building standard and label in 1998. Minergie buildings consume less than
half energy than those built under the mandatory SIA 380/1
standard, i.e. 42 kWh/m2*year for new single-dwelling houses and 38 kWh/m2*year for new apartment buildings. Minergie also promotes an even more stringent label, Minergie-P,which is based on the German “passive house” concept" Excerpt from: International Energy Efficiency Conference, London 2-3 November 2005 The G8, Europe and an Energy Efficient World – Acting and Learning Together

But you can do your own google searches too.

In order to meet the EU energy targets for new residential construction, they MUST use the most efficient heating systems, running at condensing temperatures coupled with very high performance envelopes.

Ted_9

My goal is to use the lowest possible water temps. I dont make excuses for the customer. Most will spend whatever to buy the car they want so why shouldnt they spend to do the job right and conserve as much fuel as possible. It's our duty as American citizens.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

hr

Jim, some info

on this subject can be seen in the 2002 May and July issue of PM mag in Siggys column. He did some FEA modeling of the tube staple up methods. Watts pubished a response to the article.

I recall Siggy modled a 12.5 delta t across the EPDM tube wall and Watts calculated a 13.1. Watts Radiant indicated a 8.68 higher fluid temperature required when compared to pex, in their calculated example.

Keep in mind that is getting the energy through the tube wall. The connection to the floor from the tube outer wall is also a critical link. This is where transfer plates add so much conductive tranfer area comnpared to a small tube to floor contact patch provided by direct tube staple up, regardless of the tube type.

A model of the surface temperature profile, shown here, was interesting also.

Also ASHRAE and the RPA funded a study at KSU headed by Kirby Chapman regarding the output of various under floor methods. That should be available from the RPA or ASHRAE still, I believe.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

hr

I have some additional info, Jim

In the May and July 2002 issue of PM mag Siggy modeled some tube staple up examples. You should be able to find that online still.

As I recall Siggy's FEA model showed a delta t of 12.5F through the EPDM tube wall and Watts response article titled " Which one's warmer?" showed a 13.1 delta t based on calculations.

Watts indicated in their example a 8.68 higher temperature needed compared to pex.

Keep in mind that is across the tube wall from the fluid. Just as important, or more so, is the tube to the floor panel "connection" IMO. This is where the transfer plate with it's wider contact patch adds the value.

Also the temperature profile across the floor surface was modeled with bare tube stapled to the bottom of the floor and transfer plates. Seen in these pics. Transfer plates smooth out the temperature across the floor surface.

All the methods can and do work. Care should be taken when calculating the load and the temperatures requires, as well as the temperature spread across let's say a wood floor, to provide the best, uniform spread. If in fact that is what you are promoting to your customer.

No question the transfer plates, Warmboard and the other aluminum plate products conduct and spread the heat much better.

Do you need them? that's up to you, the load, and the customer to decide, I suppose


My infared project also showed this temperature spread quite well between suspended, stapled to floor, and transfer plate, as well as Warmboard.

Watts Radiant does offer the heavy aluminum transfer plates, although not for the Onix product, and PAP should be in their offering soon to provide you and your customer all the options.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Ron Schroeder

More reading

http://www.heatinghelp.com/pdfs/247.pdf#search="radiant floor heat staple up vs plates"

Kevin_in_Denver_2

Good Data

Thanks to Hot Rod for keeping objective on the whole issue.

Now, here's a question about salvaging a staple up application that isn't working so well. Chances are it's heating the air in the joist bay just fine. If there were just a way to get that warm air into the room... hmmm....

Jim\"Rocky\"Kelleher

Nice Graph Hot Rod

Geoff has some good points, always love Hot Rods graph. My problem was with Geoff intial statement that staple up "Horribly inefficient,inefficient at best". Now if we are talking about staple up with pex on joist,(can get real squeakie), I agree. But when using Watts Radiants Onix, let's be clear, this is staple up underfloor, not on the joist.Using proper insulation, proper air space and tube placement, spacing, banding in high loss areas, utilizing proper engineered system design ( Watts Radiant software, get it at the ISH show),also proper near boiler piping, very important.In real world application, and I have done a few, including my own 2500 squarefoot house on Martha's Vineyard. Does Onix need slightly higher temperatures than pex? Yes, how much higher? 8-10 degrees. The ease, speed of installation and situations where pex can't be used ,but Onix can; stairways,12" joist spacing (it's tight turning radius), I feel it's a great product an asset to your radiant heating arsonal. I'm in this business to make a profit,offer my clients the best heating they can afford, with Onix I have been able to sell radiant, where I couldn't with pex. I use pex for slabs and snowmelt, Onix everywhere else. Don't fear the EPDM it has made a lot of people comfortable in their homes, keeping them safely away from the scorched air horrors.Check out the attachment,print it out read it and go to the Watts Radiant booth at the ISH show, talk with Rich McNally have an adult beverage with him, keep an open mind, don't believe everything you read. Hope I see some of you guys at the ISH show, good thread.

Jerry_15

A quick fix to this is just to mold the pex tightly with foil bubble for heat transfer. I never bother those sleeves anymore. Tempest in a teapot. Good luck

GMcD

Inefficient staple-up

What I was getting at was that I meant that the "suspended tube in a joist bay" is not a very efficient way of transferring heat from the working fluid to the floor above, and then staple up with no plates is a small step better, then staple-up with plates is even better, but the top of the heap for heat transfer efficiency to the floor surface is an "imbedded in topping system", or cast into slabs systems. The thing is that there is a large industry in North America built around the staple-up systems, and they do work well when designed properly, but they are still a fairly inefficient overall heat transfer system compared to other methods.

ALH_4

Onix works

EPDM is amazing stuff.....but some of the answers in that data sheet are misleading. That price comparison uses some expensive plates.

Do you ever find any rubber sludge in boiler drains or elsewhere in an Onix system after years of use?

-Andrew

Weezbo

Hot Rod...

i have spent a chunk of today thinking about oblong pex tubing and oblong ABS dwv pipe and fittings to round...any one actually make anything along those lines?

*~/:)

Tony_23

Troublemaker



To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

hr

Weezer

I have not seen oval shap fittings, maybe the gutter industry.
As for pex, install a copper crimp fitting, then drop something heavy on the tube and connection to get a nice oval shape PAP would probably hold the oval better.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

hr

Still I question the actual contact patch

my little shop demo indicated a much weaker (non exisitent in some areas) contact patch between the tube and floor. Even a small air gap breaks the thermal conduction.

I'm not sure this was ever tested in a lab or at the factory. Non contact will make a big difference in the heat transfer ability.Seems it becomes a suspended tube without direct contact?

I believe the older more flexible earlier version would contact the floor better. Cold Onix, especially doesn't lie as flat as the earlier rubber only version.

I think there are plenty of applications for Onix. Labor being the key factor.

I too question aluminum plates at 4 bucks a foot, as well as the 45btu/ sq ft output. Becareful designing around that number!

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Michael_6

Jim,
Virginia Tech did an independent complete testing of radiant systems. Rehau has used a small graph of this in their latest literature and I am told the full report will be released in a few months. Check out page three of the attachment.

Jim Erhardt_2

No doubt, depending entirely on convection to heat a dead air space between the floor joists is a "weak sister" to conduction. That said, a tube attached to the side of a floor joist is not that much less efficent in heating that space than attaching it directly to the subfloor - especially if offset clips are used to hold the tubing away from the joist.

Also, stapling Pe-x tubing to the subfloor gives (to all intents and purposes) zero heat transfer by conductance as only a very tiny (and inconsequential) percentage of the tube's surface area is in actual contact with the floor.

For low heat loss areas with "radiant friendly" floor coverings, this is still a useful technique. To discuss (and understand) the limitations of this technique is one thing, but to dismiss it out-of-hand as a "waste of time" is entirely another.

Jerry_15

Once again, I just tightly mold the foil bubble stuff around the tubing, which gives a great heat spread-out/transfer to the flooring. Insulate below. I know this is too easy. Suffer at will.