Radiant Floor Constant Flow with Boiler Reset

anotherWhitney

For the past month I’ve been leeching off of your great conversations; gorged on years of archived threads I now know everything that I need to so as to be confident while eff’ing this up. Seriously, I think that this Radiant Floor scheme makes sense, but heating is not my gig; I'd appreciate it if the sages of the Wall would “check” my work and disabuse me of any misbegotten confidence. I've attached sketches incase my description is gibberish.
 
My wife and I are renovating a prewar brick home in NJ (design day is 14F). The house is heated with cast iron steam rads. We’re going to install a separate NG mod-con combi boiler with full outdoor reset (BoD something like Rinnai QP85N, WM97+ CT, Viessman Vitodens) and replace the rads on the second floor (approx.. 800nSF) with Hydronic Radiant Floor. Two boilers because it is a 2-family home and we want separate utilities if we choose to rent.

Design intent of Radiant Floor is delta-T >=20F, constant flow with 3/8” PEX loops @ 7” O.C. routed into subfloor (a la Warmboard but not… even at trade rates that stuff is $$$), distributed from two centrally located manifolds. Modeled temperature, thermal stress and flux vectors in the hardwood floor system tolerate 150F supply, but 120F supply seems to maintain target surface temp at design day load. Control strategy intended to provide overheat protection via thermoactuators. Stats are wireless and talk to wireless ZCM at manifolds wired to relay in the basement.
 
Three zones determined by heat loss & exposure. Zone 1: Master Bed and Living Room (heat loss ~27 BTU/hr/sf = 9000 BTU/hr) served by three 200’ loops from single zone manifold. Zone 2: Kitchen & Dining Room (heat loss ~25BTU/hr/sf = 3000BTU/hr + incidental solar heat gain) served by two 200’ loops from second manifold. Zone 3: Guest Bed (heat loss ~21BTU/hr/sf = 2100BTU/hr) served by one 140’ loop from second manifold.
 
Thermostat w/ floor sensor in Zone 1 calls to thermoactuated zone valve on single zone manifold with end switch for Alpha pump & Boiler. Control authority here because it is the hardest to heat space with no practical solar heat gain; if it isn’t calling, I don’t think that anything is.
 
Thermostat w/ floor sensor in Zone 2 calls to 2-wire thermoactuators on manifold for overheat protection.
 
Thermostat w/ floor sensor in Zone 3 calls to 2-wire thermoactuator on manifold for overheat protection.
 
Hydraulic separator on flow side of Alpha for pressure relief.
 
Boiler is on full outdoor reset to modulate supply water temperature (boost disabled).

I've made some assumptions that may be problematic:
1. Stats can be set just beyond what the supply temp can maintain to keep loops open unless they’re overheating. (For such a singular thing, these controls seem like overkill)
4. Keeping thermoactuators energized all heating season is not stupid (looks like <$100/year for 4).
6. That I have at least a modicum of sense.
7. BoD is pretty much Uponor PEX-a, SS manifolds and controls. 

I've made a lot of assumptions, did I at least get close? Thanks for taking a look!

Jamie Hall

Well... the thoughts about the second floor are reasonable, at least.

However...

What are you going to do about the first floor? You don't mention it in your thinking. If you were to think of keeping steam on that floor, you would find that the existing boiler would be wildly oversized -- keep in mind that steam boilers are sized according to connected radiation, not building heat load. This could lead to some problems and some inefficiencies. On the other hand, I almost wonder if you are thinking of converting the first floor heating from steam to hot water -- a conversion which sometimes can be done, but which usually is problematic at best and which I really can't recommend.

I presume that you are doing all this because you wish to have two separate heating systems; one first floor and one second floor. I can see that; it is attractive to be able to have a tenant responsible for their own heat. On the other hand, from the tenant's point of view, it is attractive to not have that headache -- sufficiently so that they will often pay extra for it.

I would seriously consider all that -- and also seriously consider working on the existing steam system to get it working as well and as quietly as it can.

Gordy

Your radiant floors should be designed around a 10 degree delta not 20.

Secondly you talk of a warm board similar construction. Yet you refer to this as UFH. Under floor heat? Are you using plates for this?

anotherWhitney

Thank you @Jamie Hall. We had planned to leave the first floor as steam rads until the boiler needed to be replaced, at which point we'd install new hot water rads and boiler. Efficiency rebates in our area have excluded steam boilers since last year. Why do you think the steam to hot water is a bad idea?

We're working with the tech who installed the boiler for the former owner in '98. It is quiet and seems to be running well, he figures it is good for another 10 years. The whole reason for UFH was improved efficiency and quality of heating.

What you say about tenants not wanting to mess with heat sounds reasonable, I will look into that.

anotherWhitney

@Gordy "UFH" refers to staple up only? My plan had been to route the subfloor and form 0.03" aluminum sheet into the channels. The finish floor installs over the top and joist spaces below are insulated R-26. The aluminum is perforated and 0.03" appears sufficient to conduct the thermal energy effectively between the PEX lines.

I thought that delta 20 was advised for low mass floors and that the higher delta-T would increase the efficiency of the condensing boiler. What am I missing?

Rich_49

Tell us more about your assembly in which the tubing is placed . there are only a few radiant floor panels that I am aware of that are designed around a 20* Delta .

Maybe we can also talk about your Tees that go to your manifolds and the lack of one circ unless it is integral in the boiler . If it is then we can talk about moving the one you have drawn near the separator .

We also must talk about the idea of moving 1.4 GPM at 6 or less feet of head @ design and what that means the other 98% of the season . 120* water at .3 gpm per loop only offers up 4 ft of head , moves at 1 fps . This is all at your design , presuming a proper heat loss was performed taking all parts of the assemblies into account .

Where are you in Jersey ?

Jamie Hall

If when you replace your steam with hot water you replace all the radiators, all the piping, and the boiler, it's not a bad idea in one sense -- newer mod/con boilers and all their controls are nice and whizzy and are, properly set up, slightly more efficient than an equally modern steam boiler would be. However, the return on investment, even factoring various efficiency rebates (read: government bribes), will almost certainly be negative -- that is to say, you will never, ever, recover the investment. Bringing an older, perhaps poorly maintained steam system up to modern standards has a nice positive return. To give you a hard example, the boiler in the place which I maintain is fairly new -- 2010 or so. It replaced (by stages) an original boiler. That replacement paid for itself in about 5 years. I have estimated that changing to hot water, with the latest and greatest controls and boiler would probably result in a system which cost me money every year, even after the fuel savings are taken into account, due to the lost investment interest on the capital used for the conversion (or the interest on the required loan, if that were to be the way it were done).

Crunch your numbers very very hard. Steam will save you money and be at least as comfortable, if not more so. What's not to like?

anotherWhitney

Thank you, @Rich

Rich said:

Tell us more about your assembly in which the tubing is placed . there are only a few radiant floor panels that I am aware of that are designed around a 20* Delta .

I poached the 20* Delta from Uponor's Quik Trak since early concepts were utilizing that system. It appeared similar to the revised homebrew system, so I kept it: R-26 mineral wool in joists, PEX routed into 3/4" plywood, 0.032" Aluminum heat sink, 1/2" plywood, 3/4" solid hardwood. I had also interpreted conversations as saying that high Delta-T was better for condensing boilers.

Rich said:

we can talk about moving the one you have drawn near the separator .

The boilers that I've been looking at all have integrated circulators. I believe that there is an air/dirt separator in the Caleffi hydraulic separator, which I why I drew the circ where I did; is this incorrect?

Rich said:

We also must talk about the idea of moving 1.4 GPM at 6 or less feet of head @ design and what that means the other 98% of the season . 120* water at .3 gpm per loop only offers up 4 ft of head , moves at 1 fps . This is all at your design , presuming a proper heat loss was performed taking all parts of the assemblies into account .

When you put it that way it that way system does sound kind of mad. I'll need to revisit my ADS file to figure out what's going on.

We're in Jersey City

anotherWhitney

@Jamie Hall Excellent points, thank you for sharing your experience. I will speak with our boiler tech about efficiency gains... we're burning oil now but have plenty of NG in the house; how do you feel NG verse Oil?

@Rich & @Gordy You got me thinking about where I was reading delta20*, one place I had picked it up was from @Mark Eatherton - http://forum.heatinghelp.com/discussion/77310/10-degree-delta-t.

Mark Eatherton said:

And...

As you double the flow rate through the tube, the pressure drop increases as a square. Doesn't take long before you go from a Gfos 1542 to a Gfos 2699.

I use a 20 to 30 degree delta T. Planning is real important. Deliver the hottest fluids to the outside wals, and allow the cooler stuff to flow near the inside walls. They HO won't notice enough of a difference to cause them to complain. Keep your loops below 250 foot also helps.

Delta T is a subjective thing...

I took his advice to heart when laying out the loops, the "hot" loops run the perimeter first, then serpentine the floor. Please correct me, I had thought that this with Delta20* was being prudent. But as @Rich pointed out, I need to revisit my calcs.

As always, thanks for the feedback.

Jamie Hall

Natural gas vs. oil... Tuesday vs. roast beef. They both have advantages; they both have disadvantages. That said, it appears that in most situations if natural gas is available it is the better option. In terms of price, over the long run there isn't much in it one way or the other. However, oil burners do require somewhat more maintenance (not more careful, just more of it) and there is the problem of the oil tank, which has to be somewhere! On the other hand, with oil one has quite a bit of flexibility -- and thus price competition -- regarding the supplier; with gas, you have one choice only. In some area natural gas supply can be a bit iffish in really cold weather, when demand is high, but I don't think that that applies in your area.

Rich_49

End unit , middle , or detached ? Your numbers sound very high based on other jobs . Who did a heat loss ?

Uponor's Quiktrak also uses 5/16" tubing and also has the aluminum all the way at the bottom of your assembly . the Delta is 20* on that product due to the small diameter of the tubing and the fact that the aluminum is down low beneath everything . You have to find a happy balance between design flows and head loss and where you will operate for the major portion of the season . Too low head pressure especially with that Alpha and your Delta will end up way down in the weeds , you'll end up with a low delta for much of the season and will have created an issue that you seem to have desperately attempted to avoid .

Could you give us the room dimensions , exposed wall lengths , window size and type , door size and type . Like this , Living room 18' x 15 ' . 18' wall , with R19 , 2 - 3' x 4' double pane Low e windows and a 3' x 7' french door . 2 - 15' walls , no windows , common with neighbor unit ? Space below , heated . Space above not heated , if not heated include R value of insulation

Gordy

Please remember when looking at older threads there has been technology changes since some discussions took place. One is ECM delta t circulators that will maintain a set delta by varying it's speed through temp sensors. In that particular thread there was fixed speed circulators, and ECM circulators of delta p, and delta t had not yet come out.

Also recognize how they do use a higher delta yet manage to even out those temps across the panel through tube layout, and close attention to required SWT.

I question your heat loss calculations. Those are pretty high btu SF numbers.

Also if you are making your own plates. Remember conduction is king in transferring btus. The omega channel shape of quality plates wraps the tube tightly. If your homemade plates don't do this its not going to be much benefit.

I think you will find after routering 7" center grooves the price might not look to bad.

There are other over the top versions such as sunboard, Roth,etc. did you price warm board s, or r? R is a remodel , and s is structural. If you are going over the top of a pre existing sub floor then you want warm board r type panel.

Also note that warm board uses 1' centers which would decrease the amount of tubing, and manifold sizes. Other boards have options of tighter centers.

If you are determined to go home made. Skip the routering, and use sleepers which is plywood rips spaced for tube centers.

anotherWhitney

@Rich @Gordy Thanks for the catch, my system calcs were very busted; I've run them again in Uponor's ADS with simplified heat loss. The short of it is a single manifold Delta10*, SWT (Supply Water Temp?) 125F, Total Combined Flow Rate 3.3USGPM, Combined Head Loss 27FT. Total heat loss comes to 16,500BTU/hr over 1000gSF (700nSF w/ coils). Do these look better? I've attached my reports in case their of interest.

Bare in mind that this is a hundred year old home with brick veneer and plaster walls, the assumed insulation value of R-8 is generous compared to my Therm results. The house appears tight, but is still a hundred years old so I'm also assuming an air change rate of 1.2/hour. Plan data in separate comment.

anotherWhitney

@Rich Thanks for the plumbing suggestions, I've cleaned up the sketch based on your suggestions.

Rich said:

End unit , middle , or detached ? Your numbers sound very high based on other jobs . Who did a heat loss ?

Could you give us the room dimensions , exposed wall lengths , window size and type , door size and type . Like this , Living room 18' x 15 ' . 18' wall , with R19 , 2 - 3' x 4' double pane Low e windows and a 3' x 7' french door . 2 - 15' walls , no windows , common with neighbor unit ? Space below , heated . Space above not heated , if not heated include R value of insulation

I'll attach the dimensioned drawing as that will be more clear than my list. This is the second floor of a two-story detached two-family home. I did the heat loss based on values from LBNL Therm and using Uponor's ADS. All wall/ceiling/floor R-values are nominal without bridging factors.

All windows are wood frame, single pane plate glass, with storm windows, 2.5'x5.4' (R-2)
One stained glass window, 2.5'x1.5' (R-1)
Door to balcony is single pane plate glass panel with storm door, 2.5'x7' (R-2.78)
Ceiling height is @ 9'
Attic above is unheated w/ R-35 insulation
Space below is heated w/ R-26 floor insulation between
Gross Square Footage of floor is ~1000sf

Master Bedroom ~19'x9.7' with two windows and balcony door (40' exposed (360sf)
Living Room ~ 13.6'x11' with two windows and one stained glass window (18' exposed (162sf))
Guest Room ~ 7.5'x11' with one window (11.5' exposed (103.5sf))
Dining ~ 7.9'x12' with one windows (20' exposed (180sf))
Kitchen ~10.9'x11.5' with two windows (22.5' exposed (202.5sf))
Bathroom ~ 6'x6.5' with one window (6.5' exposed (58.5sf)

anotherWhitney

Gordy said:

There are other over the top versions such as sunboard, Roth,etc. did you price warm board s, or r? R is a remodel , and s is structural. If you are going over the top of a pre existing sub floor then you want warm board r type panel.

@Gordy Thank you for suggesting some others, I will look into these. I spoke with the NY Warmboard (WB) rep about both the R & S types; there was very little cost difference between them. We can PM about the figures I was given. All the same, I will call him again today to make sure that we're on the same page. I would love to use something like this but the price I've been given is just too much, even when I consider a month spent routing. One other apprehension I had with WB was vapor migration, I can't figure out how it doesn't trap rising vapor during the summer, which is of more concern to me than wasting my time routing.

Gordy said:

Remember conduction is king in transferring btus. The omega channel shape of quality plates wraps the tube tightly. If your homemade plates don't do this its not going to be much benefit.

@Gordy Absolutely, this being the case how is the flat sheet of aluminum at the bottom of Uponor's QuikTrak of significant help? In considering my home-brew I wrote myself an excuse for sub-optimal conductive surface based on what I assumed is a reputable company thinking that this was practical.

Rich_49

anotherWhitney said:

@Rich @Gordy Thanks for the catch, my system calcs were very busted; I've run them again in Uponor's ADS with simplified heat loss. The short of it is a single manifold Delta10*, SWT (Supply Water Temp?) 125F, Total Combined Flow Rate 3.3USGPM, Combined Head Loss 27FT. Total heat loss comes to 16,500BTU/hr over 1000gSF (700nSF w/ coils). Do these look better? I've attached my reports in case their of interest.

Bare in mind that this is a hundred year old home with brick veneer and plaster walls, the assumed insulation value of R-8 is generous compared to my Therm results. The house appears tight, but is still a hundred years old so I'm also assuming an air change rate of 1.2/hour. Plan data in separate comment.

Whitney ,

You have no leader lengths in here . Where is the manifold to be located in relation with where the radiant panels are ? Leader length would be the distance between where the tubing enters and exits the panel to and from the manifold . Unless the manifold is in the second floor , if this is the case , did you enter S & R piping size and length ? Only the head losses for the S & R piping , manifold body and loops get combined , not the total heads of the loops .You only need to overcome the highest head , the flows only need to be added together .

Do you occupy the first and second floor ? What is the long term goal for heating plan for the floor/s you occupy ?

Warmboard is the best 12" on center product made at present . That being stated , it is expensive as you already know , it is bulky and heavy as hell , there will be alot waste if you used it . 8" on center is what you have designed for and as others can attest to will require lower AWTs to achieve your goal . Do not be fooled by Warmboard's cherry picked comparison videos , such as their Warmboard / Sunboard comparison . Although they used a Sunboard product that was unfortunately named " Gold" which many would take as being the best , it is not . Sunboard Gold is a panel that does not have the aluminum or graphite coating through the groove as Warmboard does have . These videos have apparently been removed from Warmboard's site , I find this curious , why would a company remove such undisputable proof of their products' superority ? God and Terry Alsberg only know the answer to that , I can only guess . Sunboard Silver is in fact a through the groove coating application and WILL outperform the Warmboard products . Ask me how I know . If you are seriously considering WB for your project I urge you to look at Sunboard . I have no financial stake in the product , I just have found it more Budget , system user and installer friendly friendly over several years now . I have used both for clarity .

Personal disclaimer : When a prospective customer contacts me who was referred by Warmboard I do not recommend other manufacturers products . This is often very difficult due to my knowledge of the advantages and disadvantages of products readily available .

I might suggest that since you will have to insulate below the subfloor that you actually route the leaders for the master under the floor , there is a distinct possibility that the small hallway may reach temps not conducive to comfort , especially being that it is interior and has little heat loss . Consider also separate zones for the master and living room , if you enter them as separate / individual spaces you may see that the BTUh per sq ft requirement is very different which means that one or the other may experience comfort issues . When entered as one space there is no way to see this . Enter all the rooms separate , you can then see what may or may not be zoned together , take into account how you use these rooms , Solar heat gain . rooms should only be zoned together if they have similar BTUh per sf needs , similar use patterns , similar finish floor R values , and of course SHG . These things are subjective and some may tolerate things that others are not willing to , your desires may lean either way .

anotherWhitney

@Rich I understand what you're saying that the Master & Living Rooms may have different heat loss... they do in fact, I think it was -3BTU/hr/sf but that was per a now debunked calc. I'll break it up tonight and see. Am I wrong to think that I could restrict flow at the manifold to the Living Room in order to tweak this imbalance post facto? I assume the answer to that question is "yes, you're wrong."

Rich said:

I might suggest that since you will have to insulate below the subfloor that you actually route the leaders for the master under the floor , there is a distinct possibility that the small hallway may reach temps not conducive to comfort...

@Rich That hallway is a problem. Naturally the joists run perpendicular to the direction the PEX would need to run; I could drill the joists but had wanted to avoid that and the added scrutiny of DoB. I'll revisit it.

Rich said:

You have no leader lengths in here . Where is the manifold to be located in relation with where the radiant panels are ? Leader length would be the distance between where the tubing enters and exits the panel to and from the manifold . Unless the manifold is in the second floor , if this is the case , did you enter S & R piping size and length ? Only the head losses for the S & R piping , manifold body and loops get combined , not the total heads of the loops .You only need to overcome the highest head, the flows only need to be added together.

The manifold is located on the second floor, I had assumed that this was preferable to running each loop an extra 40'. The lengths shown are inclusive of the run to/from the manifold. I had thought S&R to be 3/4" PEX for 20' up and 20' down runs. Clearly, not my gig; thanks for the lesson. 3/4" S&R at temps adds 2FT of head to 11.4FT max, but the calculator is ignorant to gravity in the riser(?).

Rich said:

Do you occupy the first and second floor? What is the long term goal for heating plan for the floor/s you occupy ?

Right now we occupy both, but want to maintain the flexibility of splitting it up to rent the ground floor or sell as condo. I hear @Jamie Hall loud and clear about tenant preference, and I'm cherry-picking his recommendations when thinking the first floor will remain steam but with a properly sized boiler. Our boiler tech is coming by next week for routine service and we'll talk about it then.

Rich said:

Ask me how I know .

You know I want to.

Rich said:

If you are seriously considering WB for your project I urge you to look at Sunboard.

I was on the phone with Jim @ SB this morning, we'll see. WB is cost prohibitive for me, full stop. Concerns about vapor migration remain; Roth, WB, nor SB had ever heard of this being an issue but that no one is talking about it does not necessarily allay my concerns.

As always, thanks everyone for the help. If you venture toward Jersey City, I owe you not less than a beer.

Rich_49

I was on the phone with Jim @ SB this morning, we'll see. WB is cost prohibitive for me, full stop. Concerns about vapor migration remain; Roth, WB, nor SB had ever heard of this being an issue but that no one is talking about it does not allay my concerns... ask me why. Thus the home-brew aluminum is perforated.

As always, thanks everyone for the help. If you venture toward Jersey City, I owe you not less than a beer.


Why ?

Rich_49

Whitney , I saw a couple things of concern besides what's alreay been asked about . If you go into your ADS program under the design settings , change your Construction Quality settings to average or maybe even poor , I'll let you decide . Then in the Room input / heat loss settings when you click on floor you'll see on the right side of the screen under Panel attachment method 2 boxes , unheated area with loops and unheated area w/o loops . Fill in the unheated area with loops box with the square footage of any furniture like bed , dressers , chairs , do this for all the rooms including the bathroom if loops will not be under the vanity , tub .

Let us know what happens with your temps and probable need for supplemental heat . But before you let us know , change all the settings to use the ceiling as a panel , don't forget to uncheck the economical panel box though .

anotherWhitney

@Rich I've done as you suggested and accounted for the bed, sofa, counters, etc. as non-heating square footage - makes total sense. As you anticipated, doing so and maintaining 65F at the design day in the Master Bedroom requires 500BTU/hr of supplemental heat. I have kept the air changes (i.e. Construction Quality) at 1.2/hour (average) because the windows are well caulked, three of the four walls are parged 1/2", the exposed face brick is double widthe with sound grout, and we are sheltered from typical winter winds that would create high pressure differentials with the interior.

Before deselecting the "economical panel design" ADS had recommended 7sf of supplemental ceiling heating. Going to a full ceiling panel did reduce the SWT for the Master bedroom, which was welcome. Reports attached.

I think that you're absolutely right, a radiant ceiling would increase system efficiency and comfort; if this were for a client, there's no question that I would do as you recommend and specify supplemental radiant panels then let the client weigh the VE. I'm weighing the VE myself, and see that we could maintain 63F at design day without cooking the floor. We would only need the ceiling panel 1% of the time, because of this I'm inclined to use only the floor for a winter and see. The ceiling panel seems like a logical comeback when we repair/replace the ceiling down the road. I imagine that you'll disagree and I'd like to hear the reasons why I shouldn't be thinking about it like this.

Rich_49

Glad you did that but what I was trying to show you is the fact that ceiling alone would be better . no worries about overheating , floor sensors , compromising on comfort and the floors would still be of a neutral temperature . Radiant ceilings are awesome and less worrisome than floors , in your case would probably require lower SWT and thus offer lower RWT . In short you don't need supplemental . I see many projects where the unheated area due to furniture was not factored in .

anotherWhitney

@Rich Got it, that is very interesting... I will be poking my head up there when I get back.

Why does this work, is it just because the radiant area is that much larger? It runs contrary to my remedial understanding that heat rises.

Thank you.

Gordy

Hot air rises. Radiant heats objects. From below, above, and the sides. (Floors, ceilings, and walls.

As @Rich pointed out radiant ceilings do not have some of the baggage as floors can. Ceilings do not get high r value carpets, and rugs. No furniture etc. Ceilings, and walls can run higher btu outputs if need be. However in your case just the advantage of more usable radiant surface area can eliminate supplemental heat, and lower water temps. You could get carried away, and do both.

anotherWhitney

@Gordy The thought of getting carried away had crossed my mind.

I'm guessing that in order for a radiant ceiling to work, one must use effective aluminum transfer plates to ensure the heat is conducted into the ceiling assembly rather than lost to upward convection.

hot_rod

Extruded transfer plates are always one of the best way to move the energy with conduction.

Some of the wood or foam prefaced assemblies are great also. I like the Roth Panel system, light and easy to glue or staple, continuous aluminum surface, and a bit of foam R-value. Their 3/8 panels only add 1/2" to the build up.

UltraFin uses convection transfer with their system, it needs an air space and all radiant systems need adequate insulation.

With convection you need an air space between the plate and floor or ceiling. With conduction transfer insulation can be up against the tightly mounted transfer plate.

Rich_49

Sun Foam by Sunboard would be my recommendation . Graphite coated , 8" centers , eliminates or lessens thermal bridging of framing members (added benefit) ,100% conductive surface , doesn't get any better . less first cost than any other alternative .
I would design it for 3/8' tubing which would increase the resistance a bit and also give a bit more foam behind the tubing .

hot_rod

Sunboard has a ceiling specific product also. Looks like it is for suspended ceiling? Although it also states between 24"joist spacing.

Rich_49

Sunceiling panels are awesome but as you state they are made for suspended , commercial jobs . UNBELIEVABLE OUTPUT that can be believed since I have seen the results based on installed performance as per Jim S @ Sunboard
. Have one right here in my office that Jim sent over .

hot_rod

It is a nice evolution of the "dry" radiant products that we have used over the years. Glad to see someone still moving the needle.

Any idea how they arrived at the outputs? They seem quite high in some examples.

A simple calc we use is 0.71 x S&R delta.

Uponor Design Manual 7th edition chapter 9 Radiant Ceiling Tutorial suggest limiting 8' ceiling to 100°F surface temperature, and their graphs 9-3 max out at 35 BTU/hr./ft. in a 70° room setpoint.

Rich_49

It is remarkable the amount of energy lost upward into that 7/16' OSB and how much resistance although not that much the 1/2' rock retards heat flow downward huh . Guess it's just the willingness to progress and not just accept that Jim was able to identify this phenomenon . The added R value directly in contact with the tubing provided by the 1 1/2" foam behind the board and the attached Roxul comfortboard to accomplish fire and smoke rating compliance along with the fact that there is zero R value in contact with the entire sq footage of the board , the graphite coating on the board and the aluminum directly in contact with that surface makes for the newly discovered energy transfer . Maybe Uponor would like to buy the rights , test , market and sell that product from Jim , I understand it can be purchased for the right number or just time for some new math .

So , there you have it , the combination of all those little things just made radiant ceilings even better yet . Don't forget that in a large commercial project or offices the first cost would come way down also since the requirement for an insulation contractor is negated . Win , win Bob .

This is not the product I mentioned to the OP for clarity .

Gordy

The old days of chase copper and brass literature boasted

hot_rod

Rich said:

It is remarkable the amount of energy lost upward into that 7/16' OSB and how much resistance although not that much the 1/2' rock retards heat flow downward huh . Guess it's just the willingness to progress and not just accept that Jim was able to identify this phenomenon . The added R value directly in contact with the tubing provided by the 1 1/2" foam behind the board and the attached Roxul comfortboard to accomplish fire and smoke rating compliance along with the fact that there is zero R value in contact with the entire sq footage of the board , the graphite coating on the board and the aluminum directly in contact with that surface makes for the newly discovered energy transfer . Maybe Uponor would like to buy the rights , test , market and sell that product from Jim , I understand it can be purchased for the right number or just time for some new math .

So , there you have it , the combination of all those little things just made radiant ceilings even better yet . Don't forget that in a large commercial project or offices the first cost would come way down also since the requirement for an insulation contractor is negated . Win , win Bob .

This is not the product I mentioned to the OP for clarity .

I merely asked how they arrived at the output numbers, actual testing, or number crunching?

Heat transfer is dependent on ∆T, we've been down that road before.

The output of ANY radiant panel is based on the delta T, and acceptable surface temperature. Tighter tube spacing and best heat transfer materials help that transfer and keeping a consistent surface temperature.

hot_rod

Gordy said:

The old days of chase copper and brass literature boasted

Interesting, but without test data, not much value. I could design a ceiling "snowmelt output" if I use a low enough ambient, and or high ceiling surface in the calc

Gordy

Old chase copper lit. Used water temps as high as 150 degrees.

Rich_49

Don't particularly know for sure Bob but the report does state , " Test Results " .

I may have misunderstood your question because it mentioned Uponor Tutorial which is an assembly unlike the Illustration you attached from one of John's papers or presentations . Sorry for that . Uponor,s assembly does have an airspace as there is no foam boards in their assembly and both share a monster thermal bridge characteristic . I find it kinda curious that the old numbers that Gordt posted that worked for years were gone away from and now several decades later assemblies are being improved . Musta been all that testing that everyone put so much faith in . ASTM = Another Stupid Test Method . FEA will never match real world . Sorry for the confusion and that you took my response differently than it was meant .

Gordy

I think there is a distinct difference in radiant panel assemblies, and goals. Back then there were no mod/cons,fuel was cheap, there was little regard for achieving the lowest possible water temps other than protecting the plaster medium, envelopes were not as well insulated either.

I think a 35 btu per sf output from a ceiling panel is a VERY conservative number. Especially if we can expect that from a well designed RFP. More like 40-45 btu sf potential.

However one must look at the tube density of the old chase manual. Nothing over 9". But they also did not use plates, or a seamless conductive interface. That modern assembly still has to push btus through the finished surface usually 5/8 gypsum. Verses
The old that was maybe 3/8-1/2" below the surface yet embedded in it. Plaster also being more conductive than gypsum.

hot_rod

Gordy said:

Old chase copper lit. Used water temps as high as 150 degrees.

Possibly lath and plaster handled those sort of SWTs. I doubt sheetrock, especially the high sulfur acid stuff from China would tolerate that temperature for extended periods

0.71 x (150-68) gets you around 58 BTU/sq. ft.
Somewhere between their 4-1/2 and 6" spacing recommended output, shown on their chart.

Gordy

I also find the max temp of 120 a bit conservative. Especially when it is used as fire proofing. Maybe the taped joints become the issue

hot_rod

Gordy said:

I also find the max temp of 120 a bit conservative. Especially when it is used as fire proofing. Maybe the taped joints become the issue

USG

Gordy

Uh huh. Define "with stand", and "sustained". It would be interesting to know what exactly is the limiting factor in the material? Paper backing, or finished side, or gypsum itself? What exactly happens?

What about the old electric ceiling radiant

Not that 120 is even needed for a well designed ceiling radiant panel.

Seems our materials these days are more restricted due to litigation than maybe actual performance issues...

hot_rod

Gordy said:

Uh huh. Define "with stand", and "sustained". It would be interesting to know what exactly is the limiting factor in the material? Paper backing, or finished side, or gypsum itself? What exactly happens?

What about the old electric ceiling radiant

Not that 120 is even needed for a well designed ceiling radiant panel.

Seems our materials these days are more restricted due to litigation than maybe actual performance issues...

Gyprete floor products had a max temperature also, 120° comes to mind?

I agree, where would you ever need 69 BTU/sq.ft ceiling outputs. Unless you are trying to cover the load with the least amount of ceiling area. But that defeats then purpose of radiant panels in general, heating the objects in their "view"

Isn't a better goal to have heat loads in the teens or single digits.