Let me re-phrase my question about heat transfer plates… Do they “reflect” heat to the sub-floor or do they draw heat from the ( in my case,” Kitec”) tubing and spread it more evenly thru the joist bay and on to the sub-floor? Just trying to get the max. efficiency from my heating loops. I’m guessing there would be less heat transfer resistance in an air space than thru a dense material such as an extra layer of 3/4 ply or does it matter at all? Cheers to all! BTW…this is for a staple-up application.
Edited 4/18/2007 10:18 am ET by timestamps
Replies
Heat is transferred from the tubing to the plates, and the wide plate then transfers heat to the subfloor.
air is a poor conductor of heat.
The aluminum plates are conductors, not reflectors. They promote rapid conduction of heat from the tube to a wider area of subfloor, which in turn raises a wider portion of floor surface temperature, faster and easier.
Radiant performance comes down to "average conductivity" from the water to each point of floor, basically. The easier the heat can travel, the more performance you can get, the lower temps you can run.
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I wonder whether you could help me reconcile the differences between my back of the envelope calculations I did a while back, and your real world experiences with respect to the poor performance of staple up spreaders. The temperature drop for some of the thin staple up aluminum seems to be sufficient to maintain very low delta T from center to edge, even at fairly high BTU/ft^2 levels, and assuming that all of the thermal energy is transferred most of the way to the outer edge. I have wondered whether the silicon caulk that is used with the more expensive systems is part of the key. It seems unlikely that the tubing is in intimate contact with the aluminum, and I caulk does not seem to be part of the system. Caulk may not be a great conductor, but it is a heck of a lot better than air. Do all of the more expensive systems either bring the tubing into direct contact with the spreader plate or use caulk to fill any gaps? <!----><!----><!---->
Hilltop<!----><!---->
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I recently installed a Wirsbo system. They have a special caulk that's silver -- I suppose one of it's main ingredients is powdered aluminum to improve the heat transfer.
Mike HennessyPittsburgh, PA
A system that is relying on caulk to transfer heat is not particularly well engineered. Aluminum to pipe will do much better than caulk to pipe. Caulk is a band aid, and AFAIK is not used by many products out there these days. There are a few, but not many. The best aluminized methods: Warmboard, Raupanel, Extruded plates, omega-groove plates, all bring aluminum into significant direct contact with the pipe.I do know that metal thickness in part determines the volume of heat flow it can accomodate. I also know that my extruded plate systems are outperforming my light plate systems out in the field by a significant amount. However I do not have the modelling software I'd need to demonstrate this.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I've got a project coming up and was looking at Warmboard. It intuitively seems like a great way to get the heat close to where it's needed. It seems pricey but it's the subfloor as well as the radiant heating surface. Do you like it?
I do a lot of work with Warmboard clients, in the interest of full disclosure, so you could reasonably say I have a bias there.But that said, I like it very much. If it's in the budget, it's a top performer, fast installation, simple finish floor installation. all good stuff. It's not always necessary, and if labor is a cheap commodity for you it might make less sense, but if performance or installation ease are major concerns, it's a great choice.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Rob,
I did a little more searching and found a web site that gave the thickness of one type of staple up aluminum. It was noteably thinner (0.012") than I modeled. Do you know how thick the different brands are? It would be interesting to use some real numbers as opposed to my guesstimates from web images.
Hilltop
Dale Pickard, principal of Radiant Engineering, did some measurements on various thicknesses of some common products and posted them in this thread over at the RPA:http://radnet.groupee.net/eve/forums/a/tpc/f/4771065301/m/1211053232?r=2091050332#2091050332-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Thanks for clearing that up. It's great to get a straight forward response. Would you then recommend continuous strips of plywood in between the underside of the subfloor on each side of the joist bay or strapping acroos the loist bay at say 18" oc if using 18" transfer plates? I need some sort of spacer since i will be re-tiling the floor above and don't want to puncture the Kitec when i install the new underlayment. I see from your website you live in Gardiner. What a beautiful state, Maine. Gorgeous coastline drives and super friendly folks is what i remember. Mom and dad would load up the car with my two sisters and I, the trunk jammed with coolers ( I think one even had snacks in it! ) two or three times a summer when I was a kid for a 9 hour drive to Old Orchard Beach . A cousin of dad's owned a motel near the pier where we would hang out for summer vacations and the odd long weekend. The real reason of course, was not to entertain the family but to stock up on lobster until we ran out for the next trip. Can't really remember what we did during the cold Montreal winters, oh yea!...froze our a___ off! Well...a bit off topic, but a fun trip down memory lane. Thanks again for your input! ( and output!)
Edited 4/19/2007 9:35 am ET by timestamps
you should not increase the thickness of your subfloor, and you should not install tubing at 18" o.c., ever, in a residential application.You should use screws short enough not to penetrated your subfloor when screwing down your cement board.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I think you should take a look at Wirsbo Joist Trak extruded plates. They are a great product and transfer heat much more efficiently than the thin plates.
They are also very easy to install & connect the pex.
As Rob said, just use the right length screws when attaching your cement board.
The part of the screw sticking down below the subfloor doesn't do much anyway ;)
I have had a look at this and .... so that's how it's supposed to look like. You should see the mess our first heating contractor made and the second dude that was well paid to supposedly clean up and complete was so eager to get out and paid that i had to re-plumb half his copper as our install also included a new high efficiency condensing Baxi boiler that also does our domestic. The first guy used Wirsbo hepex but used pex clips on top of the strapping he told me to put up. He then had his guys (as he was never around...should have been my first clue!) cover up the bays with "Thermopan" ...looks good to a cabinet maker who knows jack about staple-up in-floor. So now looking at these plates has me wondering if I should tear out the thermopan and re-install the Wirsbo in the traxs after remove all the strapping the first guy had me put up...and our saga continues.....
I didn't realize you already had the tubing installed. You kind of lost me with the explanation about the strapping but....all you need is a 3/4" subfloor with the Joist Trak screwed to the bottom of it. Two runs to a joist bay ( 8" centers ).
Insulate well below it if you want to keep the heat up instead of down. Thermopan is not great insulation, but it's better than nothing and does a neat job. If you do take it down, you may want to add insulation on top of it.
To give you an idea of the difference between Joist Trak and thin aluminum plates:
You have to provide a water temperature approximately 35 degrees higher to a thin double plate system to get the same heat output as a Joist Trak system. That is a significant difference and will be reflected in home comfort and heating costs!
Sorry, it's difficult to lay out all the facts in one post. We have set up three in-floor zones and two baseboard radiation zones ( which is what was existing from the older boiler and original to the house). The first contractor who set up most of the system built his own manifold on site and set up one pump per zone! So now I know that it's overkill for our 1200 sq.ft bungalow, but it is now what we have to work with. He did the staple-up as I explained previously and I was going to add Roxul on top of the thermopan. (probably still will) but now that i've been talking to you guys, and from what you've shown me about the Wirsbo trak, think it may be worth scraping the thermopan ( $230. loss ) and backtrack with the transferplates which are non existing in the staple-up that he had installed. Furthermore, the second guy ( Mr. almost a grand a day dude who does seem to know what he's talking about as he's a third generation boiler guy but produces to quickly to do it correctly told me that he was going to put in mixing valves in each floor zone but made up an excuse after the first one ( which is the basement bathroom slab that has a zone sensor) probably because he didn't have the patients to do what he said he was going to do ( the nice guy even took the two other mixing valves off my bill...thanks!...but did not take the labour costs off)I'm venting...no pun intended! We are adding staple-up for the kitchen floor (should have been part of the original plan...but then again, i've proven to myself to be an idiot thinking i had hired a company that new what the frig to do...(that's the way i do business with my own clients and some even call me back for other jobs.) This zone or two as it's more than 300 ft is getting tied into the same zone on the same one half of the house (12'x45') This is the zone i'm doing myself with the help of all you guys too ( thanks for all the great advise, I really do appreciate it )
Well....to add to the other stuff he did wrong.....you should not have your pumps installed with the electrical junction boxes below the pump!
Funny thing is this was the only part of the reno I wasn't comfortable doing myself, the new heating that is! So how bad is it?...really...?
How bad is what???
I plan on using Thermalboard on my new house. It looks like a good economic option to Warmboard. Any Thermalboard knowledge/opinions here?