I am writing from Vancouver BC Canada where winter temperatures rarely drop below 20 degrees Fahrenheit and are mostly in the 30’s and 40’s during this time of year. I mention this because this will have an impact on how you may try to answer these questions. Three years ago we put in a 3 ton Hydron module water to air heat pump with 600’ of vertical ground loop spread evenly over 3 holes. This forced air system worked beautifully and even during the coldest days of close to 0 degrees Fahrenheit, we didn’t need to turn on the auxiliary heat unit. Our house was 2400 s.f. We are now renovating it, doing a full gut and adding 800 s.f. We realize that putting a forced air system back into the house will create too many drops in many of the hallways and have opted to put in a water to water system. The structure will not support putting a radiant floor with a concrete toping, so that is out. The basement is already too shallow, so putting a radiant system in the basement floor would eat up too much head space. The infloor board type of systems such as Upunor and Raupanel are pretty expensive too. If we go with a staple up system between the joists, the reflective panels are also pretty costly. I know I’m probably sounding like I don’t ant to spend any money at all, however I just want to find the least expensive solution that will work. My questions are the following: 1- What water temperature is required to effectively use an infloor radiant system from above and from below the subfloor? 2- Does anyone have any experience with Smith Environmental’s HE2 water baseboards? They are supposed to operate on a lower water temperature in the 110 F range but still have a good BTU/hr/ft output (see following: http://www.smithsenvironmental.com/html/he.html) 3- My contractor said he used aluminum foil as a reflective material for the infloor between the joists and put insulation in the cavities. Does this really work? Thank you for any advice.

www.pexheat.com/site/download/ph_StapleUpFDS.pdf

I prefer the onix product for ease of installation. The put out about 25 BTU/sqf at 115 degrees F water temperature with 3/8 pipe at 8 inch OC, key is the reflective insulation underneath. That way you do not need plates, they just cost moneyLook at the charts they will give you the output at a given temperature. Worst case scenario, you can put them closer together. While they require about 7 degrees higher temperature than PEX, they are within the operating range of the heatpump and much easier to install. Don't have experience with the baseboards. We have installed 3 of the systems, they work great even at Buffalo winters.

Other options include embedded OSB. Routed sections of ply with routed channels for 3/8" tube, raises floor 1/2". Can be used in basement as well.
joe

http://www.blueridgecompany.com/rad...fer-plates

I installed a system without plates for a customer.  8" on center.  They were going to go with a standard water heater, but they switched to geothermal closed loop instead.  I would have installed the plates!

For the most part Geothermal and Joist Radiant Heat is not a good match. Max temp for water to water Geo is 120*, 110*~115* is better, while most joist heating requires higher water temps.

Bergy

Posted By Bergy on 23 Nov 2010 04:57 PM
For the most part Geothermal and Joist Radiant Heat is not a good match. Max temp for water to water Geo is 120*, 110*~115* is better, while most joist heating requires higher water temps.

Bergy

I would argue this. The needed floor temperature depends on the heat load of the room. For example, the onix product puts out 25 BTU/sqf at 125 degrees F supply temperature (115 F mean water temp) with a 3/8 pipe at 8" OC. That is enough for most application, new houses need about 16-18 BTU/sqf, even older houses get by with 23-24 BTU/sqf. Now if you need more, you can go with 4"OC, which will lower your neccessary supply temperature by about 5 degrees for the same output. Need more, you can put in PEX, that lowers the needed supply temperature by 7 degrees at the same OC compared with onix, but then I am fighting the PEX lines during installation. Most of the time, I can get the temperatures lowered to 110-115 max. and have enough output for my 0 degrees F outdoor design temperature. Then I work with outdoor reset, so most of the time they are even much lower. The key is to create an airtight cavity which is insulated and aluminum foil reflects the heat upwards. That way the cavity gets up to temperature and you have a relatively even temperature distribution, no cold spots. That way expensive plates are unnecessary. The other key is to work with lesser OC, that lowers the temperature and you do not damage the wood.

I have put in 3 or so infloor radiant heating between the joists with reflective plates, closed loop geothermal. I am from Battle Ground, WA.  It works great!

The lossiest zone in my home has 3 exterior walls (about 65-70% of the total wall length of the room) with about 35% of the wall area glazed with not-high-performance double-pane. It is heated through an insulating layer 38mm (double layered) plywood and another 19mm of birch flooring (about R2 total before you count the rug that covers half the floor) with a staple-up using cheap sheet-metal heat transfer plates (not the nice extruded aluminum ones) using half-inch PEX 20cm o.c.. It pretty much keeps up at heating outside design temp of -18C/0F, and 54C/130F water out of the buffer tank, ~45C on the return. If I re-plated that room with extruded plates my design-day water temp requirement would drop another ~4-5C. (But since I'm not running geo or condensing burners there's little incentive to do so.)

Vancouver's design temp is more like -11C/12F, significantly warmer than mine. If your glazed area is less than 20% of the exterior, and any individual room has at most half the running length of wall is exterior, and you have only one layer of sub-floor, your peak water temp requirements would be under 50C/122F even at design conditions, using the cheapest of heat transfer plates. During more typical average winter weather the water temp requirements in such a system would be well under 45C.

But nothing works as well as doing the REAL heat loss calc to figure out what's needed eh? ;-) But I'd be shocked if a cheap-plated PEX staple-up didn't cut it in Vancouver at geo-compatible water temps at typical design temps, or maybe even the rare cold-snaps that hit -20C.

I'm not a big fan of EPDM tubing (eg Onix, Entran, Entran-II), due to it's spotty track record in radiant systems. It's not clear if it's problems are related to material incompatiblities with other elements of the heating system(s), or too sensitive to the pH of the heating system water or what, but reports of unindentifiable black goo clogging zone valves, boilers or even narrow-diameter tubing itself are not rare. They SAY they've fixed all of those issues with new-school Onix, but I'm reluctant to experiment with it on my own home when there are better-known-quantities with more reliable track records as an alternatives. YMMV.

I just looked it up- Vancouver's design temp is actually a quite mild -7C/19F, a degree or so cooler than Seattle's 99% design temp, so I'll assume that's a 99% not a 97.5% binned hourly number. (see Table B-I at the bottom of the page: http://www.nrc-cnrc.gc.ca/eng/ibp/irc/bsi/88-performance-standards.html )

That makes even MORE likely that you can run low enough temps for geo using low-cost sheet-aluminum plates & PEX.

BTW: Reflective insulation is nearly worthless in any low-temp radiant application. When plated heat spreaders are used it's worth EXACTLY nothing, since the emissivity of the aluminum plate itself is so low that the radiated heat flux downward has already been cut by 80-90% from an already paltry number when you're talking ~45C water. Even with un-plated EPDM tubing staple-up, running at such modest temps you're better off filling the 20-25mm space between the reflective insulation & tubing with more fiberglass or rock wool, snugging it right up against the tubing. The only time reflective insulation has ANY value in radiant apps is when your water temps are north of 65C/150F with bare, unplated tubing, such as in a suspended-tube application. Even then the performance bump you get with the reflective insulation may not be commensurate with the installed cost compared to what it cost to just go with a higher-R on the fiber. In most floor joists getting to ~R30 is usually possible, but rarely necessary.

SOME amount of fiber insulation is required (at any water temp) as a means of isolating the room/zone below from being heated by the warm floor & joists above. If it's conditioned space below, unfaced R13 is enough, but if it's a semi-conditioned unheated basement or crawlspace bumping that to R19-R20 is usually worth the money in a 20 year present-value financial analysis of heating fuel cost savings. Over a ventilated crawlspace R30 or more is usually cost-effective.

Great writeups - I'm not experienced in the subject matter but it all makes good sense - agrees with what I do know of thermodynamics.

I agree with the insulation, but I do not see much issue having the insulation faced with a reflective layer. The point about creating a cavity is that the heated cavity radiates the heat more evenly to the floor above, reducing any cold-spots between the pipes.. Thus it can eliminate the need for the more expensive transfer plates. We are very busy right now, but coming Jan/Feb I will put a WEL on a couple of our radiant systems, so everyone can see for themselves.

Thanks everyone for all your great comments. What if I do want heat to transfer through the ceiling into the basement? Do I forego the insulation and just put the reflective plates?
Has anyone ever ordered plates from http://www.blueridgecompany.com/radiant/hydronic/316/rht-heat-transfer-plates ? They seem very inexpensive at 100 plates for 140$ Is this a scam?

One more thing, is there a second hand market for water to air heat pumps? I've got a 3 year old 3 ton Hydron module heat pump sitting in my garage and need to get rid of it.

If you want to heat the basement, heat the basement in a controlled fashion, not with heat leaks below the radiant floor. Basements have very different heat loss characteristics from the upper floors- if you don't isolate it with insulation it'll often be too warm down there in the peak of the heating season, and not warm enough in the shoulder seasons.

BTW: The plates are not reflective (even if they're shiny :-) ). Their function is to CONDUCT heat out of the PEX and into the wood, not REFLECT heat. Conductive heat transfer is far more effective than radiated or convected heat transfer, which lowers the temperature difference required to get a particular transfer rate- you can use cooler water. The cheapo plates from blueridge aren't a scam, they're just thin, and have less contact area with the PEX than the more expensive extruded versions. They're very similar to what I have in my lossy family-room zone. Thicker extruded plates with a more positive PEX contact DO work better, but whether it sufficiently better to rationalize the cost is heat-load and system specific. The biggest heat transfer problem in a radiant system isn't heat loss from mis-directed radiation off the subfloor & tubing, it's getting the heat from the tubing into the sub floor. Even in suspended tube applications the bulk of that heat transfer is convection, not radiation. Even with EPDM it's mostly conducted, but heat transfer plates (even the cheap sheet metal stampings) increase the conduction factor by an order of magnitude or more.

Heat conduction is powerful stuff, and will dominate the heat transfer transfer between solids & liquids when there is even a small conductive path. As a mental experiment, take a pan of 100C /212F boiling water (even a dark, highly emissive pan such as cast-iron) and see how close you can get your hand to it without burning. Then see how long it takes to reach damaging levels of heat transfer with even the slightest of conductive contact. Then consider just how hot the glowing coals of a wood fire have to be before you can cook your hands at any distance. The temperature differences require for that level of radiated heat transfer is more than 100x the temperature differences you'll see in a low-temp radiant staple up.


docjenser: Reflective insulation with a gap in no way evens up the striping effects of Onix-on-subfloor, and has only fairly subtle effects on higher-temp suspended tube PEX. It has NO bearing on whether it would need heat transfer plates. The air ga is necessary for gaining any benefit at all from it, since conductive contact and very-close convection between the hot element and the insulation overwhelms any heat reflection aspects. The gap is necessary for it to have ANY effect, and that effect is truly miniscule at the geo-radiant temps- about an order of magnitude lower than just filling that inch of space with more fiberglass (with a lower installed cost). Snugging the batts directly against the tubing & subfloor has the additional benefit of impeding air-flow along the joists (but still no substitute for properly air-sealing the rim joists & foundation sills.) While EPDM tubing may be somewhat more emissive than PEX, it's not orders of magnitude more emissive, at least as far as I can tell with infra-red thermography- I haven't looked up the specs. (It's EASY to detect emissivity differences between unpainted metal plumbing and PEX or Onix, even with a $50 infrared thermometer.) The U-value of EPDM is higher the PEX too, and most of the heat in an EPDM is conducted though it's contact area (& close-range-convected), not radiated to the sub-floor. Of that smaller radiated component of the heat transfer, more than half is already directed to the floor, not the insulation, and with fiberglass batting most of that radiated heat is stopped and re-radiated in the top 2" of the material (it's somewhat translucent to deep infra-red.)

Under the hot roof decks in the desert sun (much hotter than your warm radiant subfloor) reflective insulation is only truly effective with substantial air gaps on both sides. If your sub-floor is 50C or hotter the way an AZ roof deck often is, you should probably call the fire department, 'cuz your house is ablaze. ;-) With 45C water inside the tubing, the sub floor won't be hitting even 35C even design day, and the fractional area of that 40-45C EPDM tubing is quite a small fraction of the subfloor in a joist bay, and the average radiated heat flux is quite modest.

http://www.chple.arch.vt.edu/CHPLE%20Research%20files/Khanna,%20Amit.pdf

http://www.eagle-mt.com/downloads/1036_final_report.pdf

I agree that the above floor method gives you a better heat transfer, however, in retrofits we do not have that luxury, therefore under the floor is sometimes the only choice. I also agree that conduction is the most effective way to transfer heat. The key question is: How much do you need. I have posted two studies above comparing different methodology. While the heat transfer to the above floors is increased by about 70% using the transfer plates, it only produces data for new built houses with tight plywood as subfloors. It does not account for older wooden floors where heat can move through the many cracks and spaces upwards. In that application, the heated cavity matters.

All this talk about radiant between the joists gets me wondering
about some thing my builder said.
He does not want to do radiant heat under wood floors,
because it will dry them out. Perhaps he is thinking of electric?
I assume that Geothermal /Ground source will be lower temp than any other
source of radiant heat.

Also, in the "old" part of my house, the "wood floors" are really a few....
A previous owner found termite damage and addressed it,
then he put 3/4" plywood on top of the old half-eaten hardwood.
He had vinyl, which I removed and had 3/4" oak installed.
(I didn't think of radiant at the time :-)

So that means my (first) floor(s) are about 2" thick (wood).
(Is that what I call Thermal Mass ? :-) :-)

I would like to hear your experiences...

BTW, you'll be amused to hear, I have found a LOCAL geothermal
expert who seems to understand this stuff! (unfortunately, I have
talked to a few who I don't think understand it :-)

Thanks
Seth

Sorry, but my experience with addressed termite damage, with 3/4" plywood on top of the old half-eaten hardwood, topped with removed vinyl and 3/4" oak on top....... is relatively limited.
Again, the question is wether the system you design is capable of rejecting (dispensing ) the amount of heat at the maximum temperature provided by the Geo system. Everything else does not really matter!

2" of wood adds some thermal mass, but it also adds some resistance to heat transfer by from underfloor radiant tubing - be sure design accounts for it.

The business about radiant heating drying out wood is in the category of old-wives-tales. Radiant heating neither adds nor removes moisture from the house, but elevating the temp of the wood a few degrees above the room ambient raises the vapor pressure of the moisture. Yes, it removes some moisture from the wood- about as much as it would be if the room were 23-25C without the radiant. At Vancouver's relatively high wintertime dew points, the relative humidity indoors never drops low enough long enough for this to present any sort of problem whatsoever to the wood. (Indeed, even in colder dryer Minnesota they run the floor temps much higher with much lower dew points without apparent damage to the wood.)

The floor temp of the radiant heat depends only on the heat load it needs to deliver- at Vancouver's heat loads it'll be much more modest than in the midwest. The water temps depend on the system/tubing/plating type and the heat load per square meter of floor space. The source of that hot water isn't particularly relevent, other than the efficiency at which the source can deliver it. With geo it means you really want to run it below 45C most of the time, if you can, and I'm pretty sure that you can, even with the cheap thin plates. With condensing natural gas you need to run it under 50C if you want to keep it in the 90%+ efficiency range, but even at 60C it'll be 85% efficient. With either using an "outdoor reset" control scheme to run the temps at the lowest that keeps up with the load (by tracking outdoor temps) improves the seasonal efficiency. Most of the season you'd need no more than 35-40C water, but on the very coldest nights you might need 45C+.

My floors too are 2" thick, in my lossiest zone, with a heat load 30-50% higher than yours. With thin plates it still keeps up, with ~55C water.

docjenser: Neither of the studies you posted compared with/without reflective insulation (indeed, none used it), but both compared suspended-tube vs. plated systems. The primary difference in heat output at a given water temp between above the subfloor systems vs. staple-ups is the R-value of the subfloor, but the quality of the conductive bond with the PEX can trump that. If you look at figs 5.2.2 and 5.2.3 in Khanna's thesis you'll note that at 100F & 110F, with heavy extruded plates below the subfloor you achieve the same performance as WarmBoard, Quccktrack, and Thermalboard, above the subfloor systems using thinner plates (that AREN'T a hammer fit the way extruded plates are.) Conduction out of the tubing is at least as important as the conduction from plate to flooring. And even the "enhanced" suspended tube system UltraFin is nearly an order of magnitude behind them.

PEX stapled up without plates still outperformed suspended tube UltraFin by 2x at these temps. Given the relative stiffness of PEX (compared to EPDM), that isn't very much conductive contact area at all, yet it literally doubled the heat transfer rate! Were radiated heat transfer a large part of the equation that likely would not have been the case. UltraFin is an attempt to conduct more heat out of the PEX, but convect that heat to the sub-floor, and is barely half as effective as the most basic plateless staple-up.

Thin plates will deliver about ~75% of the performance of heavy plates, but that would still beat an unplated PEX staple-up by 50%. IIRC EPDM runs a bit behind the thin-plated PEX but better than an unplated PEX staple up. Too bad Khanna didn't test those as well.

I don't necessarily disagree with any of this, but I do want to point out that the Khanna study is seriously flawed - I wouldn't trust any of the output numbers from that particular paper. The author points out most of the problems himself in the paper, but the work was sponsored by one of the companies whose products he evaluated and they seem to quote the numbers as gospel (not surprisingly since it was very favorable to them). This was discussed at length at heatinghelp.com - a great resource for radiant and hydronics, less geo-focused than this site obviously but lots of knowledge there.