That piping is darned complex was my first reaction. It looks like a primary-secondary loop which I understand, but there seems to be more than that going on that I can't figure out.

I'll be darned. Before today I would have guessed that an electric boiler would not require primary-secondary plumbing loops. I just looked the Argo installation manual and I see that it is. I guess they have to make sure the cast iron heat exchanger is does not get thermally shocked, but it seems to me that if the controls prohibited the boiler from heating unless the pumps are running, that should be sufficient. A sail switch in the loop should do that, but I guess adding a loop is more reliable.

Thanks for the picture. I hadn't seen a modern installation so it is interesting to compare. When we replaced our boiler they upgraded us to the same Honeywell control boxes you have. We also got the Alpha circulator/pumps with the digital display and selectable modes just like yours. Those are really cool. I just had one put on our snow melt to try and get higher temps sent to the driveway. The first circulator was too high speed and I needed something I could ratchet down to see if it was the pumps speed or an undersized heat exchanger that was preventing full melt in cold temps. I see you have Taco brand air eliminator and zone valves. Looks to be a very nice set up.

We also don't run glycol in the house. However we do have it in the snowmelt and garage.

ionized,

It appears the main loop comes up from the boiler and then out from the wall. Then it appears there are two closely spaced Ts for the secondary loops.

I can only find one mixing valve and it has a circulator pumping away from it but from the pic it appears to be pumping into the zone valves. This was a bit odd to me because ours are on the return side. Apparently keeping them on the cold return side prolongs their life. Now, since there is one mixing valve I figure there has to be another since there are three pumps. One for the main loop, one for the main floor and one for the basement is my guess. So I'm speculating that it is behind the piping to the left of the pump labeled P2. Or maybe not. Maybe this boiler is a the mod condensing type and sends the correct temp. for the main floor but the basement temp is mixed down? From the picture that appears to be the case since I can't find a mixing valve for the main floor.

I love all the isolation valves and they got it right with the air eliminator at the top of the system. Also nice wall support on the expansion tank. It looks like the guy knew what he was doing. He left the autofill in the off position which is good and proper, and something I can never convince my plumbing company is correct. Looks like good wall support for the piping and nice tack down of the electrical conduits. Appears to have a power kill switch right above the for the system electricity. Another item I had to fight my contractor on. Overall I would be very pleased with this installation.

One thing I would check is what appears to be metal conduit for the boiler that comes into it from the lower right. It may be resting on the copper piping. If so put something in between that is not a conductor so you don't get dissimilar metal corrosion. Also their appears to be a steel braided hose connection to the expansion tank. Stainless is probably OK but the conduit could be aluminum. I'm paranoid about leaks so don't like to see anything metal touching my copper.

mmmm, thanks for your observations. I am going there next week and will look carefully at all the details you mention. I can't easily answer the cost question, because it was part of the house build; maybe I can decipher the various bills and come up with an estimate.

Certainly is quite complex. I think a water heater could work for a mild climate like mine with my desire of just taking the chill off the floor so I would have no need for slippers. Kind of an expensive cure just for that.

My idea would be to use separate water heater for sole purpose of a floor loop. Closed system and just rig a way to fill it with water via a hose. Pressure for water heater is typically 30-40psi this is primarily predicated on incoming water pressure. Being that there would be no incoming pressure it shouldn't be anything to worry about. So the pump(s) would just circulate based on temperature from farthest spot from water heater. Probably use Bell & Gossett pump if I were to do it and to keep things simple I would just make it one loop. Most years here I would be lucky to run it more than 30 days.

Water heaters are pretty resilient, boilers I've been around them a long time ago like 22 years or so. There is no excitement there I can tell you that much. I would rather keep it simpler. It would be completely different if I was thinking of making this primary heat source. I look at it as just another amenity to a home built around the 'comfort' mantra.

It's an interesting subject until you start talking about boilers... then you put me to sleep. LOL.

Oh my, the whole world has changed with respect to boilers in those 22 years. (Rock a-bye baby.) Most everyone wants a high efficiency replacement, homeowners, utility and government programs. Mod cons catch the eye like shiny trinkets, but they are often hard and sometimes nearly impossible to make work well where a high mass, hot start boiler used to sit. Nobody wants to completely revamp the $ whole system $ to replace the boiler. That is why I like the look of the HTP Versa boilers and Westinghouse water heaters. I think that you can just cut the pipes, reattach and get good performance.

In a, maybe convoluted, way you might be able to look at hydronic systems in an analogy to forced air. The emitters are the supply and return vents. You still have one heat exchanger at the fire box..... You figure the BTU you need in the individual rooms, total up the air or water flow needed and figure out how to move it and make the total BTU. One extra layer is emitter type and temps needed to match them: high - fan coils and aluminum baseboard > cast iron radiators > radiant floor -low.

Yes I know. ;-) Nothing is the same when it comes to air conditioning either and in some various degrees forced air heating as well.

I doubt this thought of mine would be more than just for the master bedroom and maybe leading into the kitchen. You know, the ones who pay the mortgage.

Once you're dressed and clothed in my climate, it's my opinion that you're experiencing 'free cooling'. I think the annual use of this would be quite short for my climate.

We'll be in the mid to low 70's next week.

Just a point of information: I just looked at the temperatures in my home using the remote wifi thermostats (Noon on Saturday). Both are set at 50°. Outside temperature is 26° Basement is 54°, upstairs is 53°. This pattern is normal - the inside temperature is usually a little higher than the setpoint, even when the outside temperature is in the single digits. I don't know if this is solar heat coming in through the windows (less, but not zero in the basement) or geothermal heat in the basement. Last year I had them set for 40° but was a little nervous wrt possible freezing.

mtvhike, it could be solar or the heat continues to drift upwards after the system shuts off at the setpoint +1. Mine does this because there is 120-130F water in the tubes once the boiler and circulator shuts off. But it normally only drifts up a degree or two before settling in to drift down. For instance my setpoint is 73. The system was on this morning and it has been cloudy so no solar gain. We have had the backdoor open quite a bit and it is 45 out (which is quite comfortable to be wandering in and out without a coat here in Colorado). But it is 75 in the house now. The system would have shut down when it hit 74 but with the water in the tubes still radiating the house continues to heat up a small amount as the heat flows from the tubes and equalizes into the floor.

Here is a photo of this. In the left side of the picture you have a zone that has been off for a couple of hours. The heat is no longer concentrated in the tube lines but has equalized into the floor. In the right side you have a zone that is on and currently active, just starting to heat up the floor.

How do you get these radiant heat pictures?

https://www.amazon.com/Seek-Thermal-Compact-Imager-Android/dp/B00NYWAHHM/ref=sr_1_1_sspa?ie=UTF8&qid=1513451880&sr=8-1-spons&keywords=seek+compact+thermal+camera&psc=1&pldnSite=1

I got the compact version for android. It was about $168 at the time.

Those pictures are likely from a thermal imaging camera. (cost vary widely, the more professional cameras can be in the $thousands range, but prices have been coming down lately.)

I think a system like this would be pretty 'cool' to have... the more I think about it, the pain it would be to install it. But it sure would be nice to walk barefoot of a morning with the comfort of warmth coming from below.

decisions, decisions.

Austin Air,

Keep in mind that the floors are only warm feeling if the house is cold. I would say I can almost always go barefoot as the floors are comfortable. But they are only actively warm when it is really cold outside or the system is trying to move the temperature up a degree or two. Otherwise they would best be characterized as tepid. :-)

They really shine when it is below zero. But it doesn't sound like your temp. gets that way often. They also mean you are never putting your feet on cold floor which is a big difference from most forced air systems.

Otherwise it would be like living in an oven if they were constantly radiating heat. They are very effective but would bake you if you actually felt heat from them all the time.

@mmmm12 - any special considerations regarding wood flooring when installed over in floor - not regarding the heating capacity, etc. but impact to the flooring?

wish,

We looked into wood flooring but decided against it. Apparently some are rated for radiant heat and some aren't. mtvhike is probably better able to answer any questions because they have it installed.

Oh, yeah, sorry, saw the wood flooring picture is from mtvhike.

@mtvhike - any info would be appreciated. Also, what the max temp is for the loops under the wood flooring. Thx.

I will say that if I weren't such a chicken I would have installed solid material linoleum through the whole house. I had some in my old house and it was very comfortable to stand on, held up beautifully to dogs and practically repelled dirt. Very easy to clean yet not slippery. Never needed any type of maintenance like grout does.

I think it is just a commercial product now. But we were worried about resale and the patterns were not that attractive so installed wood look tile.

Subsequently in our upstairs bathroom we put in Tarkett Fiberfloor.

http://www.tarkettna.com/products/fiberfloor

It transmits the heat beautifully. Was really easy to install and is slightly giving under the feet (just a bit of foam). We liked it so much that I took some of the left over and cut it to make a mat that I put in my kitchen in front of the sink and the stove to make it slightly more comfortable than standing on tile.

If I'd known I was going to be here 15 years I would have installed a solid surface flooring like the above. Tarkett says the fiberfloor should not be installed if the floor temp ever exceeds 85F but it is so easy to install I wouldn't worry about it because replacement would not be hard. Also we've had it in the upstairs bathroom for a number of years now and it has shown no degradation from the heat. But that room doesn't get sunlight so no UV degradation has occurred. It might be different in other areas of the house which get really hot from sunlight.

Keep in mind that the floors are only warm feeling if the house is cold. I would say I can almost always go barefoot as the floors are comfortable. But they are only actively warm when it is really cold outside or the system is trying to move the temperature up a degree or two. Otherwise they would best be characterized as tepid. :-)

If that's the case it sounds like it would be perfect for how I am thinking.

If it's 60-65 air temp inside I could set the floor loop to maintain 70 measured from inlet of water heater (cold water side) I think you would notice it, with a feeling of cool about the room.

[It really wouldn't be cold water side as it would have no incoming cold water, I would just fill the system and it would be closed off from incoming water source... that is my initial thought anyway. Still a long way off from actually doing it....]

That sounds like an oasis for my climate. LOL.

Obviously, indoor set temp and outdoor temp are going to influence how much heat is going into the floor. The other factor is heat loss to the outdoors. With a conventional system, If you have a well-insulated and well-sealed structure. You won't get much floor warming in Austin's climate. I think it is safe to assume that controlling the system via inlet temp to the water will be unique.

Thinking about this a little more, I see problem or two with that control system and your plan in general. I think that the typical temperature drop (boiler outlet-boiler inlet) for hydronic systems is 20F. For low efficiency, non condensing boilers maybe that is from 180 to 160. For condensing boilers, both would be lower and it needs to be with in-floor radiant with a lot of flooring materials.

OK, now here is the problem. What I write is sometimes just more than one way of looking at the same problem and at its root is insufficient heat transfer due to low temperature differentials. My stream of thought went like this. With a 70F boiler inlet temp you are going to get insufficient heat transfer from your tubes in the floor meaning that you are going to have to have lots of tubes. (It is going to approach walking on a water bed, unfortunately.) At that temperature, you are really going to have no difference in outlet and inlet temperature unless you have a vanishingly low flow rate or infinitely long loops. If you hook it up as conceived, the pump will start and then shut off almost immediately if it is pumping at anything near conventional pump rates. If you slow the pump way down and start with water at maybe 90 in the water heater, it might get down to 70 at the end of the loop, but then you have little heat transfer at the end of the run. Your tubing layout will have to be very asymmetric. I think that radiant floor water temps are typically 85F at the lowest and go up from there when more heat is needed on colder days. Note that there is a lot that I don't know about radiant floor heat design.

I think the only way Austin's plan works is if he keeps the windows open the entire time the heat is on so the floors keep running. The problem is that the floors would warm the air space and the furniture which would warm the air. The only way to keep the floors warm would be to constantly refresh the cold air.

I don't mean to shut Austin down. He did mention a room temp of 60F. You might get a warm floor at that temperature and 70F water. That means that after a nighttime set-back, recovery with the floor loop might give you a warm floor, but then you are done for the day. Sometimes proposing the unworkable and going through the problems is a good way to learn how systems work. Again, there may be flaws in my analysis.

In my house, described above, the master bath, master bedroom, and main area (Kitchen-DR-LR) are on three separate loops, with separate thermostats. Since we like to sleep cold, but have a warm bathroom floor, I set the bath thermostat at 75°, the main area (which is remotely controllable) at 65°, and the bedroom at 40°. That works very well (the bedroom, of course, is above 40°, especially if the windows are open!).

mtvhike, Is the master bath door open to the cold bedroom so the air flows between them and the master bath floor is effectively trying to heat the entire space? If so I can see how that would keep the floor warm.

Yes, but there is some air flow under the door

With a 70F boiler inlet temp you are going to get insufficient heat transfer from your tubes in the floor meaning that you are going to have to have lots of tubes.

(I would be using regular water heater on closed loop --- no incoming cold water) There are always problems to overcome when you use something to accomplish something else for what it was not intended to be use for. So I fully understand that.

I thought about this a bit more and realize that 70F tied to inlet would short cycle the pump to one degree or another. But given my vast control knowledge shouldn't be too hard to over come.

Realize this system (of mine) is not about precision or specific temperature as in room temperature it is just merely to take the chill off the floor so it's comfortable to walk on.

Also realize a water heater can produce water at around 140 degrees. This setting is also adjustable.

Once the system is installed the system setting may become something like this:

Pump cycles on at 70F inlet temp. / controls keep pump on for specific time. Then adjustments are made to water heat temp merely so the floor doesn't get too hot.

I think that will be the bigger problem is that it produces too much heat mostly because of my climate. There is no incoming cold water to the system so the water heater (best guess estimate) would produce enough heat to maintain at least 70F under probably even the coldest conditions of my climate. (This is not known either)

So say the pump triggers at 70F, the pump is forced to run 10 min every cycle, the inlet temp hits 100F. (realize this is not known currently)

Say the inlet temp hits higher, then I reduce the temp on the water heater, until desired temp is achieved. A lot of this will come down to flow rate of the pump, the size of the loop, the temp of the water produced and how cold the floor is.

If I could get it to 10 min cycle, 10 min off that would be 3 cycles an hour over probably 30-60 days a year.

If I decide to do it, I will have a solid plan in place long before I pull the proverbial trigger.

For starters, allow me to clarify something that I wrote in my previous message ...unworkable...problems...learn....

I meant me learning as much as anyone else. It is forcing me to look at it from a different direction. A good example follows. In most radiant floor situations, nobody would have to think of this question:

I think that one thing that I'd like to figure out before picking up any tools is at your desired floor temperature, be that 65, 75 or something else, what will that do to your room temperature in your current situation (heat loss from the room at this time of year). If you want your floor at 75 and that makes your room uncomfortably warm, will that make for a sad outcome? What does your floor temp run at at this time of year? There ought to be some information out there about what temp makes peoples' toes happy :-)

I know what your saying, but as you know what is comfortable for one is not comfortable to someone else.

I rarely run heat, unless it's really cold. That for my location is rare... as an example the past 2 winters here and so far this year... there really has been no winter other than a few chilly nights here and there (woo hoo FREE COOLING). Yesterday we hit 80 degrees. (I actually set the AC to run last night before I went to bed... I'm not worried about heat loss I can tell you that much. LOL)

I have a 4 zone HVAC system in my (single story) house and because I don't run heat unless it's really cold I have a good understanding of what temperature is comfortable to me. Realize I would be doing this for me. If someone else (later) sees value in it when I decide to sell it's a unique feature to have. I will have long worked out the bugs by then.

With that said, body temp is 98 or there close unless you are running a fever. When I got up today air temp is 72 and 70 on opposite side of house. That is a little cold on the toes (for me) but bearable.

So if I were to do it, I would shoot for 75 degrees I think. If it hit 80 or 90 I don't think it would matter too much... unless it heated up the room too much I would simply shut it off.

Realize the weather here this time of year changes on a dime. One minute it's chilly (typically) the next minute it's too hot.

As I said previously this in floor radiant heat system is primarily for of a morning before the occupant gets clothed. So run time 'may' only be in morning hours from maybe 3 or 4am up until maybe 10am. Obviously if functionality proves to be good or more economical way to take the chill off the room, then it could be used more frequently.

Once you have shoes on, for my climate the floor temp isn't going to matter much.

We arrived at our vacation house last night, and I can give a few updates on our system. Yesterday morning, before we left, I raised the temperature on the main thermostat to 65°. When I got here, the temp was 65° so I raised it to 70°. The MBa tstat had been set for 60, so I raised it to 70. All night it was toasty, with a nice warm floor (door kept sThis morning, I went downstairs to the basement and raised its tstat to 70 (it had been set at 50). The actual temperature was 63, so some heat must have been coming down from upstairs. Right now, 5 hours later at 1:00 PM, the temperature has finally reached 70 (an hour ago it was 65). The boiler is a 68,200 BTU, 20 KW Argo boiler with a maximum water temperature of 230°. The water temperature is about 140 degrees, and 3 of the 4 heating elements are on (all four were on earlier this AM, but the temp was still about 140). Outside temperature is 30, but it's supposed to drop to zero tonight; I'll keep you posted.

"so some heat must have been coming down from upstairs"

Heat doesn't fall, it rises. Consider that basements are usually the best insulated part of the house and can maintain a fairly constant temperature with minimal heat loss or head gain BTU loads.

Soil temperature at 30 feet or lower in that region is approximately 45F so you should never go much below that in the basement assuming any above ground wall is insulated, and that it is thermally isolated from the rest of the home or warmed from above. Heat sources there include radiation from the floor above and the furnace, DHW heater and their pipes.

Elmer, during the last month, whenever I read the temperatures of the basement and main floor, they were always between 50 and 56 degrees, depending on the outside temperature (thermostats set for 50). I didn't change the basement one yesterday but did raise the main floor one to 65, As I said earlier, I raised the main floor temperature to 70, but didn't touch the basement. Yes, convection heat does go up, but, as ionized pointed out, there is radiant heat from the floor above; that's what I meant.

You don't have floor insulation under the sub-floor of the first floor level, and so between it and the basement?

Correct, Elmer. The basement is a living space.

Sheetrock and an air gap provide "insulation" all the same. I'm surprised no insulation was put under a subfloor having hydronic piping over it.

"Sheetrock and an air gap ...over it."

No payback for the cost unless you want it for the look or you need it to separate heating zones for comfort.

Insulation is becoming more commonly used above ceilings/under floors of living spaces of multistory homes for sound insulation. In walls too for rooms where either noise is expected or more quiet is desired.

mtvhike,

Thanks for your post about how yours operates. I kind of was estimating as such, so I think for what I have in mind for my purpose could work really well.

It is Noon and I just noticed that the furnace is off; the water temperature is 134. Inside temps match thermostats, outside temp dropped to 8 but now is 15 and sunny. Update: 1:00 PM, furnace power still not needed, water temp 108, outside temp 20. Elmer, right now, there is no ceiling Sheetrock - just open floor joists.

OK, here is a stupid idea for you, Austin, make the floor heat part of a DHW recirculation loop and put it on the tail end just before re-entering your water heater. Include valves to disconnect it in warmer parts of the year. It is stupid because only will it probably not meet plumbing code, but since it is an open system you will need a more expensive stainless steel pump, and the plumbing will have to be compatible with potable water.

I have not responded to any of the comments because I am enjoying reading them and learning. We are in the beginning stages of planning our build, but I am going to keep all of this information to use at the time of the actual build. Keep the comments coming! :)

LOL, the plan (if I do it) is to use a separate water heater for the circulation loop of radiant floor heating. I would not use this separate water heater as part of a DHW system. It would be it's own separate one purpose system used for heating the floor. There would be a fill connection point probably via hose connection to fill the system after it's filled there would be no incoming water source, except for recirculation water from the loop in the floor. The heater would also have high pressure relief valve just as any normal water heater, but would be repurposed as use to take chill off the floor for my tropical climate. (If you're just tuning in to this thread.)

Heating in my climate is a wild card, some years would need more, many years would need much less. But if I were to do this, it would be counter productive to invite the possibility of having to take lukewarm showers because a radiant floor circulation loop is taking all the hot water. When I look to solve a problem, I am not in the business of creating new ones. LOL.

As far as plumbing codes or any codes go, my house was built in 1979. I bought the house with code violations and all, not to mention a slew of other problems some have been since fixed, some are on the future list. Since I bought it I've replaced the entire plumbing system. (old galvanized pipe) - this was a non-permit event.

This isn't new construction, it would be a retro fit to existing and I am outside city limits. There is no permit pulling in this area for existing structures.

Your location and local permit pulling requirements may be different. This is Texas y'all.

Merry Christmas.

Boomer, you've tolerated what most would consider a hijack of your thread with good humor. There will be more to sift through, for relevant stuff, but learning will happen.

There are a lot of dedicated posters in this site and it is a remarkably good site for little nonsense and good judgement in staying between the lines and with little flaming and insults. There are other sites for boilers and hydronic heat, however, if you really need to get into the nitty gritty. I suggest two places that I found very useful. The HVAC and boiler areas within the DIY area at terrylove.com are good. For example, right now there is a recently-active thread there about a monoflow system. That is type of system that shunts part of the water flow in a loop through radiators in sub loops using special "monoflow Ts" I doubt any significant number of systems based on that elegant principle have been installed for 50 years. It enables you to have single pipe circulation and install valves on individual radiators (thermostatic or not). Messing with the pump rate or other parameters might cause huge problems for the unwary or careless. If I had one and felt the need for some modification, I'd plan on hiring someone that knows what they are doing or spending a few hours learning about how it works. For the curious, looking at how monoflow systems work might be fun and I greatly appreciate the genius of the person that came up with the idea to begin with and the one that applied it to hydronic heat.

Another site as good or better iis "the wall" at heating help.com. It is a well run site with lots of knowledgeable posters https://forum.heatinghelp.com. Right now there is a thread over there about steam vs. hydronic heat in a new build. That argument will never, never end even though the answer to me is clear..

terrylove.com

the wall

ionized_gw,

For the record I am not flaming you, nor am I trying to hijack the thread. The OP commented to keep the thread going...

With that said: Anyone attempting this type of heating system... a DHW will probably not keep up as this is not what it is intended to do. Heating systems output are rated in BTU's. If you misjudge the load calculations the system is either over sized or undersized.

My location is Tropical for the most part. I am typically more inclined to run the AC than heating. But it does get chilly. Yesterday we were near 80 degrees again, this morning it's 66 degree air temp in here. Woo hoo free cooling!

So take my discussions in this thread for what they are... I am sitting here drinking coffee of a morning and thinking out loud of potentially fixing a problem I encounter occasionally when it's chilly here and I stumble out of bed and head to the coffee maker. (that's the only purpose of what I am talking about in this thread.)

I haven't worked on or even near a boiler in about 20 years and I have no desire to. We don't have boilers in my location. Water heaters? yes, we have those. LOL.

Merry Christmas everybody.

My comment around hijacking was aimed at myself mostly. Austin, the flame comment was not aimed at anyone on this board. It is remarkably free of that stuff. I like the usual civil and respectful mood.

In fact, in a well-built and reasonably-sized home even in a cold climate, a water heater can provide enough heat. One aspect of that is that the return water is much warmer than the potable water coming in at ground temperature. That might be 50 F year round. Yes, a BTU is a BTU and if the radiation and heat loss are way higher than the boiler output, that mismatch won’t work. A large domestic (50 gal) gas model makes 36,000 BTU. (Of course you can go with 100 gal or “fast recovery” models.) Maybe the most common water heaters don’t fit, but if you go to someting like a gas-fired Pioneer. (Up to 100,000 BTU) I or the Westinghouse WGR060NG076 (76,000 BTU) can run a respectably-sized system.

Ok I misunderstood you then which is probably not the first time, but because the OP responded in such away above your post kind of confused me.

I would say for the most part a radiant in floor water heating type system is probably not all that common, because the initial set up would be a lot of work, not only to organize the heating loops, but then place the floor on top without putting a hole in the loop(s). Not to mention controls, circulation pumping and so on.

Anyway you've provided good points to consider, so no harm, no foul. {I'll Walk it off}

Have you ever heard of a company called Warmboard? (

https://www.warmboard.com/warmboard-s) This is a company that takes your floor plans and creates a layout for you. My husband found the company and has been talking to them.

I think that in general you can expect a lot of help from equipment manufacturers if you want it. It seems like a strong custom in hydronic. There are a lot of calculations involved, although I am not sure it is much more involved than working up solutions with Manual D.* I've seen the way it worked with at least one boiler manufacturer. The rep came to the house, he and the contractor measured radiation and looked at the system as a whole. They came up with a replacement boiler that was, get ready for the shocker, oversized. I've seen comments about circulator pump and "radiator" manufacturers lending a hand with system design..

Just to get some of the readers started, you start with heat demand for each room and that gives you emitter (radiator) amounts needed. Add that all up and choose a boiler capacity based on that number and the boiler characteristics you want. Then you determine your desired delta T for the water based on the boiler choice. (High delta T systems need proportionately more emitter capacity/BTU to deliver at the end of a loop/zone than that at the beginning or those with low delta T.) Pump rates and variable vs. constant speed is determined by its own little set of physics. That leaves zone valves, expansion tank, air separator,....

*It seems more complicated with a second set of heat exchangers to figure out, but the radiators and other emitters are really analogous to the supply registers in forced air. Figuring blower capacity must be somewhat similar to circulator pump choice.

Warmboard looks it makes tubing installation exceptionally easy. What I don't understand is how to fit tubing length to individual rooms. If you ahve a room with lots of big windows and 3 exterior walls, you probably more tube in the room compared to an all interior room. if you are stapling down tubing, you and make more and less dense heat delivery if needed by changing the spacing. You could make micro zones and control rooms individually, but it seems like even in individual rooms you might want to change the heat delivery in certain areas

We are also contemplating hydroponic radiant floor heating. We want both in floor heating and heating through the duct system. My main concern is even though the concrete will be covered likely with laminate, is it hard on your bones/joints? Or is it the dampness of concrete when not heated that makes joints hurt?

Normal walking and standing on damp concrete or on laminate should not make a normal person's joints hurt. If your joints hurt, you are probably engaged in an inadvisable activity, or you need more exercise or physical therapy. If you have damp concrete in your home, you need to fix the damp concrete, period. You might need a vapor barrier or increased drainage.