My wife and I are getting ready to build our dream home, we plan on going all out on this one. I’m not planning on ever building another house again( well not for myself that is). One of the items I will be using is “radiant floor heating”, now in my area this is not a big thing so all I know about this is what I have read about. I plan on going with lightweight gypsum pour over 1/2 tubing, and that is the only way I plan on going.
One thing I am looking at is a open loop system, has anyone had experience with this type of system and what your thoughts were on it compared to a closed loop system. Since this is not a common thing in my are their is only one company in my are that dose this, and they don’t have much experience with it either. So I have found a company that will design the system and I will install it myself. “one more thing I have complete control over”
So now to my next question has any body out their used lightweight gypsum pours before and if so how much a sqft dose it go for, this is another area I might do myself also. I was able to locate a company were I can get the material to do the job. I plan on doing as much of the work on this house an time allows me to do so with my custom that I do every day. So any ideas would be of great help.
Update
Going to go with the closed loop system. For heat source I am looking at going with a outdoor wood furnace with a electric boiler for back up. The wood furnace makes since for me we are building on 300 acres and I have been cutting wood for heat since I was a kid.
Edited 12/9/2005 10:37 pm ET by byoung0454
Replies
No insult intended, but an open system is not going all out.
What you want if you want the best , is a modulating, condensing boiler, with indoor and outdoor reset.
With an open system, there is the real possibility of legionare disease. Not a good thing.
Most open systems also use a standard water heater. The afue on a w/h is about 40%. A condensing boiler sized right can get over 90%.
Go to tekmarcontrols.com and read about control strategies and cost savings.
What part of the system is open loop- the radiant floor system or radiant floors with heated water from drain down solar collectors.
Have only heard of open loop for solar and heat pump systems!
TIA
Most "open loop radiant floors" use the water heater to supply both dhw and space heating. Radiantec pushes it . Not the best way to do it.
Not even legal in some jurisdictions.
And most water heaters are not even certified for space heating.
Edited 12/8/2005 12:03 am ET by rich1
I've been reading threads researching for my own project and the open system looks better all the time. I keep seeing this Legionnaire disease thing due to stagnation. What about a water heater? 40 gals of hot water just sitting there breeding germs? Going away for the weekend - that water just sitting in your pipes at room temp, maybe even a little warmer if it runs near some duct work. I think that argument against it is fear mongering. The open system radiant is using flushes the lines of the system whenever the hot water is used. An interesting post earlier pointed out that 300 feet of 1/2" pex has about 3 gals of water easily flushed during a shower. It isn't the only system radiantec offers. For whole house heating they recommend a Polaris condensing water heater AFU in the 90's and UL for radiant floor heat.Lots of discussion about RFH on breaktime - just looking for a case of an open system along the lines of radiantec's that hasn't worked out because of germs. I don't see how the system is much worse than the domestic water systems in most homes. The article on RBean's site is interesting but attacks open systems but doesn't really give any reason other than bugs.
Radiantec argues that a lot of energy is wasted on 2 pilot lights for 2 separate boilers.....What about a heat exchanger? Seems like this would be the best of both worlds: single boiler, keep the water systems separate.... Radiantec doesn't seem to like them, but not sure why not.....
You are on the right track with using radiant heat for comfort and efficiency, it is definitely the Cadillac. Gyp is a great way to go, but not the only way to get low temps, so don't slam doors yet. I heated my own house yesterday at -10* with 88* water. It was 70* in the living room.
The next step is to talk to the local inspector to find out what he want's to see in your system.
IF he says yes then you need to think this through COMPLETELEY. First, any water flowing through the tubing WILL affect your homes comfort, therefore, YOU need to have control over this water. Gyp and transfer plates react fast. They also use relatively cool water. Think about what a looong shower will do to your comfort. If the water doesn't move when the domestic water is used, then it won't move during the times that the heat is off. Have you ever experienced the water from a boiler? Think fire sprinkler lines. Then you also need to think about another whole host of issues such as corrosion, O2, pumps and all fittings rated for potable water, zoning, domestic hot water needs, ventilation, temperature control, etc.
Chris
"If the water doesn't move when the domestic water is used, then it won't move during the times that the heat is off"
Radiantec's open system has it so that whenever you call for domestic HW, the incoming supply runs through the tubing before it gets to the water heater this prevents stagnation.
I also have building our dream house and am thinking along similar lines as origianl poster. I also got into this line of thinking from Radiantec but will probably buy parts locally. I have already poured basement slab and intalled PEX that was bought locally at considerable savings than Radiantecs quote.
I am currently in the process of figuring out stairs which requires an exact knowledge of finished floor height. I will probably use gypcrete but be forewarned that if you are thinking hardwood floors you will end up with a subfloor, then the gypcrete, then another subfloor for nailling and then the hardwood. There are other alternatives, but none that will perform like the gypcrete IMO.
As far as a Sq Ft cost i haven't got anything current but it doesn't sound to difficult to pour. I have been told to use a larger sill plate than wall framing to use as a screed board, which also gives a perimeter nailer, and to install nailing sleepers at 16" centers. I personally am going with the SIPS walls and am going to insulate the gypcrete slab away from the sill plate. No sense in losing all that good heat right through the plate or drafting wall framing, right?
I have not used gypcrete before, and I am probably driving local guys crazy with my questions and have spent lots of time lurking on chat rooms such as this. If i was you i would get a couple of bids for materials seperated from labor and be upfront with the bidder that you may DIY, but might source materials from them. this is how i bought materials for the basement at lower cost. All of them have been very professional and willing to answer questions. I would also bet that there are loacal installers in your area that can help you. They might not be in the internet, yellow pages, ask hardwood installers, plumbers, local lumberyards, plumber supply house, it will probably surprise you.
Good luck, the hunt for information can be tedious but is half the fun.
I like the idea of the wider sill plate but for the sleepers 16" oc we plan an using alot of tile and plan on going with a glue down 3/4 engineered flooring.
this whole project is of my desighn were we are building we have no codes to regulate us. Not saying I build shotty houses, I do build houses in another county and what I build is above what they require.
A great house is the first step (gotta have something to put that heat in) and it sounds like you are well on your way. Once you have the details ironed out on your house you can do the heat loss and design the system. Just don't add or remove windows without adjusting the design for that room (been there, fixed that, and it cost the customer quite a bit). I'm curious to see how to control a system with a wood boiler, I've never seen it done. 'Course that just means you're in front not in back.
Have you thought about using an indirect water heater? They last a lot longer and run cheaper. They also mate well with a closed loop keeping the boiler water isolated from the potable water and would allow you to heat your domestic water with the wood boiler. If you use solar in the summer and wood in the winter.... Sounds exciting to me. Keep us updated.
Chris
It does sound like an interesting control problem.
I'm thinking 2 indirects, one for dhw and one for the infloor. Use an injection system directly off of the infloor tank, think of it as just a large pipe. Spirotop on top of the tank and you have the world's largest air seperater.
A tN4 control system could probably run the whole thing.
They sell them (heat exchangers) and, in my experience with them so far, they haven't said they don't like them. Keep it simple and cost effective. Why would pro plumbers install low efficiency heaters for DHW when there are electronically controlled condensing heaters with high AFUs? To keep it simple and cost effective I would bet. same with the use of FG batts for insulation and vinyl siding. Simple and cost effective. Radiantec, like other posters here, tell me to do what the building inspectors require. For a small slab like mine they recommend open system instead of a boiler. They also are willing to help the do it yourselfer. This is big. They do provide a pretty thorough heat loss calc, lots of advice and, as far as I can tell, good prices on components. Always friendly.As for the looooong showers - how long to change the temp of the floor 20 degrees? no longer than to recover it. shower will probably stop when hot water stops.Ted
There are other issues. Most rfh runs around 100 with a flow rate of 1/2 gpm when sized and controlled. When you get flow rates above that, the head loss or pressure drop decreases and the size of pump goes up. If the incoming water flushes the lines, you have cold water in the floor. If the dhw goes through the system, the water may be to hot for the floor and too cool by the time it gets to the tap.
And the AHJ has the final say on whether or not a water heater can be used for space heating.
Yes, open systems can be designed to work, my point is you will not have a top of the line system.
I'm not trying to rain on anyone's parade, but maybe we need to think about what we are trying to accomplish with the radiant floor heat and not get caught up in the hoopla.
There is a myth that lots of energy can be saved with radiant floors. That is all it is, just a myth. All energy purchased has a direct calculation to give you the btus you just bought. To save energy you need to work on the envelope. The envelope is what keeps the btus you just bought inside where you can enjoy them.
It is arguably the most comortable system out there, if designed and installed,and controlled properly.
Installing radiant floors is not "easy". Most of it requires only a strong back and a high tolerance for repetitive tasks. The devil is in the design and the controls.
Any quick response low temp system will have to have some way of controlling water temp to the floor. There are at least 3 ways of doing this that I know of. The one that works best for each situation will be determined partly by the heat source, partly by the degree of comfort (constant steady temperature) that the user expects, partly by the users technical savvy (if diy)and partly by the wallet. A simple thermostat doesn't bring out the best a well designed radiant system in a home and causes the temperature to "swing" up and down. They are, however a good enough and inexpensive way to control a garage or shop where the 4-5 degree swings aren't noticed as much.
ALL of these require an accurate heat load calculation followed up by good system design. If this isn't done properly the mistake is set in gypcrete and takes lots of work and money to fix. Some wholesalers have experience in system design, it might be worth while to make contact with some of them now and agree to purchase your materials locally and pay for good design. Most wholesalers I know would be open to some version of this. This would let you get the gyp down and keep the project moving while the near-boiler piping and controls are worked out.
Chris
The only thing I would add is that a properly sized, modulating,condensing boiler will consume less energy.
It allows you to match the load to the loss.
No other system that I know of can do that.
Combined with a well built house and you have a winner.
And you are right "easy " is not the right word. It is entirely possible to put a flooring nail right in the center of a tube, even when you can see the tube. Don't ask :)
If you design all of your loops to require the same temp water at any given outdoor air temp it is possible to eliminate the need for mixing valves and/or injection pumps as well as any need for zone valves/pumps. All that is needed is a little time spent tweaking the balancing valves and the reset schedule on the boiler. Use an indirect waterheater hooked to the boiler and you'll never run out of hot water even with a big whirlpool tub. Everything is at 90+% AFUE and you have a Cadillac with fewer parts to fail and the best there is in comfort. No more setting your beer on the floor to keep it cool. :^)
Chris
a few things.One, in thinslabs, keep your tubing on centers to 9" or less. Under low load conditions and low-R floor coverings, noticeable heat striping can occur if you don't do this.Second, I have personally designed many Polaris-run systems. The fact of the matter is, they are finicky. And in today's world, they are obsolete. A condensing/modulating boiler does the job much better, both in terms of efficiency, and in terms of comfort (add that outdoor sensor!), and in terms of reliability, and is often in the same price range as a Polaris. But the number one concern with *any* heat source selection is what can be serviced locally? Even if you do the rest of the system yourself, get a local pro to provide, install, and service your heat source. The best heat source in the world does you no good if no one can get parts for it, fix it, or verify that it is operating properly, and you don't have the equipment or knowledge to do that as a DIY'er.You can, however, install pipe and perhaps sweat copper and run low voltage wiring. I just suggest you draw the line at combustion appliances.I also want to note that Radiantec does not do heat loss calculations, they do ballpark "energy factor" calculations. They also note that their drawings are *not* designs, but are more concept drawings. They are a decent source for parts, but they (by their own admission, on their own drawings/sales lit) do not design radiant systems. At least, that's what their stuff said as of a few months ago.Why are open systems bad?1. to do them properly, you need to use huge pipe at on centers wider than should be used in residential systems. This does not save much money at all, and it results in less capable systems using hotter water than needed and often in heat striping. Of course you can do it improperly with smaller pipe, which means you won't be flushing those lines. 2. There is an increased risk of legionella. You may not want to accept this, but people can and do get sick from potable water systems, and the risk is much worse when you add a mile of pipe for the bugs to grow in. A one loop addition is one thing... a whole house is another. For a $500 or $600 savings of a heat exchanger, it's just a stupid risk to take for a whole house system.3. You risk your heat system components. I have personally seen systems eat themselves alive in as little as 5 years from the constant build-up of various materials in water. This is heavily dependant on the individual system design and your water quality issues. But even if you have good water, it's got stuff in it, and your system will run longer and cleaner if you fill it once and leave it alone. But again, simply using a closed system renders this a non-issue.4. One of the big "benefits" of open systems is using non-barrier pipe and bronze components to "save money". You can, these days, get barrier pipe at very close to, if not the same price as non-barrier pipe, and keep the cheaper cast iron components. I have not seen any savings from non-barrier pipe except in the largest jobs. and in those, using anything other than a condensing/modulating boiler is dumb... the larger your load, the more using a good heat source makes sense! Use a domestic storage tank and use the high efficiency boiler to do your domestic as well.5. if you do the "proper" open system, you are flushing your lines with cold water all summer. this "limited free cooling" gives you practically *no* cooling benefit, but it *does* promote condensation in most areas of our country, in areas that are typically sealed. That's a mold risk of the worst kind right there. The kind of risk that can render your home condemned. I'm not saying this happens in every job, but again, it's quite simply a stupid risk to take to save $500 on a heat exchanger. Your house costs a lot more than that.6. It's ILLEGAL in most jurisidictions. for GOOD REASON.7. You can't use antifreeze, and neither can anyone else who may use the system after you.Frankly I think the promotion of "open direct" systems is incredibly irresponsible (note, of course, I am a competitor, but still). You have house insurance, hopefully you have health insurance, and you're about to put in a system that EVEN CHEAPLY will cost you thousands of dollars. There are ways to save money, going "open direct" is not a way to do it, and it's cheap and effective insurance to go with a closed system, and your system will run better for it to boot.Finally, radiant can be energy saving. with a low temp system on a condensing heat source, you can hit efficiencies up to 98%, with little air stratification (which is big in cathedral areas). But the envelope is most definitely the first place to invest for energy savings.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
For my heat source I am going to go with a outdoor wood furnace "Central Boiler" and use a electric boiler for back up. Could you gime me your thoughts on this and any do's or don'ts on this.Thanks
Search the site for "outdoor boiler". There was a thread about a month ago. These things are not are all they cracked up to be!!! Be careful as you can soon get neighbours within about 1/4 mile of you riled up pretty quick.
I'm not to concerned with the neighbors I am building in the middle of my property so I have 150 acres to all sides of me. As for the boiler I have had a central boiler For 6 years now in the house we live in now, and to top it off my father is a dealer for them. In my opinion they are the best on the market today.
2 stage tekmar with both feeding a buffer tank piped primary /secondary. boiler can't supply enough, electric kicks in.
I think Rich nailed it. depends on your radiant setup for a lot of what ifs, but if you are doing or want to do injection mixing, the Tekmar 363 is capable of two-stage injection, which may be of use here.Do NOT use central boiler's radiant diagrams! They may know boilers, but they don't know radiant very well. The last ones I saw were the worst of "super simple" systems. As in, simpler than they should be. A much better system can be had for not a ton more money.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Hi,"I'm not trying to rain on anyone's parade, but maybe we need to think about what we are trying to accomplish with the radiant floor heat and not get caught up in the hoopla. ""There is a myth that lots of energy can be saved with radiant floors. That is all it is, just a myth. All energy purchased has a direct calculation to give you the btus you just bought. To save energy you need to work on the envelope. The envelope is what keeps the btus you just bought inside where you can enjoy them."People are sensitive to both air temperature and the radiant temperature they see from the surrounding walls, floors and ceilings. People will feel just as comfortable if with a lower air temperature if the surrounding surfaces are at a higher temperature and vice-versa. This is why you feel colder next to a window surface, even though the air temperature may be the same. So, I think, there is some basis for the idea that radiant systems can provide the same comfort level for less heat in. That said, I think the actual studies on radiant heated homes have shown little or no actual savings.--Being a solar junkie, I have to ask if you have thought about designing your home to take advantage of passive and/or active solar heating? Active solar collectors work well with radiant floor heating, because the radiant floors can use low temperature water that solar collectors make more efficienctly.
http://www.builditsolar.com/Projects/SolarHomes/solarhomes.htm
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htmGary
http://www.BuildItSolar.com
radiant can save energy in a few ways.1. reduced temperature stratification. your ceiling isn't 90 degrees to keep the room at 70. that's a lower delta-T and thus lower heat loss and less "wasted" heat.2. low temperature operation is generally more efficient than high temperature operation. Less parasitic losses. lower stack temps. etc.3. You can, with the right system and heat source, achieve efficiencies of combustion with radiant unattainable with any other form of heating. when was the last time you saw a conventional boiler hit 98% efficiency :DI don't buy into the lower temperature/same comfort thing myself... my clients aren't lowering their thermostats as far as I can tell. I think, however, that it's related to the fact that people who want radiant want capital C comfort, and are people who are less likely to turn down their thermostats in the first place.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Hi,radiant can save energy in a few ways."1. reduced temperature stratification. your ceiling isn't 90 degrees to keep the room at 70. that's a lower delta-T and thus lower heat loss and less "wasted" heat."I've seen this mentioned in the radiant heating adds, but I'm wonder how true it is. I have cathederal ceilings over living/kitchen area, and thought that I could save some energy by mixing up the air with a fan. Before getting the fan I measured the actual temperature difference from 4 ft off the floor to right near the ceiling and the most I ever got was 2F -- not much."2. low temperature operation is generally more efficient than high temperature operation. Less parasitic losses. lower stack temps. etc.3. You can, with the right system and heat source, achieve efficiencies of combustion with radiant unattainable with any other form of heating. when was the last time you saw a conventional boiler hit 98% efficiency :D"Well, some of the gas forced air people claim 95% for furnaces?"I don't buy into the lower temperature/same comfort thing myself... my clients aren't lowering their thermostats as far as I can tell. I think, however, that it's related to the fact that people who want radiant want capital C comfort, and are people who are less likely to turn down their thermostats in the first place."I think that it is a real physiological factor (its in many text books complete with graphs showing equal comfort lines), but, as you say the people who are into radiant probably take the benefit as a higher comfort level rather than saved energy at the same comfort level. I'm not in any way argueing against radiant floor heat -- I think its the best way to go. We are seriously considering converting to radiant heat on our main floor as part of our solar heating project.
http://www.builditsolar.com/Experimental/InWorkshop/SolarShed/solarshed.htmGary
http://www.BuildItSolar.com
The problem with forced air is that you can't modulate the output and you can't match the load to the loss in each zone. A condensing, modulating boiler with indoor/outdoor reset and a buffer tank can do that.
Can't get any better than that.
Rob:
I know it's your business (radiant) and it's a good system when well designed/executed but don't over sell it!!
"reduced temperature stratification": What ceiling height would you have to have to get that much stratification in a home with forced air or other regular heat? 20-30 feet maybe. That type of stratification doesn't occur in 8-9-10 high rooms unless you have the wood stove nearby and then the whole room is 90 degrees, not the ceiling.
"boiler hit 98% efficiency" How do arrive at this??
"I don't buy into the lower temperature/same comfort thing myself... my clients aren't lowering their thermostats as far as I can tell." Right you are. A small gov't sponsored study here had a researcher go to homes known to have radiant floors and determine the long term t'stat settings. Much surprise!! no one had the t'stats set down/most had them set up a bit. This may be due to the lag time to heat back up from the last call from heat by the stat. With a temp differential of 1deg , +/-. 5 degree accuracy, the temp of the room may fall back 2-3 degrees before the heat pulse comes to the surface and is felt. By setting the stat higher, the room never drops to an uncomfortable temp of ,say, 69 for some. This phenomenon was seen with cheap stats with electric heat. The room may get to 67-68 before the heat came back on, so people set the stat at 76 so the temp never got below 71- they didn't mind a bit of overheating as the room may get to 76-77 for a while but they didn't want to feel cool at all.
The argument about stratification is probably more theoretical than real, but just for fun I'm going to try something. My own home has no ductwork at all, everything is radiant. I also have a calibrated 3 probe thermometer used for monitoring airflow stratification in air handling units. The 3 probes will allow me to check temps without moving around and disturbing it. I won't be able to do this until this weekend, but the results should be interesting either way. If someone else would like to try something similar the with forced air, then we could either verify or de-bunk a common argument. No offense NRT, you may be right, I've just never seen any data on this and I'm curious. If I get enough time, I'll start a fire in the fireplace and check it again.
Boilers can hit 98% efficiency with low enough water temps. This has been done many times and is verified by clocking the meter, monitoring waterflow and deltT across the heat exchanger. 98% isn't that hard to hit, but the next 2% are going to be hard. The key is to keep the water temp down to let the stack temp down and encourage condensation of the moisture in the flue gasses. Most if not all modulating condensing boilers should be able to do this if the water temp is below 100* discharge.
The key to lower temps is a very large and efficient heat emitter combined with a very tight and well insulated envelope. Radiant floors, walls, and ceilings are usually the best heat emitters. Just make the heat transfer from the water to the surface of the emitter as easy as possible, for example, either get rid of that big persian rug, or use the ceiling for an emitter. Gypcrete, transfer plates, or the subfloor with the grooves in it are the most common above grade solutions for a floor emitter.
If the system is well designed, balanced, efficient emitters are used, a modulating condensing boiler with outdoor reset is used, then it is possible to use constant circulation in all zones. The advantage gets bigger because the boiler/system is never has to "catch up" to hit the target. This also saves the up front cost and maintenance/repair of thermostats and zone controls.
I put just this system in my own home (guinea pig). All rooms sit at the designed temps all winter long and never move. There isn't a thermostat, zone sensor, slabsensor, floor sensor, zone valve (12 zones) or zone pump in the house. So, yes it can be done. The downside is that the operator needs to be somewhat technically savvy to accomplish tweaking the reset schedule and the balancing valves.
Off to work,
Chris
Bender:
don't know if you saw my post #47 before you left for work but here it is:
"Get people working on "first things first" rather than fancy, high tech, complicated heating systems."
Very few people are going to try to tweak a system to get 98% (I'm still skeptical!!) efficiency out of a combustion based heater. So to be making those claims becomes "pie in the sky" and should not be used in promoting the system/s. With your large emmitter theory, the water temps are very low (better eff) but you have to possibly compromise your floor finishes, etc. for it all to work! Everyone wants to experience the warm floor sensation and may not want to go with hydronic radiant ceilings.
Everyone wants to experience the warm floor sensation and may not want to go with hydronic radiant ceilings.
Amen to that. The floor can be putting out the required btu's but may not feel warm.
"But I paid for WARM floors."
right on rich.. this is why radiant ceiling is a fantastic choice for high efficiency homes, compared to floor. 2nd cheapest install (next to putting it in an already-planned slab), very effective, and many efficient homes would rarely have warm floors if it were installed there anyway. It's even possible to do radiant cooling w/ceilings very effectively... we haven't tackled that ourselves, but I know a few people that have been with good success. We'll get there :DCathedral ceilings, however, do throw a bit of a monkey wrench in it.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I have a customer that has radiant ceilings both heating and cooling, same panels, changeover valves controlled by the thermostat. Commercial application. Works so well that I put cooling into the floors of my house. Works great in residential too. I guess the laws of thermodynamics are pretty universal.... The key to the puzzle is controlling the dewoint of the conditioned space and keeping the water above it.
Unfortunately, the smallest chiller I could locate at the time was a 3t barrel. Had to go with a buffer tank to keep it from short cycling and keep the superheat low enough to protect the compressor. Also needed a dehumidifier to control the indoor dewpoint.
It all works because heat travels to cold.
Chris
You can be skeptical, but this efficiency is real. Modcon boilers have changed the rules quite a bit, and make such systems pretty simple as well.I do ceilings all the time... works great... and if people want to do floors, then yes, they need to consider what they are trying to achieve. If you want carpet, there is a price involved as far as effective heat transfer is concerned. So what? If you want an efficient house, you need to plan for it.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
The "tweaking" was only during the first few weeks after the initial startup. It is actually easier than programing a setback thermostat. I haven't had to adjust mine since the first few weeks of use.
The 98% efficiency comes from the boiler coupled with good design (low water temps) and quality energy conscious construction. This is done often, verifiable, and repeated. If one leaves out one leg of the stool it falls over.
I don't get the "fancy, high tech, complicated" jist. All I have for heating is :
1. Boiler
2. Primary pump
3. Secondary pump
4. Flow Controls (think of these as manually adjustable restrictors, set and forget)
5. Code required safety controls (required of ALL hydronic systems)
6. Switch to shut it off in the summer
The only hydronic system that is simpler is a single zone off/on single temp system. That is the system with the several degree swings in temps. The people who want radiant heat probably aren't too interested in these systems.
Chris
Assuming you omited some sort of temperature sensor? What turns the pumps on and off?
It's constant circulation, water flows from when I turn it on in the fall until I turn it off in the spring.
No thermostats, slab sensors, telestats, zone valves, zone pumps, etc. Boiler has an outdoor air sensor included with boiler controls and is already programmed out of the box. Outdoor reset raises water temp as the outdoor air temp drops. Indoor temps are rock solid.
Solar effect is taken care of by the lower temps, heat travels to cold, therefore the sun warms the floor which then warms the water which lets the boiler turn down to a lower rate of fire or off if warm enough.
Chris
This design/system is exactly what the radiant floor heat industry needs.
Care to provide any detail on your envelope, wall technique, insulation, window area and r-value, etc? (If you've already detailed this maybe a link to the thread)
The shell itself is 2x6 with densepack, tight vaporbarrier taped, r-60 ceilings. I have about 450 sq ft of glass, mostly south facing all low-e high performance. North side is sheltered by evergreens and the highpoint of the hill.
The main entrance into the house is through a "vestibule" that is semi-conditioned. This provides an air-lock so to speak during more extreme weather. Windows are shaded by the overhang during the warmer weather. Floors are wood and slate, plates under 1st and 2nd floors.
Basement , vestibule, garage, and shop have tubing embedded in slab, 2" foam underneath, isolated from the walls by foam.
All pipe and wire penetrations through partitions were foamed to attic. Airtight fixtures and boxes were used. No plumbing penetrations through outside walls except for sillcocks. Attic access is double doored and double gasketed. All pretty basic stuff, just a few hours with foam cans and caulking guns.
The main thing is the layout and design. The house was designed to be energy efficient at the outset. It was common knowledge that energy is getting more expensive. And we planned it with that in mind. All mechanicals are in a central location so it would be relativley simple to retrofit another energy source to supply the heat in the future should it become necessary, another advantage of P/S piping is the possibility of multiple heatsources just pick the cheapest to run. I haven't had the need for this yet.
Chris
Remarkably similar to the house I put up over the last two years.
Do you have an HRV? Tougher to do with no ducting in place.
Yes I do, that's the only ductwork I have. Supplies dump out into a central stairwell. Intakes are located in bathrooms and pantry where washer and dryer are located (dirty laundry smell). HRV is located next to the stairwell in the mechanical room in the basement. Sorry about forgetting that.
Chris
If it's too good to be true then .............!! Just checked the specs of one of the modulating, condensing boilers manufactured in my area and spoke to the sales manager of another heating boiler manufacturer. From the online brochurefrom the first: Steady state efficiencies of 96-98%; Annual Fuel Utilization Efficiency (AFUE) of 91-92%
So to get the 98% the boiler burner never shuts off!!!
This is starting to sound like the "apparent sensible efficiencies" used by some ERV/HRV manufacturers and their dealers. It apparently looks like it's that efficient but in real world operation it's not.
For the pro's that are on these pages, remember there are a lot of "just plain folks" on these boards also. So let's not lead them astray with "pie in the sky"
But if that boiler modulates from 35,000 to 150,000 and at design the loss is say 50,000, in theory, the boiler won't shut off.
The burner efficiency of 98% can only be achieved with cool water temps. This is because the stack temperature is close to the water temperature, the warmer the water, the warmer the stack, the more energy that you bought is going out the vent.
The steady state is achieved by the modulating capability of the boiler. Try to think of it like this, two identical cars, trip of say 100 miles.
First car starts off, acclelerates to top speed, stops for coffee in 5 minutes, starts off again, top speed, stops to relieve themselves at 10 minutes, gets lunch too, etc. stopping every 5 minutes for a 5 minute rest.
Car two takes off, accelerates smoothly to 1/2 of top speed, drives smoothly and steadily for the entire trip.
Both cars arrive at about the same time.
Now for the $64,000 question, which trip was more fuel efficient? Which car would you rather be riding in?
Boilers aren't that much different from a car. Both burn fuel to produce energy, a portion of that fuel is wasted in the combustion process.
An off/on control strategy is what causes the indoor temperature to hunt in all but design conditions. Design conditions are when the boiler runs flat out, never shuts off and holds the indoor temperature at a steady state.
A modulating burner not only can save energy it can also increase comfort by keeping the temperature steady. Why heat the water hotter than necessary dumping purchased energy out the flue, just to shut the boiler off, let the space get too cool, repeat?
Modulating burners aren't new technology, I routinely work on burners from the 60's and 50's that modulate. Fuel prices have just reached the point that they are now available downsized for small boilers (less than 400,000 btu).
All boilers will reach a point that they must shut off and on to control temperature. Modulating boilers in residential sizes have, usually, 4 to 1 or 5 to 1 turn downs. What that means is a 100,000 btu input burner can turn down to 20,000 or 25,000 btu input. The less time that a boiler spends in on/off condition the more efficient the system is operating (assuming proper cumbustion tune), and the greater the degree of comfort for the space.
OK, so for those of us who have built "not so big" , say in the 1200 - 2000 sq ft range, and have achieved very tight and well insulated shells with passive solar...even in a 7000+ HDD climate with design temps of below 0*F....we may only have heat losses of 20K - 30K BTU ON DESIGN DAYS, and much less than that during +20 -- +30*F and shoulder seasons.
So why can't we get a fossil fuel bonified modulating boiler that modulates from 5K - 40K BTU output? Too small of a market?
With my 1600 sq ft shell, wood frame passive solar house, I resorted to a 9KW modulating ELECTRIC boiler that trickles from 0 - 35K BTU/hr, majority of the time coasting under nearly constant circulation with just a few of 5 zones calling. Fortunately my utility offers dual fuel rates of ~.04/KWhr and I plumbed a propane WH in to pick up the slack during peak demand, although I pick up most of that evenings with a small wood stove.
I'm thinking it would be a HUGE market. Look at all the areas that are not tradionally thought of as a winter climate. But they still need a small amount of heat in the winter. Probably half the pop. of the US.
I know what you mean, my house itself has a heatloss of about 35K at design and it's 2112 with a 10' deep walkout under it. I knew that any boiler available at the time would be overkill so I added the garage, vestibule, and my shop to to increase the load on it rather than have 3 separate heaters. I still haven't seen water over 100* even at -20*, boiler was still modulating at those temps, still close to or at 98% :^)
With the ever rising fuel prices I'm thinking of adding a coil and pump onto my sealed combustion fireplace. There is already a thermostat in the firebox to cycle a blower option (didn't buy it). P/S piping, should be super simple, take the load off of the boiler, circulate the heat everywhere.
Chris
You don't *want* the boiler to shut off. You *want* it to run at steady state, modulating to whatever temperature the system needs at that time to heat on a continuous basis. replacing BTUs lost with BTUs gained perfectly, in a perfect world.It won't run at that efficiency 100% of the time... but it will run at a very, very high efficiency all the time, and moreso as long as the boiler is over its minimum modulation level, which can be as low as 17kBTUs/hr if I'm not mistaken, on some units. Compare that to a conventional boiler that would ONLY run in steady-state on a design day! A modcon boiler can run steady state the whole time it's over its minimum modulation... pretty big deal there... and even below that, you're firing a burner that is only the size of its minimum modulation when you pulse instead of one sized for the whole heat load. All this assumes you install an outdoor sensor which absolutely should be installed with any modcon boiler. Well, except viessmann... they have other methods.This is all big stuff. This is all *big* for effficiency. and with a low temp system keeping that puppy condensing... it's really big. end of story.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Hi,"The argument about stratification is probably more theoretical than real, but just for fun I'm going to try something. My own home has no ductwork at all, everything is radiant. I also have a calibrated 3 probe thermometer used for monitoring airflow stratification in air handling units. The 3 probes will allow me to check temps without moving around and disturbing it. I won't be able to do this until this weekend, but the results should be interesting either way. If someone else would like to try something similar the with forced air, then we could either verify or de-bunk a common argument. No offense NRT, you may be right, I've just never seen any data on this and I'm curious. If I get enough time, I'll start a fire in the fireplace and check it again. "I have a data logger with some accurate temperature sensors, I'll set up 3 or 4 sensors on a vertical rod that goes from floor to ceiling and record the results for a couple days. My house is forced air, so it should be interesting to compare.Gary
http://www.BuildItSolar.com
We won't be a large enough sample for scientific purposes but over several days it should be pretty indicative of the real world. :^)
I'll post back as soon as I get the numbers.
Chris
Hi,"We won't be a large enough sample for scientific purposes but over several days it should be pretty indicative of the real world. :^)I'll post back as soon as I get the numbers.Chris"Hi,
I logged the temperatures in my catheral ceiling living room with temperature sensors at 2, 6, 10, and 14 ft off the floor. The total ceiling height is 16 ft.Temperature vs time plots here for about 14 hours:
http://www.builditsolar.com/Experimental/StratificationTest/stratificationtest.htmThe temperature difference between the 2 ft level and 14 ft level is about 3F. Between the 6ft level and 14 ft level its only about 1F.Does it seem (from the plot above) thay my furnace is cycling to much?
Its a forced air, propane furnace. Outside temp was about 20F. It appears to be cycling about every 10 minutes.Gary
I don't have cathederal ceilings but I will get some samples this weekend from my 9' space, majority of my friends are shorter than that so it should be OK. ;^)
Is there a span adjustment on your thermostat? I'm not too well versed on all of the electronic residential thermostats. Some of the old mercury and bi=metal stats had a way to change that. Looks like you are only seeing a "cycle" of about 1/2 degree. Might be time to check out the manual on the stat. However, it may not all be bad, the comfort level should be better with a smaller cycle.
Just for fun, you can now calculate the BTU loss of your house at that temperature and relative humidity. If you have that piece of information then you can then find out the minimum size of heating source needed for design temp. THEN the what if game can begin!
Chris
I don't have a data logger, so I used a paper and pencil.
Outside temp today,16*F
Took readings at 1', 5', and 8' from the floor in a space with 9'ceilings.
The first column held steady all day long, didn't move over .2 degrees. The next 5 columns were after I lit a fire in the fireplace. The last column was when DW started cooking supper. The readings were taken in a room that is 24' across from windows to fireplace. the readings are from the center, 12' to both fireplace and windows. Fireplace is sealed combustion, no draft in room from fireplace.
All Day Fire Supper
8' 71.2* 74.3* 74.6* 75.6* 76.2* 78.4*
5' 71.2* 73.4* 73.7* 74.2* 74.2* 75.2*
1' 70.1* 72.2* 72.2* 71.9* 70.8* 71.2*
Looks to me like the fireplace started a convection current from the fireplace across the ceiling, down across the windows, and back across the floor, just like a fintube radiator. I did see a 1* spread before the fireplace during the day. Odd thing is that the floors are the heat emitters, it was cooler there. I just got the data so I'm not sure what that means that the floor was cooler and it's the heat source.
Time to eat, more later
Chris
"Looks to me like the fireplace started a convection current from the fireplace across the ceiling, down across the windows, and back across the floor, just like a fintube radiator. I did see a 1* spread before the fireplace during the day. Odd thing is that the floors are the heat emitters, it was cooler there. I just got the data so I'm not sure what that means that the floor was cooler and it's the heat source."Hi,
Interesting stuff.Not much change for floor to ceiling, but, as you say, its odd that its not warmer near the floor. I suppose the air is transparent to the heat that radiates from the floor, so its not abosorbed until it hits the cieling (or you). But, it seems like there would be conduction/convection to the area near the floor.I take that if you put the temperature sensor right down on the floor it would read 80F or so?Ran across a couple papers on radiant floor heating:
http://www.vtt.fi/rte/projects/annex37/POVpaper.pdf
http://www.oregon.gov/ENERGY/CONS/RES/tax/Radiant.shtmlOur results make me wonder about these kind of adds:
http://www.comfortline.biz/radiant.htm
"Radiant panels make temperature distribution in a room vastly more vertically balanced – only a -1 to -2 degree difference between the floor and the ceiling (for convection heating, meanwhile, the difference is given as 1°C per mere 30-50 cm of height)."The 1C per 50 cm they mention would have make my floor to ceiling temperature difference come out 31F, when it was actually about 3F -- quite a difference.Still, for whatever reasons, people find the radiant floor systems more comfortable to live with.Gary
http://www.BuildItSolar.com
I spent the day on the slope so I didn't get back to you until today.
The articles were very interesting, I think that the gist of the articles was to seal/tighten/improve the envelope, radiant doesn't necessarily heat cheaper. I'm guessing here, but it may be that people who often pay for the additional cost of a radiant system want comfort more than energy savings. I have lived with woodstove heat, forced air, and radiant floors. Radiant floors are the most comfortable IMHO.
An un-explored advantage of the radiant floors is the possibility of multiple energy sources to provide heat. Solar, ground-source heat-pump, wood-fired boiler, electric boiler, gas fired boiler, oil fired boiler, probably a few that haven't been invented yet.
I think I want to see what is happening between 0 and 5 feet. That weems to be where the most change is occuring, I think the key to the future systems is going to be understanding these things.
Chris
What is "that much" stratification? If there were a five degree difference in stratification, that's like having your favorite thing... setback... on the ceiling surface 24/7. not a gigantic factor, but nice.98% efficiency is completely achievable with condensing/modulating boiler coupled with low-temp heating systems. And there is much less parasitic loss than your typical duct installation!-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
"There is a myth that lots of energy can be saved with radiant floors. That is all it is, just a myth. All energy purchased has a direct calculation to give you the btus you just bought. To save energy you need to work on the envelope. The envelope is what keeps the btus you just bought inside where you can enjoy them."
Well said Gary! I feel that we should use the underlined section as a permanent header for every post in the energy threads dealing with the energy efficiency and heating of homes. Get people working on "first things first" rather than fancy, high tech, complicated heating systems. Every home should be trying to incorporate at least a bit of passive solar.
I agree with about open systems and all this invoking of Legionarie's diease? - Can anyone quote a case history? Legionaire's gets enough scrunity from the CDC and health departments that such an occurance should be easy to reference. I've never seen one and I skim a lot of medical journals that lie around the house. My wife (an MD, internist) hasn't either. Stagnant water in duct work (like some mobile homes or A/C systems have) is one thing. There's air, water, and exposure to any little microbe floating around.A RFH system on the other hand is closed. Even an "open" one. And open system is only open to potable water which is, well, potable. Chlorinated from the water district, it doesn't have any nasties in it when it comes into your house, and "spontaneous generation" of life was disproved a few centuries ago.My open system is made of food-grade stuff (copper, brass, cross-linked polyethylene) and is connected to the same direct-vent HWH that heats domestic HW. You need a really tight and well insulated house to get by on 40,000 BTU/hour for everything, but some of us build that way.Another advantage to the simpler system is the reduced space needed in the house for the heating system. Since everyone has a HWH anyway, my heating system takes up only about 2 square feet of floor space for the manifold. A "boiler" or hot-air furnace with space around it for servicing and required clearances needs about 20 to 30 square feet. At $100 or so per square foot for conditioned space in your house, that's another $3000 savings on top of the equipment savings.I very much agree with the posters saying RFH has to be carefully designed. And much more important than selecting the "most efficient" or "best" system is to go with what a local installer has experience with. Experience is NOT having put in 6 systems this year. Experience, at a minimum, is having put in 6 systems LAST year and you being able to talk to those customers about how the system performed over the heating season, how it dealt with sudden cold snaps, warm spells, and varying solar input.David Thomas Overlooking Cook Inlet in Kenai, Alaska
This ought to be enough to scare you.
http://hcinfo.com/outbreaks-news.htm
Attended a seminar, the speaker had a brother who walked in front of the BBC building in London, England, and got it from the cooling tower.
Keep this in mind when designing cooling towers!
I was thinking about the best way to spill only the beans I can while protecting the innocent. This will sound somewhat vague but rest assured, I was involved with the cleanup of this mess and it is true.
A customer of the company I work for is a hospital. One section of the hospital that houses in-patient clinics experienced a sudden increase in fatalities and complications, can't figure out why. The rate increases and now employees are getting sick too, since they are normally healthy people, they go home, get better and come back to work in a couple of days. Not everyone, just a few more people than usual. However, epidemiology is involved by now, meetings are held, tests are run, etc.
When the building was built in the 80's the piping put t's on all of the stubouts with a "shock arrestor" above it. Shock arrestor was simply a short piece of copper pipe soldered in with a cap on it. All horizontal runs didn't end with a 90, but rather a piece of pipe, a valve, another piece of pipe and a cap. Water sat there for 20 years and things began to grow. Everytime someone got a drink there was a little extra in the water stream. I don't know what the name of the bugs were but I'm sure that a few lawyers in suits could name them all as well as the cost of cleaning up. From what I gathered it was all settled out of court. They are still providing bottled water to all patients and visitors at no additional cost.
I was failing to see the ACTUAL benefits of a closed system until this came up, I'm a true believer now. Granted, problems in the piping, this is the ONLY proven case that I know of, the piping may not have been properly shocked and purged in the first place, etc. but what a risk. Too many places for things to go wrong. Not with my family.
Chris
So any plumbing systems with shock arresters or a capped off line is suspect? How about that 1/2 bath that gets used once a month? maybe we should install check valves to make sure no stagnant water can creep back into the system. The argument for the open system are simplicity, 1 pump instead of 2 running for the lifetime of the system, one less heatsource (or exchanger) to buy, etc.I have to chuckle whenever breaktime comes up on my browser. There's an old thread talking about the dangers of PEX tubing for plumbing systems. "ilegal in NY" and not likely to be, ever.Fearful in MN, Ted
yes, that 1/2 bath is most definitely a risk. People get sick from those situations, whether you hear about it or not. Most of us are healthy enough to fight it off. Very young, very old, or compromised people are not. Unfortunately, most of the deaths are not correctly reportedThere is a big difference between PEX being allowed for potable... that is, proving itself over time... and current heating practices being made illegal years after their inception.adding a heat exchanger and a pump is hardly a huge jump in system complexity. here's a good article for you; http://www.contractormag.com/articles/column.cfm?columnid=98take note of the CDC figures at the end. you can also go to the center for disease control and search for "legionella" if you want the facts from the horse's mouth.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Thanks for the link to the article. It almost sounds like they were talking about the same project.
After seeing what went on I was simply amazed that there weren't a lot more cases like the one I was. 5% to 10% get diagnosed accurately according to the article. Looks like the thing that tripped it all up in our case, was all of the people who already had compromised immune systems. Like I said, the staff, normally healthy, came back to work in a couple of days. Until that job I thought all it took to prevent Legionaire's disease was to keep treating the towers. I was wrong and am lucky at the same time..... After almost 30 years of getting exposed to all sorts of water from chillers, boilers, cooling towers, etc. who knows.
I'm just wrapping up my own house, believe me, no dead legs, good filter, no cross-connections, etc. The biggest cost in any radiant system is the labor. A pump is about $200 list. How sick would one of our kids have to be before we would pay $200 to make it go away?
I apologize if anyone is offended, I just take this a lot more seriously now and don't want to see anyone get sick when it is this easy to avoid.
Chris
So for some time I've been following the great debate on open/closed systems, and boilers vs water heaters.
I have a few questions too, since I'll be putting a radiant system (my 2nd) in soon. All constructive comments, rebuttals etc. welcome.
Heat Exchangers
I'd like to "close" the heating loops, but how much efficiency is lost to heat exchangers vs straight open systems?
Hot Water Heaters
Bill Clinton (not that Bill) has an article in the November 1998 JLC on some of the myths about water heaters, and claims that in actual use, water heaters are often more efficient: (since he's not selling anything, I'm more compelled to trust the source)
http://www.jlconline.com/cgi-bin/jlconline.storefront/43b33c9f0010455827177f0000010585/Product/View/9811usin
Legionaires Disease
From the legionella.org website faq:
What are the chances of getting Legionella from open system of hydronic radiant heat where you get your house heating and drinking water from the same source?<!----><!----><!---->
The risk from hydronic heating is unknown, but we know of no cases of Legionnaires’ disease from such sources. However, as the article on our Home Page shows, one can contract Legionella from home water distribution systems and large building water systems. But the risk is extremely low and close to zero if you are not a cigarette smoker. And, if you were a smoker, I would quit smoking and not worry about the hydronic heat.
Treat every person you meet like you will know them the rest of your life - you just might!
Not sure about the hx, but I think a water heater sucks compared to a modulating condesing boiler. Water heaters have an efficency rating of .4, .5 etc. that translates to 40% AFUE. A m/c boiler will run 90% or better if the system is designed and installed properly. In other words, it will cost almost twice as much to heat with a water heater. And most water heaters are not rated as a heating appliance.
Pay now or pay later.
Not so fast - I want to know if Clinton is right - read "myth 2"
In my superinsulated house (36% better than code according to rescheck), I don't want to buy a boiler and pay to have it installed as I think it may be a waste of resources in the long and short run. If a boiler is called for, then so be it. Just trying to cut through the misinformation.
I even had a GSHP in the last house, but with such small heating loads, I don't want to throw $ away, and I am partial to the simplicity of the radiant w/water heater. We'll likely keep the house warm with the masonry heater, and radiant will be backup anyway.
The modcon boilers do seem to be pretty cool little heaters, though.
Treat every person you meet like you will know them the rest of your life - you just might!
water heaters as heating appliances are not as inefficient as their labels would indicate, that is true.It is also true that they are not even in the same ballpark as a modcon boiler supply low temp water.If your loads are low enough, you may never recoup the difference in cost between the two. However, it's rare that that is the case for anything except a small addition. Some modest superinsulated houses also fall into that category, and others in mild climates may as well.For most homes in real heating climates, a modcon boiler is really the best option by quite a good margin.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Does anybody know if electric radiant heat emits emf's through the flooring?
Are tankless water heaters a legit option in a fairly mild climate ( Western Oregon ) Winter temps usually around 40 degrees and rarely below 20.
MJaeger -
I have heard so much bull on the emf issue - you can be certain the floor will emit emfs, the debate will be on what is harmful. My friend with the electric company laughs at me for any concern about them - claims studies show no problems etc. Others have definite anecdotally based suspicions, maybe even hard proof. then again, in most houses wires are everywhere...
If you are worried about emfs, don't do electric radiant floors, or even baseboard. I don't believe they are a great option anyway except for small areas, like warming bath floors.
I don't know a thing about the on demand water heaters for radiant, but I used a regular gas water heater for a small area in my last house and loved the effect, but I am still researching the boiler pro con issue. Good luck!
Treat every person you meet like you will know them the rest of your life - you just might!
As usual, the right answer is "it depends".
When you compare a cast iron boiler to a wh, he could be right, but I don't see hard numbers in the article that would stand up to serious scrutiny. Jacket losses, flue losses etc. are taken into account with afue and energy ratings. A .5 is about equal to 50% AFUE which is not combustion efficency.
When he is talking about a wh being better at handling small loads, it depends on what you are comparing. NO boiler or water heater is sized for small loads and therein lies the problem.
Let's say at design conditions, you need 40,000 btu. A water heater or cast iron boiler will both work. But it gets nice out and only one rfh zone calls and it has only 2 loops at .5 gpm each. Not enough flow for a ci boiler. The water heater can handle the flow, but it is still way oversized for the load.
A mod/con boiler can lower it's output to say 25,000 btu. Still oversized and it will short cycle, lowering its efficency . But if you add a buffer tank the short cycling is overcome and you get the 90%+ efficency.
The big plus is when loss = load, the mod/con won't shut off and will run at peak efficency. In addition there are no jacket or flue losses. In addition, a properly sized indirect storage tank will give you almost unlimited domestic hot water.
Again, it all depends on sizing, installation and control.
FWIW, I have used water heaters in the past, and my code allows it with certain conditions. BUT, I won't spec it anymore, I don't think that there are any long term benefits.PS. I really wish I had infloor, my computer is in the basement laundry room, and the floor is freezing my feet right now.LOL.
Edited 12/31/2005 1:51 am ET by rich1
Edited 12/31/2005 1:58 am ET by rich1
Over 400 people in the US die each year from Legionella, and the belief is that the disease is exremely under-reported, to the tune of about 10% reported vs actual.
As a design engineer and a manufacturer's rep for many hydronic heating products, I deal with infloor heating daily. As a member of ASHRAE, I have abundant resources to help, hopefully, from repeating historical mistakes. The causes and sources of legionella are well know. Un/under treated water systems, below 140 degrees is the most common. Given that little bit of background, I will not design or sell open systems. The benefits are limited, but the potential for consequences is great. This a case where cheap and stupid will kill you.
IF my customers "have" to heat with gas water heaters, I make them work, and they work well. I have a tankless GWH providing hot water for my garage floor. I let them decide if the first cost outweighs the operating costs and the limited life expectancy of the option. The GWH's that are cheap enough to be a significant cost saver in such a system, operate on the order of about 65% AFUE equivalent, though they are not rated in terms of AFUE. Higher effieciency GWH's approach the efficiency (and cost) of the cheaper boilers.This is a case, all other things being equal, where you get what you pay for. Go cheap, get cheap. If the space is small enough and/or has a reduced heating load, I would prefer a CombiCor type gas water heater over the simple tank-over-fire type. This has a separate heating loop built into the unit.
The heat exchanger, if selected and installed properly, is not a significant reduction in efficiency, thermally, however, additional pumping costs will reduce the overall system efficiency some.
Not everyone who gets the "flu" is tested for legionella infection. Keep that in mind. Regardless, it's a dumb risk to take especially when coupled with all the other problems possible with an open system that are prevented by simply closing the system.An open RFH system is NOT closed. You are constantly adding new oxygen, new sediment and organic materials. That is not even remotely closed, whether your district chlorinates or not (and if you're on a well, you don't even have that). Even chlorinated water is not sterile, as you should know. I don't advocate sterile systems, personally I think it's important to be exposed to *some* bad buggies so you keep your immune system strong, but it's just plain dumb to elevate your risk when you don't have to. I suppose you could just assume the codes are being lobbied by brazed plate heat exchanger manufacturers, but the fact is open systems are banned in more and more areas every year. Perhaps you'd like to consider that the research may, in fact, be compelling.If you are using a HWH, a brazed plate heat exchanger to handle the seperation does not take up much space, either, if you want to compare apples to apples rather than comparing a HWH to a boiler system. Using a HWH to heat an entire house is typically a poor idea for efficiency, but there are certainly homes in which the differential there is not large enough to justify a more expensive heat source. Or perhaps you are in an area of Alaska where using electricity makes sense, which eliminates a good portion of the problem with oil/gas water heater combustion inefficiencies. either way, adding a plate heat exchanger is a one-shot, reasonable expense when all the factors are taken into consideration.There really isn't any good reason to use an open system. Not one. It's the cheapest insurance policy for your health, your home, and your heating system that you can buy, and you only have to buy it once. Don't be penny wise and pound foolish on this.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
"One thing I am looking at is a open loop system, has anyone had experience with this type of system and what your thoughts were on it compared to a closed loop system."
Advise against open system. Too many risks, and you will not save that much over using a heat exchanger. The extra costs associated with buying non-iron circulators would likely pay for the heat exchanger and related equipment for a medium size home.
Risks include disease from stagnant water and condensation from hot moist summer air hitting your cold floors. This could cause mold/mildew, and damage floring materials.
Even if you do not place much faith in the disease argument, do you really want to be the lab rat, and for how much savings?
Glad to see you are going closed loop.
Here is a link to a heat loss and rfh design program. It is great for doing what ifs.
http://www.weil-mclain.com/netdocs/programs.htm
Also, check out tekmarcontrols.com it can be dry if you are not into controls. The tN4 is probably the best integrated control system available.
We have a 1yr. old, ~2,400 SF timber-framed cape with SIP panels for insulation. Our timber-framer had a "sandmix" installed for the 1st floor radiant slab that was much cheaper than the gypsum. The sandmix just doesn't include the coarse aggregate (stone) that a conventional mix does.
Although I'm not sure of the "open loop" meaning, our system features the following:
Although the Buderus boiler heats both the domestic HW and the radiant HW, they're not on the same "loop". (BTW, the Buderus is very efficient, as oil-boiler go, but "hickups" if not supplied with dedicated air; house is too tight w/o).
If we had to do it over, I'd get a dedicated HW heater, because the boiler turns on all summer just to make domestic HW. The 8% heat not put into the HW heats (i.e. 100%-92%) up the utility room in the basement.
Looking at all the components involved, I wouldn't try configuring and fabricating such a setup unless you were a plumber experienced with radiant heat. If you intend to act as construction manager, I'd interview some; elsewise, have your builder find a reputable one and see their installations.
Also, be sure to include a HRV - our T-F/builder installed a Life-Breath model.
It sounds like a wonderful system. I wonder if there is all of the insulatable components are insulated? That might account for part of it. It doesn't surprise me about needing combustion air for the boiler, that's a very good thing. I bet that a conventional oil fired domestic hot water heater would heat up the room at least that much. The Buderus has a great reputation and it sounds like you got a great install with it.
Chris
From what I have checked into the sand mix is about the same weight as the gypcrete, but dose it have the same strength as the gypcrete?
sand mix is a crappy way to do radiant.Sand is more of an insulator, than a conductor, for one.For two, getting a consistent tamp on that stuff is hard, if not impossible. This can have a severe effect on performance.Sandwich installs are superior to sand in every conceivable way, if you don't want to do gypcrete or lightweight concrete. Ceiling is cheaper too, most likely, and will work better.Do what you will... as long as it's not sand mix.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Sand is more of an insulator, than a conductor, for one.I have a hard time believing sand is a insulator, glass is a byproduct of sand and heat and cold transfer through it very easy, that's why we have insulated glass. The sand mix we are talking about it a mix without the aggregate so it is a pourable mix.
sand also traps a whole lot of air. If you pour AND tamp it consistently, it can perform decently.In practice though, this is nearly impossible to guarantee, and an area that "fluffs" more than another can have a dramatic affect on the heating. As in, the system may keep up in area B, but simply cannot transfer enough heat in Area B.Do what you will... I, however, will never do another sand project.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
well what keeps the gypcrete or the lightweight concrete for trapping air. LEVELROCK Brand Floor Underlayment is a 50/50 mix with sand.
Edited 12/22/2005 4:14 pm ET by byoung0454
I'm not really sure. But I would think that for either mix, compressive strength should NOT be a requirement if the underlying subfloor and joist system is sized properly (for our 1st floor application). The slab really acts to distribute and "even out" the heat as it is transfered from the hot water to the slab, then the room. If I forgot to mention, our timber-framer/builder noted that the gypsum mix would be quite a bit more than the sand mix that was installed.
If your're reviewing properties, the most appropriate to compare would be the heat storage - maybe search for Modern Hydronic Heating by John Siegenthaler, PE. Also try Wirsbo's site.
Others posting in this thread may be speaking of a different product. Conventional concrete consists of:
cement
water
fine aggregate (sand)
coarse aggregate (crushed stone)
(optional accelerators/ reducers, etc.)
Reinforced concrete can use either steel (rebar or "welded wire reinforcement") or polymeric fibers (typically used in precast concrete products). Neither was used in our mix since the slab just sits on the subfloor.
Our "sand mix" simply deleted the coarse aggregate in order to ease finishing the surface to a relatively smooth surface. The material selection presented by our t-f/builder seemed rational - i.e. the redi-mix plant will need to stop & run a batch of gypsum just for the floor's single truckload = higher costs vs. just deleting the stone in the mix.
You may wish to ask 2 of your local redi-mix plants about who uses what for radiant floors and applicable prices. I work as a civil engineer and find that products and applications change with time so you need to "keep on top" of technology and costs, since all owners are always concerned with cost, schedule, and quality.
I hope this helps.
>the redi-mix plant will need to stop & run a batch of gypsum just for the floor's single truckloadFar as I know, you don't get gypcrete from a redi-mix plant. It's a specialty truck and mixed and pumped on site. Very runny. Very very runny. They also use silica sand with it, rather than mason's sand.
They also use silica sand with it, rather than mason's sand.
With the levelrock gypsum concrete you can use a mason's sand, not sure about the other brands out their thoe.
Thanks for the correction.
I have a radiant system in my house. I built the house but I subbed the plumbing and the gyp. My gyp was $1.80/SQ FT about 2 years ago. The outfit that did the job had a giant mixer and a truck with sand that took up the whole street. It took about 4 hours to do 1600 SQ FT. To mix that much material by myself and haul it up two flights would have taken me two weeks. Some things are worth subbing out. The gyp was self leveling and you could walk on it after 3 hours. It had almost no cracks and there was no need for an expensive membrane like Ditra. I used a product called "Blue Devil" that rolled on for a tile antifracture membrane. After 2 years there are no cracks in 1600SQ FT of stone tile.
My system has a heat exchanger with glycol and water in separate systems. The heating system runs at less than 100 degrees to heat the house. The rehau tubing is at about 9" centers. There is so much thermal mass with 1.5" of gyp and another layer of stone tile that there is no need for a fancy thermostat . I set the zones for about 66 degrees and forget about it. With forced air systems the temps drop as soon as the furnace kicks off. With as much thermal mass that my radiant system has it takes a lot longer for the temps to drop.
As for efficiency, I also own a house in Sacramento that is smaller and it cost more to heat it with forced air than my Tahoe house. Granted, Tahoe is not Dot Lake AK. but it is freezing A$$ compared to Sacramento.
Here is a photo of my boiler and heat exchanger. The boiler takes up all of about 4 SQ FT in my crawl space. It is a direct vent Laars(Teledyne).
mass doesn't make it easier to control a system, it makes it harder. What is the construction of the house? Sounds like the home is not seeing rapid temperature changes (low solar gain, high mass walls?)I've had to switch out several thinslab thermostats in well-insulated homes for overshoot and undershoot problems. It can be tricky to manage all that mass in many situations.Sounds like you have a good system though! Any "idiosyncrasies"? I always like to hear about the little stuff people notice about their heating systems.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Sorry it took so long to reply. I am just getting back from a trip.
My home does have a very tight envelope. It is a relatively small 1600 SQ FT. The 2x6 walls have dense pack cellulose and the roof has dense pack also. The windows are low e and fiberglass and I flashed the bejeezus out of them. I have 9' ceilings. The siding has 30 lb felt underneath. The house is almost brand new.
There are a few "idiosyncrasies". The thermostat has a 4 degree default that lets the temps get down to 64 before the heat kicks on. With this much thermal mass I think a 2 degree default might be better. After the heat goes off the temps continue to rise a little but they do not go much over 71 if I keep the thermostat set at 68. After about 2 years I have learned to live in that comfort zone. I pretty much fugedaboutit. 64 degrees sounds low for the thermostat default low but that is where I ended up adjusting it. It never really feels uncomfortable.
That said, I will never go back. I like the fact that there is no air blowing around and the dust that blows with it. The system is very quiet too which is nice. The thermal mass keeps the temps very even for long periods between cycles. If the power ever goes out which is common during winter storms then all that mass will keep the temps tolerable for longer periods. I have a small backup gas stove in case of a power outage that will keep the house from freezing. Warm feet in the dead of night when I visit the potty is nice too. I just came home after a long weekend and I had the thermostat down at 58. When I cranked up the heat then it only took about an hour to warm up the whole house. The drawback I hear about lag time because of too much thermal mass doesn't seem to apply to my system.
Most of the time I usually wear slippers so I don't notice if the floor is warm. Right now I took my slippers off and the limestone floor is not warm but the thermostat says 70. I would not say the floor is cold either. I just felt the manifold and it's room temp.
I worked in many homes with hydronic systems before I built my own. There is no more comfortable system. I have lot's of dogs so I installed stone floors and no carpet. Carpet just gets too funky with all those animals. I don't think a stone floor would work very well with a forced air system. It would always feel cold. Just my opinion.Mike Callahan, Lake Tahoe, Ca.
Wow, that's a big temp swing.Based on that and your speed of response, I would guess your slab water temps are too high (in addition to your differential between too wide).Do you have any way to adjust water temperature to the slab?I think with some adjustment and perhaps a better thermostat (we like Tekmar 507s) you could dial that in to perfection.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Based on the picture of your boiler, It's not a modulating condensing boiler. However, you can get good temperature control by using a mixing valve with outdoor reset, as one method or injection pumping as another. That would that improve the comfort by eliminating most of the swings by keeping the floor from getting as warm and then cooling off, more of a steady state. It may or may not save some $$ on the fuel bill. It does need to be piped to protect the boiler from low water temps though since I didn't see any bypasses or P/S arrangement.
Chris
You're right. I guess I have been tolerating too high temp swings. I should look around for a thermostat that can be more fine tuned. Thank you for the reccomendation.Mike Callahan, Lake Tahoe, Ca.
Mike,
There are some really inexpensive digital thermostats out there. I bought one by Hunter Fan Co, it was less than twenty bucks at Wal-Mart.
I can set it for 1, 2 or 3 degrees variance. You may want to check them out, I have yet to see even a 3 degree swing in temperature with my set up. Staple up with a mod-con boiler. It is really comfortable.
Garett
.
Edited 12/14/2005 3:58 pm ET by byoung0454
Good discussion item, I am in the process of designing a combination bathroom-shower, laundry, stand alone building. There will also be a seperate area for general maintenance. The buildng will be concrete on grade with 2" styrofoam under the floor and on the sides. I have a similar structure allready without infloor heat and it works fine but thought with the shower facility a warm floor would be kind of nice since I need to heat the area anyway.
I talked to my plumbing heating contractor and discussed this very idea about running a circulation pump off of the water heater that would also supply DHW for the building. The plumber said that I would need all brass pumps, etc and thought it might be more trouble that it was worth. He suggested that I install a small demand water heater for heating the floor. One draw back to in floor heat is all the fooling around if I want to shut this building down for the winter. I may go with a forced air unit like I did in my other building but am going to consider infloor heat either with hot water or radiant electric imbedded in the shower area. Need to do some more calcuations before a final decision is made.
I am familiar with hot water heat and condensing boilers(propane fuel) as my home is heated with hot water base boards. (Built in 1974) I also have an indirect heated DW tank that runs off of a separate zone. I use this year around. Boiler runs on demand for either hot water or heat zone call. When I first put in the DHW tank off of the boiler last year, I was concerned about too much waste heat in the basement area during the summer months. So I insulated the piping associated with the DW heating zone. After a years operation I found that there was not a noticable heat problem during our short summers. Part of the downstairs basement area is at grade with finished living areas it was actually a little more comfortable in this area during the summer months. Seemed like the dehumidfier ran a little less as well.
Thanks for all the advice. Not hers the 60000 dollar question, I have been doing a lot of research on different types of system between what the call wet and dry systems. From what I can tell a dry system looks to be a good system other that the fact I would have to use tile backer for my tile, but I would be able to go with nail down flooring for the rest. Like I have said before I have never used a system like this before and I want the best. So what one is better a dry system with radiant panells or a wet system with a gypsum pour over the top?