Hello, I’m new to this forum. I enjoy doing every step of a job from start to finish, no matter how much head scratching is involved. I’m most certainly a beginner, although having built our home etc. Now it is time to finish the attic space over the garage as a school room for our children. We have chosen to use radiant heat, as the built-in desks and cabinetry involved leave no room for baseboard, and compact wall panels look to be equally expensive.
Here is my proposed floor system, comments and criticism are welcomed. Consider New England Winters
The garage ceiling will be insulated R-19 (unless you suggest otherwise), and consists of 9-1/2″ wood I-joist with 3/4″ T&G subfloor overlay. Also, 5/8″ gyp will be installed per code. I have a radiant foil barrier to run atop the subfloor. I plan to run 2×4 sleepers perpendicular to the floor joists, with 1/2″ radiant tubing at 16″ o.c. and fill the bays with dry sand. I am considering putting down roofing paper atop the sleepers to keep the sand at bay when working on the flooring…will this help/hinder the effctiveness of the radiant at all? The flooring will be wide cherry planks. Does this system sound workable to the experts?
Walls will be R-19 faced, and sloped/flat ceiling will be R-30 faced (2x10s). I’ll have enough extra radiant foil barrier to do the ceiling if this is a good idea…it would be installed between the sheetrock and the insulation.
My current central heating system is a boiler and hot water baseboard. Since the rest of the house is nearly always heated with a wood stove, the central boiler generally sits idle until the hot water tank calls. The boiler is a closed loop system. I believe I need something like the variable speed mixing injector (Taco RMB1 – $700). This seems to be the simplest solution to keep temerature down for the radiant. Is there any cheaper alternative? The radiant system will be a single loop with about 300 of tubing out and back. Thanks for any advice.
Edited 1/22/2007 9:10 am ET by tuolumne
Replies
do you have acess to the underside of the the sub-floor??? install the tube there instead and the cherry straight to the subfloor...
what is the temperature of the boiler's water output???
sand will be some serious weight added to the structure... approx 1.44 tons per CY... you made not have the carry capacity...
16" oc on the tubes will more than likely leave cold spots.. target for 8"oc...
the insulation gurus will be along shortly... we hope...
expect recomended changes there...
BTW... if you break up those long paragraphs they're easier to read and less information and questions are misssed..
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
Thanks for your response. The floor is still wide open below. I felt I would get a more effective radiant system to put everything on foil above the floor, rather than below with aluminum shields. Also, the sleepers cost less than all those shields, and sand provides the bonus of heat distribution and thermal mass. I'm a structural engineer, so rest assured I've considered the load. Sand and sleepers weighs about 12 psf.
Tubes at 8" o.c. would mean two loops, which I want to avoid. Would larger diameter PEX help at all. I'm am counting on the sand to help eliminate cold spots.
This is a very poor installation.
First, you want R30 between this room and the garage.
Second, sand is a poor heat transfer mechanism.
Third, 16" o.c. is too wide.
fourth, your radiant barrier will be utterly useless in this application, as it will be in contact with your radiant installation. That's conduction, not radiant heat transfer, and radiant barriers do not stop conduction.
For inexpensiveness, I would do a 3/4" plywood sandwich with lighweight plates at about 9" o.c or so. skip the radiant barrier entirely. Use PEX-AL-PEX.
I would use a motorized mixing valve and constant circ.. but that's not the cheapest. It is the best, however.
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1) R30 - Done, I've been leaning that way anyway.
2, 4 and 5) Remember, I'm a notional engineer...I like the thermal mass of sand to even out heat distribution and store energy. Would it be better if the sand went on top of the foil, with the tubing just below the flooring. I'm not interested in buying $300 of additional plywood for this sandwich.
3) Doesn't the sand mitigate the 16". Many manufactures recommend this spacing with gypcrete or concrete installation. I don't want two loops, both for expense of the tubing and that I only have one supply and return roughed into the area. I could run 12" o.c. and have a total loop of about 380', but that would mean buying a second coil of pex and not using most of it.
6) Does the RMB1 by Taco do what you're talking about. This is a simple installation for me, but at a $700 premium on system that's totalling around $1000.
Sand is a poor conductor, and 16" o.c. is not recommended by any reputable designers in any heat transfer medium in a residential situation; you will have noticeable heat striping on the floor no matter what medium you use at that on center distance. Plus your water temperatures will be very high, and you run the risk of not having the output you need.That said, yes, you will find many websites promoting wide on center and sand installations. That doesn't mean it's a good installation.You could hook up a 2 loop manifold to the supply and return you already have, most likely. If you run a larger temperature drop across the loops to keep the flow down, you may not even need to, but a heat load calculation should be done so you can decide what to do in an informed manner; we're just guessing here that these methods will even heat the space to room temp without running the numbers.I'm not sure if the RMB does constant circ. it does do mixing. You can do injection cheaper with a separately controller and pump though. Or, if your temps are low enough, you might even be able to skip the reset and do a simple tempering valve.On the other hand, you could use a more advanced controller that could take over your boiler, incorporate your high temperature demands, and run your entire system more efficiently while doing your radiant mixing... lots of choices!The foil is a complete waste of money; skip it. certainly do not put it between the tubing and the floor surface, it doesn't insulate well, but it does insulate a little.-------------------------------------
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OK, let's say I skip the sand. Who wanted to carry 1-1/2 yards up the stairs anyway! Would a reflective material atop the subfloor be a great advantage to sending radiant energy upwards? Why do most systems incorporate either aluminum plates for between the joist installation, or formed aluminum troughs when using sand or gypcrete above the floor? Would this not serve its intended purpose if the tubing were held above the foil on spacers to avoid conduction? This extra 1-1/2" dead air space seems beneficial as well.
I have 3/4" copper to and from the attic. You're suggesting I split this to 2 separate 1/2" loops in the floor? If they were slightly different lengths would one tend to steal all the water?
Regarding the circulation, here is my understanding, albeit limited. My job is to keep structures from falling over, not heating and plumbing! The thermostat opens up the zone valve at the boiler (already in place) and sends 180 degree water towards the attic. I need some device between to cut that down to 120ish, so I bring the attic return back to this location and add a pump to recirculate the colder water with the hot to get the temperature right. That would require some device that measures temperature and turns the auxilary pump on as required. Is this right? Would there also need to be some valves that open/close based on return and supply water temp? A pump, a brain and some fittings sounds cheaper than $700 for the RMB1, but also much more complicated to install. The RMB1 also measures outdoor air temp and boiler temp to further optimize the mixing volumes.
Aluminum is used to conduct heat from the pipe to another part of the floor assembly.. such as the subfloor, in the joist application. It's not "reflective", in that application, it's a conduction mechanism. They are NOT used in gypcrete... aluminum and 'crete do not get along. They are used, though, because without them you have very limited ability to conduct heat to where you need it, and conduction is the best/strongest form of heat transfer.so "reflective" material is of NO benefit... conductive material is, but in general you want it in contact with the pipe, not just a layer in the floor somewhere.You may or may not need to split the feeds with a manifold; depends on the flow rates you need for this space, which depends on the heat loads. If you do split, we like flow meters and balancing valve manifolds, but you can keep loops similarly lengthed and skip that if it's just one room you're heating.You can mix a few different ways. In this case, you could go "simple", or "advanced"."simple" uses a 3-way tempering valve which is thermostatic, same as you'd see on a domestic hot water system to limit hot water temps. put a thermometer in line, dial it to the temperature you want. Problem with that is you are setting it to the highest temp you need all year, so during shoulder seasons you get more 'bang bang' on-off operation. We prefer longer, smoother demands and so we like the "reset mixing" you mention with an outdoor sensor and/or an indoor sensor.so for the "advanced" you'd use the RMB or perhaps a Tekmar controller and mixing device (variable speed pump or mixing valve) to vary the radiant water temps based on load. Some Tekmar controls can also control the boiler and some can do constant circ.. lots of options there.Luckily with radiant this small, you probably don't need to worry about boiler protection, so this could be fairly simple. Depends on how "ideal" you want to get.. if you want ideal, I'd do constant circ w/a tekmar that can take over your entire heating system. That would probably be similar in cost to the RMB-1 or slightly more expensive, but then you are doing more than just runnning a radiant zone. and in most cases, I would expect an efficiency payback on such an upgrade, unless your boiler already has an outdoor sensor and firing logic.-------------------------------------
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So...I could use a $90 three way valve to mix return water with the supply as required. But wait, I would need a constant circulation pump also for when the hot water (and its pump) is getting pinched off. Uh oh, now the pump which operates when the zone valve is open has nowhere to send its water?? Does this mean I have to disconnect the current pump from that zone and provide a new pump beyond the mixer that does its job? Could I send the hot water back through the boiler with a differential bypass valve? I'm learning all sorts of new terms today! The existing system I put in is "dumb" from the thermostats to the boiler controls. No outdoor air sensor, fresh air supply, no automatic daytime/nightime modes. None of this matters since the wood stove heats the house...I currently have a really expensive and inefficient hot water heater! But....I plan to add a wood boiler in the basement within the next few years to take over from the wood stove and provide some more uniform heat, so that further complicates matters.
If I go "smart" system would I still be pulling the zone valve signal off the dedicated pump and plugging into this new system? I thought I could still use that pump for simplicity sake. From my previous ramblings, it sounds like the dumb system would still be around $300 and need a panel or something to mount it all on.
You would have no need for zone valve. The circulation pump turns on or off through a relay from the thermostat. it pulls whatever hot water is needed, or recirculates its own return water as much as needed to maintain the temp the tempering valve is set for through the valve. any return water not used is returned to the boiler piping.-------------------------------------
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Still trying to do this cheaply and throwing out new ideas. I already have foil fabric as I said. What about using rigid insulation as a form with depressions for the PEX? I could run the foil over this, and dip into the depressions, then install the pex. I would run two layers of R-tech EPS between the sleepers with slots for the PEX. This would look like a warmfloor type installation for $100 instead of $1500. Any thoughts? This means no sand, more contact between conductive foil and the wood floor, and more insulation between the tubing and the cold garage.
Foil is useless for heat transfer. it's too thin to conduct much heat. A couple of products out there use foil and it's just for show. You might as well do 6" o.c. install with no plates. Setting the tubing into foam would make lateral conduction worse as well.You're not inventing any new installation methods today, I'm afraid ;) Seriously, these are issues that many of us have dealt with on many, many projects. Sandwich installs with plates are the best bang for the buck short of installing in an existing slab or going with radiant ceiling, if you're not paying for labor and don't mind the extra carpentry.If your loads are very low, then do a suspended tube install in the josts if you need the cheapest. If your loads are not very low, then you want plates and most likely a PEX-AL-PEX in this case.-------------------------------------
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You've mentioned this sandwich? I'm not sure what you mean. What if I formed 10'x10" rolls of aluminum flashing and dropped those in the insulation? How is that different than warmboard?
sandwich is the strips of plywood or strapping, with plates. Your sand idea is kind of like a sandwich, but with big gaps, sand, and no plates. Warmboard is heavy gauge aluminum, not flashing; it's in another league of output. You could use flashing grade aluminum, it's much better than foil and is similar to the lightweight plates we generally use in a sandwich. However, the second part of the puzzle is contact with the tubing. You could form it well enough for your tubing, perhaps. Or use silicon to increase the contact area. But you don't want to just set tubing on top of it.You definitely want a PEX-AL-PEX as well, unless you are a fan of ticking noises.-------------------------------------
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What is the heat output of PEX-AL-PEX vs. hePEX by Wirsbo vs. Thermapex etc. at 90 degrees, 100 degrees, 110 degrees... I have not located any charts or other means to calculate this.
Thats because there is no appreciable difference between brands, sizes, or types of pex as far as output is concerned.Now, installation method is an entirely different story. But the pipe is not going to change these figures in any noticeable way.-------------------------------------
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This does not make sense. The thermal conductance of standard PEX vs. multicore (Wirsbo) is 0.22 vs. 0.27. That is a significant difference. The multicore can conduct heat from the water inside to whatever is outside nearly 23% faster. That means that for the same "whatever" surrounding the tubes of equal length and with equal flow rate, the PEX-AL-PEX will have a greater temperature drop and correspondingly as dumped more BTUs into the room...right?
If I could use 300 ft of 5/8" multicore vs. 350 (=2 300 foot coils) of 5/8 pex vs. 500 ft of 1/2" (=2 300 ft. coils) I could do this a lot cheaper. Temperature striping is not nearly as important to me as economics and making sure the room will stay warm on below zero mornings like this.
do it with 1/2".The increase in conductance through the pipe itself is not the bottleneck most radiant systems face when determining output. You could do this in copper, which is far more conductive, and you'd see a difference, but not nearly as big as you might think. Maybe 5 degrees SWT requirements, MAYBE ten under optimal comparisons. But no more. Pipe type and style is pretty much irrelevant for heat transfer determination. Conductance to your emitter and through your emitter will be a much larger factor.. large enough that conductance through the pipe itself is a moot issue.You know just enough to be dangerous here ;)-------------------------------------
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Your last statement is far more true than you know. As I've said before, the only thing I can state with assurity is that the structure will stand up!
The budget for heat is $1000 and I just can't break that. The controller is around $700. Valves, connectors and copper in the basement are about $50. The Rigid insulation will be $80. Sleepers, radiant foil, R-30 etc. are already accounted for. That leaves enough for a 300 foot coil of multicore...and perhaps a cold room?
OK, here is my current cheap solution, I'm not sure yet what the tube spacing should be. The tubes will be in intimate contact with the radiant foil and the flooring. What say?
you do not want the radiant foil over your pipe like that. If it must go in, put it in the joist bay underneath with a small airspace. That's the only place it's going to do you any good whatsoever. Otherwise, Ebay it. Unless I'm not seeing what you're doing.. is the foil going under the pipe at the groove? It's still a waste of time to put it in, but at least then it's not hurting you. I'd ebay it, personally.With R30 under the floor already, you don't need rigid foam on top, and again it will probably hurt your lateral transfer across the floor surface. I'd use 3/4" plywood and skip the sleepers and the rigid insulation.Then I'd skip the RMB, use a $100 tempering valve and $25 thermometer for a one-temp, fixed-temp system for now (maybe upgrade later if you want). I'd use the saved money to get some real plates.With plates, I'd install at about 9" o.c.. Without, 6" o.c. maximum.But before I did ANY of this, I'd do a heat load calculation to see if this will even heat the room.-------------------------------------
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The radiant foil goes under the pipe in the notches. Does that make a difference? Heat loss is 10,000 BTUs/hr. The rigid insulation is an easy way to create a continuous recess for the tubing, and an additional R-6 on the floor for $80 seams worthwhile. If I need tubing at 8" o.c. so be it.
You need to look at ALL the conductances/resistances in series to determine the significance of a specific heat transfer element. The heat transfer resistance of the tubing wall itself is trivial relative to the other resistances in the heat transfer circuit starting with hot water and ending with hot air by natural convection. You need to consider all these resistances to determine the temperatures of each component in the system at steady state. For one thing you have a massive contact resistance between your wood floor and the tubing. THAT is what the aluminum plates give you versus not using them. Forget about 0.22 versus 0.27- the aluminum has a thermal conductivity a few orders of magnitude greater than that of wood!
If running with low water temperatures matters greatly to you, consider something which will actually effectively conduct heat away from the tubing into your floor- that means extensive use of aluminum emission plates OR something which is a poorer conductor but in much more intimate contact with the tubing- gypcrete etc. If not, do a staple-up installation of ordinary O2-barrier non-composite PEX tubing in the joist bays, two runs per bay, insulate below WITH a radiant barrier and proper air gap, and be done with it!
What say you regarding the foil? The thickness should not matter; we have a product that will readily conduct heat, which is in intimate contact with both the tubes and the flooring. Any radiant heat will be conducted upwards by the foil. Convective heat will not play a great role, with minimal air in a dead space. Conductive heat will take the path of least resistance from the foil into the wood, rather than into the rigid insulation below.
metal thickness matters. it's not a magic conduction plane.. X thickness of metal can only carry Y amount of heat.This is part of the reason why extruded plates are dramatically better than lightweights.. though in typical sandwiches, it's not a problem. But "lightweights" are 11/1000ths, not foil.-------------------------------------
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Foil will do you no good as a conductor- it's too thin to do much good. It would help you as a radiant barrier if you located it ~ 1" below the hot tubing with an air gap between it and the tubing. But if you want to conduct heat away from the tubing, you need thicker plates in intimate contact with the tubes over a significant fraction of their cross section and along a significant portion of their length. Or you need a poorer conductor like concrete, gypcrete etc. in absolutely intimate contact with all surfaces of the tubing. What the gypcrete etc. lacks in thermal conductivity it makes up for in terms of low contact resistance. But all of this is to lower water temperatures to raise efficiency and minimize the risk of heat striping (uncomfortably hot areas on the floor surface). If you don't need low water temperatures, you don't need plates, gypcrete etc. Staple-up with a radiant barrier underneath and an adequate layer of insulation will do you fine, for less effort and cost.
Check out Ultra-Fin website for the calculation tables of proper spacing according to joist width. It provides a good technical rationale and the fins attached by rivets to the piping increase the effectiveness. By the way the foil should be unimpeded by sand since the foils primary job is to reflect radiant heat upward into the floor.
I think that you have to know what system you are installing unless it is going to be home built. Most manufactors will give their recommended installation. Any questions will be answered if you use that strange device; TELEPHONE! Lots of luck.
"If all else fails, read the directions"
Why don't you want to run the pex under the decking like I see in all the books. We installed a wide plank floor over a heat system a few years back like the system you described minus the sand and it was a liitle unnerving trying not to puncture the tubes.
Do I want a vapor barrier between the garage and the wood floor. I was planning on putting unfaced R-30 in the joists below. Intalling them kraft side up does not seem like a great scheme. If I put something like tyvek atop the sleepers would this affect the radiant heat transmission at all? This would be the most effective place to put a vapor barrier. Would some other material be better/more cost-effective than Tyvek? Thanks.
tuolumne,
Cheaper? absolutely!
don't use a boiler!!! use water heater instead..(or water heaters, use enough and big enough ones to generate the BTU's required).. they are designed to operate at he proper temps and don't need mixing to cool down what you paid good money to heat up!
One other point.. read the fine print.. an 80 gallon water heater does not have a bigger burner in most cases than a 50 gallon one does. you have a lot of water in that tubing so you don' t need more water capacity, you need to be able to generate more heat.. two 50 gallon heaters are better than one really big heater.
remember with set back thermostats, a few hours set back will take a long time to recover due to thermal masses involved.. I haven't figured out a way to calculate it so I'm in the experimental stage..
The boiler is my water heater! Buderus G115x, 80 gallon indirect tank on its own zone and pump with priority. Like NTRob says, I know just enough to be dangerous. I am certainly a beginner, but like to do things myself (and my way!). I did every part of my house just so I can feel the satisfaction when I come home every day. Here is my first boiler intall...did I do OK? Lots of head scratching for sure, but this technique usually gets the job done. I am so thankful for knowledgeable suppliers who know the code and help put material lists together.
Your pumps are installed wrong. The motors are supposed to be horizontal.
Eh? Why? They've been working this way for over 4 years.
-Curious
Any air gets trapped in the can and you can buy a new pump. it's in the instructions.
tuolumne
I think everybody is right that you need to provide some sort of surface to radiate your heat off the tubes and into the floor. What I did was order a bead roller from the stock car racing boys and made up a bead big enough to put the tubing into it..
I now buy rolls of that cheap aluminum flashing, run it thru the bead roller and nail it up in place. (My floor is 3 inches thick so 1 1/4 roofing nails are not too long) you might try a staple
I can roll out a length of flashing in a few minutes and then cut to length. Take a round shanked screwdriver and curl the edge of the bead to ensure that the pex doesn't chaffe as it moves slightly from thermal expansion..
Type in radiant floor heating on your search engine, There's these guys in vermont"Warm Toes", Who have a nice system going using a larger dia. pex like 1" and a slower moving pump off of your existing H.W. heater. Its nice and cheap and does the job.
it's cheap. it's not nice. and using large diameter pex is a waste of money with a corresponding increase in install frustration. you're far, far better off installing more, smaller diameter pex.and anyone recommending you install a heating system off of a water heater without a heat exchanger is, IMO, not considering the best interests of you or your heating system.-------------------------------------
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So dont't use it .
I'll do you one better, and suggest that no one else use it either. There is absolutely nothing to gain by using 7/8", 3/4", or 1" pipe in a residential heating system. The increase in heat output is very minimal, the increase in cost is not, and the increase in installation difficulty is also not minimal. And if you have to run a wider on center to accomodate the tubing, you have reduced your output very significantly and not saved very much money.If you want to save money by running wider on centers and you're able to deal with the reduced output, higher water temps, and heat striping, more power to you. Do it with 1/2" pipe and really save that cash.-------------------------------------
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"and anyone recommending you install a heating system off of a water heater without a heat exchanger is, IMO, not considering the best interests of you or your heating system."
I'm curious as to why you made that statement, since using a water heater for radiant heat is becoming widely accepted.
Are you referring to the concept where the water heater heats both the radiant water and the domestic water and are concerned about the longevity of the water heater with the constant inflow of fresh water?
Closed systems using a heater like the Polaris, or some other high efficiency heater, seem to be a good and maybe more practical system than using a regular boiler if you use the heater for radiant heat only.
Your thoughts......
I have no problem using a water heater on small loads.. they will perform better than most heat sources in those cases. However on higher loads they simply cannot match the efficiency of the high efficiency boilers out there today... even a "high efficiency" heater like the Polaris (with quotes, for a reason). So I don't usually use them these days unless the loads are very low... there are just much better choices available in modulating/condensing boilers these days.Beyond that, I was referring to "open" systems where your domestic hot water circulates through the heating system. It's risky, for health but also for the heating system's longevity. A heat exchanger is a relatively cheap insurance policy and omitting it, in my professional OPINION (since research on this is non-existant), is a bad idea.-------------------------------------
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NRTRob,
Hmmm your advice is in direct conflict of other advice I've recieved and accepted.
Now I probably know just enough to be dangerous so please walk me thru this like I was a 5 year old..
Here's what I've been told and please inform me as to what you know and sources so I can verify we are speaking about the same thing..
As I've been told the trouble with boilers as radiant heat sources is that they are designed to operate at higher temps than it is safe to operate infloor radiant heat at..
Thus they call for cooling water to bring their temps down.. Which seems wrong to me..I mean it takes a great deal of energy to heat water,, cooling it down seems counter intuitative.
While water heaters, are designed to operate at exactly the temps used for in floor radiant heat..
I will grant that a really efficent boiler will turn water hot with greater efficency than most water heaters are capable of but once we cool it back down to operating temps that efficency gain is lost..
I am definately a long term kinda guy so the shorter life of water heaters really bothered me untill I realized that efficencies increase with time.. In 15 or 20 years new techonolgies might mean that I can buy a boiler and not lose the efficency I gained.
IN addition I have had really good experiance with things that operate year around. my hot water system is designed to use either water heater or both depending on heating requirements, thus I can use the domestic hot water from either water heater or infloor radiant from either water heater.
A boiler on the other hand used to for domestic hot water applications would be a real waste if required to fire up for a few cups of hot water..
Modulating/Condensing boilers are built to operate at low temps and get fantastically efficient when you do. No mixing is required if you are using a one temperature system. You can run them from 92% up to 99.6% efficiency in true efficiency (and I stop there because that's just the highest measured efficiency I've heard of yet).Also, they run around 90% and are low mass when heating a storage tank for domestic.. far better than a tank water heater, and better than most on-demands. Though you do have some standby losses, which may or may not be a big deal.Tank water heaters can still require you to mix down for ultra-low temp radiant, as if you run them cold (like 100 degrees) they die faster. They do last longer in heating applications than domestic applications though. But they cannot hold a handle to a mod/con boiler efficiency.5 years ago, if the only other choice was a conventional boiler, your arguement would hold a lot more weight. These days though, well times they have changed.-------------------------------------
-=Northeast Radiant Technology=-
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Well, just to thrash this out a little more....would you throw a little expertise at this one?
I have a wood-fired outside boiler (not really a boiler - it heats water to 175-185 degF). I have 1" pex running underground to my basement where I convert to 3/4" copper. The water then goes to an insulated 400 gallon tank I made, then through the circulating pump, a domestic hot water heat exchanger, a forced air heat exchanger, then back out to underground pex, to my shop and a forced air heat exchanger then back to the boiler. The single pump in the basement runs continuously.
What I want to do is put heat into the living room floor. The living room is above the basement. The floor is 3/4" t&g ply atop 2x8 joists 16" oc. I want to install hardwood flooring in the living room to replace the carpet we currently have.
Here are some questions:
What size pex should I use for under-floor heating?
How far below the ply should the pex be placed? (I will insulate beneath the pex)
What should the water temperature be under the floor?
The three-way mixer you spoke of - does it require another pump? Is it controlled by a remote thermostat? What do these things cost and where do I get them?
Would this actually be something other than 'radiant' heat?
The house thermostat, which is in the living room, currently operates the fan on the forced-air heat exchanger. How would I coordinate the under-floor stuff with this thing? Maybe just leave the floor heat at a constant low-level?
How do I calculate how much heat is going to get through the floor to the room and what its effect on temp will be?
Any help (particularly practical help) would be appreciated.
http://www.radiantcompany.com/system/open.shtml
http://www.radiantcompany.com/details/joists.shtml
The second link states if using 7/8 or 1/2 pex etc.etc., Just sub with your size 1/2 is recommended. The link was used to help with install.
Edited 2/22/2007 9:51 am ET by AllTrade
Two questions First:1. Is the storage tank pressurized or unpressurized?2. Are you doing the radiant for primary heat, or just floor warming?The joist installation shown in the post before mine is a very poor installation, and is very difficult to install. Never use larger than 1/2" pipe in a joist bay. There is never any reason to use larger unless you're trying to avoid choking off flow to your showers because you have all your domestic running through your floors, which is generally a very poor idea.-------------------------------------
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http://www.NRTradiant.com
The system is not pressurized. The storage tank was an attempt to make the burn more efficient by making it longer. The under-floor heat will not be primary, but a floor warmer and an attempt to keep the heat lower (altitude-wise) in the room (vaulted ceiling ~ 14' at peak)
then I would isolate the radiant (we're not fans of unpressurized systems) with a heat exchanger.However if it's just floor warming and partial heat, then this would be one of the few times I would say that a suspended tube application, 8" o.c. 1/2" or 3/8" PEX, would probably be a fine choice. If you do want to upgrade to primary heat, you need a heat load calculation to determine if floor will do the job and what water temperatures/plate styles may be needed.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
So hang the pex below the ply, leave an airspace, then insulation below? It seems to me a heat diffuser plate would be superfluous in this setup because the conductance of the wood is so bad, it'd all be about the same temp on account of the air space, no? Is 175 degree (or so) water too hot for the floor? Do I need to mix it?
I'm not sure we're all of the same understanding here. My boiler system is in no way connected to the house water except that there's a heat exchanger between it and the water heater.
If water can go from the unpressurized system into your boiler, that's not good. that's a path for oxygen to get into the system and rust out your boiler. If I misunderstood what you meant there, no problem, but basically you want the boiler and the heating system to be pressurized and closed to oxygen diffusion.Plates would allow for more output as you would conduct heat into the wood directly; suspended tube radiates and convects some heat under the subfloor, which are weaker forms of heat transfer and require much higher water temps.However if you are not trying to achieve primary heat, that may not be a big deal. I'd consider perhaps a 3-way limiting valve set to something like 140 to 160, put in a floor sensor, and go.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
OK, thanks for the advice. Does the 'floor sensor' control the valve? I'm not familiar with any of this hardware.
Some thermostats can take a floor sensor input (like a Tekmar 508 or 509), and run the zone based on both inputs. You would then set a room temp and a minimum.. maybe a maximum as well.. floor temp, and it would maintain both as best as it can by turning the zone pump on and off. the pump would pull through the 3-way tempering valve (like you might see on a domestic hot water tank, that limits the outgoing temps, but one capable of higher temp usage) which would keep the radiant temps limited to something like, say, 150 or so.That way, even if the air system is maintaining your air temp in there, the floor sensor can still maintain its floor temp. But, if the air system isn't running and the room starts to get cool, the thermostat can run the floor to add some heat as well.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Got it. Thanks Rob for your help. Nothing like experience.
"the trouble with boilers as radiant heat sources is that they are designed to operate at higher temps .."
Some boilers are, some are not. Knowing the difference (and how to accomodate that difference) is something heating professionals understand.
"Thus they call for cooling water to bring their temps down.. Which seems wrong to me..I mean it takes a great deal of energy to heat water,, cooling it down seems counter intuitative"
When lower supply temperatures are required from a boiler that has condensing limit, the supply is mixed with the return in a ratio that produces the desired temperature. This is commonyl done with a 3-way mixing valve. Nothing is actually "cooled down" except the water that travels to the heat emmitter (floor/ceiling surface, radiator or coil). Simply a smaller volume of the higher temperature water is required, and therefore, less is produced. Overall, the boiler only produces enough heat to meet the heating demand. The controls modulate how much supply and return are mixed.
"the shorter life of water heaters really bothered me untill I realized that efficencies increase with time"
This is a "realization" better re-examined. Present technologies in low temperature, condensing/modulating boilers provide for combustion efficiencies in the 99% range. Not much room for improvement there.
Tank water heaters are primarily used for infloor heating jobs because they are cheap. They are shot-term, inefficient and for the most part disposable. Combustion efficiencies are in the 60 - 70% range for most. Those that acheive efficienies in the 80+% range and higher cost on the same order as smaller boilers, without any of the basic controls that a boiler comes standard with. For those that believe that electricty is cheaper because of "western coal mines and wind power", yet do not know their actual rates, I can make no no argument to that nonsensical perception. However, for the rest of us, electricity is seldom if ever a long term cost effective way to provide comfort heat.
"A boiler ...used to for domestic hot water applications would be a real waste if required to fire up for a few cups of hot water."
If that is how they operated, which they do not, you would be correct.
Tim,
I read your answers with a great deal of interest. You'll have to elaborate because you made some statements which my actaul experiance finds to be not true so maybe I'm looking at things wrong and you're right or maybe we have differant situations.
Let me examine the statement Electricity is seldom if ever a long term cost effective way to produce comfortable heat.
Since the house isn't heated by in floor radiant heat yet I can't be real definate but let me explain why I don't believe that is going to be valid..
I used to have a gas hot water heater, I could count on at least $80.00 a month gas bills. The only thing I had which was gas operating in the summer was the water heater.. No stove no BBQ nothing except the water heater..
Since late last summer I've had electric water heaters and my electric bills are $80.00 a month plus or minus $5.00 That includes lights and the power required to run all my shop equipment..
The old electric bills were around $35.00 a month or so..
IT seems then that I heat my domestic hot water for around $45.00 a month. compared to $80 My last water heater lasted 22 years. It hadn't failed when removed simply that I choose to go another direction. I assume that this one will do the same. The ratings for efficency list this electric water heater (50 gallon) at .94 (My 80 gallon heater at.92) seems fairly decent to me especially in light of the lower cost to operate it than my old natural gas unit..
According to my calculations once I switch to in floor radiant heating I will need to use the 50 gallon water heater for about 75% of the usage, on the colder days I have the 80 gallon plumbed in for additional heat source.. in the event I miscalculated or did something wrong I have the original forced air furnace as back up (currantly heating the whole house) and there will be two gas fireplaces and a wood burning one..
Yes you are correct, I don't know my actual rates.. all I know is that for me electricity is cheaper than gas.. I used to feel exactly as you do that gas was cheaper than electricity. I'd heard it so much that that I never questioned it..
What caused me to question it was last winter, with the water heater turned off, I was up on the roof and I placed my hands over the exhaust stack to warm them up.
On a 15 below day it was really nice and warm! No the pilot light wasn't on, just the heat from inside the house being sucked out. Nice 70 degree heat! Coming out of a 4 inch stack.. 24/7/365! I'd imagine that once the pilot lite was relit the heat coming out would have been even warmer..
I hope you can explain why I am paying less for electricly heated water than I used to pay for gas heated water..
Could you help me to understand the process whereby water is added to hot water thru the threeway mixing value and why that isn't cooling the water?
I'm guessing here so treat me like a 5year old. but assuming the water coming out of a boiler is near say 190 degrees? and the water used to mix at the three way is at say 55 degrees I can understand where just a little of that 55 degree water is required to cool the water down to say 130 degrees. OK so we're not using up as much of that 190 degree water as we would if it weren't required. but wouldn't it be more efficent to just heat the water to say 130 degrees? I mean I think the added 60 degrees of temp rise must cost something doesn't It? Plus maintaining that water at 190 costs more energy than maintaining it at 130..
Where am I wrong?
PS if a boiler is really called for I certainly will install one.. I just can't get my head wrapped around the differance in temps...
water is never added in any way to a closed heating system.Hot boiler water is mixed with cooler radiant return water, if mixing is required, to allow the radiant supply water to be mixed to whatever is needed. so you just inject a little or a lot of heat from the boiler into the cooler radiant loops depending on your needs.You are NOT mixing cold water in with the hot water in the way I think you are assuming it may be.However, mod/cons don't usually require mixing.Also you have a point; if you have a big heavy cast iron boiler, firing it up to keep a domestic storage tank warm in the summer is probably not the best choice. But if you have a low-mass boiler (such as a mod-con) then it probably is, as far as DHW production is concerned. Depends on how much you use though.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
From my research and personal experience NRTRob is one of the best "free" sources of information around. I have installed, or repaired or re-repaired five different systems based on my research including reading and cross checking NRTRobs post. He know's his stuff.Most of the bad/miss-information out on the web seems to be from people who sell specific products (ie. large diameter pex and open systems) and the "consumers" who have purchased these systems. Even a poor RFH system will provide more comfortable heat than many scorched air systems...so the "consumers" who use these systems really do belive that they have the best system in the world! But they can be better... NRTRob is a great source for information on radiant heating systems. Garett
NRTRob,
Thanks for that, I intend to go to my brother-in-law, show him your post and hopefully he will gain from it.. His system adds cold water into the stream to cool down the boiler water temp. Well actaully the cold water is added to the make up tank and that's what actauly goes out into the tubes. In spite of looking at maybe a hundred radiant heating systems installed for details I go to his place for a close examination about how to do things..
I 'd never noticed that the mixing occured after the return water not before.. Details ;-)
Are there any efficent electric boilers out there or is the elevated temps of a boiler the point where gas becomes most efficent? I ask that because of my experiance with the warm air coming from my gas water heater exhaust flue. I would love to avoid putting a 4 inch hole in the roof plus the hassle of finding a place to snake it thru the timbers in my timberframe..
as far as I know electric boilers are very efficient.. the question is only whether electricity is an economical choice in your area for heating.This varies a lot. But the beauty of hydronics is that you can always change heat sources later!-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
NRTRob,
When I last checked (fall of 06) the raw $ cost to heat an electric water heater turns out to be the same here as a natural gas water heater. Surprised me, I mean I had swaped the original electric water heater 22 years ago for a Gas one becuase natural gas was so much cheaper.. The lack of a 4 inch hole sucking heat out of the house was a bonus and if what I believe will happen in the near future I should benefit from the increased cost of natural gas and the reduced cost of electricity..
Now I fully understand the politics involved. I mean another Enron could come in buy up the electrical capacity like they did in California and sell it off, dramatically driving up energy costs..
The one semi good thing about Minnesota is that we are a bit removed from other major population centers and there are transmission losses involved in shipping power a long distance.. which may make selling locally somewhat more attractive up here than on the east or west coasts..
What brands of electric boilers should I look for? Any of them particularly good? Any to avoid?
What sort of currant demand can I expect at peak usage? (I'm getting close to the maximum capacity of my 200 amp breaker panel)...
well, they are pretty uncommon for our clients so I'm hardly an expert. I have heard people say good things about Seisco, but beyond that I'm no electric boiler expert. They are of course rated for their electrical draw and as with any heating system, you should do or have the load calcs done to size your equipment properly. I can't imagine cycling is much better for an electric unit than a fossil fuel one.I do know that trying to guess what's going to happen with energy prices... except they are all likely to go up... is pretty tough. Sorry I can't be of more help to you there! Best of luck though.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
NRTRob,
Thanks for your input I'll be meeting my brother in law later to day and am excited about telling him what you shared with me..
Really changes my viewpoint about the boiler vs water heater thing..
I can see why electricity is such a rare item out east, I've spoken to some about their electric bills and My God! do you ever pay a lot!
Tell me, do they charge by the electron? <G>
just wanted to chime in about that radiant co. from Vt. I live there as well and I want to see local companies do well but.......... They sold me on a system that was "stupidproof". Can you sweat a pipe was their question. Well yea, I've been a carpenter/cabinetmaker for 25 years, do most trades but I'm really not fond of plumbing/heating, are you going to make this easy? Said they would. Well, a year and a half later I'm still trying to get a decent schematic. for the manifolds. They sent 7/8 ths tubing for 12 "o.c floor joists (in a 2' crawl space), I had to easily make 30 plus splices for all of the kinks and get this reply..... the guy says he had to do that himself once before!!! I know he was lying. If I had the money or time, I'd seek recompense. I'll just have to plod along, figure it out and make it work (can't get a return phone call). Sorry, but felt the need to add balance when this co. was recommended by you.
Sorry about your bad experiance. I've only used their system once, that was around two years back. It was a special application. The install went smooth, the system took up little space, major issue in this application, So far a trouble free system off of a 40 gal. nat, gas WH. 1200 sqft adobe in NNM, with 18" walls. Heating and domestic HW run about less than $100.oo per month. in winter. We get some cold weather too. O degrees F. at night is not uncommon. The only problem I've had was a sticky check valve. Will I use them again? My son in law says he can redesign their system better and cheaper now that he has seen theirs work but he had to have seen theirs work first to get to that point.
Frenchy: an electric resistance heater is 100% efficient at ANY temperature- it converts 100% of the electrical energy you feed to it into heat. All of that heat will go into your home, and almost all of that will go into the water you're trying to heat. They don't care about temperature. But regardless how your electricity is priced, it's insane to burn coal to make steam to turn a turbine to make electricity, half of which is radiated off into space as heat and EM fields and radio waves in the transmission system before it gets to your house- only to convert it back into heat of such a low enough grade that it would be WASTE heat in the power plant!
If you care about energy efficiency, consider a heat pump instead. At least with a heat pump you'd get a couple watts of heat into the water for every watt of electricity you feed to the compressor. Not very practical for domestic hot water because the payback period would be very long- but if you're heating your house with electricity you shoud give a heat pump very serious thought.
Moltenmetal,
Thank you for your input. Oh yes I'd dearly love to put geothermal heat into my house.. I clearly understand the economies and frankly lust after the system..
However there just is no way to do it on my lot.. I had considered since I live on a lake, cheating and going out under the lake to pick up the required area, In fact I came up with some pretty wild schemes to do just that. One of them included a underwater trencher system hidden from view by a pontoon boat. The cheapest price I could arrive at was nearly $10,000, and would still stir up clouds and clouds of silt and mess which since I have one of those super pain in the azz neighbors I would have been reported.
I agree about the waste of coal but Minnesota is leading the nation in new wind generators so it's not quite as dirty as all of that. (more about that though if you'd like)
I've given a great deal of thought to the carbon footprint of my home, I'm going for the minimum I can achieve. I've done so in part by building a superinsulated enevelope, using local materials wherever possible, and considering every possible option before deciding.. In it's final form I expect to utilize diesel generators driven by waste cooking oil as my secondary system, to back up as big a array of photovoltaics as I can achieve facing south.
Untill that sytem becomes possible I intend to use whatever should have the minimum impact on the carbon footprint.. Frankly natural gas while realitively clean burning is not ever going to be my primary system. If I do my bit to reduce it's usage it becomes more affordable to those who will have a lesser ability to utilize other clean burning energy sources.
frenchy: you forgot to mention what a great job your home does as a (near) permanent form of carbon sequestration! Those beautiful hardwood timbers are never likely to go up in smoke or rot and return CO2 to the atmosphere!
I'm still jealous every time I read a post of yours about the access you have to such great hardwood for such excellent prices.
Moltenmetal,
Those days may be over, I went to my favorite sawmill and there was a delegation buying for China there. I've been paying $1.00 a bd.ft. for black walnut and I get to select the cuts/timbers etc..
They offered to buy the logs uncut for $2.25 a bd.ft. and when the sawyer tried to save me out some they shot up to $2.75 a bd.ft without blinking an eye.
What made it impossible to pass up was that was a stumpage price. In the forest, uncut. Their crews would cut and haul it out!
They also took all the cherry he can buy! They left there and headed straight to the next sawmill..
Here's a simple exercise, it has two parts.
Part 1:Tell me what is the electric rate (off-peak, non-summer, residential schedule) for you? Look at you electric bill or tell us who is your electrical service provider if you cannot determine the cost of electricity at your house. Get help if necessary.
Part 2: Find out what is the current rate for natural gas in your area. Get help if necessary.
With actual rates we can discuss this further and based on something real. What "seems" to be going on is irrelevant, because....
" Since late last summer I've had electric water heaters .." you have 6 months of experience, not including a full heating season. This year has been extremely mild up until this week in the midwest. Not enough data to be relevant.
"I don't know my actual rates.. " We'll try to remedy that. See the top of the page.
"My last water heater lasted 22 years.... I assume that this one will do the same." I believe that your experience is not typical. As a recent distributor of several major brands of gas and electric water heaters (Lochinvar, State and Bradford-White) I do know a little about the current state of the industry, and counting on a modern, residential tank water heater to last more than 10 years is extremely optimistic.
"all I know is that for me electricity is cheaper than gas.. " Based on the fact that your old DWH was 22 years old and was probably about 60% efficent when new, less than 50% efficient after twenty years of midwest water, I beleive that.
My point was and remains, that only when we have actual, current costs of electricity and gas can compare actual cost of heating with one versus the other. Seldom in the US, except for very short periods of interrupted gas supply, is the cost of gas so high that in all but the poorest of equipment, is it more expensive per btu than electricity.
Tim,
Ten years? OK I guess I could accept that.. I'm not sure how often people with 10 year water heaters do simple maintinace jobs like checking the sacrafical anode, or even do the routine flushing of the tank.. But it would be foolish for me to insist that they basically build water heaters as they did 22 years ago. I simply don't know that and maybe the warrantee I got with the water heater is really meaningless..
Since I did the install 22 years ago and the switch to the currant electric ones myself. I suspect that in a decade I'll do it again if need be.. so other than the raw cost of the unit there is no cost to me..
Besides, and this is the important part who really knows what technology will bring us within ten years? It's very simple to make a switch to new technology if the old water heaters are failing. Worst case the chance of both of them failing at once is pretty slim. Since they are set up on seperate lines and seperate feeds It would take me all of maybe two minutes to switch from one to ther other. let's see, click off with the old circut breaker and click on with the new one. a 90 degree turn of the water source valve and another 90degree turn of the outlet yeh, about 2 minutes if I'm sleepy and in my slippers..
What differance does outside temps make if we are speaking about water used for domestic hot water? the house is at 70 degees (well actually 68 but it feels warmer than when I had it at 70 in the old stick framed days)
I mean we take baths or showers based on when we feel dirty not by when it's cold outside.. We shower or bathe once a day. (I bathe and the wife and dughters shower if you must know)
Finally the end result is dollars! who cares what the rates are? I make my payments in dollars! Do you intend to tell me that I don't save $35.00 a month using electricity instead of Natural gas?
My check book will dispute you..
I might be willing to grant you that comparing the most energy efficent gas water heater of 22 years ago isn't as efficent as the currant state of the art is.
Maybe if I had a back to back comparison of todays most efficent natural gas units to the electric units I purchased, I might be willing to speak about rates..
I'd have to run the test during the summer in order to not have the gas used in the back up furnace (prime source currantly) affect the outcome. but even that test would fail to tell me the critical number that nobody seems to be able to provide.
The critical bit of information that is ignored is how much heat goes up the vent 24/7/365. I mean we are speaking about a 4 inch hole that takes warm heated air and lets it outside 24/7/365 all thu the heating cycle. (not to mention the cold air drawn inside to provide oxygen for burning)
As we have discussed this repeatedly in the past, your "facts" be they in dollars or what you "seem" to observe, changes from month to month and post to post. I was trying to get beyond your "inklings" and opinions and deal with real numbers. Why to you steadfastly refuse to do so? Otherwise, it is all just BS. Bluntly, you have a history of making up "facts" to support your opinions.
Unless we can discuss actual utility costs, then your assertion that electric heat based water heat is cheaper than gas based water heat is credible only to people less informed (and unfamiliar with) you.
Tim
Since you have yet to prove what you pay for water heating, the conditions of usage etc. any comparison between your numbers and mine are completely trival..
I realize that you have this fixture that I must be wrong because that would require you to alter your long held beliefs. Because of that you are anxious to "prove" it but frankly I don't know how you can do that.. short of coming here and looking at my bills.
Erronously you assume that because I do not have the ability to post data as you do I must be wrong..
Even if I were able to post as you seem so anxious for me to do I doubt that you would accept it..frankly what possible good would it do? I doubt you live near me and thus our respective numbers would mean even less.
Since you are so clever why don't you figure out what I pay and post it? Then figure out how many gallons of water I use and how much it costs to heat said water in the various methods you seem are superior.. remember your numbers have absolutely no meaning to me.. Express your findings in a common language (ie dollars)
Finally what possible benefit would I have for altering my experiance..? I do not work for the electric company as has clearly been established, nor can I benefit in any fashion from whatever choice you or others make..
"Since you are so clever why don't you figure out what I pay and post it"
The cost of natural gas this month has averaged $1.08/therm on the northeast shores of Lake Minetonka, and all surrounding areas.
The off-peak residential rate is currently $0.0565/kwh. This does not include the "base" costs that your utility charges you every month, nor does it include "fuel surcharges" which also apply.
Converting both to Btu's per $$ - gas is 92,593, electric is 60,407. If a gas burning appliance has a thermal efficiency of 65% or greater, heating is cheaper with gas than electric. That includes domestic water, air, heating water, etc.
"what possible benefit would I have for altering my experiance" Only you could answer that. A poor attempt to save face?
You made an assertion that was based on an (uninformed) opinion, and not actual information. Instead of admitting that, you proceded to make up facts and figures and nonexistant utility conditions and geographical "data". When called on it, you forgot the "rule of holes" (which simply stated is when you're in one, stop digging!) madeup BS figures to further backup the first lie with more lies.
Tim,
My monthly bills are as I said.. I save about $35.00 per month using an electric water heater over natural gas purely for my domestic hot water application. That does not include any savings by not having a 4 inch hole in the roof drawing warm air out 24/7/365.
Now I will be the first to admit that a new electric water heater is probably more efficent than a 22 year old natural gas one so that may account for some of the differance, but I have a maintinance contract with the gas company and they service it annually so I assume that it was working as efficently as possible.
According to neighbors natural gas prices have gone down recently which may account for your numbers being differant than when I did my research last spring.. I can't tell you what I was paying per therm, because I simply don't remember.
My point was, and remains, that with rare exception, in the lower 48 it is almost always less expensive to heat with natural gas or LP, than with electric resistence heating. That, as we know have shown based on currently utility rates, includes you and all of Minnesota, regardless of the proximity of "cheap western coal" or the prevalence of "wind farms".
You may be saving on your bills to heat domestic water in your house compared to using an outdated and extremely inefficient gas tank water heater, but you would be saving even more if you were using a modern, high efficiencey gas appliance instead of electric.
"That does not include any savings by not having a 4 inch hole in the roof drawing warm air out 24/7/365." As you wish to believe. However, the amount of natural draft that moves through an undampered flue is relatively insignificant in the absence of serious pressure imbalance (which would cause a great deal of inleakage/outleakage through every opening in the envelope).
I agree with all of that.....what are your favorite boilers nowadays??
Have you heard of any problems with the Polaris heaters?
HAHAH... well, yes. the previous company I worked for did lots and lots of polaris systems.First, let me say it has been 3-4 years since I designed one into a project... for the price, you might as well get a mod/con, so IMO they are totally obsolete these days.However, there is what I consider to be a major design flaw in the Polaris.. this is a "condensing" water heater.Trick is this; if you actually run it cool enough to condense, you fry out your igniters regularly. That is not a big ticket item, and once you get the trick down replacement isn't too bad.. but you better have them on hand, and the system better not be unattended when it fails.Otherwise, you can run it at about 160 degrees to avoid the issue, in which case you are not condensing and I cannot believe that efficiency is anything near what they claim. And the whole "don't heat up and then mix down" arguement goes right out the window.Back in the day, again, compared to conventional boilers and when the polaris was about a grand cheaper than it is now, it stacked up a little better. But these days, it's an overpriced dinosaur... again, obviously in my own opinion. But, been there, done that, not impressed.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
.....and did you have an answer to my first question or are you playing the field?? ;)
The typical answer is "whatever the local pros can install AND SERVICE with confidence".Lots of good boilers out there, but they are only as good as their install.
-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I am in North-Eastern Ontario....today -20C outside.
My main floor of 2000 sq ft living space has TJI's for floor joists, 5/8" OSB for floor. I screwed 2x3's to the floor running parallel to the floor joists. These are 8" OC, one on the floor joist and one between.
I then put tubing between each 2x3 which is approx 8" OC. Filled the void with sand. Stapled paper to the 2x3's (red rosin paper). Put 3 1/4" Kempas wood floor down. Kempas is 30% harder than oak and minimum movement.
Result is great for heating....running 120 degree water in, 100 degree coming back to manifold. 8 runs in total.
From my experience, sand retains heat well in comparison to 4" concrete in basement radiant flooring. 16" OC for wood floor on sleepers is too much distance....you will get bounce between sleepers when walking. I have a little bounce if two floor boards meet between the 8" OC sleepers even though floor is T&G.
And I put my foil insulation (R4) on the TJI in the basement and tacked it to the web of the TJI so I have the 1" air space between the foil insulation and the bottom of the OSB floor. This will reflect the heat upwards instead of going into the basement area which has radiant in the concrete floor.
By the way, my cathedral ceiling is 20' high on main floor with small portion 8' ceiling.
No trouble nailing down flooring as you can feel the sleepers through the paper.
Just my 2 cents worth speaking from experience.
Edited 1/27/2007 6:51 am ET by valleyboy
valleyboy, how is your house insulated, and what room temperature are you maintaining?I am a little surprised you're achieving a 120 SWT in a large cathedral space with this installation, with what I would consider to be substandard insulation under the assembly as well. Sand retains heat well, but it's generally a better insulator than a conductor. I expect that you did a very good job insulating the building as a whole? More details! That's interesting info.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
The walls of the main floor are 8' high on one side and 10' high on the other side (32' long) with the interior like a timber frame house. Roof is 16" TJI with holes pre-cut for cross-ventilation. Insulation in walls is R20 fiberglass insulation with 5/8" drywall. Insulation is ceiling is R40 fiberglass insulation with 3/4" pine T&G.
Main floor thermostat is set at 70F.....during daytime, two dormer windows (2'x4') and two large windows (9'x5') will heat the main floor to approx 73F when the sun is shining.
Basement (9' high) thermostat is set at 72F. One side (32' long) is walkout with two large windows (8'x5'), a couple of smaller windows, one steel door(mostly glass), and then office area with about 50sq ft of window space. All basement walls framed with 2x4's, R12 fiberglass insulation, 5/8" drywall. Floor is all ceramic. Ceiling is suspended ceiling tiles 2x4' and on home-made pine grid system.
House is built on approx 90' of sand so you can see why I used sand as it was free for the taking. Basement slab is insulated with 1 1/2" pink SM and slab does not touch anything but SM.....totally insulated from all surrounding material including cement piers. Same SM under all floor with 1/2" pex tubing run at 12" centres with total of 6 runs.
Basement temp in at 100F....return at 85F.
Main floor temp in at 120F....return at 100F. Was a little cautious about the 120F in after reading lots on subject but with sun shining on floor the floor heats up much more from sun than it does from the tubing. Floor is 3/4" Kempas hardwood.
System works real good with only two thermostats....one in basement and one on main floor. Had originally spec'd out with more thermostats and more runs but the heating guy that installed everything talked me out of it and said he would install a super simple system and he sure did. One main circ pump at boiler. One pump for basement and one pump for main floor.
Any more info ?
Actually valleyboy, I'm very curious to run a quickie load calc on this. It is sounding like you kept the glass to a minimum relative to the amount of floor space you have? My speculation is that your per-square-foot load is lower than normal for a cathedral space for some reason. But if you're willing to email (robATnrtradiantDOTcom) or fax me a sketch of the main room, I'd love to check the numbers.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Rob:
Actually there is quite a lot of glass space on both the main floor and the walkout basement area.
I will, over the next few days, put together notes on both floors showing the floor space, wall space, glass space, door space, etc. as don't have a small diagram of floor layout and the plans are just to big to reduce on the scanner.
very cool, this will be interesting. Thank you!-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com