I am trying to understand the choices for efficiently heating water for radiant heat. I am planning a new home with radiant heat, and no baseboard hot water heating. I remember seeing an article in FineHomebuilding not long ago that addressed this, and I believe recommended a hot water heater over a boiler. However, I cannot find the article now.
The home I am building is a 26×40 cape with good insulation, … 2×6 construction and wall insulation, dual pane insulated glass etc. etc. It will be located in central Maine. Backup heat will be available from a wood stove.
I would appreciate it if someone could direct me to the article on-line, or other comments relative to this question.
I have heard of “system 2000” which is supposed to be a very efficient boiler based hot water heater. Is anyone familiar with this? Would you recommend this over a more traditional high efficiency hot water heater?
Thanks for you help.
Allen
Replies
Go to the JLC forums and search for an article written by Bill Clinton.
It's about 10 years old, complete how-to using a gas water heater as heat source for radiant.
Joe H
Conventional boilers need mixing valves to produce the low temperature water (generally 80F to 100F) while keeping the boiler hot enough (140F to prevent condensation inside the boiler which will lead to corrosion. These boilers are not very efficient, achieving about 80% efficiency at best.
Radiant heating is an ideal match to the newer, high efficiency boiler which is designed with an aluminum or stainless steel heat exchangers which can operate at a lower temperature, condensing much of the water vapor out of the flue gas and achieving up to 98% efficiency. Weil-McClain makes such a boiler. It is my understanding that are now some high efficiency hot water tanks that operate in the condensing temperature range and can approach the efficiency of a condensing boiler, but if you use the $500 hot water tank from the big box, you are starting with a 60% efficient beast. You get a cheap system this way but not an efficient one.
I cannot remember the issue date, but it was either the most recent one or the one before.
I believe what was recommended was a condensing water heater.
they do make electric boilers for these kinds of applications.
have you had any real heat-loss calcs done or are you flying by the seat of your pants?
For our ~3000 sq ft house in CA (mild weather) it turned out we only needed 27,000 btu/min to heat the place. We could of bought a much cheaper elec 35,000 btu unit and saved a lot of hassle and space...but of course I bought the much more expensive 60,000btu mod-con boiler cause I'm a dumb a$$.
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
"For our ~3000 sq ft house in CA (mild weather) it turned out we only needed 27,000 btu/min to heat the place.Per minute?? Whew! But I guess those Californians like their homes really "open," like no walls at all! Every party a block party!
ya actually I don't think that /minute thing is correct I don't have the docs here in front of me how are heating appliances spec'd?
I've got a 180,000 BTU tankless water heater but is that heat delivered /sec, /min , /hour?
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
Heat flows are BTU/hour (British, US), KiloWatt (rest of the world). 1 KW is 3412 point something BTU/hr. I thought your /minute was just a typo.180,000 BTU/minute would be only a California politician making an election promise.
Edited 2/26/2009 2:16 pm ET by DickRussell
Dan's house used to be insulated with rat poop.
Now that he's cleaned that out there's no insulation at all.
Joe H
Backup heat will be available from a wood stove.
Is your plan to use wood strictly as an emergency heat source? The reason I ask is that RF isn't compatible with other types of heat when used in combination.
I've been planning around this problem because I want to use heat from a woodstove interchangeably and seamlessly with the other source.
Thanks for your comments.
I found the article I was looking for. It was in the February/march 2009 issue. Thanks for the tip.
I also appreciate the references to other system design information. My plan now is to have the system designed and installed by a contractor. They will do the heat load calculations etc. One of the contractors I am talking to is selling the "system 2000" so I am trying to do some digging to see if the sales pitch matches with what seems to be the best practices in water heaters vs boilers for radiant heat.
I am curious about the comment that radiant floor heat is not compatible with a wood stove. I expect you mean that the radiant heat has a long period of time to bring a room up to temperature, and a wood stove is much quicker. So the mass of the radiant heating system is still "heating" the room while the wood stove is running etc. I also expect that if you heat the room with the wood stove, the radiant heat goes off. Then when you go to bed and the fire burns out, the radiant heat comes on, but the room cools off faster than the radiant heat can compensate for. I am aware of the conflict in principle, but not in practice. Any elaboration would be appreciated.
Thanks again,
Allen
I too am building a new house utilizing infloor radiant hydronic heat. I have yet to settle on a heat source for the system. Most hydronics pros that I have talked have recommended a gas-fired mod/con boiler in the 110K btu/hr range. I believe this is rather large for my needs. I have not had a professional heat calc done but have used several free online calculators provided by heating equipment manufacturers and a "by-hand" labor intensive calculation as well. Based on these calcs, I am looking at around 10 to 15btu/hr per square foot of finished space. This is much lower than the "rule of thumb" some calcs go by.I have been recommended an electric boiler as well, lower upfront costs and supposedly lower, regulated power prices compared to propane. I'm not sure that Obama's energy program will continue to price electricity cheap in comparison to other fuelsThe FHB article was primarily written by the Hannel Radiant Direct company and they are proponents of the Polaris water heaters and open system piping. I priced them and there is not much savings between a mod/con and high end water heater.I will most likely go with a Triangle Tube PS60 mod/con and indirect fired tank as my heat source. I think this is the most value for the money in mod/con boilers and the maximum efficiency long term. I don't have a PUC regulated electric utility and I don't like the inconsistency in power delivery and the chance of being w/o power and heat in a storm outage.Lots of choices, lots of $$$, good luck...
I have the triangle tube solo 60 and it can not be used to indirectly heat potable water. the 110 is the only model that can do that as far as I know.
Also look into rel costs. The 110 + the indirect tank was a lot of money. I saved a ton by using a tankless heater to heat my potable water.
If you have skecthy elec service having a gas fired boiler isnt going to help you. The pumps and control circuits need elec to make the entire thing work.
If I was going to do it again I'd go with the elec boiler-its not like an elec tankless where you have to dump a ton of current to heat the water fast. That and no venting to deal with, and the units way smaller and cheaper to use.....
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
"I have the triangle tube solo 60 and it can not be used to indirectly heat potable water. the 110 is the only model that can do that as far as I know."---TT 110 is factory plumbed w/ internal circ and indirect supply port. All other boilers in the world can run an indirect tank as an additional zone or loop in the system. A plate style or more common internal coil or tank within a tank heat exchanger separates potable domestic water from the heat source."Also look into rel costs. The 110 + the indirect tank was a lot of money. I saved a ton by using a tankless heater to heat my potable water."---60 gallon stainless indirect tank is around $800-$1000. No vent, no fuel plumbing, way more btu/hr than even the biggest tankless. What's a tankless cost? Around $600-800??"If you have skecthy elec service having a gas fired boiler isnt going to help you. The pumps and control circuits need elec to make the entire thing work"---Boiler + controls + circulators = ~10amps. Even that figure is probably high. A generator or small wind turbine would be more than adequate to fire boiler and circulate water during a prolonged outage.From my research, tankless heaters reach max efficiency when heating water from around 50 degrees to peak. Re-circ apps heating water from say 90degrees to operating temp is not efficienct and prone to short cycling.My quote for a Siesco was great for initial upfront costs, the 75-80amp power load is pretty substantial and would not work in many retrofit applications. I have 200A service and panel space for that system but am reluctant to go with electric water heating.
Edited 2/26/2009 8:32 pm by Haystax
---60 gallon stainless indirect tank is around $800-$1000. No vent, no fuel plumbing, way more btu/hr than even the biggest tankless. What's a tankless cost? Around $600-800??
Not sure where you got that number but the Triangle tube dual coil indirect WH was ~$3000 when I was pricing it out.... Here's a link to where you can buy it online for the low low price of $2889.95
http://www.ecomfortusa.com/product_info.php?products_id=445
I'm not sure what you are talking about with the btu/hr thing but the s60 model only supplies 60,000BTU's max and if you're heating water while heating the house thats a lot of load for the boiler? My tankless is 180,000BTU and it can knock the socks off the s60 in terms of getting water hot fast.
Ya if you got battery backup then ya then you can still run the system.
Also in terms of heating a room with the stove. Most t-stats can be had with floor sensors so it does not matter so much how hot the air in the room is.
Daniel Neumansky
Restoring our second Victorian home this time in Alamdea CA. Check out the blog http://www.chezneumansky.blogspot.com/
Oakland CA
Crazy Homeowner-Victorian Restorer
I'm not sure that Obama's energy program will continue to price electricity cheap in comparison to other fuels
I don't know how much the price of electricity will go up, will it double? Will it triple?
None of that "Green" power will be cheap either.
Might be a wood stove or solar hot water will be the only cheap heat out there in a few years.
Cap & trade will cost us all, only question is how much?
Joe H
I'm not sure about the potential costs or severity of power rate increases - I'm sure that the PUC oversight and public outcry regarding a drastic widespread increase would temper Obama's dream a little. How much I do not know. I would hate to be on par with Europe when it comes to energy prices.Our local REA is a co-op with G&T agreements with large coal plants in Utah and Wyoming. Two major targets of cap & trade strategies. They have a little hydro power from Glen Canyon but not enough to make up for carbon taxes. Plus, enviro pressure on hydro projects doesn't help.Additionally there is the potential of a new mining project that would decimate the existing transmission capacity of the small REA system and wreck havoc on our little community's grid.Looking seriously at solar integration into the water heating and possibility of small scale wind turbine. Not sure the payback on PV will EVER be worthwhile.
http://www.bloomberg.com/apps/news?pid=20601109&sid=a_b86mnWn9.w&refer=home
See this?
Joe H
I'm not sure I understand. I did a radiant floor with a little Ariston 1500w 4 gal hot water heater and a Grundfos circ pump. 1500w is a little small for the studio I am trying to heat in the snow country but after a couple of days the room is comfy.
If I needed more watts I could have used a bigger hot water heater. Theoretically, I could have used a gas hot water heater (in my case the propane drains were a problem so electric is my only option). The circ pump is all that must be on the thermostat. The heat loss from the hot water heater and the thermal mass of the extra hot water is miniscule compared to what the floor needs. Set the HW heater thermostat to "low" and the losses (and scalding floors or mixers) are not a problem.
I'm not opposed to tankless (the hot water for the house is tankless) but it is expensive. A standard HW heater is a few hundred bucks - lots less than the $800 to 1000 that have been mentioned here. These fancy systems look complicated and expensive. What am I missing?
Eric
I hadn't seen that piece - thanks for the link!As far as I am concerned Pat Mulroy and the SNWA are public enemies #1 and #2! We are not in the area proposed for pipeline transfer of water but the article names our close friend who is at the forefront of the opposition to this outlandish scheme.Las Vegas needs to tax and price water at a market level based on the scarcity of the resource. The amount of subsidized population growth and gross mismanagment of water resources in Suouthern Nevada is criminal.I really like the quote by John Wesley Powell - too bad it fell on deaf ears in 1893. The levels of hormones and pharmaceuticals in Lake Mead already make it barely suitable for drinking water before the feats of engineering it takes to get the water out and put to use. Las Vegas and Southern California need to be given a rude awakening about water. Unsustainable growth in such an environment is reidiculous!
Southern Utah has a wackjob idea to build a pipeline over the mountains from Lake Powell to Washington County.
According to the powers that be in the good ol boys club that runs the water district in Iron & Washington CO, there's 100,000AF of water that is theirs according to the 1923 agreement.
It's supposed to be in the Flaming Gorge reservoir just waiting for the pipeline.........What a crock of #### this is, but they're taxing us for the preliminary work to build it.
I saw that probram on PBS about water last year, that Mulron woman is gonna eat our good old boys alive if they go up against her.
Your buddy was pretty eloquent in that show, but she's got the big money on her side. Think you're screwed.
Joe H
Joe H
I don't know if she has big money on her side anymore. The article says that they are basically broke and the State of Nevada damn sure is.The economy and statewide recession in the southern and western counties should take care of her "pipe dream"At this rate, Las Vegas may have the highest DECLINE in population nationwide over the next ten years...She can't build a pipeline that will flow from here but that doesn't stop Vidler et al. from attempts at the next water grab.
Las Vegas and Southern California need to be given a rude awakening about water. Unsustainable growth in such an environment is ridiculous!
The mayor of Los Angeles, Antonio Villaraigosa, announced last week that the City of LA will be under water restrictions beginning in May of this year, due to the below average snow fall in the Sierras over the winter.
This means that watering of lawns will only be allowed two days each week and that there will be meter by meter penalties for using more water than in previous years.
I salute the mayor's leadership on this issue during an election year. Now if he would only get behind saner legislation about the construction of new homes and apartments, the area might be better able to address other problems, like transportation and air pollution.
Edited 3/1/2009 12:00 pm by Hudson Valley Carpenter
I also expect that if you heat the room with the wood stove, the radiant heat goes off. Then when you go to bed and the fire burns out, the radiant heat comes on, but the room cools off faster than the radiant heat can compensate for. I am aware of the conflict in principle, but not in practice. Any elaboration would be appreciated.
The other point...the way it's been described to me...is that when the floor is warm, the air temperature at thermostat level doesn't need to be nearly as high as it would with convection heat sources. So in the scenario where the wood stove is used for hours, then dies out in the middle of the night, the floor will be cold and the RF thermostat won't call for heat until the air temperature is in the low sixties. I'm not sure how long it would take for the RF to respond but on a very cold night the air temperature could possibly become quite a bit lower before the RF became effective.
I've never had that kind of lag problem with my RF heat. It kicks on when it's needed, regardless of the prior alternate heat source, without any discernable difference. I'm not HVAC expert, but I think the thermostats "learn" the heat lag of the system and compensate accordingly.
Mike HennessyPittsburgh, PA
I've never had that kind of lag problem with my RF heat. It kicks on when it's needed, regardless of the prior alternate heat source, without any discernable difference. I'm not HVAC expert, but I think the thermostats "learn" the heat lag of the system and compensate accordingly.
Mike, Would you please expand on that a bit? I'm really interested in your experience.
What kind of floor is the radiant system in/under, all materials? What type of thermostat does the RF system use? What alternate heat source(s) do you employ? Are they regulated by thermostat? Is it the same thermostat for both systems?
Edited 2/26/2009 4:44 pm by Hudson Valley Carpenter
I have forced air in most of my house, RF in an addition -- 3 floors. Heat in the addition is a Munchkin modulating boiler with Uponor controls, 3 zones, one each floor.
Basement (laundry room) is 1/2" PEX in slab, Ditra and tile over top. Uponor stat.
First floor (sunporch) is wood subfloor w/ 6" of insulation underneath, QuikTrak w/ PEX, Hardiboard and quarry tile, Uponor stat. This is off the living room where there is a fireplace. This room (as well as the laundry room) is generally closed off from the rest of the house when we're not home, but is often not closed off when we're home.
Second floor master bath is the interesting one. Same flooring system, but we don't generally close this off from the rest of the house. The house is on a setback stat, so we swapped out the Uponor stat in this room for a Honeywell setback unit. This room works well irrespective of what the forced air is doing and comes up to temp after a 15* setback almost as fast as the forced air. (But it's comfortable and stable long before the forced air rooms are, since the forced air ends up ratcheting to get there until the walls, floors and ceilings heat up.)
The upper two floors are low-mass systems, so they react pretty quickly. I have noticed that the stats are smart enough to stop calling for heat when the room temps approach the set points so it doesn't overshoot.
Like I say, I don't know the details of how the stats anticipate the heating calls, but they've been just fine in that regard. For example, the sun porch gets a lot of solar gain during the day, but cools off pretty fast when the sun goes down. No problem for the RF to catch up quickly. Same deal when the house is "cold" and the big double doors to the sunporch are opened. The RF has no problems with that.
Two things to consider: 1) Don't put the stat in the same room as the wood stove if you can avoid it, unless its a one-room zone. The problem isn't so much with that room, but with the others on that zone. They will be cold if the stat is being warmed by the wood stove. Our forced air stat is in the living room, and the rest of the house (except the addition) gets cold when the fire's going. A RF system would make it easy to zone off the room with the fireplace/wood stove. 2) I'd be surprised if you had such a drastic/fast heat loss that would cause a room to cool more quickly than the RF could deal with unless you open all the windows or something. ;-) 3) OK, I lied. Three things. The wood stove does not get cold instantly, but gradually cools down, making it even easier for the RF to stay ahead of the temp drop.
Hope that helps.
Mike HennessyPittsburgh, PA
Thank you for taking the time to describe all that. I hadn't imagined anything quite so complicated but additions and new systems are peculiar. Glad it's working so well.
Other than the sun room, are there any other rooms with greater than average window areas? What's the R-value in the upstairs ceiling and in the ext walls? Do you believe that's an important factor in moderating temperatures in your home?
Edited 2/26/2009 8:40 pm by Hudson Valley Carpenter
Well, it's complicated -- but not complicated. ;-) The complicated part is doing the heat loss calcs. Those I had done by the supplier of the equipment. They specced what tubing to use, how much, the layout, the pump, the boiler, etc. Installation is pretty straight forward once the plan is figured out.
The sunporch is the only room with max glass. The walls in the house are balloon framed 2x4s, brick veneer, old lath & plaster, blown with cells. (R-value? Your guess is as good as mine, but subsequent renovations have shown that the cells are pretty well packed and only a couple of small voids in odd stud cavities.) The addition is 2X6s, 1/2" ply sheathing, Tyvek, hardi siding and 5/8" DW with a plastic VB inside. Also blown with cells. So maybe R-20-ish? Ceilings in the main house are 8" of cells where I could get it, and about 4" of cells in the ceilings under the hips where I couldn't. (Wish it was better, but you gotta play the ball where it lies!) The addition has 10" of cells in the attic floor/bath ceiling, and 6" of unfaced FG batts between the floors to keep the RF system happy.
As for the impact of the insualtion in the house vs. the addition, I don't think it's that big a deal. Otherwise, the sunporch (with all those windows) would be the least comfortable room and it's actually one of the most comfortable. IMHO, the warm floor keeps you feeling warmer despite the cold windows nearby. You feel warmer in that room even if the air temp is 5-10° lower than the room next door that's heated with forced air.
When I first fired up the system last winter, I was still doing finish work in the sunroom at the time, so I had the stat turned down to about 60°. My Lovely Assistant walked in from the house (set at 67°) and said "Man, this is toasty. I'm gonna live in here!" Made me wish I'd done the whole house with RF.
FWIW, I dug out this pic of the boiler setup. Note that, since the pic was take, I added a differential bypass valve at the suggestion of a poster here (whose handle I forget, NTRob or something along those lines, but he seems to know his stuff when it comes to radiant) even tho' the Munchkin factory rep said I didn't need one. Frankly NTRob seemed to know more than the rep, so I went with what he suggested.
View Image
Pretty simple 3-zone setup, but as you can see, you need to be comfortable with a soldering torch!
Mike HennessyPittsburgh, PA
even tho' the Munchkin factory rep said I didn't need one.
If you had let the Munchkin climb up on the washing machine he'd a been able to see that you did need one.
Thanks for another excellent description. I appreciate that comment from your DW too. I've heard many similar remarks from owners of RF systems and, from a couple of brief experiences in older, retrofitted homes, I have to agree.
The only reason that I'm reluctant to invest in an RF system for my new home is that I plan to superinsulate it so I expect that RF would be serious overkill. The temperature of the floor wouldn't be much warmer than the air so that warm, cozy feeling wouldn't be present, as it is when the floor is at 80degrees or higher.
It's a three story design, with the lowest level being the least used space. I'll have the wood stove down there so that it can heat the entire house, even when the power is out, as often happens in that rural area where freezing rain/ice storms are common.
Currently I'm planning for LP fired HW baseboard heat with Electric Thermal Storage heaters as a second option. I'll wire the house for them anyway. If the present government emphasis on energy continues on course, electricity may well be the predominant heating fuel of the future. In any case the house will have R30+ walls and R60+ceiling so the amount of fuel used should be pretty minimal, by today's standards anyway.
If it wuz me . . . and it ain't . . . I'd consider putting some serious mass in the house, or at least the basement, like a double-thick slab with extra insulation underneath as a heat storage medium. I would at least run the pex in the slab, even if you don't hook it up now, rather than the baseboard. Heck, the PEX itself is the cheapest part of the system. If you do end up w/ electric (or even solar) that will let you store heat, perhaps at times when rates are low. ("Smart grid" and all.) If the house really does only need a small amount of heat, a small electric "boiler" would fill the bill. I have a friend with a hay bale house who heats this way and loves it. The boiler and QuikTrak were probably 80% of my cost, and you could avoid much of that cost by running the PEX between the joists and forgoing the fancy boiler.
FWIW, the floors never really get "toasty warm". The system is a pretty low temp setup and, contrary to popular lore, your feet don't really feel warm from the floor. They just keep you from feeling cold. In my view, the extra insulation would only add to the benefits of RF. Have you done heat loss calcs yet? That's where I'd start before considering heating options.
Mike HennessyPittsburgh, PA
Mike, I really like the idea of RF in the slab, always have, over baseboard heat.
Baseboard has been at the top of my list for compatibility with wood heat but now you've got me thinking that such compatibility isn't really needed.
To be honest, I'm leaning more toward the Electric Thermal Storage heat system as my primary heat source. Its ceramic thermal mass holds heat delivered during off-peak hours. And it fits very well in a super insulated environment where air movement and venting are also important considerations.
ETS is also the most economical to purchase and install, by quite a bit. The savings on the heating system pays for a lot of the added expense of super-insulating the house. http://www.steffes.com/
Nonetheless, an RF floor downstairs could also be superinsulated and heated by a small electric water heater during off peak hours. Perhaps those two systems would be the best combination, with the wood stove as a third option/backup.
Edited 2/27/2009 1:03 pm by Hudson Valley Carpenter
Check out the Seisco electric water heater. (None of us is really talking about a "boiler", btw, for clarity's sake.)
They are modulating units that have 2 or 4 chambers to heat water to which the electric heat is proportionally applied. If only one chamber is required, the unit alternates between the array so one chamber doesn't take the brunt of the load. The inventors seemed to think of everything during the design instead of afterward...refreshing.
I did an installation in 2007 for a friend who's been saving over half what she'd been spending on her non-modulationg, on-demand, propane water heater in the MT winter months. We used the RA-22 for a 3000 sf log home. The price then was $1300...i see it's selling for $825 now!
So simple even a girl can install it: http://www.seisco.com/
The chambers are polymer - no metals to corrode: http://www.seisco.com/pages/fourchamber.html
Do you know what you're doing when you use electric power to heat water?Utility throws away almost 2/3 of the heat to make a unit of electric power. Then you convert the unit to make heat.Better to burn fuel directly to make the heat, even if it's only 90% efficient, you only throw away 10%.You could discharge the CO2 and water vapor byproducts into the hoophouse and be even further ahead. Get a CO detector first!
Edited 2/26/2009 9:35 pm ET by mike585
Without the option of natural gas, a person is really at the mercy of propane companies, the only other energy supplier here. When i ran the numbers for my friend's system, the cost per BTU with expected efficiencies from a propane heater (85%) and the elec were such that if propane when to $2.11 or thereabouts, then the systems would be at the break-even operational cost. A benefit to my friend, who's husband is very ill and she's very broke, is that elec rates aren't nearly as volatile as LP. At the time, propane was just under $2 a gallon. It got to nearly $3 before it headed back down, while elec rates have remained virtually the same over two years. The other driver was the available space to put the RFH water heater. The original heater for the failed 'open' system, combined DHW and RFH, was a Rinnai not rated for the load, which never functioned properly for space heating requirements and in fact underwent extensive repair just to get it functional again for her DHW. Unfortunately, the exhaust location for the Rinnai meant i couldn't route a second exhaust for a RFH heater without moving the W/D hookups and whacking another exhaust hole in the basement wall. =^O Our non-profit elec co-op buys power from Bonneville, mostly hydro, some wind, and one nuclear plant. I guess that's cleaner than coal? To be sure, the decision was primarily driven by cost, not environmental concerns, bec i had to front the money for it and won't likely be paid back for a long, long time. No Tagaki's in my budget! I think i could still make a case for this use of elec being as environmentally sound as propane, though.Oh, i forgot to mention that her road is impassable in winter except by 4WD. The elec lines are there even when the propane truck can't make it. Hello from Outer Slobbovia!!!
I should have known you'd have a well thought out plan and a reason for what you were doing. Carry on. Tough situation.
Your post reminded me of a question my brother (who will be building his retirement home sometime soon, maybe) asked me--is it cheaper/better to use electric heat mats in the floors, walls, or ceilings to do radiant heat, or better to use electricity to heat the water in tubes under floor? Seems like more direct (resistance electric heat) would be more efficient, but I didn't know. Certianly easier to install and maintain.
im doing the same thing now...at my house in gearhart oregon , its on the northcoast not quite as cold but damp...
im using an A.O. smith vertex , it has continuos hot water capabilities and is 94% iffecent
it goes for about 2k
it will save me alot of space in the machanical room the one thing i am putting it with the system is an ERV or HRV heat exchanger..i thing those are nice because tight houses need to breath
what im not sure of is if i need a plate heat exchanger to seperate the drinking water from the heating water? i think you might need gycol in your system incase of freezing