Since I first started following this forum and asked some novice questions about geothermal sourced radiant heat, I've seen an unending dialog about fixing these systems. I found out what I wanted with respect to warranties from Water Furnace, et al; but now I'm starting to question the decision making process because of all the problems I've read about. Now I know that people that DON'T have problems have no reason to seek help, so I don't really have a sense about the percentage of systems out there - that have problems. I'm now starting to think that a high capacity, high efficiency water heater - with the right controls - might be the way to go. It seems so much simpler and the initial investment is significantly smaller. I know that using a commercially available hot water heater that uses propane or electricity is not the "greenest" way to go, but I'm starting to think I can't afford the geo system and all the potential for problems.... I am planning on running my source water through a storage system built into my primary fireplace mass as a means to preheat the water going into the hot water heater anyway, so perhaps the fuel requirements won't be that bad... I've read about some stainless steel hot water systems that are used for radiant heat. Anyone used one? comments? All the companies have testimonials, most of which look like they were written by company employees.

geo makes sense for almost nobody. but maybe for some. I do prefer air source (disclaimer is that I distribute air to water heat pumps... but I started doing that because I believe in the tech).

super efficiency water heaters are good, but not as good as super efficiency boilers. and NEVER do systems where you drink your heating water.

I don't like fireplace tied heat exchange typically. most of the time they are bombs waiting to happen. if yours can boil off safely, great, but that means you need a heat exchanger and some controls somewhere in most systems.

First the most important thing is that you decided radiant heat. That is a very flexible system and means with a little planning you should be able to add geo later if you change your mind.

Being "green" is your call... It's very relative depending on how you meaure it (inputs, sustainability, pollution\carbon, etc).

Did you price out the options yet? First get heating prices for propane, natural gas (if it is available) and straight (no geo) electric. Note propane is more efficient at heating per pound than natural gas but costs more, so you must factor in BTUs\pound in addition to price. Also note a lot of electric companies give a cheaper rate for off-peak or controlled heat provided if you have backup or enough thermal mass in your house (or under your slab which is the most common). Then do the cost analsys. Geo will give you a COP of 3 or so in the northern USA. That means a straight heat (no geo) electric bill of $100 will cost $33 with geo. Depending on where you live, air source heat pumps may have similar COP and be less expensive so don't rule those out either. Determine the pay-off period of geo, and also consider how long you plan to live in the house. For me, I would hope to get a payoff period of less than 15 years, considering every system requires maintenance and eventual replacement. The same goes for solar PV -- today the payoff period is too long for me to consider even with various rebates, tax savings, etc.

Also, since you mention you will have a fireplace, consider using an efficient wood boiler instead (or in addition to) especially if you can get wood for cheap\free and don't live in the city. It's messy and a hassle, but if you have the time and motivation then consider it as well as a water storage system along with a backup system like electric.

To get to rational decisions on heating equipment starts with a heating/cooling load calculations. Without knowing how much heat needs to be supplied, there's nowhere to even start.

For most mid-sized homes in the lower 48 of the US the heat loads of new houses (even code-min) are lower than what makes sense for ground source heat pumps(GSHP), even with subsidy, and in new construction spending the difference on beefing up the thermal performance of the building envelope beyond code-min is often a better investment than GSHP. At heating/cooling loads under 20,000 BTU/hr it's usually cheaper/better/nearly-as-efficient to use modulating air source heat pump technology, and that's an achievable number without enormous expense in new construction for a mid-sized house.

Open hearth fireplaces (even with glass doors and better dampers) are an efficiency disaster, and often require more combustion air than a decently tight house can supply. I'm hoping you're talking about an engineered air-tight high-mass woodburner? Unless you're using it as your primary source of heat, there's no point at all of trying to engineer a hydronic pre-heater for the hot water system, and meeting code would be a nightmare. As Rob correctly points out, they can be ticking time bombs when done wrong, and doing it right takes some design time and more hardware. High-R houses can often do pretty well with point-source heating like woodstoves (or mini-split heat pumps), but it usually has to be designed for point source heating or comfort will suffer at the temperature extremes.

Building low-temp hydronic heating systems around condensing propane tank type water heaters can make some sense, but depending on your local grid sources using heat pump technology for both heating & hot water is usually greener in all but the most high-carb local grids in the US. (Is coal the source fuel for 75% of the kwh delivered from your local grid, the propane is slam-dunk better, but if your base load generators are primarily combined-cycle gas you're better off with heat pumps, and if most of your local grid is hydroelectric even resistance electricity is greener than condensing propane.)

Woodboiler north-American style are an efficiency and air-pollution disaster, independent of the steady-state efficiency data on them. They're almost universally WAY oversized for the actual heat loads, and the controls usually starve them for air a the end of a call for heat, resulting in several 10s of minutes of VERY heavy soot output at the end of a call for heat when it goes in to smolder-mode. No matter what the steady state combustion efficiency is, in smolder mode its ZERO, and even a 50% efficiency wood boiler that's actually burning at it's rated output is FAR more efficient and cleaner burning than an 80% wood boiler that spends most of it's time in smolder mode. In areas where they are becoming common, lawsuits by neighbors over the smoke issues are becoming common. Even the STATE sued a couple of woodboiler operators over air quality issues in one recent case.

if you want a wood boiler, look for one with a "lambda sensor" which monitors exhaust temps, O2 and often CO2 and adjusts the firing rate to keep it clean burning. Unfortunately, the majority of those available are European and more expensive than their American competitors. Outdoor boilers are getting banned all over the place and are often out there for insurance reasons.

Like my current fireplace, which uses outside air for combustion, my plan for my new log house is to use a big stone mass as a heat sink. As I am very happy with my existing fireplace combustion system, it seems logical to try incorporate a built in water heat capture system into the construction of the new place...still utilizing outside air for combustion. Ideally, it would be great to "pre heat" fluid that is used in the radiant floor - thereby lowering the need for purchased btu's from "the man". Despite the above, I'm seeing some great info on stainless steel water heaters and boilers that can provide more than enough capacity for my 1,000 sq ft slab.

Storing water for radiant floors makes sense and can include batch fed boilers as the Garn. Dana has the smoldering boilers down pat. Rob is right, few residences will make GSHPs look good.

When the heating loads get small and the DHW loads remain high we use condensing water heaters with various emitters. Just commissioned a VersaHydro for a customer today and filled their big tub with hot water, first time in 8 years...brilliant.

Unless it's been engineered as a system it's hard to get even 30% efficiency out of a DIY fireplace.

Engineered high-mass fireplaces/stove (eg Tulikivi: http://www.tulikivi.com/en/fireplaces/Tulikivi_fireplaces ) and some DIY "rocket" stoves can hit the mid to high 80s, which will do a LOT more for getting you away from payin' da man for fossil fuels or electricity. (How does heating your whole house with 1.5-2 cords/year instead of 5-6 sound?)

Turning a high-mass masonry heater into a low-temp hydronic thermal buffer with fossil-fired backup safely & reasonably isn't a back-of-napkin kind of design though.

But any heating system (even specing a wood stove) starts with room-by-room heat load calculation based on realistic indoor & outdoor design temperatures. Log homes aren't exactly green from a heat load point of view, since most of them barely meet code min (if they do at all) on R-value, and they're damned-near impossible to air seal to IRC 2009 standards, let alone IRC 2012.

But to get a handle on the order of magnitude of your heat load, describe the wall construction of this house, the attic/roof R, the number of square feet of floor/windows/doors/wall (less window & door area), etc. and the U-factors for the windows/doors, and what is your location (for weather data purposes)?

Hi There Thanks for the succinct answer / opinion. I'll expand on describing the project with the intent of keeping it to a "Readers Digest" version. I'm using 14 - 18"dia. white pine logs from my own property. In addition, the 40 acres has all the oak wood I will ever need. These 2 things helped make my decision about log construction / fireplace, easy. (of course implementing it is another story) I am located in NS Wi. about a hour from the Twin Cities. My building site is on a south facing hill. Both the basement and main floor will have high E windows on the south face. Main floor is at grade, with one bedroom. The basement is exposed to the south only. The building plan calls for 12" rafters with R40 insulation, although I'm being told that R60 would be better of course. I am planning on using ICF for the basement walls, with radiant floor heat in both that slab and the main floor, although the method of doing it on the main floor needs to be finalized, as I'm not convinced yet that putting pex under wood is right.... looking for an alternative to that. I know that log construction in general has some weakness as far as air infiltration goes, however the builder that custom built my neighbors house did such a fine job that my neighbor has yet for find any leaks, after 5 years. He's gone around with a candle looking for drafts. He is using an outdoor boiler and burning his own wood, and spending no money. Overall sq ft is about 1800. Been looking at Radiantech systems online, which seem pretty interesting.

If you're happy burning a lot of wood forever, then a log home can be ok. but even if you manage to not get leaks, wood is not a great insulator. buildings in cold climates should have real insulation both for energy efficiency and comfort. if you want log siding, great. timberframe, no problem. but logs are horrible building materials for outside walls.

I would *almost* always prefer a wood boiler tied to hydronic distribution to a fireplace in the living space. much more controllable. safer than homegrown firebox solutions too, and more effective.

If you are actually using a firePLACE as opposed to a masonry heater, I firmly second Dana's statements. efficiency disaster. whether your wood is free or not, cutting stacking hauling and splitting it isn't. fireplaces are horrible ways to heat. wood stoves are better, Masonry heaters are much better but much harder to control, and wood boilers are better still.

you can get fine results from a lot of different systems out there. but never install a system that involves showering in your heating system water.

I guess I got off track and created a wrong impression, here. I thought my first choice for primary heat was going to be geothermal, but after reading about all the problems it finally seemed a waste of money. Then I mentioned my fireplace, along with questions about high efficiency water heaters. I was never intending to use the fireplace as primary heat. I was just wondering about "pre heating" well water. What I really want to know about is the new water heaters that are designed and intended to heat both household and heating water (separately). Radiantec seems to have it together, but I don't know and have not heard from anyone (a real customer) who has used their system and how expensive/efficient it is... There seems to be more and more of these $3k+ water heating systems around. Is it a fad or really viable?

Bugzee, if I may throw in my 2cents. I am not a HVAC professional (but I am a building contractor for what it's worth & I probably live about 1/2 hour from you). If I can address some technologies you have been talking about; 12 years age I built a hand scribed log home (about 3000 sq ft) w/a duel source geo-heat pump; in-floor heat in walk-out and in-floor heat on main floor w/gypcrete. Geo supplied hydronic in-floor heat & hot/ cold air through ducting. All that being said, we also had a stand alone high-efficiency wood stove, contrary to what some think; a wood stove heats up the logs and supplies a real nice stored and even heat. To me there is no system that can get the house (logs) hot enough to benefit from this, other than a real wood stove. I have built 7 homes in the area over the years and will swear by in-floor radiant heat, but would never again put in a geothermal heat pump. IMO the geo is too much money. I have currently found that in my area a wall hung electric mini-boiler on off-peak pricing is financially more responsible. Lastly, if you don't have in-house wood stove as part of your HVAC system then you have no source of back-up heat (unless of course you have a very large generator. PM if you want . Hank

Hank I guess my conundrum is whether or not I can rely on a fireplace for my main floor back up ... using outside air for combustion and a large stone mass seems like it might be enough, but only in the main room. I have a Quadrafire Cumberland Gap woodstove in my shed, that I'm planning on putting in the walkout basement as a downstairs backup, but maybe I should just put it upstairs and have the fireplace downstairs. It's all about aesthetics I guess, as seeing a fire burning works either way. The only difference is the structural requirements change depending on which way to go... The in floor heat is a foregone conclusion, just the right heat source has to be decided on. Does the wall hung electric mini boiler you refer to keep up with demand when it is -20?

The thermal mass of the phase-change of the lignin in log homes makes R-value comparisons complicated, but at 14"-18" there can be a comfort-factor due to the thermal mass characteristic, provided the house can be made sufficiently air tight. But achieving reliable and long-standing air-tightness to IRC 2012 levels ( 3 air changes per hour @ 50 pascals pressure) is damned near impossible due to the seasonal dimensional changes of the logs with temperature & humidity. (I have a brother living in a log home, and it clearly changes by season & year. No horrific drafts, but I doubt it's ever been better than ~8-10ACH/50 even after some air-sealing efforts, and probably averages over 12.)

R40 is probably below current code min in your location (R49 is required for most of northern WI.) R60 would make it though.

Leave the wood-burner out of the radiant floor plans- it's just an unnecessary design complication. But with a decent efficiency mass-heater or woodstove you can get more use out of it than raw thermal mass & ambience. If it's a fireplace rather than a well designed heater, even with it's own combustion air supply ducted in getting better than 30% out of it is sheer fantasy. (Even 30% could be tough.) Air-tight with appropriately sized baffles & flues you might beat 50%, but it takes a very good design and heated combustion air to light-off the exhuast gases at the top of the firebox are usually necessary to it 75%. At 75%+ it's a LOT easier to make it a significant heat source. Open hearth fireplaces typically run 7-10% efficiency. Adding tight glass doors and better damper controls can roughly double it, but that's about as far as it goes without some careful design work.

These people made a fireplace unit that qualified for energy tax credits back when (efficiency >75 percent.) http://www.icc-rsf.com/c/iccrsf/file_db/pdfs.pdf_en/Focus_Handout_EN.PDF.pdf It is expensive, particularly after pricing the required custom chimney pipe. It has hvac ducting to tie it to central forced air as well. It's possible to adapt an air/water heat exchanger to make it hydronic output. OWB folks know how to do the math.

On that subject, you can avoid OWB pollution issues by installing a heat storage system. (I.e., the boiler runs flat out heating several thousand gallons of water. Goes out. The radiant system draws on the storage tank. The process starts over in a day or two after the heat storage tank cools.) hearth.com has any number of DIY approaches, most of which seem to involve reusing propane tanks. Or Garn sells systems with major storage. With a boiler that accepts logs, the workload drops more. If you own a woodlot, your cost drops to the point where fireplace efficiency and log construction no longer matter.

My solution was to buy one of the small indoor wood boiler stoves that are common in Europe. My 60k btu/hr Statford Eco-boiler is 70 percent efficient and puts out 70 percent of its heat as hydronic. I couldn't find an online dealer who would export, but I found a retailer on ebay.uk.co who was delighted to help me. Indoor boilers are exempt from EPA certification, but as dana says, some states are stepping in. A vented (nonpressurized) boiler shouldn't require UL certification but it's something you want to check first with your inspector. The stoves have CE or European ratings instead. Europe is light years ahead of the US in biomass technology.

Bugzee, I have pasted a link to the electric mini-boilers I am familiar with: http://www.thermolec.com/en/productView.aspx?type=product&id=58 I currently have an appartment/workshop slab on grade 3400 sq ft w/11ft ceilings and it cost me $125.00 to heat per month the last 2 months. Sold the log house 3 months ago and am now building the new house. I am not suggesting using wood as a primary heat source, nor do I think it matters what floor your wood burner on, but if you do lose power than the wood burner will come in handy. For reference I put in an air-source heat pump on a custom build 2 years ago requiring an air-handler for cold air and hot air(limited hot air in very cold temps). The house also has a mini-boiler running the hydronic in-floor heat in house and garage. After countless hours on forums like this and having and building with all types of construction and HVAC systems, I am putting a high efficiency gas furnace and outdoor AC unit w/traditional ducting & using a wall hung electric mini-boiler (off-peak) for primary heat in the house and garage. House is ICF walkout foundation & vary well insulated main floor. Just doing what I know and what works best for me. I am also planning on a traditional wood stove in the basement, just because I like the feel of wood & for a power outage. BTW- I had an energy audit on the log house years ago and it came back as the same as traditional stick frame house. Probably might do things differtly if funds were unlimited. Cheers Hank

the high end water heaters (condensing, or condensing/modulating units) can be good choices. but by the time you spend the money, you could technically do better with a mod/con boiler and separate or indirect water heater for domestic usage. again, no solution should have you showering with your heating system water. We prefer "fire tube" style gas boilers if gas is the choice.

electric boilers can be good. if you have offpeak rates, you can add mass by using concrete emitters and/or tanks of water to time shift your loads. several options there. we like Electro boilers but thermolec is a reputable brand as well.

and I have to take issue with a log home coming back the same as a stick frame house on an energy audit. if that happened, you're comparing to a pretty bad stick frame house, or numbers that are very charitable to the logs are being used, or your logs are H-U-G-E.

Posted By toddm on 11 Feb 2013 01:50 PM
These people made a fireplace unit that qualified for energy tax credits back when (efficiency >75 percent.) http://www.icc-rsf.com/c/iccrsf/file_db/pdfs.pdf_en/Focus_Handout_EN.PDF.pdf It is expensive, particularly after pricing the required custom chimney pipe. It has hvac ducting to tie it to central forced air as well. It's possible to adapt an air/water heat exchanger to make it hydronic output. OWB folks know how to do the math.

On that subject, you can avoid OWB pollution issues by installing a heat storage system. (I.e., the boiler runs flat out heating several thousand gallons of water. Goes out. The radiant system draws on the storage tank. The process starts over in a day or two after the heat storage tank cools.) hearth.com has any number of DIY approaches, most of which seem to involve reusing propane tanks. Or Garn sells systems with major storage. With a boiler that accepts logs, the workload drops more. If you own a woodlot, your cost drops to the point where fireplace efficiency and log construction no longer matter.

My solution was to buy one of the small indoor wood boiler stoves that are common in Europe. My 60k btu/hr Statford Eco-boiler is 70 percent efficient and puts out 70 percent of its heat as hydronic. I couldn't find an online dealer who would export, but I found a retailer on ebay.uk.co who was delighted to help me. Indoor boilers are exempt from EPA certification, but as dana says, some states are stepping in. A vented (nonpressurized) boiler shouldn't require UL certification but it's something you want to check first with your inspector. The stoves have CE or European ratings instead. Europe is light years ahead of the US in biomass technology.

The only way that fully avoids the pollution issue with bang/bang outdoor wood boilers is when the storage capacity is bigger than the BTU capacity of the firebox of the wood boiler and it burns to depletion every time.  I've seen multiple in-situ examples of systems where 1000 gallons of buffer wasn't enough at the water temperatures needed, but it's not difficult math to get there.  At "several thousand" gallons it's easier, but it still takes up consequential amounts of space. (Worth the price, in some cases.)

States have started to regulate wood boilers by their emission rates while up to temp and burner freely, and even there the model lists are pretty short. Steady-state is one thing, as operated is another, and the track record isn't very good. It seems to take lawsuits like the one the state of AK is leveling at individual boiler operators in Fairbanks to really fix the "as operated" emissions problem.

The Euro imports are definitely better engineered for higher efficiency, high safety, and lower emissions. (Some of the European pellet boilers are PHENOMENALLY clean & efficient- as well as modulating.)  I'm surprised that the crude & dirty 'merican style outdoor wood boilers have skated by without much regulatory interference until now.  Good on ya to seek out something half decent and not settle for the typical ungodly oversized beasts that seem to dominate the market here!

If you want to read up a bit on wood boilers see here Hearth.Com

Some things to look for:
- Batch gasification system (e.g. having a fast, hot 3 hour burn or so)
- Storage capability (500-2000 gallons depending on sizing)
- Ability to add backup electric. My local power company has time-of-day service with rates about half with service from 10PM to 6AM.
- Ability to add solar heat.
- Auto-start.
- Lambda support which is the ability to automatically adjust air intake\exhaust based on oxegen sensors (3-5% higher efficiency, and maybe less smoke during start\end)

IMO the Garn is a nice unit. Huge with lots of integrated storage. Should last a long, long time. The Froling Turbo 3000 is a really good one too -- higher tech than the Garn with Lambda, optional autostart. Some people dislike that tech, however -- more things to break and circuit board availability 15 years from now...

NRT.Rob, My log house is averages 18-22 butt & tip with 10 courses. The audit was same as R19 (so yes nothing about min. standards. The places where the most energy was lost were not at all expected; gable ends where ridge pole and perlins cut threw & air and thermal bridging in areas of the vaulted ceiling. Windows and doors were actually not a big heat loss loss as I originally suspected. I guess I would think that the concrete in basement and gypcrete or lightweight concrete on main floor would be enough mass to keep the house comfortable. My plumber swears my the Mod/con set up, but I have gotten used to the 105 gallon marathon (off-peak) for domestic hot water. I should really try to run numbers again and compare electric mini-boiler and marathon to an LP set-up for in-floor and domestic HW.