We've been through the geothermal "well" issue.

A well can be described as a source of water to be withdrawn from an aquifer, used and discharged elsewhere. A workaround may exist in calling the vertical holes in the ground "bores" Such may be exempt from a "consumptive use" permit or similar.

Returning all water from an aquifer back to that same aquifer may exempt the arrangement from being labeled a "well" for permitting and covenant purposes.

In  Utah, geothermal loops are listed on the permit as non production wells

That's very interesting there Lbear, never heard of that. What kind of wattage does it use?

Posted By robinnc on 13 Jul 2013 07:36 PM
That's very interesting there Lbear, never heard of that. What kind of wattage does it use?

Depends on the model but the 5,000 BTU version runs at 1,440 Watts/120 Volts/12 Amps

At an average kWh electric rate here in the USA, they estimated 9 cents per hour with heat (cycling at 50%).

Here is a video of it: OPTIMYST

Oh wow - revolutionary new concept - electric resistance heat!

With its COP of up to 1.0, who would want anything else!

Posted By engineer on 14 Jul 2013 09:55 AM
Oh wow - revolutionary new concept - electric resistance heat!

With its COP of up to 1.0, who would want anything else!

Its an alternative to real fireplaces which are very inefficient and ILLEGAL in places like Phx. The electric fireplace is for ambiance and the resistant heat is merely a backup heat source, not primary. But thanks for the sarcasm.

What about a small, efficient wood stove in the basement that feeds in to the geo when auxiliary heat is needed? Does that blow the performance of a super insulated home?

Another reason I don't like gas/propane fireplaces: Corpus Christi Natural Gas Explosion Levels 3 Homes and Damages Dozens Others

The gas industry likes to downplay the dangers of natural gas and fracking brings its own divisive debate on the environmental impact.

Posted By agagent3 on 14 Jul 2013 03:33 PM
What about a small, efficient wood stove in the basement that feeds in to the geo when auxiliary heat is needed? Does that blow the performance of a super insulated home?

Anything that has to be vented outside can take heat from inside/let cold air in. The higher end you buy the less heat loss it will cost you, but they all have an impact.

Posted By joe.ami on 16 Jul 2013 08:49 AM

Posted By agagent3 on 14 Jul 2013 03:33 PM
What about a small, efficient wood stove in the basement that feeds in to the geo when auxiliary heat is needed? Does that blow the performance of a super insulated home?

Anything that has to be vented outside can take heat from inside/let cold air in. The higher end you buy the less heat loss it will cost you, but they all have an impact.

Most non-catalytic EPA rated woodstoves run in the mid-70s or higher for raw steady-state % combustion efficiency between half and full-fire, and the size of the combustion air & venting penetrations in the thermal envelope of the house are quite small. Most are dampered only at the air inlet, which becomes a fraction of a square inch of infiltration when trottled back to "minimum". (To avoid lengthy polluting smolder mode operation the minimum is not fully zero, but small.) 

A woodstove with a ~60,000BTU/hr or lower max fire the minimum-fire air inlet is on the order of 0.25-0.3 square inches, and with piped-in combustion air the effect on whole house infiltration is negligible, not measurable with a blower-door.  When not burning there is a tiny heat load from the cool air entering the stove and leaving out the stack, but this too is quite small, a small fraction of a percent of the total heat load of even a PassiveHouse.  Even the cheapest cast iron or steel EPA rated wood stoves without piped in combustion air represent a significant parasitic heat load when dampered down, and doors closed. 

Put in perspective, most houses have well over 10 square inches of parasitic air leak (even pretty tight houses), and a half-inch more isn't going to break the thermal piggy bank.  At 10 square inches of total leakage you're looking at ~500 cfm @ 50 pascals in a blower door test, which would be close to PassiveHouse-tight on a 4000' house.  Pretty-tight houses that have had some amount of retrofit air sealing or new houses built with some (but not obsessive) air sealing test at 1000-2000cfm/50.  Only deep energy retrofits & new housing built with very careful air sealing detailing will hit under 500cfm.  There are many PassiveHouses testing in the low 100s for air leakage that use a small woodstove as the only dedicated heat source.

Wood stoves can't really be automated, but very few pellet stoves can. Don't bother trying to integrate it into any type of heat pump system. Most people can crack the front door for 0.5 seconds an hour or two before they go to bed and tell if it's going to be anything like a peak heating night and fire up the wood stove before they go to bed, to make it a significant auxilliary (or even primary) heat source.  I have a ~55KBTU max ~ 80% efficient soapstone stove in my house, and fully loaded at 12PM and throttled down to half fire or bit less it's still warm with a few live coals at 7AM, and the house is warm. In that mode it's covering well over half my ~3-ton design heat load.  It takes more than an hour to get it fully up to temp before throttling back on a cold-start though, unless starting with the worlds-driest fuel wood.  Once the secondary-burners light up and have been going for more than 15 minutes it'll stay in high-efficiency mode even at ~1/4 throttle (which what I'm guesstimating is about half of the full fire rating.)  As an auxilliary heat for GSHP with a 4-5 ton load something that size could be about right, provided there's good convective circulation within a fairly large zone, at least 1/3 of the total.

While there's really no "feeding the geo" with a woodstove- just heating a large zone, but that can be PLENTY for ensuring that even an undersized GSHP has the capacity for handling the rest.

So an efficient woodstove or fireplace can serve a home owner well? And better yet, have outside air piped in to feed combustion?

Posted By agagent3 on 16 Jul 2013 03:50 PM
So an efficient woodstove or fireplace can serve a home owner well? And better yet, have outside air piped in to feed combustion?

Well, yeah, 'ceptin' that there is no such thing as an efficient fireplace (at least not in the US, and the imported European high-efficiency fireplaces are more expensive than a decent woodstove with a nice big viewing window for ambiance.)

Expect to spend a few grand. It's possible to spend quite a bit more for super-high-mass Tulikivi or similar, but that's WAY more than an auxilliary space heater.  A ~50BTU/hr soapstone woodstove will usually come in well under $5K installed if you shop around & dicker, and don't buy more stove than is appropriate.  The selections are fewer if you need something in the sub 35KBTU/hr category, but they exist.

Efficient woodstoves exist though, and most (but not all) have outdoor combustion air kit options. It's important to pay attention to the clearance & material specs on the combustion air piping- more than one fire has been started by embers back-drafted from the firebox into ill-considered PVC piping under high wind conditions. Assume that it's possible, no matter how long the combustion air run.

As with any heating equipment, sizing it properly for the load is key, and rampant oversizing seems to the norm, leading to higher soot emissions, lower efficiency, and the need for more frequent flue-cleaning.  If anything, undersized for the peak load is better.  That's triple-true for inexpensive cast iron & steel stoves which can turn the place into a sauna in under an hour if oversized, and can't be throttled back to a comfortable level without smoldering, and will yield uncomfortable under/over shoots on temp if fired intermittently. High mass ceramic & soapstone woodstoves can be intermittently fired at efficient burn rates, letting the thermal mass of the stove dampen the under & overshoots. 

Heating with wood on a regular basis takes some user involvement/interaction, but if it's just used for auxilliary heat during cold snaps, loading it up for the overnight burn is pretty straightforward- most people can tolerate some amount of overheating on a zone when its -5F outside, if it happens to be oversized for the zone.

What about a small, efficient wood stove in the basement that feeds in to the geo when auxiliary heat is needed?

A wood boiler + a water tank will store much more heat and provide for even and controllable distribution of it. Better than any non hydronic wood stove and without you needing to get up in the middle of the night.

Not disagreeing here or anything
1.There are not many woodstoves
in this list with 80% eff and 50k BTU OUT.
http://www.epa.gov/compliance/resources/publications/monitoring/caa/woodstoves/certifiedwood.pdf

2. A stove or fireplace is the master, not the servant of the homeowner:}
Someone who may never have been a frequent operator of a woodstove might not have the skill to get the most out of a stove. My personal experience is that it took me plenty of fires before that stove was in the red coal and hot and efficient stage.

3. Mass Fireplaces are a possibility; no first hand knowledge here. The use of thermal mass makes this burner interesting. They can burn quite cleanly.

http://www.epa.gov/burnwise/fireplacelist.html

4. Using a stove to purposely vent an area with controlled air entering through passive vents such as a Panasonic model FV-GKF32S1, is acceptable (again with my opinion:})

The EPA list only has placeholder default minimums for the efficiency, does not test the efficiency nor BTU output, only tests the soot emissions once up to temp using a standarized fuel & procedure. (That is stated directly in the EPA literature.)

The manufacturers DO test the combustion efficiency of their stoves- those figures appear in their sales- literature, and they can usually produce the independent lab test data to back up their numbers when pressed. (When competitors think anothers' claims are BS they can and very occasionally will pay to have the competitors' numbers checked with independent testing, but I suspect that is extremely rare. Independent test labs have a lot on the line for getting it right before issuing a report to a manufacturer.)

50+ KBTU/hr stoves that test over 80% are often listed by the EPA as 63% & <35KBTU/hr. for example, the Hearthstone Heritage model 8021, (the beast I have in my own home) has been independently tested to support a claim 55KBTU/hr continuous output capability and and average 81% steady-state efficiency when up to temp. It can actually be fired hotter than that if you keep it maxed out using dry pine or something, but running hotter than 55KBTU/hr regularly voids the warranty, since it would consume warp the after-burner tubes, etc.. The EPA list gives that same unit a default untested 63% efficiency & 11,700-32,800 nominal firing rate, but a fairly stingy & tested 2.7 grams/hr soot emissions.  I accept the tested efficiency & BTU numbers of the manufacturer's contracted test house over any  default place holder numbers on the EPA list (which are typically based on the size of the firebox or something.)

Bottom line, neither the firing rates nor the efficiency can be gleaned from the EPA emissions test lists, and the manufacturers' claimed efficiency is usually correct & verifiable. But the efficiency YOU get out of it relies heavily on keeping it at some minimum stove temperature, and using sufficiently dry fuel.

SFAIK there are no woodstoves currently manufactured in the US with internal hydronic coils. There are retrofit kits (eg Hilkoil), but intstalling one voids the warranty & safety agency ratings of the stove, which may impact the code-legality & insurance-liability of the final assembly (varies by jurisdiction.)

Yes, there is a learning curve to the operation of a woodstove, but most non-catalytic EPA rated woodstoves are far easier to deal with than the goods available 25 years ago. It doesn't take a rocket scientist or combustion engineer to get there.

Passive inlet vents aren't really necessary for combustion air for tight woodstoves and will not prevent a woodstove that is drawing it's combustion air from conditioned space from backdrafting into the conditioned space under all exhaust-venting & wind load conditions. Tight homes would normally have an ERV or HRV, which presents a fairly substantial makeup-air cross section (many times that of a ~5 square inch passive vent like the Panasonic FV-GKF32S1) for neutralizing the depressurization of high cfm bath/kitchen/dryer exhaust vents.

Mass fireplaces/stoves ( like the aforementioned Tulakivi series) make great heaters and do burn cleanly, but that's a whole other subject. They're definitely not an appropriate intermittent use auxilliary heater, since even getting them up to a temp where they are emitting a substantial amount of heat into the room takes several hours. (Also getting one installed for under 10 grand can be tough, and 15KUSD+ isn't unheard of.)