Most Efficient In Home Heating

I spent a lot of money on my new boiler setup, but it would have been 2x that to go geo. Then I would have had seriously increased power bills for the rest of its life. So I decided to max out my time left on this earth by investing it in free fuel for as long as I'm able to do it. Then I can always switch fuels on the boiler if I just can't do wood any more. Or invest in the ever-increasing efficiencies of mini-splits or whatever else might be on the horizon.

Our geo system was about the same price as a conventional system. If I was to get A/C and a oil or propane system the cost for geo was nearly the same probably within 1-2k in the end. I quoted everything. I did have some wild quotes when I had companies come out though for geo. Some were 40% more then others. A lot seemed to depend on whether they were digging wells or trenches wells were significantly more. We have trenches.

The highest quote we had was 33k the lowest was 17k after tax breaks for a geo system. A new boiler install would have been 8-10k while A/C and ductwork would have been 6-8k. The decision was pretty obvious when I had companies come out and compared costs.

As advised earlier in this thread, a new house in a place like Wisconsin really ought to be superinsulated, if only for the sake of comfort. Depending on what's envisioned in the way of size and shape, it can be shown in many cases that the relatively little extra cost to make it superinsulated, amortized over 20-30 years, is less than the savings in heating cost, so it could well be sound economic advice as well. But comfort alone is enough to tip the scale.

With a superinsulated house, a "geothermal" (ground source) heat pump (GSHP) can make a lot of sense, particularly if either the digging of trenches for ground loops is easy (cheap) or if a new well must be drilled anyway for domestic water supply and the quality of that water is good. While a heating system that burns a fuel doesn't come in progressively smaller sizes as the design load is reduced, a GSHP does. For a superinsulated house, that would be a quite small system. Your 1800 sqft of house is half the size of mine (around 3700 sqft net conditioned space, on two levels), in central NH (CZ 6). It's superinsulated, and it's heated by a two-ton GSHP. Last winter it kept the house warm while running in just first stage. For the electrical power it used, the heating season cost me less than $600. The extra cost for GSHP vs a propane system zoned the same way might well have been recouped by now, and I get cooling with humidity control all summer as well. For my situation, geo was a good fit. I suspect it would be a harder sell for a house of "ordinary" construction.

I do have a small woodstove in the lower level (Quadrafire 2100 Millenium; 11-28 KBTU/hr firing rate), mostly because I like watching a wood fire in the evening. But it does provide backup in the event of a prolonged power outage. We actually used it to heat the whole house in the 2010-11 winter when the crew was finishing the interior, before the GSHP was installed.

In my area, I had little hope of finding a builder with experience in building this sort of house. But I had done my homework over the years, knew what I wanted, down to small details, and designed the house accordingly. I found a local builder who liked "different," understood that this house would be quite different from anything he had built, and was eager to work with me to get me what I wanted. I particularly didn't want a builder who didn't want a homeowner telling him how to build a house, something he had been doing for the last 30 years. I didn't want a house built the way it was done 30 years ago. The arrangement worked out very well, and the house came out the way I wanted. Actual performance in bitterly cold weather has been slightly better than my heat loss model had predicted. If you are willing to invest a lot of time reading up on the subject, looking at sites like www.greenbuildingadvisor.com and www.buildingscience.com, you can specify your own exterior shell design and insist on the actual construction accomplishing that. But you have to be very involved throughout the project.

Why not a corn burning stove? Ours burns corn, wheat, wood pellets and other stuff. This year we can get wheat for almost nothing - due to infections in the crop. Can't be fed to animals or people but burning poses no problems.

Corn/wood pellet stove backed by Propane and a few portable 'radiator style' plug in electric heaters do us well in Northern North Dakota. Our propane heaters work just fine when the power goes out - a major consideration during winter storms. Doesn't take long at 20-30 below zero for problems to surface when the electricity is off.

As the OP was trying to minimize grid use, what about incorporating a wood burning rocket mass stove as primary? These are incredibly efficient and inexpensive to build. Besides all the solid tips above, I'd also consider the core principle of a smaller home if it's an option. That, an insulated slab, minimum of glass and maximum of passive solar features would make for a super efficient home. I doubt you'd need even a cord of wood for a 1500SF new home built right.

Bill Zelman
www.Hot-Tubes.com

Recently completed construction and test installation of of a rocket stove type heating system.....The rocket unit supplies hot combustion gas to the system while generating radiant/convective heat to the surrounds......Gas then exits rocket unit via a crossover tube and enters a secondary heat exchanger/heat bank before exhausting....Secondary exchanger is actually a rebuilt, resealed cast iron stove affording three effective passes for exiting combustion gas....Test burn results (averages) as follows: Top plate of rocket unit---695 deg. F avg., Rocket casing---578 deg. F avg., Crossover tube---525 deg. F avg., Cast iron stove shell---275 deg. F avg., Exhaust outlet---145 deg. F avg.

Unit incorporates a Tjernlund AD-1 draft inducer to assist with cold light-offs and to counter adverse wind (pressure gradients) conditions respective of the through-wall exhaust configuration.

Unit was designed to burn any quality/type of wood and will undergo exhaustive testing this winter to determine fuel consumption, thermal output and overall operational characteristics/flaws.....Theoretical maximum fuel consumption is 1/4 cord per season (6 months).....I've included a photo of the complete unit in its current test configuration.

Regards,
Chief72

In the picture it looks like aluminized bubble wrap on the walls......isn't that combustible and very close to the radiant stove?

I don' t think you'd heat much of a space with 1/6 cu.ft. of wood per day.

Edit: there must be some condensation in the flue too?

Manufacturer's specs. rate that specific insulation for 180 deg. F max.......There is no fire rating given for it.....Before installation I subjected samples of it to some rather rigorous testing in the shop......A propane torch flame, directed at it from a distance of 6" only managed to melt it.....It took direct contact from the flame to initiate slow combustion of the plastic......Not to say this is the best stuff to use in a residential (or any) setting.....Stone, concrete or non-combustible backer board would definitely be more appropriate not to mention "code-worthy"....Bear in mind that the unit is currently being tested under shop/lab conditions by a qualified/trained engineer.....The test parameters require walls and ceiling to be covered with a material capable of reflecting radiant energy....To that end, the FBF insulation turned out to be the most cost effective expedient....To date, I've had no issues with insulation degradation during testing BUT time will tell.....BTW, that secondary HE is 12" from the insulation and runs at 225-275 F; a good litmus test for the FBF.......Future plans (if this system proofs out) are to encapsulate the unit inside a fireproof, insulated, reflective plenum chamber and duct the heat to the desired location(s).....All of that said; thanks for your safety concerns.

Regards,
chief72

maple1 said:

I don' t think you'd heat much of a space with 1/6 cu.ft. of wood per day.

Edit: there must be some condensation in the flue too?

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Theoretical fuel consumption is what the tests will prove or disprove.....To date, it appears as though the unit will operate (fire) on a 20% duty cycle......By that I mean that once up to operating temperature (about 20 minutes) it will be fired for a 15 minute interval then shut down for a 60 minute interval....15/75=.20.....The heat bank located in the rocket unit along with the secondary heat exchanger's mass will give up their stored heat during the "down-time".

Condensation is one of the issues that will be addressed during testing......So far, no condensation or precipitation has been noted anywhere in the system....Third stage combustion temperatures in the rocket generator are running about 1,800 deg F and appear to be generating 100% quality exhaust gas.

Um. Looks like the (single wall?) flue pipe is penetrating the wall adjacent to a combustible material (bubble wrap). A chimney fire in that flue, and the plastic in contact with the flue will go up. Whether that flame spreads to engulf the entire space will depend on the fine engineers at the reflectix corporation of america.

And, whats behind the bubble wrap....more combustibles?

Kudos to analyzing the feasibility of a rocket stove type heating system.

But if the stats are intended to represent something close to a final production stove, they just don't add up.

Exhaust outlet---145 deg. F avg. *** Unit was designed to burn any quality/type of wood ....Theoretical maximum fuel consumption is 1/4 cord per season (6 months)

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1/4 cord of oak at 20% MC has about 6 million btu's (or make it 8 million assumed for 145F stack temp compensation). That's 33-45,000 btu's/day over a 6 month period, or 1,400-1,900 btu/hr. And since the stove is designed for any quality/type of wood, for oak reduce that by about 50% for green wood, and if the wood is pine, reduce the dry/green btu's another 40%. That might be enough btu's to heat a single room in a cool/cold climate. Keep in mind that a 1500 watt electric heater (near 100% efficient) provides about 5100 btu/hr, about 3 times the maximum btu's the rocket stove is spec'd to provide. I don't know of anyone who can heat a house with a single 1500 watt electric heater, and the rocket stove design only provides maximum about 1/3 the btu's of the electric heater.

Next is stack temp - keeping in mind that the rocket stove is intended to burn any type/quality of wood.. The vaporized water from boiling off water in the wood (seasoned or green) and from combustion has to go somewhere, and that vaporized water at 145F going into any chimney in a cold environment is going to condense to liquid -- a matter of physics, not stove design.

So, interesting concept but at this point I would have to conclude not practical or feasible.

Hang in there chief72. Your system has created an interesting discussion. Its easy to pick on the work of others.
I myself would be concerned about the use of what appears to be galvanized flue pipe where it might get hot enough to create the potential for zinc metal fume fever. In general we're a safety-oriented bunch so you'll need to endure those criticisms first before the technical aspects can be discussed.
You may want to start a new thread though to avoid hijacking of this one.

jebatty said:

Kudos to analyzing the feasibility of a rocket stove type heating system.

But if the stats are intended to represent something close to a final production stove, they just don't add up. 1/4 cord of oak at 20% MC has about 6 million btu's (or make it 8 million assumed for 145F stack temp compensation). That's 33-45,000 btu's/day over a 6 month period, or 1,400-1,900 btu/hr. And since the stove is designed for any quality/type of wood, for oak reduce that by about 50% for green wood, and if the wood is pine, reduce the dry/green btu's another 40%. That might be enough btu's to heat a single room in a cool/cold climate. Keep in mind that a 1500 watt electric heater (near 100% efficient) provides about 5100 btu/hr, about 3 times the maximum btu's the rocket stove is spec'd to provide. I don't know of anyone who can heat a house with a single 1500 watt electric heater, and the rocket stove design only provides maximum about 1/3 the btu's of the electric heater.

Next is stack temp - keeping in mind that the rocket stove is intended to burn any type/quality of wood.. The vaporized water from boiling off water in the wood (seasoned or green) and from combustion has to go somewhere, and that vaporized water at 145F going into any chimney in a cold environment is going to condense to liquid -- a matter of physics, not stove design.

So, interesting concept but at this point I would have to conclude not practical or feasible.

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Hey, I already said all that - I just put a Coles Notes spin on it.

Seriously, it's nice to see people trying to advance the science of wood burning, and I can appreciate that a test setup can be far from what some final version might look like (talking scale & safety things), and you might be on to something overall - but some of the things you stated just don't pass a first smell test. Such as, being able to efficiently burn any type of wood (and without condensing at the temps you posted?), and keeping anything beyond the size of a small room warm for 6 months of winter with 1/4 cord of wood. The BTUs just aren't there in that much wood - let alone wet or green wood.

Would like to follow progress though, and keep at it.

Absolutely outstanding.....Didn't expect such a volume of constructive input to my post this soon......Many thanks to all.

Let me address a few issues/concerns:

Safety: This project is being conducted in a controlled, industrial environment....The unit is actually set up in a test cell that was formally used to house my hydrogen heat treating furnace....The cell itself is constructed of 8" reinforced concrete (like a pillbox) and equipped with numerous safety/monitoring features designed to suppress fire, evacuate fumes and relieve excess pressure....Since this is a prototype project, there are still LOTS of variables to be explored; many of which could present serious safety issues....Definitely NOT a project for hobbyists.

Unit construction: Insofar as the unit is a prototype, a great proportion of the material utilized consists of short ends, drops and various components left over from other jobs....Semipro voiced concern about the use of galvanized, single wall duct pipe/fittings for high temperature application....The photo is somewhat deceptive in that respect....The duct pipe/fittings were actually fabricated from 30 gauge, T-316 stainless sheet....Having a completely equipped fabrication/machine shop at my disposal is very advantageous.

Operating parameters: Lots of input here from folks who have obviously been doing research in this area.....Several have commented on the unusually low exhaust temperature with regard to precipitation/condensation in the breaching duct.....The 145 deg. gas temp. occurs ONLY when the draft inducer is in operation....Once the unit attains operating temp. (15-20 minutes) the inducer is shut down, flow/pressure stabilizes and the system goes into natural draft mode.....At that point, the breaching temp. stabilizes at approx. 220 F.....The AD-1 inducer is designed for 5"-8" round ducting and is well over-capacity (at its lowest speed) for this system....In order to compensate for this, I installed a bypass system on the suction side of the inducer to lessen the effective air flow.

Fuel quality/consumption: Everyone's arguments regarding fuel and its calorific content are consistent with facts/statistics/science.....I'll be the first to admit that I'm bucking the tide on this issue.....Hopefully, the design/construction of the rocket unit will get me close to that "1/4 cord goal"....The 20% duty cycle I mentioned is an absolute worst case scenario....Previous test firings indicated that the heat banks (primary and secondary) effectively retain/radiate for almost 3 hours once the fires are extinguished.....After 2 hours of downtime, the outer casing of the rocket unit registered 250 F in an ambient environment of 75 deg. F.....How this will all shake out remains to be seen....For testing, the heat will be force-ducted from the test cell (10' X 15' plenum chamber) into my 750 SF office area which is moderately insulated....I plan to have Bermuda shorts as well as my woolies and a parka handy during the testing phase just to cover all the bases.

Best regards to all,
chief72

chief72 said:

Semipro voiced concern about the use of galvanized, single wall duct pipe/fittings for high temperature application....The photo is somewhat deceptive in that respect....The duct pipe/fittings were actually fabricated from 30 gauge, T-316 stainless sheet....Having a completely equipped fabrication/machine shop at my disposal is very advantageous.

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Great -- just what I needed, another poster here who's fabrications skills and facilities I can drool over.
Seriously though, I'm impressed and love it when this type of stuff is posted.

semipro said:

Great -- just what I needed, another poster here who's fabrications skills and facilities I can drool over.
Seriously though, I'm impressed and love it when this type of stuff is posted.[/quot`

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LOL, Semipro.....I spent almost 50 years learning the trade disciplines and building up my shop/business.....Still learning more with each passing day.....A few years ago I closed the doors but retained the shop and most of my equipment.....Retirement has allowed me to work behind closed doors without the day-to-day concerns associated with management, help and clientele.....Now I can concentrate my efforts on a few projects that I feel are intrinsically worthwhile....If this heater project bears fruit, I plan to make the design available in the public domain......That way, anyone may feel free to build their own or to improve upon my original design.....To do other at my stage of the game (IMO) would constitute wanton negligence and greed.

Not that I care, but you will miss the basement. It is cheap space per sq. ft. It cost very little to heat a basement. I live 20 mi. south of Fon Du Lac so I am a bit less cold than the poster. I do live in open farm country and it is not so much the temps as it is the wind. I have a 12 course basement (8') basement walls and 9' walls on a 2200 sq.ft ranch house so I am not much bigger than your house plans. I went with 2x6" walls with 4-5" of closed cell foam. I went with 2" foam on the outside basement walls, then I studded the inside of the basement with R11 fiberglass. That actually helped very little. I had foam sprayed between the floor joists (3") . Then I had sprayed the space shut between the roof trusses and up the roof sheathing about 4'. I went with 8" energy heel trusses. This is important cause it does away with ice daming. I then went with R60 in the attic. I used Anderson 400 windows? and most were double hung with storms on them. The patio door has a storm that is made from another patio door so I have a thermal pane patio and a thermal pane storm . It is new this year but sure I will notice the difference on a windy day. . Honeslty, The windows use a lot of heat. On a windy night it feels a bit cold and slightly drafty cause the wind blows so hard here by the wind mills. On a calm night -5 and even -10F is a very comfy home. I have an east facing home so sun does not do a whole lot of good. Many say build the house to face the south side with windows. I can't put my house sidways on my 4 acres. I went with an EKO 25 gassifier and have 1000' of 1/2" pex. It is staple up under the floor in the basement. It is very comfortable heat like Jebatty mentioned. The pex is under the kitchen floor (hardwood floor) ,, and under the family room floor ( carpet) , under the front door area ( tile) and some in the master bath ( tile). This woodboiler runs constantly at 160-165 degree temps. I used 4.5 cords of wood to heat and the hot water. 1 full cord was popple and basswood so if it was all good hardwood I most likely would have used 4 cords. In the 2011-2012 winter I used 3.5 cords. The temps in the house stays at at 68-71 dgrees depending on the wind, temps and sunlight.

I'm jumping in late here and skipped a lot of the posts but wanted to share my experience with home construction. We built our home 8 years ago and acted as our own GCs because we could not find a local builder or contractor that would build a custom home for us exactly to our specs and material requirements. My wife and I are meticulous researchers and both had project management experience so we went for it. Like you we wanted to build as energy efficiently as possible and focused on the construction materials to achieve this.

For our exterior walls we went with Insulated Concrete Forms (ICFs). The company we used is TF Systems and they are right here in your state. There are many other ICF companies out there. We chose this one specifically because the sales rep worked with us on site from start to finish of both the basement and 1st floor walls. That included pouring the concrete for us. He charged us an hourly rate, but it was reasonable and well worth the experience and equipment he brought to the table. We ran the numbers for both conventional stick framing and ICF construction and IIRC it was about 10% more expensive to build with ICFs. 8 years later I would not have done it differently. Combined with energy efficient windows and Icynene insulation in our roof, we have the quietest and most EE house around. Our primary heat source is forced hot air (propane) but the cost of heating was signifcantly offset once we installed a wood burning insert.

It may be difficult to find a contractor that will work with ICFs. I can speak from first hand experience that they are not at all difficult to install. Anyone with construction experience should be able to do it. As I mentioned, the sales rep acted as the GC while during the ICF installation. We hired local Amish carpenters to assist with the process and they picked it up on the first day. It took 1 week to install/pour our basement and another week for the first floor. Once they are up, you don't have to worry about sheathing, insulation or vapor barrier steps with the exception of anything below grade. Below grade does require waterproofing and there are more options on the market now than we had at the time. We used a membrane called Platon and it seems to be doing the job fine. I'm sure proper grading plays mostly into this, but we've never had a single leak in our basement. Your house will be so tight that it will require mechanical ventilation. We have an air exchanger (ERV) that runs every six hours.
Feel free to PM me if you have any questions - short summary: build your house with ICFs!

Clyde, What is your heat load on your house?

ihookem said:

Clyde, What is your heat load on your house?

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I'm not sure and had to google the term "heat load". I can give it try if someone can give me the cliff notes on how to calculate it. Glad to do it if you are serious about ICFs.

One suggestion on ICFs , if you have carpenter ants in your area you may want to consider that they love to nest and tunnel in foam.

Not interested in them but wonder what it would do to reduce your heat load. Heat load is a term used at how many BTU's per hr. ya use at -10F .