Hi Bruce,


Interesting thought. I would be greatly interested in a house with close to zero heating costs in NY State myself. I need a vote, if there is enough people here to get a decent return ...

How many people here would not buy a house at market value plus $20,000 because it had no heating bills?

How many would?

If I am selling a house, I am not selling to a universe of buyers, only one. Then the more you sell, the less the number of disbelievers. But as I said before, and I understand if you did not read every single one of these posts, I would leave my gas fired furnace in place for 20 years or until it rotted out from lack of use ... Not chicken, just careful.

I am not saying don't think outside the box. That is how I got where I am now with this house and our HVAC guy stops over regularly to see what I have messed with, most of it increases efficacy, but with no potential for payback.

You may want to look in to what true solar generation plants are doing. They are trying to regulate the "sunlight" by storing it over night to continue to generate 24/7. They are doing this by superheating salt, something like 1200F and then using another heat exchanger to get back to something to make steam for the generators. The losses they were looking at by "storing" the heat as liquid salt were over 50% for the total overnight as opposed to making steam right away. I am not sure why they are trying to store it that way, I think it had something to do with regulation on producing power, silly since we use more power during the day anyway.

Most of the stuff I mess with has no real payback, the geothermal does, solar is a LONG way out, probably the quickest thing with a real payback was the drain water heat recovery unit.

My real point is even if what your talking about could be achieved at what cost? Heck a basic solar hot water system is $20k. The kind of collectors your talking about, the tank, the heat extraction equipment and the complexity of the system, your easily taking $100K, probably closer to $200k for a smaller sized house. Scale that up to a "typical" new construction house and you’re talking $500K. That is where the rub come in, the payback would be 50-100 years. That just won't fly no matter how much it make sense or how "green" it is. Not to mention most people don’t have that much extra $ to buy a house, even if it will come with no HEATING bills. You will still have to cook, run the microwave and everything else. So you still have a utility bill, maybe 1/3 of what it would be with a conventional.

Solar PV is in the same boat right now. Sure I could buy enough panels and batteries and go "off grid" but I don't have $150k to do it, with a payback of about 80-100 years (battery replacement) in my area. If I go grid tie I could cut that almost in half, and I still don't have that kind of extra money sitting around and still with a break even out at 40 years. It just doesn't make financial sense at this point. Our system is really intended as a generator, with benefits :)

Having said that it took a bunch of people going at it alone to get all the bugs out of solar and to get us to where we are now. So if you want to take on the task, go for it. I am a dreamer and tinker, and even this plan is way out there for me.

Hey Brock, does your pool serve as storage?
Anyway, combining storage and heat pump looks even better on closer inspection. A 4 ton water to water heat pump costs ~$5k. Skip the ground loop. Your Uncle Sam should give back up to $1500 of the cost at tax time if you call it a water heater, which it is. With 70 degree input, an FHP pump puts out 110 degrees at a COP of 5. Now you are looking at an effective 25M btu in a 10k gallon tank. My preference in backup would be a cheapo outdoor woodboiler for <$5k. You'd need a two-day burn to reheat the tank. You'd do it maybe twice a season.
On the solar side, the tank is a surprisingly light load spread over 180 days, not counting heat loss. Needless to say both would be happening so slowly you'd want to make sure that the needle moves in the right direction. Add an extra collector to a normal DHW rig to start, and figure $2-3k after credit and rebate.
You'll still spin the electric meter after all of this. But if you can hold the COP at 4 or above, there won't be many people spinning it slower.
While there is no air conditioning in this approach you could put a water to air heat exchanger on the cold side at the expense of adding ductwork.

Yes. I understand the cost is a consideration. But lets remember how this works. The first rezepa joint might cost $200,000 to build. The second $100,000. Then lets say we figure out a crome plated feegle joint works half as long as a gold plated, but costs 1/100 of a gold plated ... The first one we are not *real* concerned about the cost, but we are real concerned if it *works*. I mean works, not wishful thinking. If works becomes part of our vocabulary, then reducing build price is the next. The biggest part of the cost I see here is the excavation. Thats fixed. After that its possibly heat exchangers, insulation, radiators, pipe, mag glasses, and circulation pumps. I really have a problem seeing this going over $20,000. Thats about 20 years of gas bills for me. Without gas price increases over the next 20 years. The problem is, if you havn't replaced that gas heat with something, the gas bills are an anchor around your neck. If you can build something like this, your gain increases every time gas prices increase.

Hey Brock, I remember that 1200 degree salt and heat exchanger. Wern't they heating that with solar in the midwest somewhere? Couldn't we do a small scale of that? They were generating quite a bit of electricity with that wern't they? There are major losses in steam, but they don't care. Could you imagine reducing that to 600 degrees and heat exchanging with your house heat in the winter? Can't we do that? How expensive can stainless steel pipe be? Ouch. Is there such a thing as 600 degree rated plastic pipe? Chromed steel pipe? No, chrome and salt do not mix. Teflon lined?

The PassivHaus approach is well modeled and proven, would be about a 15-20% cost adder to a house in most NY State climate zones (less, on Long Island.)  The key to their success is to spend the money on insulation and paying close attention to all thermal leakage paths, and incorporating a modest passive solar aspects.  Since the houses don't genrally need heating systems beyond a small amount of resistance electric money that would have gone into more complex heating systems are applied to the thermal envelope at the design phase.

The Riverdale Net Zero house in Edmonton Alberta was arguably more complex & expensive than it would need to be for NY climates, but they utilize a creative method of using a small heat pump for drawing heat out of a moderately large heat storage tank operated at well below room temp to supply heat to a hydronic coil in the ventilation air supply, as-needed. The advantage of lowest-possible storage temperatures is that it allows the solar collectors to operate at very respectable efficiency even at 0F & lower outdoor temps.  See:  http://www.riverdalenetzero.ca/Home.html  and http://www.cmhc-schl.gc.ca/en/inpr/su/eqho/rinezepr/index.cfm In your application, by running the storage at low temp the delta-T driving the heat loss is low, and you could get away with less insulation on your storage.

The economics of solar and larger-scale thermal storage tends to favor spending the money on better thermal envelopes than more solar or more thermal storage, but in retrofit apps the balance point shifts toward solar somewhat earlier, but achieving net-zero will alway be more expensive when it requires more solar.  It's a heluva lot easier to unsulate to high R value under the basement BEFORE the thing is poured than after, eh?  You can add another R20-40of iso or EPS of above the roof deck &/or similar amounts of spray foam under the roof deck, but it's a lot more expensive than blowing R100 cellulose or fiberglass into an energy-heel framed structure designed to accomodate it, and walls can sometimes be nearly-impossible to convert to high-R as retrofits. You'll be continuing to use your gas-fired heating appliances for some time to come no matter what else you do, but with a much-improved building envelope you can use it a whole lot less.  The size of the solar systems required to support the loads of a lesser building envelope are quite substantial, no matter how much thermal storage you think you can build into the system (even if the storage is quite cheap.)

Have you calculated your annual thermal load of the existing house based on fuel used & presumed efficiencies of the applances?  That would give you at least a minimal handle on the minimum size of the solar array, and put a marker at the required peak storage temps for the given volume assuming zero thermal loss (and you'd have to derate it from there based on more realisitic losses from storage & distribution.)

I do not understand why the industry still builds houses the way they do when much improved techniques are proven. Building codes had to be written to move from 2X4 exterior walls to 2X6!! Intelligence wasn't enough fer crying out loud! Thats the problem with us science types I guess.

However, I am looking at after the fact installations, where people already own houses made from mud and straw, and do not want to start over with a $150,000 house to get cheaper heating bills. On that note, my house is a perfect example. It was built 20 years ago using old oatmeal boxes and Scotch tape, so I am about the worst case scenario you can imagine. If I am successful at bringing the heat bills to zero here, the point is made. Hey, anybody could do this the *easy* way!

Now, la la land. I would like to build my house 20 feet underground. Once the ground temp was established, and the ground was insulated secure, the heat would rarely have to run. I would have to provide emergency egress points, solar tube lighting with electrically operated lights for evening hours, just like a normal house, an elevator, a couple of flat screens in every room to simulate windows, (hooked to the internet so my living room could be next door to the hills of Scotland) fire security in the kitchen, air / heat exchangers to provide fresh air, and a very intelligent computer system to monitor conditions like air quality, temp control, light control, and this goes on and on but it is fun. Maybe serious some day. The thing would be an intelligent machine. I love machines ...

I dunno, 20 years ago they at least put some oatmeal in the wall cavities for insulation before they scotch taped it all up.  I have a pretty good imagination, but I don't even need it:  I'm personally quite familiar with several houses built 60-80 years ago devoid of any cavity insulation the walls, with owners too cheap or too cash-poor to upgrade 'em with some blown cellulose, even with substantial subsidy. Yours is hardly a worst-case, it's not even close!

But the fundamentals don't change- with the building envelope as-is, the annual heat load is calculable, and the amount of solar collector & storage required to support that load is also calculable.  Start doing the math, and you'll see just how tough it really is to do the whole shebang on site-available insolation at ca. 1990 vintage insulation levels & tightness, even with 10K gallons of thermal storage.  Retrofitting the envelope to cut the load by 50-75% using judiciously planned & staged upgrades is likely to be the cheaper path before active solar becomes the next-most cost effective step, at which point the size & cost of the solar required has been cut 50-75%.

Living in a subterranean cave 20 feet under you still have a heat load, and in cooling dominated climates it's still quite substantial.  Subsoil temps in MN are well below 45F (the outdoor temps at which people in Miami start dropping like flies! :-) ).  Even by me (central MA) it's around 50F.  The only thing you get by going deeper is year-round consistency- the heat load is still there, but it's now a constant throughout the year as opposed to a wintertime phenomenon.  It's still a function of the delta-T, R-value, and surface area of your subterranean thermal envelope.  How often your heating system has to run is a function of that constant heat loss.

But if you're using big flat screen TVs for windows, at 300-500watts screen, you already have your space heaters built-in, eh? :-)

Zero heating bills are a demonstrably realizable goal in much of the lower 48, but it's far more about insulation than it is about thermal storage or solar gain.  It's expensive, but well under $150KUSD even as a retrofit if you do the math and design it right.  (But it's well OVER that if your plan was to put up a bunch of photovoltaics & batteries to run heat pumps on a 1990 code house.)  Just throwing ever more solar-thermal & thermal storage at it would also be very expensive.

A few things that you may have considered:
What does the EPA have to say about your use of an old oil tank? (there's a reason they're digging it up)
What is the groundwater situation 40 feet down? Any groundwater at all will suck your heat away fast.
You keep mentioning very high temperatures as if they are good - are you sure you want very high temperatures? (which I think you understand is not the same as high heat)
Can you get more heat out of a 10 x 10 freznel lens system or a 10x10 flat plate collector?
How do you get a refrigerator in a 2'x2'x2.5' (10 cubic) foot room?

Hey Greg ... 10 cubic feet! Sorry about that, it should have said 1000! Gawd I love math!
Now, to the meat ...

The company that removed it had told me they must meet the EPA rules before they could despose of it. I was told that I could not use it for potable water, but that was the only limitation as they had removed all gasoline from the tank as they were required to by law.

The delta computations are what make high temps an issue, but past this, high temps are a point of reference thing. The delta issue.. Higher temps allow for a smaller storage area. So I have to figure a way to balance the temps with storage area size. The larger the storage area, the lower I can go on the temps. I would love to go with 72 degrees F, but I think the area necessary to do that would be diffucult to say the least. Or, to million degrees if I used something the size of a thimble. But I am going to experiment with a 10,000 gallon fibergless tank. I will shoot for about 200 to 250 degrees F and see how long that gets me into a cold season, then after, I will modify the parameters to meet my goal of free heat for the entire season. And understand, that may mean installing another tank to keep stored temps down.
Absolutely. In my application here, the ground is shale. The water traveling through this shale is zero. (To be verified). If this were not the case, I would have to be sure I sealed the field where I was burying the tank just for that reason. And that would increase the hole size, by educated guess, by about ten times if the water is in great amounts. But very few solutions solve all problems.
>. My thought is that a flat plate collector can not increase a 90 degree sun temp beyond 90 degrees while a fresnal lens can greatly exceed those temps. This does not create energy because it will take much longer to heat a cubic foot of water to 200 degrees than 90 degrees, but if we need 200 degrees the flat plate collector would be useless. Your thoughts?

I'm still worried about that tank. They may satisfy the EPA that they've drained it but will they actually scrub all the gasoline from it and purge all the vapors or are they just getting out the bulk? It would take very expensive equipment to scrub the tank of all gas residue because it would have to be inert while doing so and you would need special powered air teathered moon suits.

I know once it's clean then it's just a tank but people are very concerned about buried fuel tanks these days. You practically can't give away a property that has one unless it's a very prime location because the potential risk of a huge remediation expense is too great. You would need to figure out what all documentation you might need down the road that will satisfy all that might be concerned in the future: Future buyers who would be worried about the presence of an old fuel tank on the property, the EPA 20 years from now when someone says there's an old fuel tank on the property and you have to prove it's ok, and very importantly your Insurance Company.

I just don't want that "free" tank to become a financial millstone around your neck.

Have you tried calculating how many btus of heat you'll need for a winter and work backwords to determine how to get that many btus in your tank and how big of a collector you'll need to harvest that many btus from the sun??

Another thought is that your property is a giant solar collector that is bigger than any collector you could fit on your place, it serves as it's own heat storage chamber and best of all it's already there. Run some piping through it and extract the btus the sun put there. The temps will be a little low but the heat is there and a heat pump can up it to a useable temp. And if you need A/C you can pump those btus back into the ground.

Thanks Greg, I think I will heed your warning and contact the EPA directly to check into this. I will post the answer when I find that out.
The BTU requirement is one of the steps I must do before I break ground. It will be how I determine wether I need one collector or twenty. More calculations pre ground break, but I have about 60 days to get it that far. I do have a few acres to work with here but I am hoping the surface area of my roof will do the job. Two reasons here. Let me explain a bus I saw from the middle east that validifies my ideas. This bus had two roofs. A regular roof, and another open on all sides on top. The top roof collected the sunlight and the air moving through it dispersed the heat, keeping direct sunlight off the under roof, greatly reducing the heat inside the unairconditioned bus. Because there are no trees around my house to shade it in the summer, our AC bills are as bad as our winter heat bills. By using the roof as the solar collector mounts, I hope to reduce the heat build up in the house in the summer. If I only cover half the roof with solar collectors then I might add a 'second roof' over the remaining roof to complete the solar barrier.

OK I spoke with both EPA as well as DEC, and the general consensus is that as long as the contractor licensed by the US Gov to remove these tanks followed protocol, they will not introduce any dangerous elements into the environment. Now, with that said, might this cause someone to not want to buy a house without heating bills in Western NY? Possibly. But in my case, I am not in the real estate market, but I am big time into the natural gas market ... not as an investor, but as a consumer. The savings over a twenty year period might exceed the propertys value if gas prices skyrocket. Property value loss? Not that important to me.

Tim, your house should already be functioning like that bus. Your insulated ceiling is roof 1 and your roof is roof 2. You just need to make sure you have adequate ventilation between roof 1 and 2. So make sure you have enough clear soffit vents (they often get blocked with insulation) and enough ridge or turtle vents near the peak.

Solar collectors on top should certainly cut down on heat radiating into the attic

Glad you spoke to EPA and DEC. So is this tank going to be scrubbed clean of all residue before they give it to you or just drained of liquid?

No, they had to scrub it before it could be transported on the highway, so it was EPA approved before it even showed up on my property, as the people selling it said it would be. I have the receipt from them stating it was prepared as such and I think I will keep that with my deed. Can't hurt.

The attic vent thing here in the summer is probably the most notorious energy waster here in the North East. These vents work well in the summer, but work equally well at venting heat in the winter. No one ever closes these things off when it gets cold, so that whole Delta T thing sucks energy out of the living space in the winter. My construction however has no attic. The ceiling in my house peaks right up to the center rafter with only the maybe 6 inch if I'm lucky, of rafter between me and the first layer of snow. In the summer you can feel the heat radiation from the living room ceiling. Adding a solar shield has got to help in this case. I am hoping to rebuild this house just before it falls down around our pointed heads! <;-P

Can there be any off-gasing inside the tank of fuel that was stored in it? I have been told that the gas seeps into the metal and can be released later. I dont know combustion temps but with welding being done?
I will say I like your attitude and even though I am uneducated I have never liked the word "CANT". I have preached to many younger and older people about that stop you in your tracks word. Most people let that word alone rule thiers lives. Good luck with your project and who knows you may change the world with something that hasnt even been thought of yet, maybe some small something you have to design to just hook a pipe up? Who knows? We have all at some point in our lives thought/knew we were right/correct about something only to see we were so obviously wrong, that can also work the other way around. Good luck !!!

Hey B Edwards,

This tank is fiberglass, but I think you are correct about some metals and off gassing. EPA says these tanks can be cleaned and deemed safe for landfill.

My personal philosophy. The two strongest words in the world, whatever language, “I can't.” The two strongest, “I can.” I can does not guarantee you won’t fail, while I can’t guarantees you will.

I knew a man who held a doctorate in nuclear physics. His Fiat got a flat tire, and he snapped off all four lug nuts trying to change it. (A big smart guy!) He was educated much more than I, however I know a Fiat has left handed threads on the passenger side! Do not let someone else’s education intimidate you. Only God knows all! But because you could be wrong, be humble!!

Sounds like you have the tank situation all in order. Definitely save that documentation.

The key to a ventillated attic is having good insulation - then the attic temp in the winter really doesn't matter. It sounds like, in essence, your solar shield will be the same as a well ventilated attic. The key

Keep us updated on your project.

While true, I'd elaborate on the "good insulation" bit:  The air infiltration into the attic & insulation layer from the conditioned space below has to be very well controlled, or you'll have condensation, wet insulation & rot on structural timbers at some attic temps.

As for physicists & broken lug nuts- don't under estimate those who can to the math but not the plumbing.  I once took a summer job modeling solar wind stuff for my thesis advisor, and met a highly respected tenured professor (a cosmologist) in the same building who we'd lunch with often.  During a lunchtime conversation we discovered he literally couldn't understand how a water pressure reducing valve worked when presented with a simple diagram on a napkin, but with a formula using spring constants was placed in front of it the lights came on.  I'd never hire him as a plumber, but I'd trust him entirely for coming up with a 2nd order partial differential equation that modeled the problem well.  (His lunchtime feedback on some of the problems I was working on was quite valuable, and made a difference in the speed, accuracy, & clarity with which the data could be analyzed numerically.)

Conversely I wouldn't trust the plumbers & tinkerers to come up with cost effective solutions to energy gain/loss/storage if their grasp of the fundamental phyics of the problem was fuzzy and they couldn't quantify the problem to even an order of magnitude.  Without good physical intuition they're too likely to miss something really BIG.  Do the math- math is your FRIEND!  And while there's plenty room for creative thinking on these problems, bear in mind that a lot of very smart & creative people have been at it for a long time, many have published their work, and much is available online. There aren't enough hours in a lifetime to be spending them barking up trees that have already been assessed, so it's good to read up on things before investing a lot of time & money.

Hey Dana,
*There aren't enough hours in a lifetime to be spending them barking up trees that have already been assessed, so it's good to read up on things before investing a lot of time & money.* There is wisdom and truth here ... but. Barking up a tree is the study time your Prof did that allowed him to understand the math he mastered. The ‘plumber’ drawing the valve needs his intrinsic abilities that will not require strong mathematics. So we may not actually require the mathematician, however we must have the plumber! Mathematically he might be barking up the wrong tree from the mathematicians’ point of view, but the dog (plumber) and he are looking at two different animals in that tree, they just don't know it! So is the dog really wasting his time, just because we cannot see what he sees?