My grandfather, William L. Holladay, was a refrigeration and cooling engineer. Decades ago, he wrote a pioneering, speculative article on ground-source heat pumps, “The Heat Pump: What it does, and what it may do someday.” The article appeared in the October 1948 issue of Engineering and Science Monthly. (For a basic explanation of how a heat pump works, and the difference between an air-source heat pump and a ground-source heat pump, see Heat Pumps.)
Even back in 1948, my grandfather realized that the Achilles’ heel of ground-source heat pumps was their high cost. He wrote, “To use earth heat, a hole must be dug, and the cost, while not always predictable, will surely be high: maybe from 25 to 50 per cent of the entire project.”
In the six decades since my grandfather’s article was published, engineers have not given up on ground-source heat pumps (GSHPs). Among those who remain enthusiastic about these systems are a group of true believers who are convinced that (a) this is a wonderful technology, and (b) there must be a way to bring costs down.
Ground-source heat pumps are still expensive. One fan of the technology, Brian Clark Howard, has provided the following guideline to system costs: “In our book Geothermal HVAC, my co-author, Jay Egg, crunches the numbers for a typical homeowner, based on his 20+ years in the business. For a home geothermal system, he estimates the total installed cost at $42,000.”
This estimate is similar to those made by two installers of ground-source heat pumps from Maine, Jeff Gagnon and Jim Godbout. In an episode of the Green Architects’ Lounge series on the GBA website, Gagnon estimated the cost of a residential GSHP system (including the cost of a drilled well) at $30,000 to $42,000, while Godbout gave an estimate of $40,000 to $50,000.
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Is there any new equipment coming down the pike? I've always figured I need a GSHP like I need a hole in my head, but if there's a reason to reconsider I'd be interested. Jim Godbout & I have had many conversations on the subject - my sense is he doesn't typically recommend them for residential.
Response to Dan Kolbert
Evidently the irony in my chosen title is a little confusing. I guess it's time for me to add a paragraph or two at the end of the article to warn readers away from GSHPs in residential applications.
I've added a P.S. I've made my conclusions explicit in the new section at the end, "These systems don't make sense for homes."
Utility Room Size
I don't have any direct experience with GSHPs. One thing that always shocks me about these systems is the sheer size of the equipment---and the space requirement for that indoor equipment. Kind of evokes the old basement furnace look. Retro-techno-groovy . . .
I wonder how often the additional square footage costs are included in the calculation?
Heat pump efficiency exaggerations aside, if you are working to reduce square footage and improve efficiency, GSHPs seem like a step in the wrong direction.
It's that dry Yankee wit
Ayuh. But now I get it - ground, horizon, etc. On the internet no one knows you're a dog.
Response to Dan Kolbert
I refuse to draw faces with punctuation marks -- I'm to old to learn text-speak -- so I guess I need to be more careful with my irony.
It's still April
all is forgiven. And Friday the 13th comes on a Saturday this month.
high costs ...
i didn't read through it all ..as i was uninterested to learning more after the first 3-4 paragraphs...but i agree with the conclusion that a 40 000$ heating/cooling setup , + hight maintenance , tuning and setup cost is ridiculous for any regular residential building ..
a friend of mine , locally ( near Montreal ) who is a tradesman ( excavation entrepreneur ) built a ~ 1million$ house ( his own ) a few years ago , and installed a ground loop heat pump system for his pretty large ( 100ft long .. ) dwelling. ( ICF + ok windows )
Even though he did the ground work himself, the installed system still costed more than 80 000$
( including the ~ 20 000$ central air + ducts ) , has already required more than 5000$ of maintenance, and still doesn't provide 100% of his heating needs.
Will probably never pay itself when some more maintenance will be required,
it is sooo complex that i couldn't even understand the pump/relay setups in 30mins of looking at it ...
also the fact that ground gets to ~5C during winter here probably doesn't help the efficiency much
for heating purposes ..
again same situation a purchasing a 40-50K$ current range limited EV to save on fuel cost,
where the limited range restricts the application to someone that doesn't work that far from home
hence cannot save enough per year to justify the additional investment over a hybrid or efficient ICE powered vehicle.
wouldn't someone be best to invest 10000$ more on insulation and sealing,
and use mini splits instead of 40 000$ on geo setup ??
2 + 2 ur points...
My argument to stay away from GSHPs, in addition to your points, is that if I make the building enclosure really tight and install good insulation, my heating/cooling loads are so small that the GSHP ROI is way too long. ;-))
It comes down to application and choice
While I agree that ductless heat pumps can be a much more cost-effective solution then geothermal, application and customer choice will always dictate the right approach. We are a residential retrofit company that offers both geothermal and ductless heat pump systems.
While we do A LOT more ductless jobs, there is a place for geothermal. Too often conversations like this focus on finding THE solution, not recognizing that there is no ONE solution, but LOTS of solutions. If they fit the application well, are energy efficient, provide good comfort and indoor air quality, etc., then why limit consumers choices?
By focusing on what is important to customers, giving them solutions to meet those needs, and providing them with the information they need to make an informed decision, they will usually make the right choice!
No one size to fit all
Adam has it right, that there is no one solution that is best for all situations. In my case, the house is superinsulated, so that the GSHP is small (2-ton) and runs in just first stage all winter. Also, the house needed a well anyway for domestic water, and the well didn't have to be any deeper than was needed to get adequate water supply for the house. So extra well-related costs were minimal and didn't add substantially to the overall GSHP cost. I wanted summer A/C, and a zoned system, so that part of the total HVAC cost was for that.
It's hard to generalize about total system cost. It would be more useful to talk about incremental costs to go GSHP vs some other solution to the whole HVAC issue for a particular house. Clearly, GSHP isn't overall the best solution for everyone, but it can make sense for some.
Unfortunately, you are both wrong.
There is always only 1 solution.
We can only strive to make the best compromises to get as close as possible to the perfect setup.
GSHP is not interesting for any regular well insulated house.
Way too complexe, way too expensive ...
now if you remove the H from GSHP ... now u get something interesting .!
GSP is da man :p
( sorry i'm tired .. )
Dick: what was the cost of ur
Dick: what was the cost of ur setup ?
DIY GSHP might be the only one worth it because it brings the costs down quite much,
such as using a nearby water source etc ...
You need a lesson
I would double check your sources for this article. My average 3 ton geo runs about $20,000 and after the tax credit the payback for it is only a few years longer than a 2 stage heat pump. I'm teaching a class on geo in Cincinnati in June I'd love to have you, message me and I'll give you a discount. In the mean time please stop spreading bad information about geo.
Response to Adam Gloss and Dick Russell
Adam and Dick,
I agree that there may be a few residential projects where a GSHP makes sense. These homes would typically be very large.
In most cases I have seen, however, homeowners who have paid for a GSHP system have paid too much for their HVAC equipment and not enough on their thermal envelope (airtightness, insulation, and windows). Time and again, I have reviewed "green" homes with overpriced GSHP systems and underwhelming envelope specs.
I have also interviewed several builders who went through a phase of specifying GSHPs for their projects, and who now say, "never again." They have reached this conclusion because of commissioning problems and maintenance problems with GSHP systems, because of the high price of GSHP systems, and because of the simplicity and affordability of ductless minisplits.
Response to Jamie Clark
You wrote, "I would double check your sources for this article." I can assure you that my quotes from GSHP contractors are accurate.
I don't doubt that you (and many other contractors) are sometimes able to install a residential GSHP system for $20,000. Clearly, a $20,000 GSHP system is a better value than a $42,000 GSHP system, all other factors being equal. Even at that price, however, it may not be a good value.
In your comments, you also raise the question of federal tax credits for GSHP systems. The question of incentives and tax credits is a political issue, not a building science or engineering issue. The existence of these tax credits tells us more about the lobbying strength of the GSHP manufacturers than it does about the wisdom of these systems.
Loved your grandfather's article on heat pumps, Martin. I was surprised by the COP between 3 and 4 back in those days, and wonder what OAT he was referencing and how it compared to today's (47F).
As we study the actual delivered performance of fully ducted air source heat pumps, and use that data as feedback to do things better, HP pros can install very simple machines that are inherently inexpensive, durable, easily serviced and maintained, and perform extraordinarily well in average to harsh climates. Average COP's between 3 and 5 with ducted distribution systems delivering 90% or more efficiency are very common and possible, even when fully concealed in unconditioned attics.
You pointed out very well the lack of data proving the actual delivered performance of ground source heat pumps as justifying the additional expense, as well as how improving enclosures further impacts the cost effectiveness. I wouldn't argue that GSHP technology doesn't have it's place, but I doubt I'll ever find that it's the best tool for the job where I live.
Good article, and your Grandpa is surely very proud. :-)
Geo that makes sense
At the Seattle Zoo the other day, I noticed a display that explains the ground loops serving the penguin exhibit, which mainly consists of a large amount of water that needs to be at ~50 F year-round. From what I've read, the install cost was around $200K, but the operating cost is very low, especially compared to the gas heaters and refrigeration equipment that would normally be used.
DAvid: that kind of situation
DAvid: that kind of situation exactly describes the problem and the good about GSHP.
With very large energy requirements, the cost of the system VS it's COP and possible output can make it worthwhile.
But if you need that much energy in a residential situation ..well ...
With current building methods, the loads should be lower than what would be required to render a GSHP system and its complexity inadequate.
the emperor has no clothes
Thank you Martin for writing this. Even if we take efficiency ratings at face value, geo doesn't generally pencil out unless most or all of the following are true:
* no access to natural gas
* relatively balanced heat / cool loads
* competitive pricing
* suitable soils
* state and/or local incentives above federal tax credit
With closed loop, soil characteristics are a wild card since thermal conductivity testing isn't cost justified on small residential projects. In many areas of the country, soils can vary dramatically from one neighborhood to the next. Are you feeling lucky today?
I'm currently working on two projects pursuing open loop geo. Open loop is much less expensive and efficiencies are higher, but it requires careful attention to water quality. And regulatory hurdles can ruin your day.
Response to Mike MacFarland
Thanks for the feedback. Unfortunately, I can't ask my grandfather any follow-up questions about his 1948 article. He died in 2001 at the age of 98.
Response to David Meiland
Thanks for the information you provided on the system that maintains the water temperature at the Seattle Zoo's penguin enclosure. That's good information to keep in mind for all GBA readers who need to design penguin exhibits.
Response to David Butler
Thanks for pointing out that soil characteristics can be a wild card when it comes to GSHP installations, and for pointing out that open-source drilled wells often require environmental permits.
GSHP installations almost always require engineering, and sometimes require environmental permits -- unlike ductless minisplit systems.
All good points, but GEO has a place at the table
I really enjoyed Grandpa Holladay's article about heat pumps in general. His use of language and ability to explain technical topics is a caliber of writing not often seen today. My dad worked his way through school in the 50s writing as a correspondent for several major mid-Atlantic newspapers, and my mom is a retired English teacher, so I was steeped in appreciation of sound writing.
We install geo (and ductless minisplits) in Florida. Both have their respective places along with traditional ducted splits. Geo shines particularly bright at the beach where 3k SF+ houses often have two or more air source systems whose outdoor units die early under the continuous onslaught of windblown sand and salt. Beach folks typically won't buy anything above code-minimum efficiency air source systems as a result, widening geo's advantage despite higher installed cost. It's a niche product / system as has been repeatedly noted above.
Ductless is great - superb efficiency, whisper-quiet operation, relatively inexpensive and easy to install. It falls flat on its face when clients don't want to look at the heads. It also fails when a load calc reveals many smaller rooms needing just a bit of conditioned air - laundries, walk in closets, pantries, small bathrooms and the like. I can't sell clients on the idea that such rooms not receive conditioned air.
There is little market in my AO for discomfort or deprivation, real or perceived.
No good deed goes unpunished
As a home builder, I'm continually striving to offer my clients the best alternatives for home performance balanced with the costs to deliver. We use an excellent HERS rater for HVAC system design as well as proper construction techniques, insulation and air sealing.
About 1995 or so, I met Dr. Eric Burnett at Penn State as well as Joe Lstiburek, John Straube, Achilles Karagiozis and others. They were all involved in the "Building Science for Building Enclosures" research and I became a convert. I've read all I could understand on the subject, and what I didn't understand, I could seek advice from Dr. Burnett.
Now, 18 years later, I'm still researching HVAC systems, refer to Allison Bailes at Energy Vanguard 2 or 3 times a week, joined RESNET, read a multitude of residential blog postings, follow Ted Kidd as well as his supporters and detractors, attend seminars, webinars and recently just for fun, read a book by Dan Holohan on "Radiant Heat".
Now my dilemma; I know it's too late to follow most of my fellow builders, take the easy path and just provide what ever has the best marketing department and advertising campaign.
I'll to continue my quest to offer my clients their best options for home performance, I just wish I was more comfortable with the "residential industry's" ability to deliver better guidance.
PS. I have a cabin in Woodbury, VT; may move there one day!
Response to John Holahan
Let's see: about 18 years ago you met Dr. Eric Burnett, Joe Lstiburek, John Straube, and Achilles Karagiozis. You've been reading their writings and following their advice ever since.
You have also evidently been performing good deeds.
All of this sounds good. I'm not sure why, however, you are complaining that these good deeds were punished.
Response to Curt Kinder (Comment #25)
I'm glad you enjoyed my grandfather's article.
Thanks for pointing out that a GSHP may make sense for ocean-front homes where the salty air can damage outdoor equipment. I agree that a GSHP may make sense in these locations -- although the cost still remains high.
re: No good deed goes unpunished
Martin, perhaps this was a poor choice of subject title. My complaint is that The Science of Building Enclosures appears to have consensus among the experts, yet the HVAC industry still bewilders and confuses the intended end users. I've depended on advice from vendors and suppliers who were either uniformed, complicate in their guidance or just ignorant. For years I may have, and in some cases am sure, installed over-sized equipment with poorly designed ductwork in panned stud cavities. And we weren't using the low cost provider.
Of course we know better now, but presently I'm concerned about the GSHP and ASHP systems that we thought were best serving our customers needs.
I'm looking for an easier, more trustworthy method of selecting a system that best suits the needs of my customers instead of being sold a system that sounds most plausible yet specious.
We have worked with a group here in Boulder that installed a 1-1/4 ton GSHP all in for less than 20k. This was before any tax credits were applied. The system included drilling for one source loop, furnace, ERV, ducting etc. The home was approximately 2,000 square feet. The key was building with a high performance building envelope and windows. The peak load was just below 14 kbtu. Design temp was 68 degrees f. The high performing windows allowed the duct work to be fat and short. There was no need to bring heat to the windows. Ducting could be run to the room instead. Air infiltration was also very low, below 1.0 ach 50.
Only one data point, but...
"Now that a few ductless minisplit units can heat or cool your home with an average COP of 2.0 or more, residential ground-source heat pumps, like solar thermal systems, just don't make any sense."
170 year old 1400 sq. ft farmhouse in climate zone 6. Not an open enough floor plan to make ductless work well.
Most of the low hanging insulation/ air sealing has been addressed, but more could be done at much higher cost.
No access to gas.
We put in a 3 ton gshp 2 years ago. Total cost was 24k before tax rebates. This included desuperheater and replacement of all duct work, adding ducts as needed, and a whole house humidifier. System was estimated to pay for itself in savings within 7 years (taking tax credit into consideration). Our electric costs over each of the last 2 heating seasons have been $300-$400 more than our electric cost was prior to the addition of the gshp (this is .12/kwh electricity purchased as wind power). This replaces approx $3000+ of fuel oil we would have used each season. We're on track for 7 year payback (probably less). These are real numbers from a real installation. Then there are the asthetics, like temp control within a degree of setpoint, no setback of thermostat needed, excellent air filtration, whole house humidification as needed, quiet operation, and central air conditioning in summer when needed (without even noticing it in the electric bill). So I've gotta disagree with your statement I quoted above. There are many similar examples of old housing stock where gshp's would make sense, as well.
I too, would like to see some good studies of residential gshp installations out in the real world.
in response to John H.
John Holahan wrote:
"I'm looking for an easier, more trustworthy method of selecting a system that best suits the needs of my customers instead of being sold a system that sounds most plausible yet specious."
Since you asked, here's an easy answer. Hire a 3rd party mechanical expert to make this determination. Someone with no skin in the game. In full disclosure, that's how I earn my living. When I prepare a mechanical specification, it is optimized for the particular home, site, and energy mix, and allows the client to obtain competitive apple-to-apples bids from otherwise qualified mechanical contractors. Or you can spend the 15 years it took me to acquire the experience and technical skills necessary to do what it is that I do.
Optimal Building Systems
Response to Mark Attard and Scott Smith
Mark and Scott,
Congratulations to both of you -- Mark for the $20,000 system, and Scott for the $24,000 system. Mark's system is small (1.25 ton), but that's good, as long as it satisfies the load. Scott's system is two years old, so costs may have risen since then. But both systems sound successful.
If any GBA readers can find a GSHP contractor to install a system at the bottom end of the cost scale, as Mark and Scott have, then the economics begin to make sense -- as long as the system is well engineered, well installed, well commissioned, and untroubled by maintenance issues.
Far more typical, unfortunately, are systems that cost $35,000 to $45,000 -- and are haphazardly engineered and not necessarily commissioned.
I think what is important to note is the overall peak load requirements regardless of what HVAC system is specified or desired. In order to achieve the peak loads required for such a small system great care should be taken in designing the envelope with respect to the weather zone of a given project. In the example I mentioned, in my previous comment, an r- 40 wall was paired with r- 9 windows and an r- 80 attic. Also a minimum of r-25 was used below grade. Because of the excellent thermal and air infiltration performance of the envelope we were able to reduce the peak load requirements, thus reducing the size and cost of the HVAC system. We did not rely upon Manual J to size the system either, but rather, some other modeling software that took into account other mitigating factors. This is important because Manual J tends to oversize by about 30%.
Response to David Butler
Thanks David, I do prefer your suggestion of the 3rd party expert. I will heed the following advice.
"The way to get started is to quit talking and begin doing."
—Walt Disney: American film producer, director,
animator, entrepreneur, and philanthropist
Another data point
My own geo system, commissioned in 2008, heats and cools a 3400 SF house in north Florida for just under $400 per year, and its desuperheater covers about half the water heating energy for a family of 4 1/2 people, saving another $100 or so (finishing water heater is an HPWH). Both geo and HPWH are submetered, so I'm confident of the above data.
Installed cost with 4 zones and metal ductwork (uncommon here) was $25k. It uses existing artesian flowing well pressure, so low water side costs. A second recharge well and dedicated pump would have pushed total cost to $35k or so.
Another situation when GSHP's are economically viable is when the building requires piles for structural reasons. If Piles are required anyway, water piping can be incorporated into the piles for heat transfer. They are called energy piles and there are some article on the web where they have been incorporated into some houses but mostly larger commercial buildings. It's an interesting concept.
While I've always respected your opinions and thoughts on building science, I have to respectfully disagree with you on this one. While in your part of the country, costs may be as you describe, in the mid-west they are not nearly what you depict. I just finished two years ago with an energy efficiency rebate program for a variety of improvements. One of these was GSHP, with 31 units installed. The average cost and size was $18,260 and 3.48 tons, or approximately $5,200/ton. I will admit not all of these had duct installations, however some did. If we take that into account and increase the price to $7,000/ton, we still have an installed cost of $24,360, far less than the $42,000 you state. I would suggest that you may have contractors that are making these things far more complicated than necessary and are pricing themselves out of the geo business as they'd rather do the tried and true cookie cutter systems they've installed for years. I had geo installed in my 1,800 ft2 home (plus a finished and conditioned basement for 3,600 conditioned ft2) 22 years ago. For many years I had the system submetered. We would use on average about 3,000 kWh per year for heating and AC....and as I have whole house ventilation, we never opened doors or windows, it is conditioned space 24/7/365. Two years ago I replaced the system as I wished to have a two-speed compressor. While I have removed the metering system, my utilities meter indicates that my energy consumption has decreased from the previous system.
In the Midwest, we've been seeing successful GSHP installs for many years. And the prices I've quoted do not even include rebates or tax incentives. Maybe instead of trying to kill the product, you should consider retraining the installation folks.PS...i'm not on the installing side, I work for a utility.
Response to Bryce Cramer
Thanks for sharing cost information from the Midwest.
As I wrote in response to a previous comment: If GBA readers can find a GSHP contractor to install a system at the bottom end of the cost scale, then the economics begin to make sense.
A few years ago, I heard that an Earthship installed a passive system for cooling during the summer months. It probably cost just a couple hours of back hoe time (in cinder-soil) and whatever the length of 2" PVC pipe cost. Maybe total cost between $200 to no more than $500? When the space heated up during the day, a window is opened and the warm room air passively drew the cool air from the open pipe into the room. No equipment of any kind. Winter months, I suppose the pipe was capped and the passive solar energy heated the space.
I have never heard how that system worked. Anyone familiar with this idea? Are engineers, once again, overthinking a good idea? :-) (emoticon for Martin)
Response to Ed Dunn
This type of duct is called an earth tube. Earth tubes have been around since the 1970s -- or probably even longer. Many people have tried them, and many installations have been problematic.
Here is a link to an article about a recent earth tube disaster: Belgian Passivhaus is Rendered Uninhabitable by Bad Indoor Air.
A Passivhaus with an earth tube: The First U.S. Passive House Shows That Energy Efficiency Can Be Affordable
Buried fresh air intake
Geothermal house air supply
Visiting Passivhaus Job Sites in Washington State (See comment #32.)
Earth tube for make-up air
How much electricity can you buy for $41,552?
Always find your papers interesting. I'm not sure if my numbers are right, but I believe a 4-ton heat pump which is what you discuss would put out about 45,000 btu or 13.5 Kilowatts of heat if the earth is at around 45 to 50 degrees. This for the paltry sum of $42,000.
Now I can buy baseboard for about $32 per kilowatt or about $448 for and get 14 kilowatts of heat. So how much power can I buy for the difference? And the present value of power over the life of the system? Considering the heat pump people tell you to have supplemental heat I may be buying the baseboards anyway.
The gentleman who ran Power Smart in BC about 10 years ago always claimed that the cheapest system over the first 12 years was baseboard, all due to the upfront cost.
interesting point about baseboard, Charlie
in Jan 2007, Home Energy Magazine published an article about a high performance home in Ohio with electric baseboard. The owner realized that a central heating system didn't make sense in his case. The magazine initially refused to run the article because the review board felt it sent the wrong message. But the author persevered. As it turned out, the article drew an unusual amount of positive feedback and the author, Allen Zimmerman, now serves on Home Energy's Editorial Advisory Board.
I love that story. I often tell clients that the more efficient you make the envelope, the more difficult it becomes to justify the additional cost of high efficiency equipment. Mechanical contractors hate this message. After all, if their highest performance equipment doesn't make sense in a high performance home, then when does it makes sense? Exactly.
But any broad-brush statement regarding baseboard is nonsense. It depends on the load and local energy costs.
David Butler !!!!!
And here you come and serve...
Very well said and pointed out ...
My Take on the decision matrix
Just to expand on David Butler's point I think it comes down to a 2 x 2 matrix with "Building Envelope" and "HVAC Equipment".
Quadrant 1 - "Low efficiency, low cost envelope" and "Low efficiency, low cost HVAC"
This is what we've been doing. HVAC equipment should be simple and reliable. Highly sensitive to rising energy cost. Good only with low cost energy and low environmental awareness.
Quadrant 2 - "Low efficiency, low cost envelope" and "High efficiency, high cost HVAC"
This is good for retrofitting an existing structure especially where changing the envelope is difficult. ROI still depends on energy cost (electricity in the case of GSHP) and equipment longevity / performance.
Quadrant 3 - "High efficiency, High cost envelope" and "Low efficiency, low cost HVAC"
This is just adding insulation and air sealing. If done properly the cost is one time only and performance / longevity is stable and predictable. HVAC equipment should be simple and reliable compared to GSHP. Less sensitive to rising energy cost than quadrant 1 or 2. Changing or replacing HVAC equipment is easy as conditions change over the years.
Quadrant 4 - "High efficiency, High cost envelope" and "High efficiency, High cost HVAC"
A waste of money. Pick one or the other.
Obviously I prefer Quadrant 3 for new construction and retrofit, but equipment like GSHP does have applications.
Karl, interesting take...
but your choices are too binary. The optimal solution according to your matrix will always fall in between quadrants, depending on local energy price mix as well as climate zone (which you didn't mention).
In particular, I think we should be starting from a mid-efficiency baseline. For example, I would never specify an AC or heat pump with a PSC air handler. Upgrading to non-variable ECM is a no-brainer and automatically gets you to around 15 SEER.
Still, I like the concept.
Response to Jon Pierce's Comment #47
You wrote, "Any Q's , please point to the line; and not general grammar, please."
I don't think that I have any questions. It really is hard to wade through your prose, which doesn't conform to most methods of speaking or writing.
A few comments:
You wrote, quoting from a different blog of mine: "But it's time to admit that a PV array is cheaper and less troublesome than fluid-filled solar collectors on your roof." I'm not sure what relevance this quote has to the article on this page.
Examples of opaque sentences: "one or two duct discharge to warm air space heating changeover when winter HW is 'FULL' ! Air collectors of 3-layer window screen 3/4 inch separations of an OEM baked 500f charcoal gray." I really have no idea what you are talking about, but it doesn't sound like you are talking about a ground-source heat pump -- the topic of this blog.
You wrote, "has occurred through and to ALL-COSTS-CENSORED: 4 and 5 year COMONLY CALCULATED ROI's." Why were costs censored? Who is censoring?
You wrote, "Radiant in-floor all over is 20+ year ROI's." Why would a heat distribution system (PEX tubing in a floor) have a return on investment? Compared to what? Fin-tube radiation? Both systems deliver heat -- but PEX in the floor usually costs more than fin-tube. I have no idea what "return" (on the investment of in-floor tubing) you are talking about.
Response to Jon Pierce's Comment #48
I'm still lost.
"The picture ... is quite different." Different from what?
What does "$93/mo cellulose" mean?
What does this mean: "ALL UT'y HVAC+HW+HOME"?
I thought I was getting close when I guessed, "All utilities including heating, ventilation, air conditioning, and domestic hot water." But then I was completely stumped by "+HOME." This type of arithmetic sum is beyond my comprehension.
Martin, why not just hit the delete key...
saving readers from having to wade through this off-topic nonsense? Fortunately, in my group on LinkedIn, I've never had to deal with a comment so, well... incomprehensible.
A good Idea for historical districts?
With the HVAC system in my 122 y/o home in hot, humid New Orleans approaching end of life I had convinced myself that GSHP made sense vs conventional HVAC given my limitations:
1. Limited ability to achieve great air sealing or deep energy retrofit due to historic district. Decent attic insulation (R-30)but unable to address walls.
2. Large old home 4000+ sq feet with a large wall to surface ratio and large cooling load. (tall skinny house with leaky windows)
3. Quoted cost of high SEER HVAC quite high 30K+ with questionable savings energy savings over cheaper 12-16 SEER units. i.e. the myth of high SEER ratings in a Hot humid environment.
4. Old home with multiple small rooms not very compatible with non-ducted air sourced heat pumps.
The cooling/dehumidification/superdeheater and elimination of all natural gas from the home combo made sense. Utilities are only ~125/month now with OLD inefficient equipment that needs to be replaced anyway. It seems like a good move with the tax credit vs the high cost of a new high SEER traditional system. I think the reliability of the systems over a 30 year period will the true test but I can't predict which equipment will last longer!
in response to Mike Truxillo
Let's put some reasonable numbers on this. $125/mo is already pretty darn low for a 4k ft2 home. One thing that plays to your advantage in your climate is your home's relatively small roof area and, I'm guessing, well shaded windows.
Let's assume space conditioning represents half of that. If your existing AC is no better than 10 SEER, you can expect a mid-SEER replacement to save around 35%, reducing your heat/cool cost to around $500/year. I can assure you, a GSHP won't cut that in half, but even if it did, you're only talking $250/year. Keep that in mind when you compare costs.
I think you're correct to question the cost benefit of higher SEER compared to mid-SEER (I like 15-16 SEER single stage heat pump with non-variable ECM air handler). I have no idea how many systems you have or the condition of your ducts, but high $30's does sound high. I replaced my furnace+AC with a 15.5 SEER heat pump a couple of years ago and paid around $5k, but no duct mods were needed. To get a fair comparison between AS and GS, be sure to ask prospective contractors to break out any duct upgrade costs.
For purposes of life-cycle analysis, I typically allow 15 years for an air source system with one compressor change-out. For GSHP, the loop should be good for the duration. With either approach, your maintenance regimen and luck-of-the draw can reduce or extend equipment life. But due to added complexity of ground source (ground loop HX, H2O pumps & desuperheater), there's a much higher likelihood of expensive repairs prior to 15 years.
GEOTHERMAL Heat Pumps for retrofit and new homes
RIGHT I pasted with wrong solar comment window up after correcting in word for spelling...
I spoke with Dr. Steve Kavanaugh 6 years ago
because I found few were guaranteeing loop EW at 2.8 gpm per COMPRESSOR-IN-BOX TON, of 34f to 35f in northern 53-50-deg ground applications. Since 1983 implementing such, so many "experts" blathered I undersized units, but the units heated in zone 5-6 well to zero and below ( a few ~ 5-7 deg balance to needing supplemental) . Then I wrote PERFORMANCE contracts of "34 or more" saving money on equipment was allowable because the loop is warmer and these "chillers" are more efficient on warmer loops: like ANY air source refrigerant auges read on a 40-degree day or warmer, HX to compressor stage/ apples to apples.
Now having HANDS ON 300+ GT Well-Water open systems ((one NOT NECESSARILY must bore a hole- STILL TODAY)) -
GT units and ones I have reviewed others installed with apples to apples deducting well distributed ducting that is , and deducting costs of "going to do anyway with any HVAC-HW" ---
common plumbing and HW tank are then with Priority all-inclusive.
$16000 costs of a Mitsubishi 5 ton applicable minisplit or high eff heat pump and high eff propane gas (ducted or radiant)... and a 5000 to 8000 comparative tax credit and ut'y co rebates...simply has had these
GeoThermal Earth-Heat Exchanging Systems have com in as a LOWEST first cost .
Noting also the more so on a well that qualified and quantified in 3 to 4 days tests at under 50% draw down of static waters--- not to lift over 110ft usually.::
Adding closed loops of now still complete under $1600 per AHRI rated ton (1800-$1900 with flowcenter and reservoir complete) even per COMPRESSOR-Ton (C-t) on w:w is a great ROI , I believe.:
~ ALL-COSTS-CENSORED/accounted for, leaves us only finding nice: 4 and 5 year COMMON ROI's. ((sometimes the LOWEST first cost, removing all non-geothermal items of say a boiler or other water heaters or a bunch of MINI Splits and still have cold feet, not as with ducts that do radiate to flooring also)
GENERALLY accounting for all:
I see 20% of the remaining 4000-6000 dollar variations of difference leaves w/inflation, 10-12 year returns way over $10,000. Plenty to replace meager parts installation and OEM deficits.
In to losing credits in 2016 those will be 6-10yr ROI's...
[better - return air systems] gas or GT HtP both need this generally in all retrofits especially..
I believe, which in 25 to 35 year concurrent lifecycle studies of the VERY LOW MIANTENANCE I have had with over 300 well-open 'loop'
and out of 1600 hands on (maybe 1700 geothermal calls to commercial and schools etc and process cooler to preheater industrial ECL, GLE loops) -- are to be expected.
The Air-Solar (see some recent comments at 2011 and 2012 posts of older HW and Solar thermal...)
The Air Solar- of 1980, instructions is why I put in only a little more effort to sealing ducting since 1983 for all my HVAC like those solar systems.
WOW! 3 ton compressors in 3000-3400 sqft over uninsulated basements zone 5.1/2 (1994 peaked -18f below there).
NOW: with the Hydro-Temp patented HW 100% On-Demand Priority and RECLAIM 100% in cooling since 1981, and their first in the country net-zero-school, and blowing away so many in 2008 study retrofitting a stick-built to a near by compared Gas-HeatPump school showing 50% savings on all accounts...
THEN they were at their HIGH 1.8kw per sq ft per school year (other GT at 2.3 to 2.1, compared)...!
I used their variable ECM 1 blowers on dual compressors (sm+lg, then both for 3 staging) since 1996 and with oversized HX coils hitting 2010's efficiencies in the 90's.
SAVINGS DRAMATICALLY VARIES with full Heat-Reclaim (loop pumps OFF) during HW recovery in AirConditioningCooling mode.
Well see the un-rated Hydro-Temp com for yourselves. since the 80's, that's 480 watts on 8 to 9 compressor-tons(C-t) ) which is like 22 or more "RATED-Size 'tons' "per pump horsepower if more efficiently piped at the loop, etc. building headers for flushing but operating under 22ft Wtr TDH by design.
Any Q's , please point to the line; and not general grammar, please.
Affordable Geothermal or 20yr ROI radiant ?
IF you were to picture what I did in 2007 at a 4 zone radiant residential system in Harrisburg PA it is quite different than posted above (Mr Gadgeet looking things above).
A simple oversized header loop of 1.1/2" and three pumps hanging below the feed - bottom-header with one tempering valve has no need of a reservoir because of Dual-Compressor 3-staging used 2t+3t for 5 is of a more load-matching: A first hottest zone is 17,000 btuh output at ~ 115 deg and so the first compressor staging on at 2 tons runs a long time before cycling at a reasonable design. [now residential IQ Variable V-Star compressors have replaced duals to under 7.1/2 tons as of March 2013, here described above, a 4.1/2 ton V-Star by Hydro-Temp of AR, not hydrodelta-hydroheat, would fit nicer even at 25% first staging ~ 14,000 btuh, ramping to load matching by programmable temperature controller settings (all IRD Wireless since 2007 for the controller)]
NO radiant loop storage tank.
Hottest first zones off header first. (saving plumbing)
w/ one full rec-area basement mixing valve.
FORCED AIR Heating and cooling from ONE GT System-unit...and domestic FULL INSTANT On-Demand by temp control/ OEM HVAC+2 HW exchangers.
Simple continuous 1.1/4" x 800ft Vert-Bore ground loop (stays over 34EW in zone5)
Walk-out basement in 2700 other living sq ft @ $ BUDGET $93/mo
for a couple of years running, was in insulated walls of cellulose insulated standards.
300 sq ft glass.
This year might break $100/mo budget: ALL UT'y HVAC+HW+HOME.
3nd and 4th year some light maintenance by the owner with internal on-off of the water pump accessable : flush Domestic Coil for HW with vinegar each two years/ change air filters once/year.
a defect up front was - Found loop circ pump (like any boiler application) OEM defect, the owner replaced quickly. ( he built his own duct system completely of buct board and flex throughout, I designed with his material choice to be appeopriate to concerns of resistance calcs.
ECM Air circulation with proper return air system cleans the air from most dust 24/7 4" pleats, at the low blower (adjustable by Infra-Red-Palm controller) etc etc.
Radiant: Living room 115 degree 1st zone, other 1st flooring 111 deg; and 109 deg 2nd floor, third zone and 4th zn : 78 deg to basement.
This can be done with W:W unit and a Forced Air combined, or W:W with HVAC fancoils , but was not here so needed as the HVAC Double Prioity is : All one unit 34x32 footprint 74" tall
MOSTLY AFFORDABLE WHEN ACCOUNTING FOR (Censoring means to "ACCOUNT") ABOUT SAVINGS:
( DUAL Proiority HW 100% on-demand and 2nd Radiant Priority / OEM 4 zone boards since the early 90's... nor multi-=programmable and here a first IRD Wireless logs and snesors read and programming since 2007 for various water temps and air speeds and regulated bonnet temps selectable for Air Distribution Variable load Matching comfort at a highest savings found among GeoThermal [ which is why you see adv of others 'highest RATED eff in the world] hydro-Temp meeting all COMPLIANCE with ENERGY STAR(tm) has never been rated and surpasses requirements each year. I ordered this unti in 2007 with 2-ton oversized coils for superior efficiency.
... and now residential IQ Variable Compressors 2.1/2; 4.1/2; and 6 tons on the compressor label.(like some AHRI-Rated's at "7-size-tons"...wont run in to the Dr Steve Kavanaugh censorship which only exposes truths of "rated' systems)
The DeHumidification of 3 Stages and in now Variables is second to no single or two-staging compressor.
This installation assisted by the owner @ 17,000 plus radiant zones he installed himself, was nearly 6,000 less than all by a local installer. TOTAL electric bills of under $100./mo? in a walk-out basement? WOW! That's why he sends Harry and Davids gifts at Christmas- , you really can give a customer what they want and what they needed and comfort they did not ask you for !
Setting the record straight
Inflated Efficiency Claims
The performance standard AHRI/ASHRAE/ISO 13256-1 became effective January 1, 2000 and replaces ARI Standards 320, 325, and 330. This new standard has three major categories: Water Loop (comparable to ARI 320), Ground Water (ARI 325), and Ground Loop (ARI 330). Although these standards (ARI and ISO) are similar there are some differences.
So a study was conducted by the National Institute of Standards and Technology with a grant from the Department of Energy to test the same equipment via those 2 different standards. Equipment was tested with and without air ducts installed. ISO cooling energy efficiency ratio (EER) with and without ductwork units were 4.5% higher and 3.9 % lower than the ARI, respectively. ISO heating coefficient of performance (COP) for the ducted units were 6.2 % higher and for the unducted units 1.0 % lower than the ARI, respectively. Meaning that the new rating improved the efficiency rating by 4.5% in heating and 3.9% in cooling for ducted heatpumps. In unducted systems, the newer rating system actually penalized heatpumps by 1-3.9% lesser performance. This data suggests that the difference between the systems mostly comes from the testing conditions not accounting for the energy used by the blower to overcome the resistance of the ductwork, which indeed is the flaw of the new rating.
The study can be accessed at:
You continue to cite Prof Kavanaugh:
"In the February 2013 EDU interview, Kavanaugh said, “To calculate performance on these multi- and variable-capacity models, the standard [ISO Standard 13256-1] calls for water temperature in the loop to be 68°F, which is ridiculous, because loops operate at much higher temperatures in cooling. Essentially, what you have there is a something similar to rating the efficiency of a car or truck … when it’s rolling down the hill. If the evaporator coil is 80.6°F and the water coil (condenser) is 68°F, you can get a ridiculously high efficiency reading. On top of that, these calculations assume that the fan has no static pressure. … When you take that piece out of the rating, you get a very deceptive, high efficiency rating.”
Geothermal efficiency benefits from colder loops in A/C mode and from warmer loops in heating mode.
So Prof. Kavanaugh (your expert) states that 68F loop temperature is ridiculous and way to low. Really?
Our monitored loops start to provide cooling in May at 35F and top at at the end of the heating season between 55F and 65F, meaning that they perform about 15-20% better in cooling mode than rated, which is more than enough to compensate the not account ductwork in the rating system. Similar things occur in heating mode. The ISO 13256-1 standard uses 41F in 1st stage and 32F in second stage. Our loops start the heating season in October at 55F-65F degrees with the heatpumps running in 1st stage until mid December (the the average 1st stage temp is around 45F), when the loop has dropped down to 35-40F and the second stage starts more running. Then they drop further down to 30-35F, for an average 2nd stage loop temperature of 35F.
Again, here are the links to some energy monitoring sites, monitoring our system where this can be verified.
This math can change if your move further south, where the heating would run more efficient and the cooling would be less efficient, but the fundamentals remain the same. If the designer is skilled enough bring the entering water temperature within the temperatures used for the rating, the geothermal heatpumps will perform better than the rating system indicates.
High installation costs
Our system between 2 and 6 ton run consistently between $20,000 and $30,000, with horizontal loopfields, two hot water tanks, and dual stage heat pumps. Turn key.
Geothermal is not for everyone, and competing with cheap natural gas, having increased loop costs due to drilling or dealing with older radiant applications needing inefficient high supply temperatures can increase payback to a point where it becomes not economical.
Also if you build passive houses with a minimal load, sure a strip heater can carry the load. But this is the exception rather than the rule. Don't forget, us humans need fresh air to breathe.
High equipment prices
Yes, the equipment got more expensive, but you forgot to mention that it is newer equipment which significantly development costs and significantly gained efficiency. At the end it adds value for the homeowner. Yes, the new variable speed pumps are 50% more expensive than the dual stage pump, but it only adds 10% to the total price of the system. However, it adds 22-25% efficiency to the system, for life.
Most equipment vendors want to sell larger and inefficient equipment?
Who cares want they want, I am simply not buying it. It is me as an installer and designer who decides what equipment goes in. What would happen to a car manufacturer who puts more equipment in the cars which also make the car less efficient and increases the costs? I understand where Steve Kavanough is coming from. The solutions is very simple. In his example, you simply design the loopfield for the smallest pressure drop to fulfill the flow requirements needed by the heat pump, and use the smallest and most efficient pump to push the water through. Again, simple for an experienced installer.
We live in a competitive environment, to suggest that I make the systems less efficient and increase the costs thus reduce my profit margin would assure that I neither serve my customers and myself well. Those systems sell because they are mean and lean, similar to competitively prices fuel efficient cars.
Yes, equipment got more expensive, but brought significant improved efficiency and durability. No, the efficiency claims are not inflated, the rating methods are not significantly flawed. I am not even sure that equipment manufactures want to sell more and larger equipment. No one ever came to me and wanted to sell me more.
So what is left from your argument that geo system don't make sense for residential applications? Many times they do, rarely they do not. Your blog here is misleading, and you did not fact check the arguments you bring forward. You seem to lack the in depth understanding of the technology which is not surprising, given that this week you wrote about passive houses, last week about thermal mass and a month ago about roof insulation.
You need to be aware that you cannot only inform but also grossly mislead consumers, thus you have a responsibility here. This blog should not be about cranking out one article per week on a new subject. If you don't understand a subject well, don't write a blog about it.
Response to Jens BuffaloGeothermal
First of all, thanks for providing the links. The real-time data display for installed systems is certainly valuable and interesting.
Thanks also for the link to the study comparing the ARI and ISO methods of calculating efficiency. The fact remains that the ISO method does not account for the electrical input of loop pumps.
I stand by my reporting of the writings and statements made by Steve Kavanaugh, a professor of mechanical engineering at the University of Alabama and a nationally known expert on GSHPs. It does not surprise me that his conclusions sometimes differ from yours, especially considering the fact that your company installs ground-source heat pumps.
You report that the systems you install cost between $20,000 and $30,000. I don't doubt that your systems are efficient. The fact remains, however, that the high cost of the equipment makes these systems a very poor match for efficient single-family homes with good thermal envelopes. In almost all cases, it makes more sense to invest more in the thermal envelope of the home, and less in the home's HVAC equipment.
Your statement that I did not fact-check the statements in this article is not true. Nor does this article "grossly mislead consumers," as you allege. While it is perfectly reasonable to disagree with my conclusions -- in fact GBA provides a forum for our readers to do so, and the dialogue that results from these conversations is valuable -- I think that your characterization of my reporting is unfounded.
Continue to set the record straight
while I am inherently bias as a certified geothermal installer and geoexchange designer (CGD), that does not mean I should not point out the incorrectness in your article.
If you paid attention to what I posted and also actually read the document to the study comparing the old ARI and the new ISO standard, you would have found that I pointed out that difference between the systems mostly comes from the testing conditions not accounting for the energy used by the blower to overcome the resistance of the ductwork, and not the water pumps. In addition on page 1 of the study document I posted, the differences between the old ARI method and the new ISO method are described.
You originally stated:
"The problem dates back to 2000. On January 1, 2000, a new standard (ISO standard 13256-1) replaced two earlier standards (ARI 325 and ARI 330) used to rate the efficiency of GSHPs. Whereas the ARI standards included an allowance for the electricity used by pumps to draw well water or circulate fluid through ground loops, the new ISO standard eliminated all pumping energy from COP calculations. The effect was that COP ratings jumped up: for the same piece of equipment, the COP rating under the new ISO standard was higher than the COP rating under the old ARI standards."
Again, this is incorrect!
Under the old ARI standard, this energy input for circulation pumps was not included in the calculation of the total energy input, and the standard specifies the water flow rate that results in a 5.6 °C (10.0 °F) temperature change across the heat exchanger. Under the new ISO standard, the test must be performed at the mass flow rate specified by the manufacturer, and the energy input to the water pump is calculated and included in the total energy input. A pump power correction has been added onto the existing power consumption. A standard formula is used to account for the pumping power, to ensure customers can make direct comparisons between different models.
Within each model, only one water flow rate is specified for each performance category, and pumping watts are calculated utilizing
the pump power correction formula: (gpm x 0.0631) x press drop x 2990) / 300.
ISO Capacity and Efficiency Calculations
The following equations illustrate cooling calculations:
• ISO Cooling Capacity = Cooling Capacity (Btuh) + (Blower Power Correction (Watts) x 3.412)
• ISO EER Efficiency (W/W) = ISO Cooling Capacity (Btuh) x 3.412 / [Power Input (Watts) - Blower Power Correction
(Watts) + Pump Power Correction (Watt)]
The following equations illustrate heating calculations:
• ISO Heating Capacity = Heating Capacity (Btuh) - (Blower Power Correction (Watts) x 3.412)
• ISO COP Efficiency (W/W) = ISO Heating Capacity (Btuh) x 3.412 / [Power Input (Watts) - Blower Power Correction
(Watts) + Pump Power Correction (Watt)]
So you see that water circulation is actually accounted for in the ISO standard 13256-1 rating. It is always enough power to push enough water through the entire loopfield. That depends on the loopfield design and the equipment you choose.
The manufacturers are actually quite upfront about the different ratings systems and details he differences in their spec sheets. Some examples are as follows:
You are certainly correct that a new house should be made very energy efficient. Giving the prices i posted to you, a house needing a 6 ton heatpump only has 50% higher upfront costs compared to a 2 ton system, but it will need about 3x the energy. Since the higher upfront costs is returned via energy savings, the higher upfront cost is return quicker if you have a house using more energy, either because it is larger or older.
So you have two scenarios in the market:
1) New Construction.
A conventional HVAC system (heating, cooling, domestic hot water) runs you about $12K for an 1800 sqf house, and normally about $20K for a 2 ton geo system. Now you want to make the house more efficient. But there is a limit to that, don't forget us humans need air for breathing. And triple pane argon filled windows don't come free, ICF walls don't come free, a heat recovery system does not come free, 6-12" insulation under the slab does not come for free, foam insulation does not come free. To get all those goodies to cut down your energy consumption down by 50%, your upfront costs go up by $20-30K. Or you can get a geo system which cuts your energy consumption down by the same amount, and pay about $8K more. Yes you can and should always improve the envelope, but in our climate zone 6, it is very difficult to get an 1800 sqf energy 5 star + house below 25 KBTU/h heat load.
Given that only 0.5-1.5% of the housing market are new builts every year, what do you propose you do with 90% of the houses which need new HVAC equipment every 15 years, especially with all the houses which do not have access to cheap natural gas. Yes, you should also do all the energy improvements you can reasonable do. But their loads will always be high enough to consider geothermal. We have many customers who pay $4000-$7000 annually for propane and oil, and geothermal cuts those bills usually down to $800-2000.
When you say that geothermal does not make sense for homes, it appears that all of our customers seem to disagree, likely since they are the one who pay the bills.
No, you did not fact check your sources, you simply wrote what Steven Kavanough told you, and built a story around false efficiency claims, equipment vendors wanting to sell oversized equipment, raising equipment cost and Kavanough making an argument against the newer highly efficient equipment which provide significant higher savings and comfort to homeowners. I am happy to have a pro and con argument with him about it. He might enjoy the energy monitoring on a new built 2600 sqf house with a variable speed heatpump, with variable speed ECM fan and DC inverter driven variable speed circulation pump. http://welserver.com/WEL0713/
So what else is left and true from your arguments why geothermal system don't make sense in residential applications? Look at the facts, and they start to make a lot of sense.
I scratch my head to wonder what drove you to write this article in what you expose a certain lack of knowledge about geothermal heatpump systems and did not check Steven Kavanough's statements.
Air Source Heat Pumps
Great article and comments Kavanaugh said he would never install an air source heat pump in his home. Why is that?
Response to Greg Svault
Steve Kavanaugh is a mechanical engineer who has devoted most of his professional life to the study of ground-source heat pumps. He understands the technology thoroughly, and is capable of designing an optimum system and ensuring that it has been installed perfectly by insisting on a proper commissioning process.
There is no doubt that ground-source heat pumps work, and can be extremely efficient. Their main disadvantages are the high installation cost -- a cost that Kavanaugh is willing to pay, because he loves the technology -- and the high likelihood that the systems will be poorly designed and installed due to their inherent complexity and the need for system engineering -- a disadvantage that doesn't apply to a client like Kavanaugh.
Gold-Plated Heating Systems
I couldn't agree more with those who question spending more than $20,000 on a heating system. I also agree with Blasnik's statement that installing a complicated heating system is an invitation to disaster.
affordability of ground source heat pumps
I was searching for split zoned ductless geothermal ground source heat pumps and happened on this blog/comment thread.
I've worked as an electronic technician for 27 years . One of my coworkers who used to do solar hot air and geothermal ground source installations put a ground source heat pump in his dome home. He laid a horizontal loop through his septic field when he put up his house over 30 years ago. It did not cost him $20k, the system is still working, and he is happy with it.
The idea I have is to install a horizontal loop and run it to a water to refrigerant heat exchanger in an efficient commonly available single zone ductless unit.
I am seeing prices in the newspaper and on Craig's list in the range of $1,200 for 12,000 btu (1 ton) precharged complete split ductless energy star units which claim SEER's of 25 or greater. This will heat/cool an efficient 2k sq. ft. home.
My idea is to set up 2 units, one upstairs and one downstairs. The upstairs one I will put in with a standard installation following all the instructions. I will add a raspberry pi controller ($25 with arduino interface card $12. Basically a Udoo). And I can accumulate data for a year while I dig in the horizontal loop and acquire the parts and purge and fill the second unit which will have similar instrumentation. I should have the capability of controlling the pumps and compressor and an intelligent controller can duplicate the measurements on the upstairs unit on the downstairs geothermal loop unit
My ultimate goal in this is to create a non-proprietary, in the public domain, or "open source" a closed horizontal loop geothermal ground source heat pump system that can be installed in an efficient home for under $5k, turnkey.
It should not be dependent on any particular hardware, so a Japanese or a Korean or a Chinese single zone split ductless energy star unit could be used. I see less efficient energy star split ductless single zone units selling for $800 for a complete pre-charged system. If one were already required to put in a septic field, the cost for installing a geothermal ground source split ductless zoned system could be lower than the cost of a conventional heating/cooling system.
Intelligent thermostats like the "Nest" TM or "open source" public domain equivalents, which already exist, could be used to place these units on line, record data, update programs, and allow the average Joe to become independent of the grid with an affordable solar powered geothermal heat pump.
I am right there with James Lynch
I have a well that flows constantly at about 2.5 gallons per minute. The only exception to that is when I run water and pump it out of the ground faster than that. I am more concerned with air conditioning than heating because I heat with wood but in the spring and fall it would be nice because I tend to cook myself out with wood. I was thinking that it would be quite simple to take a mini split ductless system and take the outside unit apart and remove the radiator and fan and replace it with liquid to liquid heat exchangers. I would want 3. One to circulate through a tank in my basement to heat domestic hot water. One to circulate the water from my hot tub. The last to finish cooling with the runoff from the well. When I put my addition on my house I ran lines for the runoff to go into my basement so I have no digging requirement. I don't quite understand why something like this isn't an option. It would be cheap and easy to install. What's not to like? This technology is nothing new. It shouldn't be so expensive.
Response to Eric Bosworth
I'm not quite sure what you are suggesting. If you are suggesting that it makes sense to take apart a ductless minisplit air-source heat pump and use the parts to jury-rig your own ground-source heat pump, here's my reaction: feel free to experiment. My guess is that any experienced R&D engineers -- like the ones who design and manufacture ground-source heat pumps -- who read your comments are probably shaking their heads at your suggestion.
But go right ahead and tinker. You might create a system that works for less money than an off-the-shelf system.
Most homeowners can't do that, of course. They have to call up their local HVAC contractor and get a bid for a ground-source heat pump system. They will discover that the cost of these systems is as I have reported in my article.
40 K for such a system?
If you have land space for a well (Here you cannot drill a well on under 10 acres) then you have space for a green house. In my climate 10,000 F degree days per year, (Plant hardiness zone 3) an impossibly badly sealed home made from a stack of used aluminum windows green house *still* gets warm enough during the day to keep barrels of water from freezing. Daytime temps in this green house are 20-30 C degrees above ambient on a sunny day.
* Seal it. (+10 C)
* Orient east west, and insulate north wall (+5? C) and it won't cool as much at night, so more degree hours)
* Use dark colours on your water containers
* Use an asymmetric roof to maximize low angle heat gain. (+5 maybe +10 C
I bet that a 2000 sq ft green house could heat a 2000 sqft house. Greenhouse frames are under $3/sq ft. Another buck gets you double poly cover and inflation. The water system is up to you. I bet an air to air heat pump with the cold end in a toasty green house would get wonderful CoP
can GSHP loops be run along inside basement walls?
I have a 1920's frame 1 1/2 story bungalow, with gas heat and cast iron radiators; the boiler is 105,000 BTU and 25 years old. House is 1352 SF, excluding unfinished basement. We have added insulation to walls and ceilings, R 38 in the ceiling, R 13 nominal in the walls, new windows and doors, added plenty of weatherstripping and sealing. I am looking to find a heating source to work with the radiators if possible, that is fossil carbon free. Our electricity is 100% wind power, through the grid, so heat pumps seems to make a lot of sense. From the article I see that GSHP costs are going up for the indoor unit. Is it that installers are gouging the market for this? That seems stupid to me.
Question I originally searched for is: can GSHP loop run on interior side of basement wall? My basement is 50-60* year round. House footprint is 30 x 30, or 120 LF, at 6' height, and loops spaced 6" apart, that's 1,440 LF of loop, not including doors and windows.
Response to Brian Higgins
Q. "Can GSHP loops be run along inside basement walls?"
A. Briefly, no.
There are a variety of reasons why this idea won't work:
1. Your basement doesn't have enough easily gatherable heat to heat the upper floors of your house.
2. Ideally, your basement should be inside of your home's thermal envelope -- and you can't remove heat from one room in your house to heat another. (At least this tactic won't work for long.)
3. Ideally, your basement walls should be insulated. If they aren't, that's the first place to invest your energy retrofit money.
4. If you tried this, you would discover that the temperature of your basement would drop very quickly, freezing all of your plumbing pipes.
There are more reasons, but that's enough reasons to get you started.
That's a HUGE boiler for a 1352' house!
Brian: Where are you located? That's enough boiler to keep my 2400' (+1500' of insulated basement) 1920s 1.5 story bungalow house toasty at -100F! Most houses of that description would come in at about 20-25,000 BTU/hr @ 0F (which could be colder or warmer than your 99% outside design temp: http://articles.extension.org/sites/default/files/7.%20Outdoor_Design_Conditions_508.pdf )
If you haven't already, estimate your 99% outside design temp heat load using this methodology:
With the load calculation and the measured EDR of the radiators it's possible to estimate the water temp required to heat your house with that radiation. Build yourself a spreadsheet, do it a radiator at a time, then go back and do some I=B=R load numbers on a room by room basis to see if the EDR/load ratio is pretty similar room by room.
If the load numbers are 25 BTU/hr per square foot EDR and your outside design temp is 20F or higher it's at least possible to use an air source hydronic solution, but I'm not optimistic that it will work out that way.
Is the foundation insulated? If not, it's likely to be 15-25% of your current heat load, and well worth fixing before hacking on the heating system.
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