I recently purchased an existing home on 4 acres in Minnesota and feel it could greatly benefit from a geothermal heat pump.  It currently uses a oil fueled boiler that needs to be filled 3 times per year at a cost of $2200 each time.  If I switch to geothermal my cost per million BTUs is 20 percent of fuel oil.  The main problem I am finding is that all 4 levels of my home are fully finished and will need to have all the duct work put in if I want geothermal.  The house was built in the early 70s and only has R-12 in the roof but that will be changed shortly to R-49. 

My question is about the feasibility of high velocity geothermal in a heating dominated area.  I can find far more information about high velocity cooling put very little about heating.  It seems only one of my 5 contractors is willing to even consider the idea.  The others have said its a bad idea and wont work but I have a feeling it might be because they haven't done it before.  They have all agreed that with standard velocity ducting I will have to remove a huge amount of the ceilings in the house.

Does anyone have any experience using or installing a high velocity geothermal in a northern location?  If so please give me you opinions on it.

                    Thanks in advance for the information

Not an expert here, but one who thinks outside the box.

Have you considered radiators in conjunction with a liquid to water GSHP v forced air?

In addition to radiators, I would consider:

hydronic toe-kick heaters

hydronic floor fan convectors

hydronic towel warmers...

It's possible to do geo with low-temp hydronic radiators or radiant ceilings without gutting the place- you're not necessarily stuck with high-velocity ducted solution for heating, though it might be nice to have for coolig. But you're probably getting way ahead of yourself here.

No matter what, you'll need a room-by-room heat load calculation (Manual-J or similar) at realistic 99% design temps.  Since it takes time to do a heat load calc it's something many or most contractors will just ball-park it, and won't do until/unless you've signed the contract (even then some will skip it or exaggerate the load by tweaking the design temps or R-values until it matches their ballpark number). 

But every ton of geo has an associated cost, and it's not small- you need to get heat load number right, and make all of the cost-effective changes to bring the heat load DOWN before calling the geo contractor. Almost any 1970s house will have far more low-hanging fruit for getting the heat loads down than mere attic-R, and while you might be able to figure out some of them, it's worth paying a pro to find more.

There may be energy efficiency contractors or state agencies willing to do full house energy audits that include blower-door testing to determine leakage and infra-red imaging to find any gaps in the insulation etc.  Some of these contractors would also be able to do the formal heat load calculation on the before/after picture of any intended upgrades. 

In a house that's 4 levels (is that 3 storys + basement?) the stack-effect infiltration losses can be large even in relatively low-leakage houses. Air-sealing the attic is a must before adding insulation, since that's the top of the stack.  Air-sealing the foundation/basement is as-important, since that's the BOTTOM of the stack.  Insulation contractors who do blower-door verified air-sealing as a separate service should move to the top of your list.

In my neighborhood geo runs about $9K/ton (probably higher than the national average, but not 2x), and even if envelope upgrades to bring the loads down cost $10K/ton it will be be worth it on both operating cost & comfort grounds.  The financial crossover points will be different in every case, but PLAN on making significant upgrades to the building envelope as a critical part of the whole project, not just squirting in R50 celluose into the attic.  The first ton or so of load reduction is likely to be a bargain, even the second might be pretty cheap compared to a ton of geo in your area.

When you have the "after" picture of the heat load numbers (even if it's before the work is performed), then you'll have a pretty good stake in the ground when dealing with geo contractors. It's not uncommon to solicit 4 bids and have proposals that come back anywhere from 3 tons to 6 tons, even if the true load is 2.5 tons.   If it were a condensing gas furnace the cost delta wouldn't much matter (but the comfort might), but with geo the difference is usually in tens of thousands of dollars.  Whatever you pay for a deeper energy audit and heat load calculation, it will more than pay for itself in up-front geo costs (and in confidence when negotiating the system size.)

If there is room in your attic, you can box it in such that some of it becomes part of the house. Then put hvac and ducts in there. Note - don't consider this "putting hvac in the attic", call it "raising the ceiling" or something. R49 insulation should surround the new space.

You can add hydronic radiant loops to existing floors, walls and ceilings. You can also undersize a geo system (perhaps 80%) and use the existing boiler when the geo can't keep up. Perhaps on a room by room basis, mix hydronic and air heating based on how convenient it is to run ducts.

I like the idea of hydronic attic airhandlers for cooling and maybe auxiliary electric heat and replacement of existing baseboards with high output models.
Water to water boiler gets it done. Cooling top down you can count on lower levels benefiting even if number of ducts is less desired.
Not a fan of high velocity as there is seldom a place I can't do the same with less expensive conventional ducts that don't diminish system capacity.
I would move the attic within the envelope as jon suggested and reduce load wherever possible as Dana suggests.
j

Posted By Dana1 on 31 Aug 2012 06:03 PM In my neighborhood geo runs about $9K/ton (probably higher than the national average, but not 2x), and even if envelope upgrades to bring the loads down cost $10K/ton it will be be worth it on both operating cost & comfort grounds. The financial crossover points will be different in every case, but PLAN on making significant upgrades to the building envelope as a critical part of the whole project, not just squirting in R50 celluose into the attic. The first ton or so of load reduction is likely to be a bargain, even the second might be pretty cheap compared to a ton of geo in your area.

It always sounds like that if you can reduce the load by a ton you save $9000, which is not really true. Yes, 2-ton geo systems start at $19K with us, and then in crease by about $3K per ton. The reason for this is that the labor is almost the same to bold in a 2 or a 6 ton heatpump, the two buffer tanks and the flowcenter. The material for the larger loopfield and the larger heatpump plus the additional labor for the loopfield make up the $3K per ton. So the price for residential 2-6 ton systems is not linear but saturates, kind of the opposite of what you describe with the insulation upgrades. The first ton load reduction is the cheapest, like geo, where the last ton capacity is the cheapest upfront. Operational cost savings are more linear.

Wile what doc said is true, $3,000 will buy quite a bit of envelope improvements.

The best Watt, ton, Btu, or CFM is the one not needed, purchased, or operated. In other words, do whatever feasible to shrink the load by improving the envelope. Load reductions not only reduce system installed cost (smaller is cheaper) but also operating cost.

That said, while high velocity seems an elegant retrofit solution for exosting homes it imposes both unique design challenges to ensure the high velocity thrown air doesn't cause discomfort via drafts, and also a penalty in the form of increased blower power (and, potentially, noise) noise, to get air moving so fast.

Whooki,

You’re definitely smart to research the feasibility of geothermal for your new home since over $6,000 per year for fuel oil is outlandish. I agree that improving the insulation will also help but the big savings will come from switching to geo.

Here’s a few options to consider (some have been mentioned already):

1. Add standard ductwork
2. Investigate high-velocity ductwork
3. Augment/Improve the hydronics
4. Utilize “ductless” heads

The best system will probably be a combination of the above and will start with a solid heat loss analysis (Manual J calculation) as others have mentioned.

We have done a number of similar types of retrofits across Minnesota and the homeowners have been very happy with their savings and their comfort.

If you aren’t satisfied with your geothermal proposals, I suggest you keep searching until you find someone who has the experience to do it right.

-Erik

www.ThermLink.com

Posted By docjenser on 02 Sep 2012 09:07 PM

Posted By Dana1 on 31 Aug 2012 06:03 PM In my neighborhood geo runs about $9K/ton (probably higher than the national average, but not 2x), and even if envelope upgrades to bring the loads down cost $10K/ton it will be be worth it on both operating cost & comfort grounds. The financial crossover points will be different in every case, but PLAN on making significant upgrades to the building envelope as a critical part of the whole project, not just squirting in R50 celluose into the attic. The first ton or so of load reduction is likely to be a bargain, even the second might be pretty cheap compared to a ton of geo in your area.

It always sounds like that if you can reduce the load by a ton you save $9000, which is not really true. Yes, 2-ton geo systems start at $19K with us, and then in crease by about $3K per ton. The reason for this is that the labor is almost the same to bold in a 2 or a 6 ton heatpump, the two buffer tanks and the flowcenter. The material for the larger loopfield and the larger heatpump plus the additional labor for the loopfield make up the $3K per ton. So the price for residential 2-6 ton systems is not linear but saturates, kind of the opposite of what you describe with the insulation upgrades. The first ton load reduction is the cheapest, like geo, where the last ton capacity is the cheapest upfront. Operational cost savings are more linear.

Fair enough, the $9K/ton is an overly simple model, but I doubt the price structuring in my neck of the woods is even under $5K per additional ton above a bare-bones 2 ton system.

The average size of the residential systems in the CT rebate program from which the $9K/ton number is derived was 5.63 tons, not 2 tons, not 3. 

I doubt that a 2 ton system in CT & MA is "only" $39K, (almost $20K/ton) with the cost adder for upsizing  only $3/ton.  There's still some serious $/ton to be reaped here- WAY more than $3K, if not as much as $9K.  (I'm still waiting to see a hard quote for any geo system, any size, in MA come in at <$20K, and I'm not holding my breath.)

When the home is larger in size, I'm not sure I'm aligned with all of this emphasis here on reducing usage (particularly at all cost) before putting in geo.

For here in the Dallas area, a very much cooling dominant climate, where heating oil cost and need for aux heat subjects don't enter into the discussion:

Every ton of geo has an associated cost, and none of the ton's get to be small?

A 3K+ SF one or two story brick veneer home in the Dallas area, that's 80s or 90s era with nothing special about its insulation or air leakage,  that's ready for HVAC changeout after using about 15 - 20 years of lifetime, and you're saying to go spend upwards of $10K/ton on envelope improvements first?

I say get the 5 ton geo unit in asap and then figure out what makes economical sense toward envelope improvements.  You're already looking at the investment of changing out the conventional sourced A/C or heat pump system.  So the incremental investment for geo is 5 to 10 years, without having significant expenditure toward envelope improvement.

Five ton geo costs about $27K (including the vertical bore hole field, a couple of water tanks and the flow center).  That's a little more than $5K/ton.   And then subtract out the cost of conventional replacement, at let's say $20K (probably more actually).  Now you're down to $1.4K/ton as your definition of 'low hanging fruit' to attack via envelope improvements.  I.e., if the envelope improvement being contemplated costs more than $1.4K/ton (likely), then get on with the geo before doing the envelope improvement.

This rules out window upgrades, and door replacements.  Instead, get on with the geo replacement, look at increasing attic insulation perhaps, get out the caulk gun, plant some trees for shade, put in some window shades, shop for a lower utility rate, replace every incandescent bulb with a CFL, change life style to turn stuff off and actually use a programmable tstat, and call it a very outstanding economic day.

I'm not convinced spending upwards of $10K/ton on envelope upgrades is money well spent at all.  Nor am I convinced putting in significant upgrades to the envelop have to be critical parts of an HVAC replacement effort.  I'm not convinved it would be worth it on operating cost or comfort grounds.

In summary, if it's a larger home, in a cooling dominated climate like Dallas, I say call the geo contractor before making costly changes to bring the cooling load down.

Best regards,

Bill

Sure, ask a geo contractor about geo prices, but don't rely on his response about spending money on insulation. But if you get the right (ie, impartial, properly motivated, educated) person, they can do all the calculations and give you a good idea about what is most cost effective for your situation.

Bill- My recommendations were for whooki, who lives in MN (US climate zone 6 or 7), not for Dallas (US climate zone 3). This isn't intended to be a generic discussion or recommendation other than to say,

"Take a big step back and sharpen your accounting pencil".

Dallas loads have little bearing on MN average loads (or even southern New England where the per-ton costs are apparently substantially more than TX). It shouldn't come as any surprise that the economics OF COURSE pencil out very differently in US climate-zone 3 compared to climate zones 5-7.

Yes, even in Dallas air sealing is going to be more cost effective as a rule (unless you're already below 1.5ACH/50) and higher roof-R (up to R50-ish or so, maybe a bit more).

Window replacements are going to be a tougher financial argument to make in any lower-48 climate zone, but would still possible in places where the marginal cost of upsized geo is over $5K+ per marginal-ton (which is Bill's average cost per ton) and the cost of power is 15-20cents/kwh instead of 10-15cents, etc.

But the comfort difference between a circa 1990 code min window and a U0.20 window is very real in zones 6 & higher (where heating outside design temps are in negative double-digits F), whereas the comfort differences of high-performance windows over 1990 code-min are barely noticeable in zone 3, (even though it has a measurable impact on system sizing.)

So while there may be at least some rationale for paying up to $10K/ton in load reduction in my location (and maybe in whooki's location too- I don't have cost data for MN) by no means would that be a justifiable upper bound elsewhere. My comments of where the rational limits might be for my climate & market should not be misconstrued as a general recommendation.

But doing the real math for YOUR location is highly encouraged. And even in Dallas calling the geo guy before the energy-nerd consultant to fine-tune what the loads really are and where the low hanging fruit could be reaped would probably be a mistake.

I say, for Dallas area locations, for larger homes (3+ KSF), that are 80s to 90s vintage, that are 1 or 2 story brick veneer structures, where the HVAC system is ready to be replaced (probably at the 15 - 20 year point), where the duct work is already at least adequate (i.e. there isn't a major air distribution problem), and where a 30% tax rebate applies, you 'go straight to Go.'  You find a residential geo installer you can be comfortable with.

Further, you skip all of the Man J, S, D, and T stuff, and simply use whatever tonnage was working for the structure with the existing system, and put in vertical holes at the 300' per ton rule of thumb for this area.

I say you'll save more money faster this way than any other route.

You're going to air seal at $1K or less per ton (including 30% tax rebate consideration)?  Where do I sign up, anywhere in the country?  You're going to need some big holes to reduce the cooling load a full ton for just $1K.

Likewise, I don't believe taking an old R-38, attic that's down to a 15-20 year settle R24, and bringing it back up to R50, is anywhere near less than $1K/ton of cooling avoided.

Overall, I think we sometimes do readers here a disservice, getting carried away with the least expensive watt, BTU, etc. is the avoided watt, BTU, etc.  It just isn't true in some locations / climates.  I'm increasingly figuring out that, at least here in the Dallas, just get on with the geo replacement with 300' holes per ton spaced 20' apart, and then study all of the other utility bill reduction strategies later (given the situation is as I started with above).

I think the subject changes materially for smaller homes here, where only 1 or 2 tons is needed.  Now I think geo is dead here.  It's time to get on with mini-splits, multi-splits and ducted minisplits.

Best regards,

Bill

As of March we can no longer skip all the ACCA alphabet soup. Changeouts must be certified to Man J and S to meet code.

One thing missing from the foregoing is a discussion of where energy costs are going in the next decade or two. Nat Gas is down for the moment, but will that continue? Will a global economic recovery coupled with ever increasing regulation drive up all energy costs?

Dana cites intangible comfort gains with modern windows up north. I heartily agree, having spent 4 winters in school in New Hampshire in a dorm with 1908 single pane windows.

To that let me add a southeastern corollary - spray foam attic insulation. Pricey? Yep, about $2-3 per square foot. It knocks a ton or more off the typical 4-5 ton calculated cooling load. Intangible knock-on benefits include civilizing the attic for both ducts and storage (much cooler, cleaner and drier up there post-foam) Even better, done right, foam reduces infiltration by capping the stack effect as well as sealing the attic itself. Post foam, small duct leaks are rendered moot. Finally, foam either greatly strengthens roof (closed cell) or greatly reduces noise (open cell)

Clients in a post-foam house with right-sized AC nearly universally report being much more comfortable in the home, nearly always at higher thermostat setpoints owing to substantially reduced humidity. I and others find 77*F and 45%RH more comfy than 74*F 55%RF, typical post and pre foam conditions.

While new windows are rarely justifiable down here on energy grounds alone for any home built after the Korean War, window film often pays off in both comfort and efficiency on select (typically unshaded west) exposures.

When the home is larger in size, I'm not sure I'm aligned with all of this emphasis here on reducing usage (particularly at all cost) before putting in geo.

I would say that particularly when the home is larger in size there should be an emphasis on reducing usage.

I'm not convinved it would be worth it on operating cost or comfort grounds.

What about in terms of reducing unnecessary consumption? You know; a "Green" approach, as in "GreenBuildingTALK"?

Through Dana's lobbying and Curt's wise counseling I keep load reduction in my arsenal for many applications.
I sub electrical and ground loop installation to other installers who benefit while my pay to GC a project and do the sheet metal/plumbing are relatively fixed.
So in cases where load reduction is likely to cost less than attacking the load with a heat pump I am on board with improving envelope first. Where I already have a relatively modest load, I counsel the benefit of improving the envelope through insulation or sealing. Where I have inadequate duct work for a larger heat pump I encourage customers to attack from envelope side first to reduce the requirement and minimize duct modification.

However: against propane or fuel oil I am saving my customers 60-70% over existing bills, so in saving energy (GREEN) geo is the greatest potential consumption reduction and good bang for the buck.

In spite of all the suspiciousions about us geo guys, I try to advise my customers in the way that benefits them most. Remember I sell furnaces too, so if they wanna go 98% efficient furnace and insulation, I make a greater percent on dollars spent on fossil and I'm in and out in a day. The only thing I don't sell service is electric baseboard, but I recommended those and envelope improvements lately to a customer I paid to meet (through pay/click advertising) with a 700SF house- because it was the best advice.

The energy auditors I know recommend and profit from/arrange work for insulators, so suggesting all are impartial is naive as well.

Alton and Dana appear to be completely technology neutral and informed (selling design and good advice). Unfortunately there are a lot of flakes out there that know little of local conditions and over reach their wheelhouse, selling faulty advice for profit which is worse than a good plan by a local contractor (regardless of approach).

What I do and what my customers get is a team of open minded contractors interested in the best possible outcome for the customer. I get the geo here, Dave gets the solar there or Jack gets the insulation there......All (customers included) profit or benefit.

Interesting discussion.  Thanks.

Best regards,

Bill

Joe - I think you are on the right rack, particularly with regard to situations where reducing the load renders previously undersized ductwork suitable with minor mods.

I alternately wear HVAC and auditor hats. As an auditor I push for envelope improvements that will reduce the size and complexity and cost of the high efficiency HVAC system I want to deploy. I constantly push the envelope of downsizing HVAC (just as you do), except that I can't fall back upon "auxiliary strip cooling" since it does not yet exist.

I do bring in foam subs to participate in deep energy retrofits, and I do profit from that work since I am obliged to test the foam installations so as to be sure they'll support the downsized systems.

To keep everything above board, I ask the client to pay me a percentage of the foam sub's invoice. That way the sub doesn't have to pad his bid, and the client is crystal clear on the value I add and how I'm compensated.

I encourage every client to share their energy bills after the project is complete. Every project we undertake is tested every month...by the utility bill

You know Curt everytime you mention lack of auxiliray cooling, I think "why not?".
With portable ducted ACs or even central dehumis to ditch some condensate load, why can't you have the "after burner" button when you need it for those "blue moon" loads. We should kick this around some time.

I wear a few hats myself. My favorite is the "consumer advocate hat". I use it here as well as inspecting and on estimates.