Hi everyone.  We are building a new house this year and have our plans drawn up. It is a 2500 Sq. Foot Slab on Grade in Central Minnesota.  We have always thought GEOthermal was the way to go and have had our situation analyzed.  We have enough water and acreage to put in an open loop system.  We have gotten an opinion from a builder that the GEOthermal is not the way to go maybe because of lack of familiarity but since we have been in our last house 13 years we're pegging this one at 20.  Of course in buiding discussions the SIPS conversation has come up.  We like the idea but are wondering if the GEOthermal is actually overkill.  My thoughts were that I could have it stick built for less in this economy and the GEOthermal would make up the savings as opposed to SIPS.  Of course I am leaning towards both as the open loop system is not that expensive and can always be retofitted to a closed loop down the road without changing interior equiptment cost.  Just trying to get one one track and stay there.   By the way we're not really trying to build "GREEN" just don't want to pay utilities and maintain ease of comfort and reliabilty. 

Can't wait to hear the opinions!!!

I would think that the harsh climate and 20 year time would make the upfront cost of SIPs (or ICF) worth it in the long run, especially if you consider the possibility of substantial energy cost increases caused by either supply or tax reasons.

Don't forget to factor in cost of pumping water for an open loop system - it can be a substantial fraction of total energy use and there is also the issue of greatly increased well pump run time and whether the well pump will last long in that service.

Builder may criticize geo in hopes you won't make him deal with it.

Personally I just don't get the open loop systems. Too many moving parts and pumping alot of well water that you may or may not want to waste. They may be cheaper but not for me. Small house go dx! My log house has sip insulation on the roof. I love it. If I ever build another house it would be a timberframe home with SIP walls and ceilings. The less dollar bills I have to set fire to every month for electric and heat the better. You can't have too much insulation or too efficient an HVAC system. Let your neighbors keep the electric company in bussiness. What's wrong with being green? Your children will thank you for leaving them something that's not paved over.

It sounds like you are trying to build green , just fiscally motivated .

It also sounds like your builder is not very experienced with what you are trying to do . A builder depends on the expertise of his subs , and if you are dealing with a " traditional " contractor neither he , nor his usual subs will have substantial experience in your potential $green$ saving home . which can lead to budget over runs and construction and post construction issues .

I do believe that nothing works better then a super insulated home with a geo hvac system , and the combination should save substantial money ( only reason cant say 100% is lack of info ie cost , fuel cost , electric rates , heat loss calc, and so on) and considering the above it sounds like the builder wouldn't be able to give accurate predictions either. I would recommend contacting a builder that specializes in green building techniques if you decide to go that route, who at least will be able to give close cost estimates ( installation and operating ) they would also have the most important thing a builder can have , a rolodex with the right numbers in it

If you are willing to invest in high end stuff like SIPs, ICF foam insulation, geo and good windows, don't screw up by going with a builder that doesn't also embrace and have experience with these methods.

The value added by the builder as general contractor is to select and manage the subs that will implement these methods. If he can't / won't then you shouldn't engage that builder. It really is that simple.

If anyone thinking about putting Geothermal into their home is located anywhere near Milaca, MN you're welcome to take a look at mine. The only catch is that you might have to listen to me talk about the installer, S & B Geothermal out of Ham Lake and the supplier, Econar. I can almost guarantee that if you look at it and hear the horror stories you'll run - not walk - away from at least the outfits I dealt with. Again, I will gladly walk you through all the problems I'm having now but hopefully will get away from in the future.

Builders first don't like geo because they are afraid that it will create issues, hold them up, does not allow them to get in and out quickly and make their guaranteed money on the job. But they don't pay the heating bill either!
In addition they are sometimes intimidated by the technology, don't understand it, and don't want the homeowners budget to shift away from the countertops and cabinets to the geosystem.

Some get the picture and realize that an energy efficient home will be a much easier sell, and customers like your self are looking for ways to control their costs of living down the road.

Some builders have a visionary thinking, understand that this is the way of the future, and try to get ahead of the competition to gain expertise in renewable energy.

Some we are partnering with are visionary and made geo standard on all their houses. You have to opt out of it as a customer.

http://www.buffalogeothermalheating.com/rivera-greens-by-natale-builders.html

We also discourage from open systems unless you know your well water (quality, amount), or the savings too large that it makes sense to deal with the higher maintenance.

"...an energy efficient home will be a much easier sell..."

WOULD that energy efficient homes be easier to sell! (Alas, there's scant evidence of such in the marketplace.)

Soaking tubs/spas, multi-side-spray showers, and granite kitchen counters are a better "investment" for the money that might have went into geo for those looking for a bump in resale value/ease.

Energy efficient homes are a lot more comfortable & affordable to live in, but it's for long(er)-termers, not for those looking for an easy sale or quick ROI.

And on new construction it always pays to balance the costs & benefits of a better building envelope (design & implementation) is compared to high-efficiency (but also high-cost) systems such as geo. I still believe the better market for geo is as retrofit rather than new-construction, even if not taking it to the PassiveHouse or NetZero extreme. Shrinking the loads 75% with the building envelope can be cheaper than the system required to support the bigger loads of a lower performance building. With sufficiently modest loads R410A refrigerant ductless air-source systems can geo-efficiencies, even in the cool northeast. (And can R744 refrigerant systems with even better cold-weather COP than R401A systems be far behind?) At what point is that most expensive first ton or two of geo just not in the cards? This has to be assessed on a case-by-case basis, but bringing the heat loads under 2-tons without breaking the bank isn't rocket science if the goals are set at the beginning, the architects know how to run the simulations, and the builder understands the concept of air-tight construction. (But yes, it does take more than the ability to enter data into a Manual-J type heat loss calculator.)

But about that side-spray shower in the master bath, can we make it a dual, with six each? It's green enough if you run them with a tankless, and use the grey water to supply the sprinkler system on the 3-hole golf course in the back yard, right? ;-)

I agree with slab on grade with a frost protected shallow foundation - or call it a fully exposed basement. Super insulation makes sense although note that unless you have a way to insulate the windows, going too far has very small returns. I'd go open loop if the water checks out - and realize that using geo for AC vs heating makes a big difference as to what that quality needs to be. If your utility offers off peak rates, then I'd use large water tank storage to take advantage of it.

Posted By jonr on 22 Jun 2011 05:49 PM
and realize that using geo for AC vs heating makes a big difference as to what that quality needs to be.

What? Water quality matters for open loop REGARDLESS of heating or cooling.

Bergy

I installed closed loop geothermal heat last fall. S & B did the work with Econar supplying the unit. So far I've had a compressor replaced due to excessive noise; then had the whole unit replaced because the new compressor was still noisy. I've been upgraded from a 7 ton to an 8 ton which I've heard may cause problems; S & B tried to re-install my wood boiler in March and imploded the boiler itself; they were back last week because the thermostat supplied with the unit was not programmed correctly and would not run AC on our only hot day this summer, now everyone involved is pointing the finger at each other and nothing is getting done - nothing but a long list of complaints. I'm getting ready to just throw the whole works out and go back to a boiler. Anyone out there have any advice? Has anyone else had these types of problems with S & B out of Ham Lake or Econar or Geosystems as they are known now?

While it has always been my philosophy that insulation is the best money you can spend, making a house too tight creates drawbacks. We learned that in Germany with the passive houses. While it is working pretty good in Germany due to the much milder climate, central Minnesota is a whole different animal. Having lived in both places, trust me, a whole different animal (Multiple -30 degree winters were enough, moved to Buffalo, NY for warmer winters!). The first "passive houses" went up recently in Minnesota, lets see how people feel who live in there. They are and should be considered experimental. All the data is still calculated. Hard to find real performance numbers.

Air source heat pumps are simply not (yet) suitable for central minnesota weather.
There is nothing wrong with going the extra mile and making your house tighter, but within reasons. There is balance point where a little more efficiency will cost you much more effort (aka $$$), With central Minnesota temp extremes, including the considerable cooling load, I question that you get the load below 3 tons for a 2500 sqf house, given the fact that you seem to have a budget, and you don't have the desire to go green for every price and join the few experimental projects.

If you do your homework you will choose your options wisely. Do the math, I predict that even with an extra effort on insulation geo will always be a worthwhile choice, especially in a new built house, where after tax credits the difference to a conventional system is relatively small, and giving the heat and cooling load you will have in central Minnesota.

Posted By SJWFARMER on 22 Jun 2011 08:55 PM
I installed closed loop geothermal heat last fall. S & B did the work with Econar supplying the unit. So far I've had a compressor replaced due to excessive noise; then had the whole unit replaced because the new compressor was still noisy. I've been upgraded from a 7 ton to an 8 ton which I've heard may cause problems; S & B tried to re-install my wood boiler in March and imploded the boiler itself; they were back last week because the thermostat supplied with the unit was not programmed correctly and would not run AC on our only hot day this summer, now everyone involved is pointing the finger at each other and nothing is getting done - nothing but a long list of complaints. I'm getting ready to just throw the whole works out and go back to a boiler. Anyone out there have any advice? Has anyone else had these types of problems with S & B out of Ham Lake or Econar or Geosystems as they are known now?

I suggest you start a new thread. Yes I dealt with Econar failure secondary to designer incompetence, and then paired with very inefficient Econar pumping equipment, resulting us to be called in to rescue the project. I will be happy to elaborate on this in your new thread.

Air source may not cut it in central MN this week, but R410A ductless systems with inverter drive is good for a bigger chunk of US Zone 6 than ever before (bigger than I'd thought possible as recently as 5 years ago). With ductless R744 refrigerant air source heat pumps it will be efficiency competitive with geo for nearly the entire lower-48. It doesn't take anywhere NEAR PassiveHouse levels of insulation to get heat loads within the output of R410A minis at design temps of 0F in ~2500' houses. With R744 systems would be good to at least 10-15F lower.

The thing about northern MN & ND with design temps of -20F or cooler is most people don't want to live there (and don't). While R410A minis don't make more sense than geo Zone 7, that doesn't mean it's irrelevant on Zone 5 or the warmer edges of Zone6. In docjenser's new found home in Buffalo NY (the cold edge of Zone 5) the 97th percentile heating design temp is +6F, a temp at which R410A minis still have a COP of about 2. The binned hourly mean temp for Buffalo in January is ~23-24F, a temp at which the COP of ductles minis are greater than 2.8. (They are north of 3 @ 30F.) Given that typical geothermal systems in the northeast seasonally average COPs of only ~2.5 when pump & air handler power is factored in, the argument for spending the money on reducing the heat load and going ductless in a new home rather than code-min or just a bit over code min + geo can become compelling in small to mid-sized homes.

At a central-MN design temp of -20F my 1923 antique 2x4 stick built would still come in under 4 tons. (That's ~2000' of fully conditioned space + ~1500' of semi-conditioned basement that never goes below 65F in winter, so from a heat load POV it's really more like 3500'.). With tighter (and fewer square feet of) glazing and 2x the whole-wall R-value (easy to do, and not expensive) it would easily be under 2 tons heating. In a more optimal layout with a lower exterior surface/floor area ratio getting to under 2 tons is neither difficult to design nor expensive to build. (But temp averages in that climate do not favor R410A. They might still work for R744.) Sensible cooling loads can similarly be designed down, easier with a tight, higher-R (but not superinsulated) home than with something at code-min or just slightly above.

The whole "house it too tight" is a non-starter too. IRC 2009 calls for a tepid 7ACH/50 for air tightness (a hurdle barely taller than a stripe painted on the floor) but even that is well under "typical". Any properly designed heat recovery ventilation system would enhance the comfort & health of even 10ACH/50 houses, and it hardly matters if its 2-3ACH/50 vs a PassiveHouse-tight 0.6ACH/50, the active ventilation rate dominates the ACH/natural numbers.

The economics of envelope efficiency vs. systems efficiency need a sharp pencil to parse finely, but even at the R-values below those recommended for Zone-5 in RR-1005, a mid-sized not over-glazed house would be within the capacity of sub-$10K ductless mini or multi-splits that would run at geo-type efficiencies. To go PassiveHouse on it would take ~1.5-2x the R (primarily due to the limitations & cost of high performance windows making higher-Rs necessary.)

http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones (The whole first section is relevant, but see table 0.2, p10 for whole-wall R values, thermal bridging factored in.)

Even the recommended R30 isn't tough to hit with "chain-saw" retrofit, with 3" of exterior iso on a 2x4 framed house, but that's more expensive than building to R24-27 with 2x6 cellulose studwall + 1.5-2" of exterior iso in new construction. (R30 is ~3x the whole-wall R of my house.)

The arm-waving sketch-up version: A not-too complicated 2500' 2-story house would have exterior wall area on the order of ~3000 square feet (not including glazing), and at whole wall of ~R25, the heat loss through walls is well under a ton @ 70F interior & 0F exterior. Then 1250' of ceiling @ R60 (20" of cellulose, also not expensive to implement in a new design) brings it close to 1-ton. The rest of the heat loss depends on the size & performance of the glazing, the quality of the air sealing, door U values, and foundation insulation, but it's not rocket science to keep the total load under 2-tons without resorting to living in dank, windowless darkness. The same house would be under 3 tons even at -35F. The installed cost of 3000' of 2" iso isn't nothing (~$10-12K), but it's less than half the cost delta between 3-4 ton geo, and the R410A ductless that could support the now-lower 0F load at similar annual efficiency ( but even lower power use, since it's a lower average load), with a somewhat lower total insulation + systems cost. Let's say the house has a lot more corners than that, the total wall surface area goes up to 4000' (a 33% increase), it's still not a difficult technical or cost problem, but it's no longer a no-brainer- every square foot of glazing has to be rationalized (or upgraded at some expense) against the cost of even thicker foam. But it's still do-able, and if the resulting uses less annual heating/cooling power at up-front cost parity the value is there, even on day-1.

But you don't get there by accident- it's only by design, with a reasonable execution of the design.

BTW: The first passive houses were built in Saskatchewan (Saskatchewan Conservation House, 1977 designed by William Shurcliff) and the early versions were way overdesigned for insulation & heating, somewhat under-designed for ventilation. The PassivHaus guys took the superinsulation concepts the Canadians (and others) were working on and modeled it better, and threw down some (some say arbitrary) specifications for a standard. There has been an ongoing refinement of the model since, with numerous European verification at MN type winter temps at higher altitude in the Alps. The lower latent-cooling loads of northern Europe are a bigger differentiator than the lower mid-winter temps or sensible cooling loads of an upper midwest (or Canadian midwest) climate. Some amount of compressor-based dehumidification is necessary in much of the US, where none (or nearly none) is needed in Germany or Austria. But once you have loads that can be handled by a cheap but efficient mini-split, it's time to compare cost/benefit for going Net-Zero with photovoltaics vs. than taking it to PassiveHouse spec on insulation.

The temperatures involved mean that geo will beat air source from an efficiency standpoint. They aren't as popular and so haven't benefited as much in price/performance and features like inverters.

Posted By jonr on 24 Jun 2011 08:34 AM
The temperatures involved mean that geo will beat air source from an efficiency standpoint. They aren't as popular and so haven't benefited as much in price/performance and features like inverters.

With design temps in positive single digits and average temps in the high-teens or higher split system air source with inverter drive can match seasonal power use of geo, if the total heat loads are within range. The advertized COP of geo doesn't include pumping & air handler power, or duct losses.  Beating total-power COP of 3.0 is possible with geo, but that's above the New England average.  Properly sized (or somewhat oversized) seasonal average COPs north of 2.5 with the high HSPF mini-splits is typical, even in central VT & NH. With R744 refrigerant cold weather efficiency extends to even lower temps.  At mid-range of compressor speed the COP of most continuously variable mini-splits is still over 2.5 @ 15F. (but can be as low as 2 at that temp at full speed, which is why oversizing is sometimes beneficial.)

And at least some geo heating systems don't need air handlers and with radiant, have very low pumping costs. And they can hit COP=5, even at 15F outside. Comparing the best new mini-splits to old geo averages is not valid.

Would it make sense for geo units to switch to using an air heat exchanger under mild, end-of-season weather conditions to improve COP and/or reduce loop temperature drop/rise - maybe.

Even in a low-temp hydronic system average ACTUAL heating season average COP of 5 with pumping included sounds like it's parked on a hot-spring. I'm skeptical, even with <110F water temp @ design condition on the radiation. (Got data?)

Comparing low-temp hydronic (at any fantasy COP) to a mini-split isn't exactly kosher either- at least make the comparison with a hydronic air source heat pump using similar low-temp radiation.

Even newer geo installations with ducted air in New England rarely break 3 for a seasonal average- some do, but then so do some mini-splits. With geo a lot depends on the quality of the design, and how well it was installed & tested during commissioning. Hitting an average of 4 is even possible, but rarer than the geo-marketing materials would suggest. But done right, yes, geo can beat R410A split systems with real margin in Zone 5, but at low heat loads and "typical" as opposed to "best possible" installed efficiencies the economics don't necessarily work in favor of geo.

The lower the heat load the less important the absolute efficiency of the system is, and the greater the importance of the up-front costs. Finding the crossover point on envelope efficiency, heating system efficiency, and lifecycle costs takes a sharp pencil and still has big error bars, but I have higher confidence in insulation than any type of heat pump- it has WAY fewer moving parts. While clearly not the right solution for every situation, the engineering is pretty much done with a mini-split- and the installation is more straightforward, harder to screw up (despite many existence proofs that it's possible. :-) )

But for now I'm buying the notion that geo is going to be measurably higher efficiency in DennyJ's climate, but whether it's worth spending the money on fatter sips and paying close attention to the rest of the envelope design. Somewhere in the middle cost-wise would be a hydronic air source heat pump. The 97.5th percentile design temps for Minneapolis is -12F, and the mean January temp is about +12F. With a Daikin Altherma hydronic split system heat pump and a radiant slab the January COP could still run around 2 , and the seasonal average could be bumping on 3. Bigger Althermas still put out 2 tons @ -4F, with a COP north of 2 at that temp. See p.20, (p.24 in the PDF pagination.):

http://thermalproductsinc.com/wp-content/uploads/2010/06/Daikin-Altherma-Engineering-Data1.pdf

With lower-than typical BTU/ft2 requirements on the radiant slab and a correspondingly lower water temp requirement you can probably beat spec by a bit, but don't count on making it into the 3s on the cold edge of Zone 6 just yet...

A COP over 5.0 is possible. Attached is data you requested. If we pay attention to design the distribution system focusing on maximum efficiency, this is possible. In this case, in slab radiant is 6-8 " OC, lowering the design load temp. We do not run the load temp at 110 F, we run it around 75F. In combination with a slightly oversized loopfield, we measured a COP of 5.04 in the middle of february including the load and source circulation pumps. The average COP during the heating season was 5.68. Possible with a groundfos alpha for the radiant floors consuming 17 watts. We use now a Wilo Stratos on the source side, bettering the COP by an additional 8%. In the graphs in the attachment you can see the thermostat was calling for heat for a 4 hour period, and the LLT (leaving load temperature) started at 73F and went up to 78 F when the thermostat was satisfied. Room temp was 68F, which is actually pretty high for radiant floors. After that the buffer tank was "parked" at 85 F. The EWT is at 32F at the peak of the heating season. You would not have that flexibly to play with the load temp with an air sourced split. Plus, what happens to that air sourced coil in a typical Minnesota ice storm with 3 inch of ice on everything, or 3 feet of icy snow piling up behind or on top of the outside unit.

Avoid builders that aren't saavy to the technologies you want to employ.
Understand depending on the size of the system, the difference between open and closed loop may be as little as $2k (pre tax credit), so while I don't mind open loop, it doesn't always save much.
Once you decide how you are going to construct your house a heat loss calc can be performed and then the best heat plant can be selected.
j