Why No High End Split Geo Equipment?

Discussion in 'General Discussions' started by Alexander Wood, Jan 7, 2018.

  1. gsmith22

    gsmith22 Active Member Forum Leader

    what you are saying might be true for the specific case of a net zero home in a cold weather climate, but there is no way that all or even remotely close to some large % of new construction is being built to net zero. I have no issue with someone wanting to live out their green fantasy with a net zero home, but lets be real, that is most certainly not the average or even above average build. It gets exponentially expensive to make the envelope tighter and tighter to squeeze the last BTU of heat loss out of the home. maybe more so then installing geo - priced triple pane windows from europe lately? So to generally say that geo in new construction doesn't make economical sense is totally wrong. That might be true for the very very specific case of a net zero home, but only because they have so little heat loss to start with that any low cost heating system will work.
     
  2. Most new construction is garbage, and the current energy codes are 1/3 what they should be in terms of insulation, air sealing, and equipment efficiency. However, the average cardboard box of a house also doesn't have geothermal installed in it, so the argument that "well the average house is garbage, therefore geothermal makes sense" just doesn't add up. In fact, it's even worse than this, as a modern net zero energy home costs little, if any, more than traditional garbage construction due to huge savings in HVAC ducting and equipment that can be re-invested in the envelope. There is a non-trivial savings to be had by getting rid of all the ductwork, the gas hookup, the scorched air furnasty, and the central AC unit, and replacing it all with a couple of Mitsubishi mini-splits, which covers the vast majority, if not all of the additional cost in building a properly insulated envelope that can get the BTU load down to the 3-5 BTU/sq.ft. required to heat and cool with such a system. The 12" walls and dense-pack cellulose is one way to get there, I've also seen 2x8 walls with another layer of foam insulated board installed outside of that with a hybrid closed-cell foam and fiberglass insulation system, and there are other methods as well.

    Geo in new construction makes zero economic sense. A geo system is going to cost tens of thousands of dollars to put in wells and ductwork, none of which is actually needed if the house is insulated properly in the first place so that it can be heated and cooled with a few mini-splits. Even a house built 50-100% over code with a geothermal system consisting of a maze of ductwork to cover 2 zones and the 450' of well required for a 3-ton packaged system is going to cost significantly more than a house built 200%+ over code with a pair of Mitsubishi mini-splits, and the two houses are going to use a similar amount of energy accounting for the better envelope vs. the better equipment and system efficiency. If there is a slight energy efficiency edge, it will go to the well built home with the mini splits, as you give up a lot of COP, but you also lose the ducting and pumping losses associated with geothermal.

    So therein lies the truth- the house with so little load that basically any low cost heating system will work is going to be a lot cheaper than the house with geothermal that uses a similar amount of overall energy, assuming a higher design load, but with a heat pump with close to double the seasonally averaged COP of the mini-splits. Can the well built and insulated house come in at the same price, as a to-code piece of garbage with a scorched air furnasty? Maybe. There's certainly a lot of cost savings to work with by not putting in ducts, gas lines, and a furnasty. If it's more expensive, it's only going to be marginally so up front, and a lot cheaper to heat and cool over even a short period of time.

    So that leads to a logical conclusion that geothermal is for retrofit applications where you cannot significantly improve the building's envelope, except via attic insulation, air sealing, windows, etc, just to get it to a point where geo is economical to do as a retrofit. These are the applications where remote air handlers are going to be useful, which the Series 7 split provides for, but also where dual-fuel hydro air or scorched air gas/LP furnasties are going to be really useful, which the Series 7 split currently provides no provision for. I'm not sure how much of a challenge it would be to get Series 7 control and performance out of a dual-fuel system, but it would cover a lot of applications where there currently is no equivalent product, and make geothermal a lot more accessible to a lot more applications.
     
  3. Also, while there are less efficient split geo systems that can be installed with hydro air or gas furnasties, they do not compete well against going with an ASHP in Carrier Greenspeed due to the additional up-front cost, and marginal efficiency gains going from a dual-fuel Greenspeed system to a two-stage geothermal split system. What I don't understand is why Carrier doesn't make a Greenspeed split geothermal system that could get the COP over 5.1 and the EER over 41, probably significantly higher and industry-leading judging by what they're getting on their ASHPs, since they already have the AHUs, hot water coils, scorched air furnasties, thermostats, humidifiers, and everything else in the Carrier Infinity system.
     
  4. ChrisJ

    ChrisJ Active Member Forum Leader

    You can't hire the same builder to build a spec house as to build a near net zero house. I think most builders don't want anything to do with double stud walls or exterior insulation, they are stuck doing what they have always done. A builder that is willing to do those building science details in a home will be quite a bit more expensive.
     
  5. Except that they're not, if you compare apples to apples. Some net-zero builders have done "normal" houses without a ton of high-end fancy custom stuff, and they're able to build them at close to, or the same price as bare minimum code junk. And resistance to change is why the code should be updated from the current decades-old technology and standards, with the envelope requirements tripled, combustion appliances banned, solar required etc. There is just no excuse for the crap that they're still building out there with R-19 fiberglass in the walls. It's not 1960 anymore. The same should be true for the equipment, the code standards are pathetic, and should be significantly increased. But no, the builders don't want that because a lot of them want to slap together the cheapest possible junk, even though it will guzzle energy for it's lifetime, cost the homeowner far more, and be far less comfortable than doing it right in the first place.

    But the point here is that your average cheap-junk cardboard home builder isn't putting geothermal in, they're putting in a scorched air gas furnasty with central AC, and selling the myth that scorched air is somehow "luxurious" or "comfortable" even though it's a lousy way to heat a low-performance home, and will never be as comfortable as hydronics. Looking at new construction, geothermal is still not economical compared to just building the envelope right in the first place and using cheap ASHPs. If a custom job wants to squeeze every last drop of efficiency out, do both, but the geothermal is never going to pay for itself. The marketing lies about "energy efficient" building are also ridiculous. The term means literally nothing in home construction.
     
  6. ChrisJ

    ChrisJ Active Member Forum Leader

    It doesn't have to pay for itself, just the difference in additional costs for geo. Still have the base cost of traditional equipment.

    I think those builders are few and far between.
     
  7. So when comparing GSHP vs. ASHP for a well built new construction house, most of the system that would have to exist for a GSHP simply doesn't exist for the ASHP. Yes, you have to buy a couple of ASHPs, but you don't need ductwork, wells, water piping, any of that stuff, it's basically just a couple of outdoor units connected to indoor units, so the price differential is massive. There is a LOT of labor involved in a heating "system" as we traditionally think of it, whether scorched air or hot water that doesn't have to happen to install a few mini-splits.

    Sure, builders who build well built houses are few and far between. Most of what is out there is cardboard junk. But the cardboard junk builders aren't building with geothermal, the builders who build their houses properly in the first place end up with <5 BTU/sq.ft. design loads (often around 3 in New England) and don't need geothermal, so you're left with retrofit and rehab applications where geothermal actually makes both economic and energy sense. Plus, we just don't build that many new houses in this country, so again, retrofit is the market.
     
  8. gsmith22

    gsmith22 Active Member Forum Leader

    ChrisJ, we are being trolled. he is apparently here to promote the use of air source minisplits in net zero houses (based on all prior posts). That probably makes up 0.001% of the existing and new building stock so obviously it means geothermal is a useless technology :) I've decided to no longer feed the troll.
     
  9. ChrisJ

    ChrisJ Active Member Forum Leader

    I hear you...

    I hate ductless heads!
     
  10. I am absolutely NOT trolling. Go back and read the thread. This is an interesting discussion, but if you go back and read the thread, my question is about why there aren't high efficiency split geothermal systems. There is one now, but it doesn't address the majority of the use cases that would dictate the use of a split system, i.e. dual-fuel applications, either with a scorched air furnasty or a hydronic coil.

    Geothermal has a HUGE potential for retrofit applications in tens of millions of homes, but there isn't any way it works economically in new construction, as I've pointed out several times. Houses that are well built don't need geothermal, and houses that are poorly built aren't going to use geothermal, they're going to use scorched air gas (or maybe ducted ASHPs). Where it gets really interesting is the competition between ducted ASHP and GSHP for retrofits. GSHPs can be competitive, but not with COPs below 5 for heating, due to their much higher upfront cost over Carrier Greenspeed.

    I don't know why you are falsely accusing me of "trolling", but apparently you don't like the discussion on it's merits, so you've resorted to name-calling.
     
  11. Why? Ductless units are the best solution for millions of homes that don't have ductwork, as well as new construction, as they are far more comfortable and efficient. However, there are tens of millions of homes where ductless mini-splits wouldn't be economical to retrofit, and that do have existing ductwork that can be fixed up, sealed up properly, and retrofitted with geothermal. Package systems work in some of those applications, but don't work in others. The Series 7 split will address a few of those applications where you want a pure geo system, but need to install remote air handlers. However, it still doesn't address the dual-fuel applications, which will be more common in large homes, and in exurban areas where the power often goes out. Most of those houses don't have any other form of heat to fall back on, so they need to be able to handle a dual-fuel application.
     
  12. Stickman

    Stickman Active Member Forum Leader

    Aesthetics?
     
  13. That's subjective. Do you have any real technical reasons for not liking them?
     
  14. Stickman

    Stickman Active Member Forum Leader

    You asked a question and received a response. Subjective, yes, but I'd bet some others would agree. If you wanted a specific type of response, maybe you should have framed the question differently. And, no. I do not have a technical reason for not liking them.
     
  15. ChrisJ

    ChrisJ Active Member Forum Leader

    In homes with a point source heat cool "wall wart"(technical term...HaHa), the room to room temp difference can be significant, especially with people who like to close their bedroom door.

    We don't have compressors "uglieing" (another tech term) up the outside of the home, no raceways up the wall.

    There's not enough demand world wide (yet) for high end split GSHP's to justify many companies creating them.

    The End....
     
  16. True, I suppose. It's six of one, half a dozen of the other, as mini-splits don't take up space like ducted equipment does.
     
  17. In low-performance buildings, you typically put one head per room. In high performance buildings, the mass of the building keeps all the rooms within a degree or two.

    Then you have to run a maze of ductwork everywhere. And retrofitting still requires a raceway.

    Well now there is one.... except that it doesn't address many of the use cases that would demand such a unit. Making the Series 7 split compatible with hydro air and a scorched air furnasty would significantly expand it's market.
     
  18. Deuce

    Deuce Member

    It seems to me that you want to stir things up or why would you come on a Geothermal heat pump forum and put it down?
     
  19. Stickman

    Stickman Active Member Forum Leader

    I have a retrofit split installation, and the line set is run from the basement to the attic in a chase wall. No raceway.
     
  20. So if you go back to the beginning of the thread, you will see that my original question was posed prior to the Series 7 split system being introduced. However, the Series 7 split only really addresses 1 out of the 3 major use cases for such a system due to it's lack of ability to be combined with either hydro air or a scorched air furnasty in order to create a dual-fuel system. Carrier currently has the most efficient dual-fuel system, but it's a two-stage split geo system that isn't nearly as efficient as the Waterfurnace Series 7 split, and likely would be hard to justify economically versus a Carrier Greenspeed ASHP.

    So that was a long thread of thoughts there, but what I was referring to was mini-splits versus a ducted split system (either air sourced AC or HP or geo) being installed into a house that did not previously have duct work or any sort of AC/heat pump system. In your case, you may be able to use the existing piping to connect the new unit.

    While there are a lot of efficiencies to be gained with a mini-split system, they are less likely to be economical or practical if there is already halfway decent ductwork in place versus in installations without existing ductwork, where mini-splits are the clear choice. To tie the conversation back to geo, retrofits where there is an existing heat/cool ductwork system (heat only ductwork often won't work for cooling, and cool only ductwork often won't work as a primary heating system) are where geo makes the most sense, and that's tens of millions of homes in the US. Retrofits where no existing ductwork is present, or that have heat-only or cool-only ductwork probably don't make sense for geo, as there are no residential mini-split geo systems, so it makes more sense to go with a mini-split ASHP and retain the existing heating system as backup.
     

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