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Radiant basement floor as “redundant” heat source?

user-1137156 | Posted in Energy Efficiency and Durability on

I’m building a ” pretty good house” and as you know, from my other discussions,planning to heat with high performance mini split heat pump or pumps exclusively. With no back up heat I want REDUDANCY. I want to, in the event of a “partial” failure 1. First priority avoid “freeze-up” if it’s unoccupied during a cold snap. 2. maintain a ” livable but reduced IDT, in all or parts of the house. 3 have an efficient system . Other priorities, not associated with “failure” are, not in any particular order are: A happy wife,she says wall units unacceptable, controlled temperature in occupied areas, three temperature zones ( 1 unfinished, therefore unoccupied, basement, 2 bedrooms, 3.daytime living area).
Untill the thread about using a heat pump water heater to lower the cost of operating a radient mass heater I was happily designing around 2 slim ducted systems . That thread caused me to re-think and reevaluate, and consider some other options.! New option 1 add a “hack job” radiant floor, in the basement and call it the back up system (posrsibly eliminates the cost of redundancy it the main floor system and changes the efficiency situation. New option 2 include DHW and go for a GMVS-HS160 WOW! new option 3 use both a “hack job” radiant floor and a GMVS-HS160 as a fail soft pair. Question, How well will a radiant basement floor heat the main floor if it has no other heat, how much “hydronic” heat will I need to install on the main floor? . . .

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  1. GBA Editor
    Martin Holladay | | #1

    It seems to me that you are using a sledgehammer to install a pushpin. That said, I'm guessing you'll proceed regardless of my advice -- and that's OK, because it's your house.

    Here's my feedback:

    1. If you build a thermal envelope that approaches Passivhaus or Pretty Good House standards, it will never freeze, as long as it has a few unshaded south-facing windows, and as long as it isn't located in Alaska.

    2. If you want to keep your house comfortable during an electrical outage, I advise you to install a propane-fired space heater with through-the-wall venting. One of these can be purchased for about $400.

    3. Either of these approaches will work, without the need of a "hack job." But of course, you will miss out on the "WOW!"

  2. user-1137156 | | #2

    I'm now going to adopt your suggestion but not give up the sledge hammer. The propane fired space heater will soon be in the plan, it adds protection for grid outages! And it'll probably cost less than any of my alternatives. I should have, as you suggest adequate freeze protection because It'll have both a near passive house envelope and have 180 sq ft of south facing windows with SHGC of 0.4 and certainly Kentucky is not Alaska. That reminds me that my heat load estimates are likely WAY off as I've ignored solar gain. I see no reason to give up on the WOW! A GMV-HS is far and away the "best" non solar thermal DHW heat source, with lots of other benefits, if I can get it.

  3. GBA Editor
    Martin Holladay | | #3

    If you like my idea of installing a propane-fired space heater, just make sure that you choose a model that doesn't require electricity. Empire is one brand.

  4. user-1137156 | | #4

    I have done a quick online search and so far the winner is Williams @ 22kBTU available through Lowes, my grand daughter works at one. Do they all have a "pilot" ? I've learned a little more about WOW. The largest, single phase unit is 60K Btu with water tanks of 250L or 500L. If I can get one sooner rather than later, I'd replace the upstairs HVAC, (2 ton Carrier installed poorly in the attic) in my current house either with one mini duct, still in the attic or 4 wall wart heads linked as one zone if that is possible. Otherwise wait for new construction which uses one 18K slim duct in "dropped" ceiling of common hallway.

  5. chrisjri | | #5

    If I could ask, What is a GMVS-HS160 WOW?

  6. GBA Editor
    Martin Holladay | | #6

    Like you, I'm baffled. Jerry Liebler is a very cryptic writer.

    On this thread, he makes a reference to a "GMVS-HS160." I'm assuming that the "Wow!" is just Jerry's expression of excitement.

    In comment #2, he changes the designation -- or perhaps refers to different equipment -- and calls it a "GMV-HS." (He moved the hyphen.)

    I thought he might be picking up an idea from a previous thread ("Heat-pump water heater for radiant floor heat?") -- the thread where Liebler first mentioned a "hack job" -- but I went back to that thread and re-read his Comment #1, and it turns out that he was excited about a different piece of equipment back then -- something he called a "GMV-PD."

    I tried Googling these terms, but came up blank.

  7. calum_wilde | | #7


    I just went through the same process. My results were also the same.


  8. chrisjri | | #8

    "A GMV-HS is far and away the "best" non solar thermal DHW heat source, with lots of other benefits, if I can get it."

    This statement has my curiosity peaked.

  9. calum_wilde | | #9

    Chris & Martin,

    I think I may have found something. Maybe. Take a look at "Gree Multi Variable".

  10. user-1137156 | | #10

    First I apologize for the confusion. As I said, I'm in the process of building a "pretty good house near Lexington Kentucky. How best to heat a "pretty good house is not settled "science". I've been struggling with choices and options for HVAC and DHW. I've nearly settled on the HVAC, thanks to Martin's suggestion. The HVAC will include a direct vent propane fueled back up furnace that will provide "emergency" only heat. The primary HVAC will be an 18KBTU "Midea" 2 zone "flexible" multi split with 2 indoor mid static 18KBTU slim duct units. The Primary heat system rating of 18kBTU falls slightly below predicted needs of 24K BTU @ 0f but it produces the required heat @17f. Either I may burn some propane on the coldest nights, but far more likely is I've ignored other heat inputs an my actual requirement for heat is less. That leaves DHW. I'll use a heat pump water heater for sure. Simply stated I want a split heat pump water heating solution!. The available all in one indoor HPDWH
    can never be as efficient. The rest of the world has largely adopted air source water heating and there is a VERY wide range of equipment choices. We only get access to "the good stuff" if it can run on the UNIQUE power,60HZ, present in the North America. Alibaba is kind of a window into the world market. Thru it's cousin Aliexpress anyone can buy anythnng available anywhere, if it was made in China. WOW is a set of equipment that uses an air source split heat pump to supply both HVAC and DHW. Meaning one large mini split that does both HVAC and DHW heating and uses the heat removed in air conditioning to heat DHW. One option I've found, on Alibaba, is branded Gree, has different component selections and configuration model designations. This Gree family of systems model numbers begin with GMV-HS, they include, HS to separate household from commercial and the numbers are the thermal power output rating in killowats (divide by 3.412 for BTU). The 160 kilowatt unit's ODU looks like the typical large mini split. To me, ideal is a three zone configuration with one full capacity, heating only, zone for DHW and two much smaller zones for HVAC Commercial VRF systems do allow different zones to simultaneously be heating and cooling.

  11. GBA Editor
    Martin Holladay | | #11

    Thanks, Jerry, for clearing up the confusion. Here is a link:
    Gree GMV

  12. user-1137156 | | #12

    Thank you for the link, the best explanation I've seen! If I were in Greece, my energy dragons would all be slain. However, I'm in the U.S. so the battle continues. How do I get one?

  13. calum_wilde | | #13

    Damn, now that is interesting.

    Jerry, can you share a link for the split DHW heat pumps you're looking at? Or one you'd suggest for a climate zone 6a house?

  14. GBA Editor
    Martin Holladay | | #14

    More info, this time from Bulgaria: Gree Service Manual.


  15. Expert Member
    Dana Dorsett | | #15

    "We only get access to "the good stuff" if it can run on the UNIQUE power,60HZ, present in the North America. "

    Let's see, Taiwan, Korea, and half of Japan run on 110V/60Hz power... do Venezuela & Columbia in South America and all of Central America. Peru's standard is 220V/60hz though the more southerly SA countries are 50Hz.

    So while it's nowhere to be found in Yurp or China, 60Hz power is far from unique, covering much of the Asian first-world population as weil as a good fraction of the Latin American population. From a market wealth perspective 60Hz power covers a big market, a minority market perhaps, but not unique to the US & Canada.

  16. user-1137156 | | #16

    When I find one that I'm sure I can get I'll be glad to.
    Edit: Palm branded mono-block units have been obtained, and successfully deployed, through Akiexpress by a Canadian "hacker"
    but they only support hydronic heating & cooling which I want to avoid due the complexity and cost.
    Great find Thank you! Evidently they offer a lower cost version that is cooling only +DHW for those wanting to use all hydronic heating. It appears the IDU family matches the Midea & Pioneer offerings here in the USA.. The service manual style and pictures are very similar to the multi split Pioneer brand.

  17. user-1137156 | | #17

    Thank you. But I really did know that & ignored it for the sake of brevity & as a possible excuse for our slow acceptance of energy saving technology such as heat pump clothes dryers, almost unavailable here yet mandatory in Sweden. I've always wondered how the population of Japan deals with two diffrent grid standards.

  18. Expert Member
    Dana Dorsett | | #18

    The 50 Hz & 60Hz grids in Japan are even (somewhat weakly) interconnected with massive inertial converters. Tokyo & further north & east are all on the 50Hz grid, delivered at both 100V and 200V into the house. everything west & south of Tokyo is on the 60Hz 110V grid, with the exception a few prefectures where both grids are available.

    Many appliances and other equipment sold in Japan are designed to operate from 90-120V and 45-65Hz, but others are voltage & frequency specific. People just get used to reading those specs, and retailers are careful about what to stock too, but plugging into the wrong voltage or frequency is still a common problem there. The wall-sockets are the same everywhere- similar to US 2-prong plugs but without the wider connection for the neutral as found in the US, making accidentally plugging into the wrong voltage or frequency WAY too easy to do. Even in the 50Hz-only areas it's possible to plug 100V equipment into a 200V socket (and conversely.)

    The Taiwanese, Korean & Japanese domestic markets for mini-splits are huge (larger than the US & Canadian markets), and the design changes for Asian 60Hz equipment to work in 120/240 VAC 60Hz power environments of the Americas is pretty small.

    Energy has been traditionally cheap in the US, and even cheaper relative to the average incomes when compared to the EU or Scandinavian countries, which blunts the relative personal-financial drive for energy efficiency. Being climatically regionally and culturally diverse hasn't made it easy in the US arrive at a national consensus about how energy or climate change issues. Comparing US national policy where the national average residential electricity prices are ~USD$ 0.13, about half the € 0.19/kwh average in Sweden, where consensus around MANY issues is a lot easier achieve is a bit silly. Sweden is a rich country, but they're not twice as rich as the US or even at parity with the US. See:

    "If it were to join the US as a state, Sweden would be poorer than all but 12 states, with a median income of $27,167"

    That makes it a LOT easier to market & implement energy conservation policies.

  19. user-1137156 | | #19

    THANK YOU Dana!
    Even though Sweden may well be richer than Kentucky, it is comparing median purchasing power but not income,, their thought process isn't disturbed by fond memory of the glory days of coal and slavery, far greater causes of irrational behavior around here. And that's who the senate majority leader "represents"? As often as I've tried Mitch just doesn't take calls!!!

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