Replies

1. GBA Editor
   Martin Holladay | Jul 06, 2016 08:58am | #1

   Mark,
   You've got a cart-before-the-horse problem here.

   I have no idea why you installed hydronic tubing for space heat in your floor systems before you designed your heating system. What's that about?

   If you want to heat your home with electric resistance heat -- an approach that is expensive to run, but possible -- you don't need hydronic tubing. The usual approach is to install electric-resistance baseboard units or electric resistance in-floor heating wires. As I said, expensive to run but very doable.

   If you want to heat your house with electricity, the obvious approach is to install a few ductless minisplit units, which will use between 1/3 and 1/2 as much electricity as an electric-resistance approach. Again, if you go this route, you certainly don't need hydronic tubing in your floors.

   Finally, you can't use a heat-pump water heater for space heating, because a heat-pump water heater robs heat from the indoor air to heat the water in the tank. If you are cooling the indoor air with the compressor on your water heater, you don't end up with a warmer house -- you end up with a cooler house.

   You might consider purchasing an air-to-water heat pump system with an outdoor compressor -- but this is an expensive approach that few HVAC technicians will be able to service. For more information on this approach, see Air-to-Water Heat Pumps.

2. 
   user-2890856 | Jul 06, 2016 10:52am | #2

   Cart before the horse may be an understatement Martin . Hos does this still happen ?

   Mark ,

   How did you figure out how much , what spacing , water temps that the tubing would require without first having a system design , heat loss (room x room) performed ?
   You will have to have all this examined and evaluated by someone who is highly skilled , especially at this stage to determine whether or not the installed tubing is even configured for even mediocre performance . Room loads , solar heat gain and varying BTU per sf requirements must be taken into account . There are very few whom possess the skill to do this properly although many will tell you they are the best there is . Problem is they don't know what they don't know . Your best bet is to find someone who knows what he does not know and is willing to listen to someone who does .

   If your tubing install is acceptable you could use something like a Chiltrix unit and a few of their convectors for A/C and still have radiant with heat from that unit . If the tubing is not sufficiently installed the same Chiltrix is able to still do heating and cooling with those convectors . Water is a great medium for heat transfer , better than anything else , Mother Nature has determined that for us . It also allows for multiple sources , no matter what the fuel may be .

   Water to water HP is another type unit one could use . Done properly also it probably offers the highest system COP . You have alot of thinking to do along with thoughts that should have been done long ago . Please take a look at the short presentation that was just recently done . Everyone needs to start to think HYBRID SYSTEMS . Good luck to you .

   http://homeenergypros.lbl.gov/video/pg-e-energy-house-calls-solar-water-heating?xg_source=msg_mes_network

3. 
   user-6104388 | Jul 06, 2016 05:08pm | #3

   Martin & Richard,

   Thank you both for your replies.

   Now that both of you have pointed out my follies, maybe you can take another look at the actual circumstance.

   I had a radiant heating system pre-designed based on ST with a propane boiler backup. The calculations for energy needed were done by a professional before we installed the tubing in the 1st renovation (300sq/ft). No other tubing work has been installed. No boiler or ST has been installed yet. So the remaining 1700sq/ft of radiant is not installed, it does however have a system design which was accounted for heat loss, spacing etc by a professional. At this point, I am not married to ST/Propane heating system. I can accept that I jumped the gun on the first radiant loop install but I know what water temp (120deg) and the BTU's per/hr I need for that loop, so it is possible to switch horses before I build the rest of the cart.

   I have read much of your articles on ductless minisplits and they make good sound sense in most applications. However, I choose hydronic for couple reasons. One, my house is built of old growth redwood and has no ceiling/wall space to run ducts through. The interior is all exposed redwood as well, so I do not want to cut holes to install unsightly plastic wall mount units. The floor has crawl space under it, so running tubing between joists is the least destructive option. Another room has no crawl space but there is room to install a warmboard type product over the existing slab. Also, I chose radiant because I prefer this type of heat. Furthermore, the climate I live in on the coast does not need AC, so cooling is not an issue.

   As far as electric resistance in-floor heating, I was under the impression it doesn't work between floor joists for the retro-fit I'm doing. Also, I didn't think it could be embedded in concrete like hydronic. If there is such a product that is recommended, I'd love to know about it.

   However, if I'm indulging on radiant heat and at this stage can re-design the system to fit other heat sources, then I can either stay with the ST/Propane system that was already designed or look at options. I question if ST/Propane is the best system?

   Richard, the system you sent the video link to was ST but did not elaborate on it's backup heating source. Probably natural gas, which is not an option for me. The system that was originally designed for me was in essence this system with propane as the backup. It was clear the propane would need to do quite a bit of the BTU's over the course of the year, possibly as much as 50% regardless of how many panels or gallons I could store away. This is still an option but Martin's case against ST has me thinking otherwise.

   Martin, you have done a lot of math to show that PV beats ST for HW costs. Do you not feel the same way regarding PV beating ST for radiant heating? If a PV with electric resistance HW tank can cost less to supply 65% of DHW than an ST system, then shouldn't it be able to do same for 65% of the radiant heating requirements? Sizing up my pre-designed PV is a lot less than installing an ST system.

   That's the question I'm really after at this point. If I'm priced out of an air-to-water or water-to-water HP for radiant, then what is the next best option? 1) ST + propane 2) PV + electric boiler 3) PV + Electric HWT (preheat) + electric boiler backup 4) Or just bite the bullet and get a HP with complex/expensive installation.

   Thanks
   Mark

4. 
   user-2890856 | Jul 06, 2016 08:53pm | #4

   The HTP unit that was featured is in fact a NG / Lp fueled unit . There are as well many other HTP options that would cost much less than a Versa Hydro possibly , dependent upon many factors . Check out Phoenix Light Duty , Phoenix , Versa Hydro , all are available with a solar heat exchanger and controls that communicate with everything you'll need or that one would use . HTP also owns and produces their own collectors so one can install an engineered system as opposed to some cobbled together stuff from many different manufacturers .

   Storing heated water for later use at present is much easier and less costly than storing electric . The solar thermal can also harvest heat with a lack of sun . In the case of a power outage a generator would be needed regardless of system choice and I would venture an educated guess that the HTP product or similar and a couple of ECM circs will require less power than the heat pumps .

   The Chiltrix units are probably not as expensive as you think . It can do your radiant also , it'll just require more circ but still an ECM .

5. GBA Editor
   Martin Holladay | Jul 07, 2016 03:50am | #5

   Mark,
   I read your comments several times. I was tripped up by the abbreviation "ST," which I'm not familiar with. I finally figured out that you are using "ST" to mean "solar thermal."

   I have never seen a system using solar thermal equipment (solar collectors that circulate fluid) to provide space heating that is cost-effective. The cost of the solar thermal system is always much more than can be justified by any conceivable energy savings. These systems make even less sense than solar thermal systems that provide domestic hot water -- because people need domestic hot water in July. No one needs space heating in July, so for much of the year, this expensive equipment isn't really doing much.

   It's your house, so you should choose the heating system you prefer. But the three elements you list:

   1. Hydronic in-floor tubing.

   2. Solar thermal collectors for space heating.

   3. Propane fuel.

   ... are all three on my list of least-favorite options.

6. 
   user-6104388 | Jul 07, 2016 11:10am | #6

   Richard,
   Thank you for your suggestions.
   The HTP models look like a much better option then the current cobbled together solar thermal/propane system that I was being quoted. I'm looking into the Phoenix solar models, hoping they can do the job both radiant heating and DHW wise. I know the Hydro Versa model does both but it is almost triple the cost of the Phoenix light duty.
   I also have a call out to Chiltrix. They don't have any dealers in CA, however they feel they can help coordinate with a local HVAC. A little worried about that as I've read these systems need a fairly skilled technician to design/install. Still investigating.

7. 
   user-6104388 | Jul 07, 2016 04:53pm | #7

   Martin,

   I agree with what you are saying. What I'm trying to discuss here is having one 'Martin Holladay' evil, not three.

   I agree that Solar Thermal (ST) is not the best option for space heating (that is why I'm looking for other options). I agree on Propane, is not favored by me either. Again we are on the same page with those two.

   However, I'm wanting to do Radiant (Hydronic in-floor tubing). I don't want to turn this into a ductless minisplit vs hydronic discussion. I agree the mini-splits are more efficient and thus more cost effective. However, I have chosen hydronic in-floor for the reasons I stated in post above. Without seeing my house it's easy to dismiss this whole discussion as an impractical homeowner wanting radiant over minisplits, but I am hoping I can engage you in discussion about how to replace two of the three unfavorable options.

   Can you consider answering a question based on your knowledge of PV vs Solar Thermal for heating water? Based on your article (Solar Thermal is Really, Really Dead), if a correctly sized PV with electric resistance HW tank can cost less to supply 65% of DHW than a Solar Thermal system, then shouldn't it be able to do same for 65% of the hydronic heating requirements?

   I understand that question is hard to answer without some consideration of the demand of the radiant system and the home:
   - Hydronic in-floor system is designed for fairly low temperature delivery (140deg max).
   - The entire system needs 33,000 btu/hr to run on the coldest day.
   - Ground water is 55-60deg. Climate 3c.
   - The heating season is short 4-5 months and not severe (max 40deg temp difference).
   - The location of the home is fairly optimal for PV (Bay Area, sunny in winter).
   - There will already be a PV system regardless; the home's PV system is in pre-design stage, so sizing it up 2-3kw is not as expensive as installing a PV system just to heat water.
   - The radiant system *could* still have an on-demand electric boiler installed downstream as backup/additional heating when the HWT is not supplied enough via PV (extended cloudy weather). The HWT could be set at any temp that is most efficient for the unit and my daily average kw/h production (ie 120deg). I would treat that tank the same way Solar Thermal installations treat the SHW tank, in that some backup heat source is needed when the sun doesn't do it's job fully (or at all).

   I know it all sounds abnormal and against current practices, but so did PV outperforming (cost wise) solar thermal for DHW when I first heard the idea.

   Thanks for taking the time to read this. I look forward to your thoughts on this question.

   Mark

8. GBA Editor
   Martin Holladay | Jul 07, 2016 05:50pm | #8

   Mark,
   Q. "If a correctly sized PV with electric resistance HW tank can cost less to supply 65% of domestic hot water than a Solar Thermal system, then shouldn't it be able to do same for 65% of the hydronic heating requirements?"

   A. Yes, using electric resistance is cheaper than using a solar thermal system for that purpose. That doesn't mean that using electric resistance is cheap or appropriate for space heating -- just that there are some ways to heat water (e.g., solar thermal) that are even more expensive than electric resistance.

9. 
   user-6104388 | Jul 07, 2016 06:10pm | #9

   Martin,

   Thanks for the response.

   Ok, so it's not the cheapest (or appropriate?). Yet, it's better than Solar Thermal. So I would conclude from your statement there are ways to heat water for hydronics that are cheaper and more appropriate? What are they, if natural gas is not an option (for me) and propane is least favorite option for you?

   Thanks
   Mark

10. 
    charlie_sullivan | Jul 07, 2016 07:44pm | #10

    I haven't read through all of this, but it seems like you had an air-to-water heat pump on your original list and had it recommended a few more times. Why not go with that? For 33 kBTU, you could get two Chilltrix units, or get one and electric resistance backup heat.

11. 
    user-6104388 | Jul 07, 2016 08:11pm | #11

    Hi Charlie,
    Chilltrix is on my list and I'm looking into it. However, two units cost $7000 before installation. Even one unit is $3500 without install. I've yet to find a dealer, or more important a qualified installer in the Bay Area. I've read on these forums that one of these units can be about $6000 installed -- That is a lot of KW's of PV panels. PV Panels will most definitely outlast the heat pump. I'd probably go through at least two heat pumps within the 25yr warranty of the panels I'm looking at. Even my inverter will have a 10yr warranty (which I'm needing regardless with my PV system). I'd only be buying extra panels and an electric boiler(s).
    I found one HVAC contractor in the Bay Area who installs the SpacePak Solstice Heat Pump. They quoted me 15k for a unit installed. At that price, I can't see the payback being worth something that is probably only going to last 10yrs. Personally, I think that is more expensive than even solar thermal.
    I'm not ignoring that option that was recommended and am actively looking into it. However, until I find a unit(s) that can do the BTUs and be installed for less than 6k, I am purposing a question whether PV with electric resistance is actually a more cost effective, durable and less complicated system. I have no refridgerant, no complicated plumping... it's parts are not expensive to replace and the work can be done by my local electician and plumber.
    Thanks
    Mark

12. 
    charlie_sullivan | Jul 07, 2016 09:42pm | #12

    The expensive part of the Chiltrix install is the radiant floor system. You've already done that so the rest should not cost much. If you only use it for heating and not cooling, there's nothing too special about the rest of the installation, and anyone who can do the electric boiler should be able to do it. And if $7k for too is too much, just get one and supplement with electric if and when needed. If 33 kBTU/h is your design load, you wont need more than the 25 kBTU/h that one Chiltrix can supply something like 90% of the time, so getting one and using resistive heat as backup makes sense.

13. 
    user-2890856 | Jul 07, 2016 10:35pm | #13

    http://www.nextgenboiler.com/sites/nextgenboiler/files/Technical%20documents/NextGen%20brochure%2012-23-15_web.pdf

    http://www.uponorpro.com/Modal-Pages/Products-and-Tools-Modal-Page.aspx?id={58BC4834-4676-4A2D-B493-1EED6079AF80}

    If zoned properly taking into account solar heat gain and the like you could more than likely get away with a source that does 24,000 BTUh . Solar thermal has gotten a bad rap and I really do not wish to beat that horse again . I will say that drainback systems that contain no glycol can and will last 30+ years and that stored water can be utilized by many different types of units , many of which can include COP and reduced need for current .

    Phoenix Light Duty would be a very good choice for your project in the fuel of your choice . It will make plenty of hot water at elevated temps and a 1017 ASSE DHW mixing valve WILL increase storage capacity . You can also utilize 2 ecm circs and a flat plate heat exchanger with an outdoor reset mixing valve to do the radiant . Your PV array will not have to be much larger .

    You will not find the Light Duty shown doing space heating in their manual as you would find in the Phoenix manual . However it can be used , the rerason you will not find it in my opinion is a licensing issue between hTP and Warmboard . Warmboard utilizes this unit as a space heating only appliance for radiant systems under the trade name , Warmsource . No reason that it cannot do both applications , I mean it is shown doing a hydronic Fan coil also . Curious how that works .

14. GBA Editor
    Martin Holladay | Jul 08, 2016 04:25am | #14

    Mark,
    If you insist on installing a hydronic system, there is no perfect solution.

    Propane is an expensive fuel, but installing a propane system may be the most economical way to proceed (depending on what propane dealers are charging in your area).

    Electric resistance is kind of absurd, but it might make sense in light of the fact that you will be installing a large PV system.

    The Chiltrix option would be expensive to install, and you'd be saddled with a system that almost no HVAC contractors would be able to service. (For more information on the Chiltrix, see Air-to-Water Heat Pumps.)

    If this were my house, I'd install minisplits. If you want a hydronic system, an electric-resistance boiler may be the "least bad" way to go.

15. 
    Patrick F | Sep 02, 2016 01:24am | #15

    Mark,
    I, too, was confused by Martin's "Solar Thermal is really,really dead" article; if PV works for domestic hot water, why doesn't it work for hydronic floor heating? I live close to you in Los Gatos, CA and about to start a 2,000 sq ft house with no natural gas option to heat the house. But with new construction, I have the option to tightly insulate and seal the structure as well as store heat under the slab as recommended here - http://www.radiantsolar.com/solar_options.php . I appreciate Martin's expertise, but aesthetically mini-splits will not work for us and I like the quiet and convective feel of the underfloor heating - either electric or water - but I do want to keep the system as simple and maintenance free as possible. I apologize for hijacking the thread but I am curious if anyone has a recommendation for me working on a clean slate. Also, it would be great to get together with you, Mark, offline to see what you finally come up and if you have any local resource recommendations. Regards, Patrick patrick.freeburger AT gmail.com

16. GBA Editor
    Martin Holladay | Sep 02, 2016 04:15am | #16

    Patrick,
    Q. "If PV works for domestic hot water, why doesn't it work for hydronic floor heating?"

    A. A PV system generates electricity, and (if your local utility offers net metering) the electricity you produce is credited to your utility account, lowering your electric bill. The PV system doesn't know or care how you use electricity.

    If you want to use electricity to heat your house, you can. If you know how much electricity you use for space heating on an annual basis, you can purchase and install a PV system that is large enough to cover your annual space heating bill. So far, so good.

    So how can you use electricity to heat your house? Lots of ways:
    - Electric resistance baseboard units.
    - Ductless or ducted minisplits.
    - Electric resistance boiler hooked up to a hydronic distribution system.
    - A ground-source heat pump hooked up to a forced-air distribution system.
    - A ground-source heat pump hooked up to a hydronic distribution system.
    - An air-to-water heat pump hooked up to a hydronic distribution system.

    Take your pick. As I've written before, ground-source heat pumps are expensive to install.
    Air-to-water heat pumps are so rare that it's hard to find a system designer or an HVAC contractor who knows how to service these systems.
    Hydronic distribution systems are expensive compared to heating systems that have simpler methods of heat distribution.

    But you can choose any system you like. Lots of people have installed a $30,000 ground-source heat pump and are happy with their system. Personally, I would rather install $10,000 of ductless minisplits and $15,000 of PV, and use the $5,000 I saved on something else.

17. 
    user-2890856 | Sep 02, 2016 09:24am | #17

    Patrick ,

    There are options available that you are looking for . They are not so , or shall I say , do not have to be as expensive as some would have you believe .

    I sent you an e mail .

18. 
    user-2310254 | Sep 02, 2016 10:08am | #18

    Patrick. I think you are suggesting there is a WAF issue with the ductless minisplits. I can appreciate that point of contention since I've encountered it as well. But you might want to consider a ducted minisplit system for heating and air conditioning. While your climate conditions are mild, you do get occasional 100+ degree weather.

19. Expert Member
    Dana Dorsett | Sep 02, 2016 02:37pm | #19

    I was out the week this thread started, but a heat load of 33,000 BTU/hr for an 1800' house in Climate zone 3C sounds downright crazy- is that with the windows wide open or something?

    I would expect a reasonably tight code-min house that size to come in around 10,000 BTU/hr, @ +35F or +40F or whatever the local 99% design temp is, 12,000 BTU/hr tops (code max glazed area, code max air leakage.) A 2-ton Chiltrix would have that covered with huge margin. But so would a 1-ton mini-split, though you may need as much as 2 tons of ductless to manage the peak cooling loads.

    Talking about the solutions for some fanciful but still unknown load is silly. Before doing anything else, pay an independent third party (not an HVAC contractor) for areal heat load calculation using aggressive assumptions on air tightness & R-values. Designing the heating system to 3x the capacity of the likely heat load is well trodden path, but technically against code in CA, and downright silly.

    That said, I'd go out on a limb an suggest that the heating & cooling loads are probably within the capacity of a single 1.5 ton Fujitsu-18RLFCD mini-ducted unit, as long as the mini-duct cassette and ducts are all inside the thermal & pressure envelope of the house, and there isn't some amazingly huge "sunset view" picture window facing west to drive the peak cooling load through the stratosphere.

20. 
    user-6104388 | Sep 05, 2016 01:28am | #20

    Patrick,
    After considering all options for a hydronic heating system, I did decide to go with an Air-to-Water Heat Pump. Specifically the Chiltrix. There were several factors for me:
    1) In our climate these units can be very efficient at heating water. Far more so than propane or electric resistance.
    2) I will have PV offsetting electricity charges which makes it a more earth friendly option than propane.
    3) While Solar Thermal is also earth friendly, the infrastructure needed was so much more. Both space wise and moving parts wise. Also, after consulting with solar thermal installer he actually advised me to look at air-to-water Heat Pumps. He was thinking of it as a back up to solar thermal, but after running the numbers it made little since to spend that much up front on both systems.
    4) So far the cost of the unit and the install is not that much more than the less efficient options. I see the pay back as the best option for me. The install is planned for late October, so we'll see... The trick is making sure you adapt your system and design for these units (more on that below).
    5) While an inexpensive electric resistance boiler could be cheaper and less trouble in the short term. I was not comfortable with that amount of KW draw, even if I could afford the PV to offset it. Also, there can be some significant upgrades needed to electric panel which made it a lot more expensive. I think if I had a more efficient home an electric resistance could be feasible. It certainly is simpler.

    Probably the biggest draw back with the route I'm going well be (as Martin points out), the lack of knowledgeable service professionals that deal with these units. I have had to pull together a team of people that will help with install. A solar thermal/hydronic installer, a skilled hydronic plumber and an electrician. I've also done a mountain of research into these systems to make sure we design/install an effective system. I enjoy this work, so it's cool, but not for everyone.

    Here are some points I can pass along if you go air-to-water heat pump:

    1) Read this: https://www.greenbuildingadvisor.com/articles/dept/musings/air-water-heat-pumps

    2) Design your system with lower temperature heat requirements. I have learned that basically means using low temperature emitters. This is good video to watch: https://www.heatspring.com/courses/low-temperature-heat-emitter-options-in-hydronic-systems. While radiant slabs and suspended slabs are capable of low temperature delivery, make sure you insulate the these slabs really well to take advantage of warm floors with a low temperature system.

    3) Get ready for a lot of hydronic install companies to tell you that these units don't work. That you should just use propane. I found this tough as I had to take some of the matters into my own hands and delayed install so that I can adapt the system to match the specifications of the unit.

    I hope this helps.
    Mark

21. 
    user-6104388 | Sep 05, 2016 01:33am | #21

    Dana,
    I see my post wasn't that clear and I left out info.
    While I currently have a 1800sq/ft, I am renovating and adding sq/ft. This is happening over the course of the next couple years. The total will be 3100sq/ft. Yes, the current house is a retro-fit of a 70's sea-ranch style home that has floor-to-ceiling single pane windows and was poorly insulated. The property actually has three separate buildings a main house, a studio and a sleeping quarters. Separate buildings make for more heating and that cannot be shared by one mini-split. Since posting, I have worked on retro-fitting insulation during the renovation and have reduced the heat load of the existing buildings considerable. I also have looked into some better options for the expansion construction. I've been able to reduce the total to 24,000btu/hr for 3100sq/ft over three buildings. Not great but cost wise it was difficult to do more to the existing buildings.

    Ultimately, I prefer hydronic heating. Ascetically, mini-splits are just not a fit with my wife and I. We also prefer the heat that hydronic supplies in our damp coastal climate. I think with air-to-water heat pumps becoming more cost effective, the possibility of a cost effective hydronic system is possible. No, they will not match mini-splits in cost, but I think hydronic is superior in several ways that can make it attractive to people who want a little extra control and comfort.

    Thank for your advise.
    Mark

22. 
    DrDanger | Sep 11, 2016 03:55pm | #22

    Mark I would love to know more about your experience with the install of your Chilltrix unit. For reference we have a house with hydronic heating and has a solar hot water heating system with an electric resistance heater for back up. The resistance heater has started to have issues and will be needing replacement in the near future so this might work well for us. Thanks in advance, Kevin

23. 
    skierpage2 | Oct 11, 2019 07:54pm | #23

    Mark, who did your install? I'm in a very similar situation (see "Can my hydronic radiant heat system be saved?" in this forum) and am having a stupidly hard time finding any installers in the Bay Area who will even countenance a hydronic radiant heating system that isn't powered by burning gas.