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Community and Q&A

Heat pump heating system alternatives

John Williams | Posted in Mechanicals on

Hi guys,

Our initial budget came back from the gc 25% over. We’re on a very strict budget and builder knows this as well as the build level,im trying achieve, “pretty good house” level 1200 SF footprint w loft space and 16kw pv setup at a cost of $18000 after credits and rebates with a supposed 6 yr payback

Im wondering if rather than our spec’d $17000+ heat pump system which is a york 18 seer azh affinity series heat pump. In fairness contractor did say we could drop to 16 seer and save $2000 but i think we may miss rebates with that system. This cost seems excessive and unnecessary for our sized building

Thoughts on our setup?

Some sort of oil filled electric baseboard system would be super cheap and given our solar output does this not make more sense?

I know heat pumps have a higher coefficent of performance but does this difference merit such an expensive system?

Thanks from a rookie!

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    John,
    1. We need to know your geographical location or climate zone.

    2. The first step when designing a heating system is to perform a Manual J heat load calculation. Has that been performed yet? If so, what is the home's design heat load?

    For more information on Manual J calculations, see these two articles:

    Saving Energy With Manual J and Manual D

    Who Can Perform My Load Calculations?

  2. Steve Knapp CZ 3A Georgia | | #2

    16 KWh seems like a lot for a 1,200 square foot home. Or did you mean to type 6 KWh?

  3. John Williams | | #3

    of course, sorry, i always forget that part, especially typing on an ipad.... the build is white mountains NH. so zone 6

    have not done a heat calc yet, though the GC tells me (tells me a lot of stuff actually, hardly anything yet in writing) that one will be done by hvac contractor once we finish off our spec choices for insulation, windows etc.

    frustration is settling in because he trying to scale back insulation/envelope from an r37 ish wall, 6" cellulose with 2.5" zip r sheathing, lose the basement exterior insulation etc. asking how much we wanted to pay to add these high performance items in, when i stated the build goals from day one.

    he knew the goal of this project was high efficiency, beyond the norm and certainly beyond code, and despite my strong objections during design mtg's, things like a bump out to add a full staircase was added, additional bathrm, etc. when i balked, i was told, let's put it in, price it out and see where the price comes back. "we can always take it out " i was told. well, here we are in need of substantial redesigns and likely to miss our build window for the year, due to a month turnaround for redesign and clearly having subcontractors committed to other projects by now when our goal was to have foundation poured as soon as road bans came off.

    we'll get there just not sure with this builder

    sorry for the add'l rant, love the site keep up the great work and help you all provide here!

  4. John Williams | | #4

    i've attached the estimate for consideration by those who know what they're talking about, as opposed to me, who just asked for a system that could "run everything"

    i guess the system would more accurately be called a 12.5-13.5 kw system, but the "production" line says 15kwh for one option and 16kwh for the other

    i was told we'd be close to "net zero" with these options, given current net metering rates and actually given that those were subject to recent change was told best to file the app (no money changing hands) to get in the queue for the current net metering rates

  5. GBA Editor
    Martin Holladay | | #5

    John,
    Good luck with your redesign.

    In terms of your cart-and-horse problem, here is the necessary order of events: First, perform the Manual J calculation. Then, and only then, you can begin to choose your heating equipment and design your distribution system.

  6. GBA Editor
    Martin Holladay | | #6

    John,
    Steve is right. There is no way that a 1200-square-foot house in New Hampshire needs a 16-kW photovoltaic system to hit net zero. It should be possible to meet your goal with 5 kW to 7 kW.

  7. John Williams | | #7

    here you go, sorry.....

  8. John Williams | | #8

    it's entirely possible i read the estimate incorrectly. i just saw "payback sub 7 years and figured, "ok, that sounds pretty goood

    i figured since we're trying to run:
    -electric oven
    -electric hot water heater
    -electric heat
    -1500 watt electric fireplace (it is the mountains after all)

    we'd need a big system

    our overall build budget is $350k (not including land, design permitting) plus 10% contingency plus about $25k in add'l items, so while this isn't an extravagant build, by many standards, i figured that should be sufficient to get us where we need to be. we're not rich, have just saved for awhile and don't have kids. point is, this isn't some luxury, this is a change of lifestyle, which is a big reason for the push for small or no utility bills

    thanks again guys

  9. GBA Editor
    Martin Holladay | | #9

    John,
    No, you read the estimate correctly. Those are huge systems.

    Who performed the calculations to determine your annual energy budget? What type of energy modeling program did you use?

  10. John Williams | | #10

    hi martin

    my assumption is the solar provider with based upon info provided by the GC

    it bears mentioning, the final sq footage as figured by the gc was nearly 2000SF. the 1200 SF footprint, then the 600SF loft, which is completely open to 1st floor and the +/-150 SF staircase bump out, again within an open floorplan

    ive attached the floorplan if anyone's interested

    so that info is important, to be fair to the GC and create the most accurate picture.

  11. John Williams | | #11

    oh and if there's been any energy modeling done, im not yet aware of it

  12. GBA Editor
    Martin Holladay | | #12

    John,
    If you want to build a net-zero house, you need to hire a designer with experience designing a net zero house. This designer will optimize the envelope design using an energy modeling program like BeOpt or PHPP.

    If you are letting your contractor design your net-zero house, and if your contractor doesn't have a lot of experience in the field, you may not have the designer you want.

  13. Stephen Sheehy | | #13

    John:My pretty good house is in Maine, zone 6. Conditioned space is about 1650 square feet. House is all electric, including a hot tub. Our annual power use is about 9-10,000 kwh. Our 6.6 kw solar system produces about 8,000 kwh per year.
    There's no way you need a 16 kw system, but there's also no way a 16 kw system would cost $18,000 unless NH has extremely generous rebates or credits. Assume about $3 per watt before any state or federal credits or rebates.

  14. GBA Editor
    Martin Holladay | | #14

    Stephen,
    He posted a link to his estimate. His contractor will install the system for $2.40 per watt. Then the customer gets $11,575 in incentives (federal tax credit plus state rebate).

    Here is the link again:
    https://www.greenbuildingadvisor.com/sites/default/files/Roof%20Mount%20Estimate%20copy.pdf

  15. Steve Knapp CZ 3A Georgia | | #15

    John,

    Since you are in Maine, you should check out Ecocor (https://www.ecocor.us). I would.

  16. Expert Member
    Dana Dorsett | | #16

    The odds that a 1200' Pretty Good House actually needs a 2-ton AZH Affinity (the smallest in the line) for heating & cooling is pretty remote. With any sort of design optimization with BeOpt or other the peak loads would likely come in at or under 12,000 BTU/hr @ -10F for both heating , and even less for cooling, possibly even under 10,000 BTU/hr.

    Which size Affinity are they specifying for that $17K price tag?

    SEER is almost meaningless in a heavily heating dominated NH climate, where on many summer days the cooling loads are primarily latent load (humidity). The numbers of highest interest here are HSPF (=heating BTU per watt-hour) and it's capacity at sub-0F temperatures.

    A 1 ton or 1.5 ton modulating mini-ducted Fujitsu (12RLFCD or 18RLFCD) mini-split would almost certainly cover the loads, at a price point much lower than that. Both will modulate down to 3100 BTU/hr @ modes, delivering optimal comfort & efficiency by running nearly continuously, even in low-load homes. Sized correctly to a reasonably accurate Manual-J, is should pretty much hit it's 11.5-ish HSPF efficiency, and would have enough capacity even at -4F. Your actual 99% design temp is probably cooler than -4F, which is the coldest temperature at which they specify the capacity, but this series keeps running and putting out decent heat at temps below that, the output & isn't specified below that temperature.

    The 2-ton Affinity at it's lowest speed delivers ~17,000 BTU/hr @ 40F, which is probably more than 5x the heat load at that outdoor temperature, which means there is no way in hell it will hit it's ~9ish HSPF numbers at your house. The lowest temperature at which that series has a specifed capacity is +10F. That specified +10F outdoors/+70F indoors capacity is 14,700 BTU/hr, which may be twice your actual load at +10F. That means it will probably be able to cover your load at -10F, but it's so ridiculously oversized it'll still be cycling on/off most of the time even in winter, rather than stepping up/down between it's high/low speeds.

    A 1 or 1.5 ton modulating Mitsubishi MVZ series ducted minisplit with a heavier duty air handler would probably still come in under $15K, and has the benefit of a 2.5:1 modulating range, and a rated output a -13F. Since the modulation range is much lower than a Fujitsu RLFCD mini-duct unit, sizing has to be done very carefully to ensure it modulates rather than cycles.

    A 1.5-2 ton 2-3 zone ductless multi-split may come in cheaper than a mini-ducted solution, but it's likely the minimum output of the compressor @ 47F still be too oversized for your actual loads. Without an reasonably aggressive room-by-room Manual-J there's no way to tell if this would be an option.

  17. Brian P | | #17

    John,

    I'm over on the east side of the White Mountains (Jackson). We've been living in our house for two years: 2 story, 24x32', 1500+ gross sq ft, Pretty Good House insulation levels, all electric, and a 6.72 kW solar PV system. There are two of us (no kids) and we are careful about electric use. In 2016 we used 6736 kWh and the solar generated 8497 kWh, making the year net positive by 1761 kWh.

    Where are you in this process? Do you have land? Are you committed to the builder or still pricing options to sign a contract soon?

    Your builder's residential portfolio shows houses from 3,000-7,000+ sq ft, so I wouldn't be surprised if you run into pushback on a smaller home with high energy efficiency goals. If you find the relationship not working well, I'd suggest looking into Unity Homes since they are in NH:
    https://unityhomes.com

    Some comments/notes:

    The electric fireplace sounds like a waste of money and space, I'd suggest ditching it. You should be able to heat/cool your house with 2 ductless mini splits if you are open to those. That should come in around or under $10k.

    A solar PV system sized around 13 kW sounds like overkill if you are trying to be net zero. That is a really good price though that you've been quoted. A system of that size could make sense if you drive electric cars. But if you want to just zero out your home use, a system of around 7-10 kW would probably get you there depending on how frugal you are with electric use.

  18. John Williams | | #18

    thanks guys...

    martin, any direction you can point me for local-ish designer with net zero experience and what their input may cost with us at the stage we're currently within?

    steve: im checking out ecocor now, nice line of homes, difficult to get too much detail from their site, though pinterest and outside sources seem to have some

    brian: i like unity, feel like pre fab in general is obscure in their pricing until you commit more deeply to them tho' have found most prefab to be just out of our range as well. we have land and are choosing options, pre-contract. agreed on the fireplace, but i cant win every battle with the boss... she was shocked we wouldn't have a woodstove in the mountains so i'm giving a bit where i can...

  19. Anon3 | | #19

    This is why you lock in the price before you sign the contract.

  20. GBA Editor
    Martin Holladay | | #20

    John,
    I can recommend the services of Marc Rosenbaum. Of course, I have no idea how busy he is, or whether he can take on your case. You can reach him by calling 508-693-4850 or by email:
    mrosenbaum [at] southmountain [dot] com

    I can also recommend the services of Kaplan Thompson Architects, 424 Fore Street, Portland, ME 04101 (207-842-2888). The company's web site is at http://www.kaplanthompson.com .

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