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  1. #1
    Join Date
    Oct 2009
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    Question Best system for new home: NG Furnace w/ AC + NG WH or NG Boiler + Indirect WH + A/C

    I am in the process of planning a new home in Idaho Falls, Idaho. Summers are warm enough to merit air conditioning (95 to 100 F degrees in July and August). Winters are quite cold with many days not exceeding 15 or 20 F degrees. We will have natural gas available (avg $0.75 per therm) while electricity averages $0.12 per kWh.

    Our current home is 1800sq ft with a full unfinished basement. It is heated with an electric heat pump (York Affinity YZH 3 ton). The system works quite well (backup kicks in below 0 F degrees) but we have hot and cold rooms even with the fan running continuously (bedrooms are always cold even with vents in the living room closed). Maybe we should have done a zoned system.

    The home will be single story (2000sq ft) with a full basement. We also intend to put a bonus room/apartment above the garage (500sq ft). The home will be tight, with tri-pane windows and spray foam insulation. I am curious about several approaches to heating and cooling this home. Your responses will help me decide which contractors to evaluate since not all of them do boilers, hydronics, ect.

    Option 1:
    I assume the most common approach would be an NG furnace with A/C coil (or heat pump if it makes any sense). A standard NG hot water heater (or possibly tankless/vertex/polaris). Would it be advisable to break the house into seperate zones? Should one system supply the whole house, or should we put a small system or mini-split heat pump in to handle the bonus room?

    Option 2:
    I am interested in how effective it would be to install an NG boiler, indirect water heater, and then an A/C air handler with hot water coil in the main home and another small unit in the bonus room.

    Additional:
    Is hydronic floor heat a better option than the hot water coils in the air handler? Is there a way to provide cooling or would I still need to have a forced air A/C system? The basement floor could have hydronic tubing poured in I assume, but what is the best approach for the main floor and bonus room (3/4 TG) over TGIs or floor trusses?

    (Feel free to suggest your preference TGIs vs floor trusses for ease of install, floor quality/feel, and quietness. Our current home has TGIs and squeaks and pops in cold dry weather.)

    Since construction is to be tight, should we install an HRV to provide bathroom exhaust and continuous ventilation?

    We are willing to invest in quality and efficiency, but are not wanting to buy a Lexus when a Chevy will serve just as well.

    Thank you for any advice and suggestins you can provide. Also, if you are a contractor in the SE Idaho area please let me know as I am looking for a good heating/mechanical contractor.

  2. #2
    Join Date
    Nov 2006
    Location
    Athens, Ohio
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    IMO the uneven temperatures in your current house are because of poor duct design.
    You must have a Manual J load calculation performed for the new house. You will be surprised at how small the load will be as a result of the spray foam insulation. Do not be persuaded to use bigger equipment. The duct system should be designed according to Manual D for proper air distribution and comfort.
    I suggest a gas furnace with a heat pump or an air conditioner. The bonus room will be best served by a ductless heat pump.

  3. #3
    Join Date
    Oct 2009
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    9
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    Thread Starter
    Thank you very much for your advice! This time around I will make sure the Manual J and Manual D are performed. Should I expect the contractor to be willing to share the actual results of the calculations and a detailed list of all equipment they are proposing in the estimate? I am sure I would need to pay for the calculations first, but I don't want to get locked into the job without knowing exactly what I am getting. Maybe I have trust issues, but then again I learned a few things the hard way when, and as a result of GCing our current home. Thanks again for your help!

  4. #4
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    7,300
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    I share the manual J calculation if the customer buys from me. If they want the results without buying from me, I charge for it.
    Too many customers are shopping for the lowest price and I will not design a system only to have them go to someone "who'll do it for less."

    You should offer to pay for a load calculation from a reputable company. Look carefully at the design parameters they use. They should be appropriate for your area and type of house.

    When we provide a bid, we specify the model, efficiency and warranty.

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