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best gas heater for shed/greenhouse

jpm995jpm995 Posts: 6Member
Hello everyone i'm new here and need some advice. I have a well built shed 12' x 18' and i want to add a lean to greenhouse [21' x 10'. I have natural gas heat [Navian] in the main house. The sheds about 50' behind the house. The total sq ft is around 450 but the greenhouse is only about a 3 R rating [6mm double wall GE plastic]. I think the most cost effective way is to trench the gas to the shed and use a high efficiency gas/hot air burner. Was looking at Rinnai FC510N or FC824N no vent heater, or a Monterey 25,000 BTU Natural Gas Top-Vent Wall Furnace. I assume the Rinnai is much more efficient but i'm worried about the safety no vent. The Williams burner fits IN the wall and has a rear vent option so i could maybe heat shed and greenhouse as i plan on a large opening between them. Will the Rannai save a lot and the no vent a good way to go? I'm sure there's other options, i'd like to here your onions. Thanks.

Comments

  • Jamie HallJamie Hall Posts: 8,534Member
    Do NOT use a no vent heater in a greenhouse. Some plants don't mind so much. Others? They die... which, I presume, is not really what you want.

    I doubt that the difference in efficiency is that much -- certainly not enough to justify using a no-vent in that type of application.
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • jpm995jpm995 Posts: 6Member
    Thanks for your input, i wanted to use the Rinnai for ease of install [no vent] and assumed efficiency. Would you recommend any other solutions?
  • Jamie HallJamie Hall Posts: 8,534Member
    Go with a direct vent heater, or that Monterey. I agree that the no vent variety is easier to install -- but as I say, they are pretty tough on plants.
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • SWEISWEI Posts: 7,356Member
    The Rinnai is a direct vent, no?
  • Paul48Paul48 Posts: 4,492Member
    Efficiency is not possible.I'd use Modine heaters.
  • jpm995jpm995 Posts: 6Member
    Rinnai has both direct vent [81%] and ventless [99% efficiency] heaters.
    https://www.rinnai.us/documentation/downloads/R-CNHT-E-07.pdf
  • jpm995jpm995 Posts: 6Member
    I don't understand your comment Paul, can you explain? I'm thinking Rinnai but the direct vent one. It seems more modern than the others. Needs electric to run but it has no pilot always running and had multispeed fan and different heat temps. It's more complex but if reliable seems like a better unit. It's 81% efficient not as good as i hoped and it's more money but i've always heard good things about Rinnai.
  • Paul48Paul48 Posts: 4,492Member
    It was my thought, that you are essentially heating the "Great Outdoors". Having a greenhouse in the winter may be a necessity, or a luxury, but heating it with a furnace is probably not the most efficient way to do it. I'd imagine there are some very resourceful folks that heat their greenhouses efficiently with solar, passive or otherwise. IMHO
  • Jamie HallJamie Hall Posts: 8,534Member
    Paul48 said:

    It was my thought, that you are essentially heating the "Great Outdoors". Having a greenhouse in the winter may be a necessity, or a luxury, but heating it with a furnace is probably not the most efficient way to do it. I'd imagine there are some very resourceful folks that heat their greenhouses efficiently with solar, passive or otherwise. IMHO

    Depends on your climate, @Paul48 . In some southern climates, or, say, Kalifornia, you might be able to. Most of the northern US east of the Cascades and especially New England, never mind Canada? No hope. Sorry. No can do.

    And I might add that for some farmers, at least -- and the OP may be one -- a greenhouse isn't a luxury at all, but the only way to grow some of the crops which the market demands.
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Paul48Paul48 Posts: 4,492Member
    "And I might add that for some farmers, at least -- and the OP may be one -- a greenhouse isn't a luxury at all, but the only way to grow some of the crops which the market demands".

    My statement covered that possibility, but then it becomes about profitability. I could be wrong, it is just my opinion. Maybe there is an efficient way to heat a greenhouse. You know better, than I.
  • Paul48Paul48 Posts: 4,492Member
    I worked on a house, years ago, that was passive solar. It was a replica of one in Nova Scotia, that spent under $200 year round to heat.
  • Jamie HallJamie Hall Posts: 8,534Member
    Paul48 said:

    I worked on a house, years ago, that was passive solar. It was a replica of one in Nova Scotia, that spent under $200 year round to heat.

    My father in law, now passed away, was one of the real pioneers of passive solar heating, both for domestic and commercial uses. I have great admiration for his work. A number of his full and partial passive solar houses and buildings are scattered around New England.

    One of the things which made his work great was that he recognized the limits of the technology...
    Jamie



    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.



    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Paul48Paul48 Posts: 4,492Member
    Absolutely..........And building in such a way as to minimize the run time of a greenhouse heater is probably the best way to be efficient. My only point of reference is that I worked for a company, a while ago, that sold greenhouses and greenhouse heaters. They were anything but efficient. Things may be different now-a-days, as far as the furnaces go. I don't know.
  • hot rodhot rod Posts: 8,592Member
    Funny thing about greenhouses and passive energy, sometimes you need to dump heat, even in cold climate conditions. Seems like ventilation fans are a key component.

    On the heating side, it seems like r-value and green house are oxymoronic. They are typically energy pigs.

    Root zone heating is another method, where warming the soil, not necessarily the entire volume of the space, is adequate.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • jpm995jpm995 Posts: 6Member
    I'm no farmer and the greenhouse/shed is strictly for my pleasure. I want the GH to be a mini zoo/botanical gardens with ponds for fish and turtles and the shed to be a man cave. I know it seems like an expensive hobby but i really enjoy the thought of having my own botanical gardens. Just moved into a new home with this big shed and i'm getting crazy ideas. Plus my wife is sick and tired of all my plants and tanks in the house.
  • hot rodhot rod Posts: 8,592Member
    It can be done, with renewable energy, too. Amory Lovins grows tropicals at his home in Snowmass, Colorado


    http://grist.org/climate-energy/amory-lovins-high-tech-home-skimps-on-energy-but-not-on-comfort/
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Paul48Paul48 Posts: 4,492Member
    I think that's an awesome idea. You might want to talk to a greenhouse manufacturer. Tell them you're interested in alternative ways of heating a greenhouse. They may be able to help. Don't get me wrong....you'll need a furnace, but you don't want to have it running 24/7.
  • SWEISWEI Posts: 7,356Member

    My father in law, now passed away, was one of the real pioneers of passive solar heating, both for domestic and commercial uses. I have great admiration for his work. A number of his full and partial passive solar houses and buildings are scattered around New England.

    One of the things which made his work great was that he recognized the limits of the technology...

    I suspect I would have greatly enjoyed meeting the man. After decades of studying and messing about with various aspects of buildings and energy my understanding of the value of passive solar design continues to grow. There's literally almost no place on earth where it does not represent a good investment. Insanely good on some places of course, but pretty reliably good.
  • jpm995jpm995 Posts: 6Member
    The shed also had a brick fireplace [the shed was a sauna] and i was thinking of adding a wood burning stove for extra heat. Aqua shield has a lean to greenhouse 10w by 20l for @ $12k. Hope i can get this done without breaking the bank.
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