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Thread: Heating/cooling/humidifying

  1. #1

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    Hello. As I've mentioned on here, I'm building a hoop greenhouse. It's going to be 12x10x6.5 ft. (I changed it from 12x14x6.5). So the total volume inside will be about 565 cubic ft. To heat it I was planning on getting an electric space heater. This is the one i was thinking about: Heater To humidify the greenhouse I was going to get a regular humidifier. Is ultrasonic or wick type humidifiers better for a GH?? I thought that maybe a wick type would cool the air somewhat since it passes the air through a cool wet wick (at least the cool mist kind do). Also, I thought about a small misting system. What types do you guys have?? I'm guessing you use purified water since regular water has minerals and stuff in it. So then do you have some sort of a pump to pump the water through the misters?? I'm planning to get some neps after I build it. I've never really been able to grow very many, except a few small ones in terrariums. So I'm really looking forward to my greenhouse. Thanks everyone,



    -buckeye

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    Quote Originally Posted by [b
    Quote[/b] (buckeye @ Mar. 16 2004,15:08)]Hello. As I've mentioned on here, I'm building a hoop greenhouse. It's going to be 12x10x6.5 ft. (I changed it from 12x14x6.5). So the total volume inside will be about 565 cubic ft. To heat it I was planning on getting an electric space heater. This is the one i was thinking about: Heater To humidify the greenhouse I was going to get a regular humidifier. Is ultrasonic or wick type humidifiers better for a GH?? I thought that maybe a wick type would cool the air somewhat since it passes the air through a cool wet wick (at least the cool mist kind do). Also, I thought about a small misting system. What types do you guys have?? I'm guessing you use purified water since regular water has minerals and stuff in it. So then do you have some sort of a pump to pump the water through the misters?? I'm planning to get some neps after I build it. I've never really been able to grow very many, except a few small ones in terrariums. So I'm really looking forward to my greenhouse. Thanks everyone,



    -buckeye
    i would go with a gas heater. electric are too risky in a humid dripping greenhouse [img]http://www.**********.com/iB_html312/non-cgi/emoticons/rock.gif[/img]

  3. #3
    Nepenthes Specialist nepenthes gracilis's Avatar
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    Quote Originally Posted by [b
    Quote[/b] (buckeye @ Mar. 16 2004,06:08)]Hello. As I've mentioned on here, I'm building a hoop greenhouse. It's going to be 12x10x6.5 ft. (I changed it from 12x14x6.5). So the total volume inside will be about 565 cubic ft. To heat it I was planning on getting an electric space heater. This is the one i was thinking about: Heater To humidify the greenhouse I was going to get a regular humidifier. Is ultrasonic or wick type humidifiers better for a GH?? I thought that maybe a wick type would cool the air somewhat since it passes the air through a cool wet wick (at least the cool mist kind do). Also, I thought about a small misting system. What types do you guys have?? I'm guessing you use purified water since regular water has minerals and stuff in it. So then do you have some sort of a pump to pump the water through the misters?? I'm planning to get some neps after I build it. I've never really been able to grow very many, except a few small ones in terrariums. So I'm really looking forward to my greenhouse. Thanks everyone,



    -buckeye
    I wouldn't use electric, unless you pay 10cents a kilowatt hour! Electric heat is a killer. Go with propane/natural gas/ or Kerosene like I did, I have a 43,000BTU Kerosene vented Monitor heater for my 22 ft long greenhouse, and it does a fine job of heating it even when temps are -50F which we saw here with windchills this winter! I spent around $450-$500 heating it this year so far, hopefully the last fill up will be the last for the year!

    I have a misting system and an ultrasonic humidifer as well an an evaporative (swamp) cooler (used only in the spring/summer months) to cool and humidify the greenhouse. With the ultrasonic running in conjunction with the misting system I can easily obtain 90% or more humidity and it rarely drops below 60% right now. If I was using the exhaust fan it might be a little lower... Anyhow, as far as a misting system goes I bought mine from this place: http://www.cloudtops.com/misting_systems.htm

    It is a VERY reputable place to purchase from. I bought the 45psi pump and it works great! Makes almost a fog mist. Very nice quality material they have. I actually have another $100 worth of accessories coming here any day for exapnsion onto it.

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    Ok thanks. [img]http://www.**********.com/iB_html312/non-cgi/emoticons/smile.gif[/img] Good point about electric heat. I was planning to plug it into a GFI outlet but even with that it's not worth the risk. I'll have to take a look at kerosene heaters. Thanks again,


    -buckeye

  5. #5
    Nepenthes Specialist nepenthes gracilis's Avatar
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    I think I'd be more shocked seeing the electric bill rather than getting shocked by 110v of electricity!

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    Is this a greenhouse for tropicals like Nepenthes or just for overwintering hardy plants like Sarracenia. A tropical house heated to 55-60 F will probably bankrupt you if you try to use electricity.

    Will you be using a double layer of greenhouse film inflated by a fan or just a single layer?

    Since you are in Ohio, your biggest expense will be heating in the winter, so your most important decisions will revolve around that issue. I would suggest some back-of-the-envelope calculations to estimate your required heater size and fuel cost. That way, you won't have any nasty surprises.

    try this calculator:
    http://www.littlegreenhouse.com/heat-calc.shtml

    I think your greenhouse will have a surface area of about 500 sq ft (it's surface area that counts, not inside volume). If you use a single layer of film, the minimum winter temperature is 5 F, and your inside temp is 55 F, then you will need a heater that puts out approximately 28,000 BTU/hour. That doesn't take into account heat loss through the floor and leaks around the door and vents, etc.


    For what its worth, I used pressure treated wood for my 10x16 greenhouse frame and twinwall polycarb for the covering. I've been very pleased with its wind, snow, and ice resistance. I've got a 25,000 BTU vented heater in Zone 7.

    Regards,
    Nick

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    I finished my greenhouse but i still have some questions on heating. Without any heat on and a very overcast rainy day, like today, the temp inside the gh is around 10 deg. above the outside temp. At night it's about 3 deg. above the outside temp. We had an old 1500 watt space heater and i decided to try it in the greenhouse just to see if electric heat could work. After about an hour or so the temp was 20 deg. over the outside temp. So the space heater warmed the air 10 degs. Our cost per kwh here is around .07 and i think it may be cheap enough to use electric heat (I figured it to be about $1.40 for day if it runs for say 12 hrs. each day) but I don't think that electric heat will keep up in the middle of winter. So I started looking at some regular kerosene heaters which are around 23,000 btu. Most have about a 2 gal. fuel tank and run for 12-16 hrs continuous. I assume continuous means the time the thing's actually burning. So I think it would last a couple of days before a refill due to the fact that it will shutoff after reaching the right temp. Since these heaters are unvented I'll probably crack the window open or something. Does this sound ok and does anyone have suggestions??


    -buckeye

  8. #8
    Tony Paroubek's Avatar
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    Have you tried the heat loss calculator? This is very handy. The big question is what temperature range will you keep it at? Will you have a single setting or different settings for day and night?

    I ran some figures with 68 maximum setting on the heater and -20 coldest outside temp. with 6mil single layer poly. 10'x12'x6.5'(height) I came up with 26,000 btu. needed to maintain 68deg when the outside temperature is -20.
    I would think about a vented heater.. fumes may not be good for the plants (or you). You should also consider a fuel tank outside the greenhouse. Refilling a 2 gallon tank on a portable heater twice a day isn't going to be much fun.. particularly if you miss it by 30 min and the heater runs dry in the middle of the winter and the greenhouse is now a deep freezer.



    Is that a Nepenthes in your pocket or you just happy to see me?

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