early

Thoughts on heating a greenhouse

20 posts in this topic

I have had a south facing 12x24 foot double-paned glass lean-to style greenhouse attached to my shed for 5 years now, but I have never been real successful with it. My main goal has been to use it to grow through the winter, but have problems with maintaining warm enough temperatures during the cold winter nights. I'm in USDA zone 5. I have tried using black painted drums filled with water on the back wall and that has helped a marginal amount, but I've always ended up losing plants because of the cold nights unless I used an electric heater. I am not hooked up to nat gas and I don't have a propane tank. I am all electric. I would like to get this thing churning out vegetables in the winter without spending an arm and a leg heating it. I also have some problems on real sunny days in the winter with the GH overheating. It can get up to 120F during the peak of the day when its clear out and then I have to vent off a lot of that heat that I would have been able to use over night. The floor is poured concrete so I can't do much of anything underground. It's also far enough from the house that I don't want to have to go out late at night to feed a bunch of wood into a stove.

You good folks have any recommendations for how I can get this thing heated without spending a fortune or needing constant attention? Thanks for any ideas.

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I used something similar to this.     It's a different brand, but they are all the same manufacturer.  I used diesel fuel  to heat my 24' x 32' greenhouse as it was a lot cheaper than kerosene, but did smell worse.   WIth nightime temps in the 20's, it typically cost around $60 or so dollars to heat a month if I set the thermostat at 45F.   It's pretty loud though.

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Hi Early,

I'd be looking at a rocket mass heater.  They are already used in situations like yours.

Have you considered a thermal blanket for the chilly nights and the hot extremes?

Gary

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Radiant Floor Heating.

By keeping the root zone at a constant temp. the air around the canopy can be way lower.

Same principle used by hunters during the winter, they use heated socks, gloves. Keep the extremities warm, that warmth is radiated thru the blood stream to the core of the body.

Using a simple setup of 100 l/f of 1/2" CPVC pipe and fittings, a 30 gal hot water heater, temp controllers, and a circulation pump, and minimal logistics materials, you only need less than 1.1 gal of water.

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Make a Winter Vegetable Garden Work for the CSA 

northern Wisconsin + 16-by-24-foot greenhouse + 70-degree, that costs less than $50 a year to heat.  

Imagine living in northern Wisconsin where winter temperatures are regularly measured in windchill. By January, one can’t help but dream of warmer weather, a winter vegetable garden and fresh-picked produce. Now, imagine bundling up and jetting across your yard to a 16-by-24-foot shed, throwing open the door and harvesting fresh veggies in a 70-degree greenhouse that costs less than $50 a year to heat 

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Hi OP,

The article, while a nice story, actually said very little about how to construct a greenhouse, and even the link to the book that the site is trying to sell is broken.

My assessment.....1/10.....about as useful as tits on a bull.

Gary

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27 minutes ago, GaryD said:

Hi OP,

The article, while a nice story, actually said very little about how to construct a greenhouse, and even the link to the book that the site is trying to sell is broken.

My assessment.....1/10.....about as useful as tits on a bull.

Gary

early has a GH already, he just wants to heat  it, a cheaper way. The link worked for me, 10/10

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1 hour ago, Old Prospector said:

early has a GH already, he just wants to heat  it, a cheaper way. The link worked for me, 10/10

You're quite right.....my mistake.  What I meant to say was that the article contained very little information about heating a greenhouse....and the link to the book (the real purpose of the article) is broken.  Still 1/10.

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13 minutes ago, GaryD said:

You're quite right.....my mistake.  What I meant to say was that the article contained very little information about heating a greenhouse....and the link to the book (the real purpose of the article) is broken.  Still 1/10.

http://www.localharvest.org/elsewhere-farm-M7970

Contact Information

 

Contact
Clare Hintz
(715) 774-3153

 

Location
Elsewhere Farm16550 Nicoletti Road
Herbster, WI 54844
Edited by Old Prospector (see edit history)
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Hi Early

Some thoughts on the matter in this thread

cheers

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Thank you for the great ideas and suggestions! Ravnis - Did you have any problems with soot from that heater? Any ventilation concerns? Fire concerns? Something like that might be my best approach for now until I have the time to do some of the other things mentioned here that would help improve efficiency further so I was curious.

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@Old Prospector The radient flooring is a great idea and something I have wanted to do for a great while. Old man time keeps getting in my darned way though. I was thinking about putting down foam board insulation over the current pad, running radient lines and then adding another thinner layer of concrete over the whole thing. I can't budget paying to have it done so its all a matter of me finding that time I need to get 'er done.

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No problem with soot, but my greenhouse was not air tight being it was just plastic secured to  a wooden frame.   I used a carbon monoxide monitor in the greenhouse, but never got a detectable level above it's preset set point.   You will need at least 4 ft of clear space in front of it.  I had to tweak the fuel rate to keep the flames from extending past the metal casing.  I had an adjustment on it that could be set with a screwdriver and it took a little trial and error.   I've heard of models that output infrared heat that are supposedly more efficient, but have not really looked into them as this heater was easily purchased at a hardware or feed store.  You will need some method of ventilation if your greenhouse is airtight.  Carbon monoxide is no joke.

Also, don't overlook the importance of setting up a solar water heater to heat the water. Just keep in mind that heat loss from the water goes up as the air temp goes down. 

I had looked into the radiant heater thing, but could not justify the added expense in zone 8, but in 5 it might be worthwhile.  You could lay the insulation and radiant heating lines and build a wooden pallet type support over it to hold your system. You could make the wooden support rest on the concrete and the foam board cover the concrete in between depending on how large a system you built.

Edited by Ravnis
add caution about carbon monoxide. (see edit history)
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http://www.worldcat.org/title/northlands-winter-greenhouse-manual-a-unique-low-tech-solution-to-vegetable-production-in-cold-climates/oclc/435438027

That link will provide you with a way to get the book from a library if you wanted to read it before you bought it.   It sounds very similar to the Sunny John subterranean heating/cooling system.  Beware those type of systems loose efficiency in damp/moist environments typical of an aquaponic setup , so your mileage may vary wildly depending on local climate and solar exposure.

For your convenience a link to solar map is provided.

The link that OP posted did have some useful information, but it's not spoon fed and was really similar to the preface of a book. The name of the book is provided and a simple google search yielded multiple hits.

Edited by Ravnis (see edit history)
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Hi Early,

Hace you considered something like the Jean Pain method?  Murray Hallam has just done a video where he buries a heap of plastic water pipe in a large compost heap (contained inside a corrugated water tank).  You have to provide an email address to access the video (and a heap of others like it) but it might be worth a look.

As the compost heap heats up (begins very quickly and persists for months), he pumps water through it.  The temperatures that are produced by this method are quite amazing.

Is this a possibility for your location?

Gary

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To get me through the winter I went with a similar portable heater to what Ravnis suggested. I also draped poly over all the plants and tanks at night and on cold cloudy days to help keep the warmth in making sure it had plenty of air space from the heater to prevent a fire hazard. This way I only heated the area under the poly. It worked out great and really didn't go through that much fuel. The one I picked up had a basic thermostat on it that I kept at its lowest setting. It kept temps around 52-58 F inside the poly. Thanks for the great advice Ravnis.

I hope to get the floor insulated and improve on it some more for next winter but this simple solution really worked out a lot better than I expected.

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Posted (edited)

This may not work for you but........

I have two greenhouses, a 24'x50' A frame about 15' tall at the peak and a 20'x30 arched.  The larger GH  holds 28 IBC totes with tilapia, 14 totes down each side plus two more IBC totes that each contain home made RDF filters (that are AWESOME)  down the middle of the GH are 6 600 gallon lined tanks.   I use the water in the tanks to not only raise tilapia but also to heat the GH.  I own a fig nursery and start about 2000 fig plant cuttings a year for spring sales and they like to root with bottom heat and they sit on shelves over 3/4 of the top of each tote.   Last winter I relied on 1000' of 1/2" black tubing strung back and forth along the rafters of the GH in 4 runs and pumped water through those lines and back to the main sump.  This system worked but given the volume of water I could only gain 4-5 degrees per day if it was nice and sunny and on a very cold night (28 F) I would lose 6 degrees.   Being in central FL it worked out as we dont get a LOT of cold generally.  Front comes and the tanks drop 10-15 degrees over the course of a few nights then weather gets warm and using thge solar could bring it back up.  Even still if a front came through and stayed cold and especially cold and cloudy it saw a constant loss of temp over several days and lowest the water got to was 50 but last year was a pretty mild winter.  I knew that if we had an exceptionally cold winter that we get perhaps once a decade it could be a real problem and would have a LOT of dead fish and a too cold GH, was just a matter of time.    

Did a lot of reading and finally I settled on a plan.  

My first thought was a wood fired boiler but they use a LOT of wood and are smokey and while I am not in the city i'm also not rural either so I crossed that one off.   What I did was buy a wood fired hot tub heater, think some call them cowboy heaters?  The one I purchased from a company in Canada is called a Timberline volcano.    It is small, 38"H x 27"L x 11.5" wide made from SS and the body is aluminum.  Even that small the manufacturer stated it was 100,000 BTU but I was dubious about that claim to say the least.  The entire heater sits underwater except for the feed shoot that sits 6" or so above the water line and the fill lid acts as the draft control.  I did not want it inside the GH so it was situated about 40' away outside the GH and inside an IBC tote.  I placed the tote so it was the same height as the tanks in the GH.  

Added a second small 1/2 hp dedicated pump and ran a 1" line from one of the IBC totes that holds one of my two homemade RDF filters.   Because the hot water return pipe would flow back to the GH by simply gravity that line was 2".   I knew the ground would chill the water stealing some of the heat in the buried hot water return pipe so I ran 4" non perforated drain line and cut a slit the length of it.  The 2" line was placed inside the 4" line and then made batches with the cement mixer and filled the pipe with a combination of 1 part portland cement, 1 part sand and 6 parts perlite to make lightweight insulating cement.  I wedged the 4" pipe open so i could fill it and when the 4" line was 80% full I laid the 1" supply line from the new pump on top of the 4" line and poured more cement over all of it to a depth of about 2" above the 1" line.  

The IBC Tote that is 40' away and holds the heater I was a bit concerned about it losing heat to the atmosphere especially on a windy day and our cold normally comes with a lot of wind.  My solution was to bury 4 4"x4" PT posts 6" out from each of the corners and built an enclosure around the IBC tote using recycled black plastic twinwall GH material.  In the 6" gap between the twinwall andtote I poured more perlite completely filling that airspace up to about an inch from the top of the tote insulating it.  I added another piece of twinwall to the top and the 6' tall 6" wide smokestack comes out through it.  

The 1" line was run into the tote about 1/2 way down the tote and the 2" heated water line is through the tote 1/2 way down also then elbowed and runs up and pulls the hot water from just 1/2" under the surface.  

To say it worked is a collossal understatement. I was BLOWN away.  On a cold day I would light the heater and in 45 minutes the water at the surface was already 120+ degrees........now if you stick your arm down in the water the water just a foot deep was still cold. You can touch the outside of the heater underwater while the fire roars inside and it was just warm to the touch, maybe 85 degrees or so?  My setup which is roughly 12,000 gallons of water the heater would raise the water temp in the system 1.5 to 2 degrees per hour.  The heater being small uses up very little wood and once burning well is 100% smokeless.  I never even bothered to use the 1000' of 1/2" solar lines at all during the winter.  I would let the heater run 6 or so hours and refill it about once an hour but each fill is only 4 pieces of small firewood.  Once the heater is running(and pump on) temp in to the sump would settle at about 85 degrees and the 1/2 HP Goulds pump pushes a LOT of volume.  It was a dang good idea I put it in as this winter was our coldest in over a decade.  Without that heater the fish would have been dead as we had front after front move through in a 30 day span of time.  With the heater my water never dropped below 65 and I ran the heater total maybe 30 days.  

Also and this was simply an accident.....in the late afternoon I would fill the unit with wood and close the lid/damper completely.  I did it so I would have a nice bed of coals in the morning and would not have to relight it, even though lighting the thing is so easy and fast.  One morning before I had added any wood and the pump was off and had been off since the previous afternoon I was in the GH and happened to walk by the sump and noticed the temperature gauge on the outflow water and it was at 80 degrees.  I looked at the temp gauge in one of the tanks and it was 70 degrees.  Thinking the other  digital gauge was broken I pulled it out and put the sensor in the fish tank where it dropped to also 70 degrees so it was working.  Popped it back into the outflow pipe and put my hand down in to the sump water and sure enough 80 degree water was flowing out of the pipe even with the pump not running. Came back in the house and googled and found the answer I had made an inadvertent thermal siphon.....had no clue such a thing even existed.  So even without the pump running cold water still goes to the tote and warm water still flows back to the sump.  

I plan to drain the heater tote of the fish water and add piping to plumb it in to my inground pool to also heat that, just need to see if chlorine will harm the aluminum before I do it.  

I have no affiliation with Timberline at all and I know other companies sell similar heaters.  If I had had the time I would have probably welded one myself but my aluminum fabrication is generally not pretty, to say the least.  Also was worried I might not be able to get it 100% waterproof.

Edited by WillsC
typo (see edit history)
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Early,

 

I apologize for invading your thread but Andre wanted some pics of the setup.

 

The heater inside the tote.

 

image_26730.jpg

The surround I mentioned, before the gap was filled with perlite.  Btw i filled it with loose perlite, not perlite cement.  From memory I think it took 16 cf.   

image_26731.jpg

Looking down in the burn chamber.  The air enters between the side wall and that metal plate and the plate extends to about an inch from the bottom so air is forced under the fire, though there is no bottom grate. 

image_26740.jpg

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Is ash clean out any trouble?  Really impressive setup.

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It is a bit awkward.  The stove comes with a long handled ash scoop, in fact mine came with 3 of them:)   They were wrapped together and I assume the employee doing the packing did not notice??  So picture a metal dust pan welded to the shaft of a metal golf club.  It works and there is not that much ash.  In the aprox 30 days I burned it I believe I cleaned it out 3 - 4 times, took a couple minutes each time.  I might have got a 5 gallon bucket of ash total from all the clean outs, wasn't much.  Not like a normal wood stove where you are burning a lot of volume of wood.  Each fill is like 3-4 pieces of 5" wide 5" thick and 15" long pieces of wood so low volume so low ash. 

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