What's the Best Way to Heat a Small Greenhouse?

comments (25) October 19th, 2009

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ChrisMcLaughlin Chris McLaughlin, contributor
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Whats the best way to heat a greenhouse? This would not be my small greenhouse...but its cool, right?
 
Photo by substack under the Creative Commons Attribution License 2.0.
This actually is my greenhouse. Heat, anyone?
Whats the best way to heat a greenhouse? This would not be my small greenhouse...but its cool, right?
 
Photo by substack under the Creative Commons Attribution License 2.0.Click To Enlarge

What's the best way to heat a greenhouse? This would not be my small greenhouse...but it's cool, right?

 

Photo by substack under the Creative Commons Attribution License 2.0.



A while back I mentioned that I'd like to add some heat to our small, 6x8 greenhouse this winter for the first time. The planning stage is one of my favorite parts and I tend to drag it out as long as I can. Should I grow orchids in there? Pretty houseplants like poinsettias? Tomatoes? Or encourage my fascination with the man-eaters, grow a little shop of horrors all my own? Yes, beginnings hold all the promise and I'm keeping a list of some exciting possibilities.

On a more practical note while I do want to keep the greenhouse toasty inside, I'm also interested in keeping my electric bill down to a manageable size. Which isn't as simple as it sounds. Here in Northern California we pay in spades for our gas and electric, and "manageable size" in other states translates to enough power to run a small corporation. So, my first goal is to make sure I'm using the most efficient heating source.


Some gardeners heat their greenhouse by building a hot compost pile smack-dab in the middle if it.  I've heard some great things about using this technique and being the compost freak that I am - seems like the natural way to go. The problem is that my greenhouse is paved with brick and I intend to keep it that way. Our low-class cats, Puma and Nike (so named after tennis shoes brand names while we went through our gym phase) seem to enjoy using the greenhouse as a kitty-potty. So, a brick floor it is.

What's the best way to heat a small greenhouse? Greenhouse enthusiasts, shout out your thoughts here. How do you heat it, and why did you choose that heat source. Also, if you had it to do again, would you have done it differently?


posted in: heat a small greenhouse, greenhouse heating

Comments (25)

wraithv writes: i live in central idaho at 800ft elevation but it still gets fairly cold here. supposed to be around 0 degrees farenheight this week and next. i have a double wall 16x16 green house.and i am considering using a rocket mass stove. has anyone else used this method? i am gonna try it.
Posted: 1:24 am on December 3rd
greenzone writes: This may be a little too advanced, but what an efficient way to heat a greenhouse using a subterranean heating system. http://www.infolightandliving.com/projects/high-altitude-gardening

As for my existing Solexx greenhouse, I use a small electric heater that kicks on when the temperature gets below 40 degrees. I also find placing a seedling heat mat under my more delicate plants provides enough heat.

Chris, I was reading your bio and it looks like you wrote a book about keeping rabbits. Have you ever tried housing the rabbits in your greenhouse for extra heat? Wondering if anyone has tried that or had success with that.


Posted: 3:27 pm on November 19th
GoodGreenGuru writes: Last April a bought and put up a Snap-N-Grow 6 x 8 aluminum frame, thin lexan panel greenhouse here in S.W. Michigan Z6a. I actually put it up too late for the Spring season. Part of it is hydroponic basil, strawberries, lettuce, determinate tomato. The other part was peppers, tomato, basil, oregano but I took all that out in October. We've had some cold nights - down to 25F. So far I've been heating it primarily with a Dietz Jupiter Lantern. It seems to keep the greenhouse about 8 to 10 degrees above the outdoor - depending mainly on wind. These lanterns were originally developed for greenhouses and have a very large fuel tank. It will burn steady for up to 72 hours on one filling although I have to trim the wick about every 24 hours of burning. The best place - price and delivery - to get one is from Amish Creek http://www.amishcreek.com/dietz-2500-jupiter-kerosene-lantern-choose-blue-or-black/.
On really cold nights I have used either a small 600 watt electric heater or an old Aladdin Blue Flame kerosene heater.
This week I'm in process of closing the greenhouse down for Winter. It's just not well enough insulated to heat during the really cold months and the daylight hours are too short for most plants to do well.
I've thought of adding bubble wrap to the inside or making a smaller greenhouse inside the greenhouse - almost a cold frame - but haven't done that.
Posted: 2:08 pm on November 19th
Rhodorah writes: I have a gas heater in my greenhouse. My bill usually goes up during the winter months. Somebody has advice me of utilizing the heat of the laundry dryer so I can save on gas. I started the greenhouse to grow orchids just for a hobby, but I am now using most part of it to start growing fuchsia and a few other plants which I sell at the farmers' market from spring till summer. Although, it's located in the south side of our garage, a big spruce tree on end to the west side is shading most part of the greenhouse, so I cannot get much of sun's heat when the sun is out. The greenhouse is 12x 16, and I just purchase grow lights also from Craigslist for $50 only for two. I plan on keeping the lights on only for 5-6 hours a day since that's the minimum requirement most plants need to bloom. The green house has exhaust fan for summer, and a small one to distribute the air. I have the gas heater at least 3 feet above the ground, and keep the heat at around 50 degrees f. during the night at least and 65 during the day. When the sun is out, that saves my heater from going off.

Posted: 4:52 am on November 4th
katiebates writes: im loving this site!! i live in Saskatchewan Canada. I have had a big shock as i moved here from the UK and we dont have winters like this back home!!! (minus 47)
anyways i am really wanting to buy or build a green house of a good size and of course i want to heat it in the 6 months of cold here.
Am i crazy?? i this possible?? anyone have any advice for me please. thanks!!
Posted: 4:54 pm on June 13th
Cheryl5607 writes: Thank you everyone for all your ideas on heating a greenhouse. My greenhouse is 19W x 36L x12H has a dirt floor, 2.5 ft concrete walls and a patio door. I have quite a few epiphyllums and other cacti in it along with other plants. We never get to 0 or anything in the minus in ferenheight temperatures here, worst is -10 celcius. All my cacti and succulents are hanging in the center. I will let you know how it goes and what way I went to heat it.
Posted: 5:40 pm on May 16th
JackieGooch writes: I suspect you have tried out one heat source or another and am curious on what you ended up with. I'm running into a bit of trouble with extreme temperatures and looking for a second heat source for these types of winters.

I'll share a bit about ours as we live in a pretty harsh climate. NE Nevada, high desert, 5600' and the high today was 8 degrees F.

Our greenhouse is attached to the garage on the south facing side of our home. It's 10x14'. We have two horse tub waterers painted black, filled with water and covered in black plastic set in the ground a bit along the long southern facing side. Plant shelves are set about a foot above the water troughs. We saved plastic juice bottles for years, painted them black, filled them with water and line the window area on the shelves where the plants are. I also have large potted plants and another set of shelves on the wall closest to the house as well as some hanging. In the winter I move everything in away from the walls and tack up a curtain of visquine, tape shut the outside vent and turn off the summer vent fan. Turn on one small 10" hanging fan to circulate the air. We plumbed propane to the greenhouse and use a 10K BTU Propane LP Wall Heater set up at one end so the fan can circulate the heat.

This has always worked fine in the past with us bringing into the house only the most fragile of species, but this year it is getting a lot colder than we have experienced in a long time. So I added bales of straw outside around the bottom and inside in all the big gaps created my moving the plants closer together. I picked up some compressed bales and they fit pretty well. They are away from the heat as they are on the outside of the visquine curtain. The propane heater is really working hard to keep the temps no lower than the 40's at night (it was -21 last night) so I brought out the old space heater with the coils and fan and plugged her in. I can just envision my power bill going through the roof. I went searching on line for efficient space heaters that do well in uninsulated spaces and am torn between a radiant ceiling mount garage utility heater or one of the oil filled radiant heat. This would be my secondary source and the fan I use will be able to circulate the air.

So there you go. Any suggestions? Does anyone else live in cold land and grow a variety of plants? We grow everything from mini fruit trees and plumeria to succulents and exotic cacti along with herbs, blueberries, and tomatoes, crazy ferns and a few odd flowers. The orchids come inside, they can't take the extremes. The sun was out all day, the heat was off and it was 80 inside. I actually have a 4 year old miniature rose blooming. I turned the heat back on as soon as the sun goes down. By 7:00 the inside temp was 50 degrees and as of this post it's 41 inside and -9 outside.

Please share your thoughts and experiences, I appreciate it.

Thanks a bunch, this is a great site!

Jackie Gooch
Spring Creek, Nevada

Posted: 5:03 am on January 5th
DomC writes: I also had barrels painted black in the greenhouse but the sun may not shine for weeks at a time. The radiator had a small vent fan on a thermostat that would turn on at a set temp.
This year I am trying a wood stove that will burn engine oil or wood and wrapped some copper tubing around the stove pipe and pump that around the greenhouse to my radiator and to my water fall before going back to my tank. I am using a plastic water tank. Would prefer to have a metal water heater tank that I could use the element in to make things easier. And I raise lettuce and spinage. Love to sit and read in the winter time and munch on fresh veggies. You will get the most enzymes out of stuff eaten within 12 hours of picking.
Posted: 5:28 pm on December 26th
DomC writes: I used a 30 gal water heater with a 110 volt element with thermostat set at about 120 degeres. A small pond pump pumped water from a 1 foot long 5 inch wide 5 inch deep container into the top of a radiator from a small car. the water gravity flowed out of the radiator into the water heater and then into the container to be repumped back into the radiator. I held no less than 45 degrees on the coldest nights when it was below zero in a 25 x 12 x 7 greenhouse. I doubled the plastic by placing some on the inside of the top and front.
Posted: 5:17 pm on December 26th
kitcarson writes: I have just finished my 9x8 greenhouse (leanto) and have built a heat sink into the floor this consists of a 1 metre x 1 metre x 1 metre deep hole insulated and a gridwork of pipes layed in the bottom with holes drilled in the top .i then placed 2 litre bottles of water on top and layed barley straw between all the layers of bottles had 6 layers in total the whole lot is then sealed with insulation and a small port left so the heat can escape at night which is sealed during the day .then i ran a 3 inch pipe connected to the gridwork of pipes up into the roof of my greenhouse where the warmest air is and connected a 12volt fan to the pipework this is powered by a 40w solar panel on my greenhouse roof and connected to 2x 12volt 150Ah batteries connected in parallel to a 12volt regulator .
In the evening when the sun goes down i open up the port from the insulated chamber and the fan in the greenhouse roof circulates the air inside the greenhouse and blows the warm air from the sealed chamber into the greenhouse and keeps recirculating all night .results look promising at the moment ,but im waiting for winter here in the UK too see the real results .will keep you posted .
Posted: 4:15 am on August 30th
wildflowers23 writes: I need help on heating my greenhouse.
Does the oil lamps really work?????
Posted: 10:05 pm on February 29th
Jmastersinc writes: I am new, and just found this great site, I have a tall (9') green house that is 12x12, I live in a fairly mild climate, and while I havnt got it finished yet, my plan is to get some 55 gallon drums, paint them black, fill them with water/antifreeze to use them as a solar heater theyll soak up heat all day and radiate it at night. In addition to that I plan on using the wasted heat that my dryer vent puts out by piping it under ground (my dryer is on the opposite side of my house from my green house) to the green house to also heat the house. On cold nights right before bed I will turn the dryer on wich should keep the frost off threw the night. The 3rd part of my plan is (since I am an electrician) to place a thermostat switch that will both kick on an emergancy heater in the event that the house gets below 45 degrees, and will also open a window and turn on a small fan in the event it gets too warm. Thoughts? Anyone tryed this already?

Thanks and great site!
Posted: 1:49 pm on February 19th
MaryMD writes: I have a 6 x 8 greenhouse at 1600 Ft. in the Cascade Mountains of Washington State. Last year, I insulated the inside with bubblewrap, but did nothing to heat it. We had a hard freezing spell in November and nothing int he greenhouse survived that.

This year, I am going to put up bubblewrap again, and use heavy spun poly fabric on individual plants. I am also thinking of hanging two or three lanterns in the space. They usually burn kerosene, but I saw someone comment about using lamps using vegetable oil and I am curious about details on that system. It may or may not be cheaper to use vegetable oil, but it is easier to get an safer to transport than kerosene.

Mary Deaton
Silverton, WA
Posted: 5:31 pm on November 10th
JoeNavyGardener writes: I have a 6X8 ft master grow greenhouse that I just bought a greenhouse cover ($80 on ebay) to form an air barrier around the greenhouse. My next step is to use an oil lamp with vegetable oil (Very Cheap Heat) to heat the greenhouse at night. From my research this is the most economical way to do it without having to invest allot of money into a gas or electric heater. Based on the size of my greenhouse and the weather in Upstate New York this should provide enough BTUs through the winter months. r/ Joe Gardener 845-380-9575
Posted: 7:02 am on October 31st
ChrisMcLaughlin writes: Harrisdog43: Yes - thanks! This is the one I was going to go with but I wanted to see what other ideas gardeners came up with.
Posted: 9:05 pm on October 27th
Harrisdog43 writes: Try one of these: http://www.amazon.com/DeLonghi-EW7707CM-Oil-filled-ComforTemp-Technology/dp/B000TGDGLU/ref=sr_1_6?ie=UTF8&s=home-garden&qid=1256643635&sr=8-6

Other than being a customer, I have no monetary interest in Amazon or the maker of the oil-filled space heater. In a prior life, we heated our bedroom in an uninsulated house once with one of these. It used much less electricity than the window ac/heater did.
John
Posted: 7:43 am on October 27th
ChrisMcLaughlin writes: xoxommc - Good point - thanks!
Posted: 12:33 pm on October 24th
xoxommc writes: adding a layer of floating row cover (over plants or greenhouse) helps a lot
Posted: 10:50 am on October 24th
ChrisMcLaughlin writes: kandella: Ooooohhh...how much do I love this idea? Functionality AND festivity! I'm a Christmas light freak anyway and love having little white lights lining my back porch over-hang all year round.

I know that the old-fashioned lights do get pretty warm...let's see if I can find some still out there for sale...thanks!
Posted: 4:42 pm on October 22nd
ChrisMcLaughlin writes: JadaE: *gasp* That is like the Holy Grail of greenhouses, LOL!
About the space heater - yes, that's my first inclination to use. I'm just hoping to get several ideas to choose from as to keep my bill decent. Plus, it's great to see everyone's ideas!
Posted: 4:39 pm on October 22nd
kandella writes: I live in the Sierra foothills and I've heated my 6x7 greenhouse with a string of Christmas lights - the old fashioned large ones - not the little twinkle lights. I have a key lime and a mango tree in large pots that overwinter in the greenhouse as well as several hibiscus, various tender succulents and a tender bouganvilla. The heat from the lights kept everything alive and frost free. My electrical bill goes up about $30/month in the winter, but I also hang strands of Christmas lights on my orange and lemon tree that are not in the greenhouse to keep them from frost damage, so I'm not sure how much the greenhouse lights actually cost in electricity.
Posted: 8:40 pm on October 21st
JadaE writes: I forgot the original intent of my post! LOL I've got to stop daydreaming...
My coworker has a 6x8 greenhouse, that he heats with a small spaceheater with a timer. He also heats his garage, which acts as a 2nd greenhouse. (The garage has windows.) He tells me that his electric bill doubles in the coldest months! Usually a total of $120-180 a month total! WOW!! I never realized how much energy those spaceheaters use. That dollar amount is probably a low figure for you in California...here in Georgia I think we pay much less.

Hope you get some good ideas! :)
Posted: 3:19 pm on October 21st
JadaE writes: Since you posted that FAB-U-LOUS greenhouse, I just HAD to post this link of my dreamhouse. Notice the fireplace, that will keep YOU and your plants nice and toasty. I suspect that this owner doesn't worry about electricity bills all that much!
When I get rich and famous, I will have this house! I'm working on the rich and famous part... :)

http://www.greenhousemegastore.com/Luxury-Greenhouses/products/1098/
Posted: 2:56 pm on October 21st
ChrisMcLaughlin writes: * As a reminder, if someone wants to try lettucegrow's idea in their greenhouse, be aware this is an open flame and every consideration needs to be taken into account before attempting to use an unsupervised open flame.
Posted: 1:09 pm on October 21st
lettucegrow writes: Disposable turkey roasters. Aluminum, deep pans you can get at the dollar store for a buck each. Take two of them, poke a small hole at one end of the lip on each one. Wire them together...kinda like a hinge. Next, use a sharp knife to poke holes in the top and a few on the side, top pan and sides of bottom pan. (So the candle flame can breath)
Buy cheap candles at the dollar store. Melt wax to hold two candles in the bottom pan. Light the two candles and shut the lid. Place on floor away from stuff.
The lids heat up nicely without the worry of the flames escaping.
I have used them a lot. They keep the frost out without a heating bill. You won't grow maters and squash but lettuce, kale and other cool weather veggies benefit greatly.
I find them to be very safe.
You asked, that's how I do it in my greenhouse.
Posted: 2:57 am on October 20th
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