How do you keep your greenhouse from freezing?

I've read in other posts about filling large barrels with water during the day to help generate warmth at night, but what other methods have you used (heard of) that might also work. I tried the milkhouse heater last night, but found that it ran continuously and the temp still dropped below freezing.

I'm interested in hearing what others say here.

I have four 26 gallon black trash cans (Wal-Mart $3) filled with water.

Additionally, if the forecast calls for temps below 40, I run the space heater. This keeps the plants alive, but is expensive on the heater. I'm looking for alternatives.

I've wondered about generating compost in the greenhouse. Seems like the heat from the compost may help warm the place up? Just an idea that I haven't yet explored.

Dave

Dave, that might be a good idea. That is the difference between a cold frame and a hotbed...the heat off manures and compost warm the hotbed. Research hotbed construction and you may come up with a very good solution.

Hello Heidi
I have three little oil heaters, not sure what you call the fuel, we call it parafin, they keep the temp up nicely, how many i have on, depends on how cold it gets, at the moment it about 48f out side, its 68f in GH, and thats with just one little heater going, i have lined the inside of the greenhouse with bubble wrap, and that goes a long way to keeping down the costs, i had a problem getting fuel a couple of months back, so my plants froze and i lost most of them, so i am going to have power in there next winter, when i just used the shed up this end of the garden as a plant house, i used a little table lamp, i pulled the shade to bits and just left the wire frame, i put a tin upside down on top and heated it with the bulb, that worked well too, kept the plants warm enough, but the shed was nowhere as big as my GH, this year i am going to have a low cost heater, costs about a penny an hour, and a thermostat, its cheaper in the long run than loosing £200-£300 worth of plants, i will keep the little oil heaters for power failiures.

Alan.

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My greenhouse is heated by the same system as the house, which is heated by an outdoor wood furnace, or oil(if I run out of wood).

Hi;
I heat my greenhouse with gas, but in case it goes out in the middle of the night Ihave a back up, a torpido heater (fuel oil) it has it's own termostate I set it below the gas furnace setting. Also I have an alarm if the fuel runs out and the temp goes below 40 the alarm rings, it's an old school fire bell.
Tom

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We have a 10'x20' GH and use 2 small electric heaters sitting about 3 feet off the floor. Works pretty good but we also have a thermostat controled propane heater in case of power failure or if the outside temp falls below about 35 degrees. We plan to build a new one this summer with radiant floor heat as it seems this is where we get our biggest heat loss. Does anyone have experience with this?

I to use bubble wrap round the glass, i now use a bottle gas heater that has been champion. I would love a building that was half greenhouse/half shed.

Hi Patty;
The Cold Alarm is setup on a 110 volt termostat, two leads go out to the bell to power it, it is 110. then I set the temp at 40 so if the heat doesn't come on it well ring. Thank goodness we live on a farm, or it would wake a neighborhood.
Snowy in Northern Ohio
Tom

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At the moment I use black metal barrels filled with water to heat. I'll be hooking up a propane heater soon I hope.

Thanks everyone!
With the price of power and propane right now, using them would eliminate any profit I might make selling my plants.
The compost idea (thanks, Dave) really got me thinking...
What if I made compost bins along the inside of the greenhouse walls, then layed 2 by 4's along the tops and put the flats on them. Would the fumes kill the plants?
What do you think?
Heidi

Dave, Hiedi, i put a post on that other place last year about useing compost as a form of heating. i saw it on a UK tv programme, they rebuilt the lost gardens of helligan in cornwall, they had brick built cold frames, with a brick trench along on side, and they took out every other brick, so there were gaps, they were trying to grow pineapples the same way as the victorians did it, they filled the trench with farm yard manure, it did get warm in there, but not enough for the pineapples, so it didnt work, the whole idea was ripped a bit by gw readers, but i saw a follow on to the programme a few months later, and they did get it to work, they had to use relatively new manure to get the heat, and a lot of of it, and i think they coverd it with straw, but it worked and they had loads of pineapple fruit, just by useing farm yard manure, i have thought about it myself, one day i am going to try it, nothing to loose but an hour or so preperation, i thought of useing copper pipe and a small pump, to pump water through the copper pipe which would be coiled up in side the compost, i dont know how practicle it is, but if it works, well.

Alan.

I hope Dave doesn't mind long entries. I have a very good old gardening book that gives detailed instructions for a hotbed. I am quoting below:
"A hotbed is heated from below by the fermentation of manure...Cold manure, like that of cows and pigs, should never be used because it will not heat. Horse manure is best, but in this case at least one-third of the bulk should be straw. If pure manure is used, it will pack too tightly when firmed, so that it will not heat. If possible, the manure from grain-fed, straw-bedded horses should be used. The manure to be used should be hauled at least two weeks before it is to be used. It should be piled in a flat, compact pile, three to five feet high, and of a convenient width and length. If the weather is cold or the manure refuses to heat, add considerable water and firm the pile. When complete, the pile should throughly heat in four or five days, after which it should be turned so as to put the cool manure on the inside and the hot manure on the outside. By so doing a very uniform heating will be obtained. After about another week the pile will again be throughly heated, so that the pit can be filled.
FILLING THE HOTBED: In filling the hotbed, place the manure in the bed in layers six inches deep. As each layer is put in the pit it should be throughly tramped, so that it is firm, especially in the corners and along the sides of the bed. It is essential that the manure be well tramped, othewise it will not heat and the bed will be useless. Also the bed will settle less if the manure is well firmed before the soil is placed in the frames. When the pit has been filled to the level of the ground with well tramped layers of manure, the sash should be placed on until the manure has throughly heated. The soil should then be placed in the pit to a depth of six inches, if crops are to be grown to maturity: four inches of soil will be sufficient for starting early plants. The soil should be a finely pulverized garden loam, which has been well leveled and packed.
THE TEMPERATURE: The temperature rises rapidly for several days, often going above 125 degree F. After the temperature of the manure has dropped to 85 or 90 degrees, the bed will be ready to plant. To take the temperature in hotbeds, a plunging thermometer should be used...thrust the themometer through the soil into the manure, and read the temperature...
CARE OF THE HOTBEDS: Watering: the soil in a hotbed should be kept moist without soaking the manure. If the manure is soaked, it will cause uneven heating besides cooling the bed, so that the heat is spent sooner than it would be by judicious watering. Occasional thorough waterings are much better than frequent light sprinklings. It is advisable to water on mornings of bright, sunshiny days, and never on cloudy days or late in the day. Late watering lowers the temperature at a critical time and leaves the foliage wet for overnight.
VENTILATION: Ventilation is absolutely essential to supply the plants with fresh air, to reduce the humidity, and to control the temperature within the bed. A very good indication of the need of ventilation is the amount of moisture which collects on the inside of the glass. A little air should be given the beds each day, gradually increasing the amount until the sash can be left off during the day. A week or ten days before the plants are set in the field the sash should be removed day and night, so that the plants are thoroughly hardened..."
From the book "Garden Magic" by Roy E. Biles, published 1935.
He gives an illustration of a hotbed which I am going to attempt to copy to the photo forum. It is simply a coldframe with a manure filled pit beneath it.
He also mentions the use of an electric hotbed, using a heating cable: "...to be laid back and forth on a bed of sand in the hotbed and covered with another layer of sand and then the soil..."

Has anybody considered a small solar heater? Seems like the same panels could be used, later on, to operate a fan. Overall, venting heat is a bigger problem in greenhouses than keeping them warm, and I'm thinking you could get double duty from the solar system.

In our comercial green houses we use gas furnaces. To keep my personal plants warm and not cost a fortune, i use heat strips. They are 2 ft wide and 25 ft long and can be set at any temp between 50 and 110 degrees f. Each strip costs about $20 per month in electricity when set at 75*. There is no other heat in the green house where I use these strips. They work great to start seeds and cuttings.
Calalily

Calalily: Where do you get these heat strips? I'm interested in learning more about them.

Dave
Knoxville Seed has the best price, the thermostat comes with the strip. Sonne-gro has them too, but they are higher. The thermostat that comes with the strips will support up to 4, so the first strip is the most expensive. They also have a 10 ft one, but it costs almost as much as the 25 ft one. Email me and I will give you the phone number.
Calalily

Thanks for the great info on heating, everybody! :)

The reason I'll be using propane is because I already have a 500 gallon propane tank. I only use propane for my stove so I have a lot of propane left over. Also, I only fill my tank in the summer when I can buy propane for $0.88 a gallon. In my particular case, this will be the cheaper way to go I think. :)

Terri

Brooke - I have a small greenhouse and thought that the solar pannel idea would be great for my particular situation. I don't have an electical source and don't want to use any type of gas or propane heater since the greenhouse is against the side of my house and fear a fire hazard. I've been looking but haven't found anything designed specifically for a greenhouse or similar use. Lots of stuff out there for heating pool water but that's all I could find. Also found lots of sources for just solar pannels but don't know enough about how you could use them to power a separate heating unit. Let me know if you find anything that works along that line. This is only the second year I've had my greenhouse. Last year I didn't use any kind of additional heat source. This year I tried using some gallon jugs of water (mine isn't large enough to put in large containers like others recommend). Although the water does heat up during the day, I don't think it provides a big enough heat sink to provide enough heat at night to keep plants from freezing if the temps go down too far. Let me know how you make out and what you end up using in your greenhouse.

There are some great ideas here. I'm pondering putting together a concoction with some grow lights, chicken wire, and aluminum foil. I'll make a large hood with the chicken wire and aluminum foil and wire the lights on the inside up at the top. It'll resemble a shiny silver barrel cut in half. Just a thought... (my mind comes up with some horrendous ideas sometimes).
I'm going to look into the heating strips and solar panels also.
Thanks everyone!!! You know, we may end up inventing something here. Hmmm...
Heidi

i have a coal stoker thats quit effecant and not to expensive and off that i run a boiler system that i use for bottom heat

hey Talorghouses,
crazy enough, I was just think about something like that.
We have a friend that heats her water from a pipe that runs along the back of her fireplace.
Could you give us some details about how you did it?
Thanks so much!
Heidi

put in some live turkeys and chickens if you have them and cover plants.

wont they eat the plants ?.

i just used some 1/2inch copper tubing and wrapped it around the outside of my firebox then put a 25 gal barrell on top of the stove with an airconditioner pump in it then where your out put comes out of the stove i reduced it down to 1/4 inch air conditioning plastic tubing whitch i run on my benches and then run a return back to the barrell its a very simple and cheap way of heat my system costed about $75 ill try to get you a pic if youyld like

I wish this cold weather would soon go, its starting to get exspensive to heat the GH this winter, dont normaly need heat this time of year.

I'm impressed with all the brain-storming! Although I have no greenhouse, I DO want one, no matter the starting size. So, I've been considering how to heat one. I like the Monitor heaters, but too pricey to run in a GH where so much heat escapes through the glass. And insulated glass is too expensive, and harder to ventilate in warmer weather. I guess I will go back to my library of solar design books and look for ideas that would work for GH. I do know I had already decided that excavating the GH floor to about 3 feet below ground level, and using large water tanks would be a help. Seems like I remember Helen and Scott Neering did a similiar one... but I find my memory often faulty! I had also considered a methane converter from all the horse and chicken manure when I still had a farm. Free fuel then for a heater!

Talorghouses, Yes! I would love to see a picture!! I'll check out the photo forums just incase you have already done so. That's something in my price range, and like Alan said, this HAS been a cold winter/spring. I've been packing all my seedling flats into the house during the night and then back out to the greenhouse during the day. I would MUCH rather keep them out there.

Darius, that idea of putting the floor 3 feet lower is a great idea. That would also help to keep the wind from getting under the plastic.
Thanks everyone!!!!!
Heidi

Check out this site for heat generating!
http://www.rdrop.com/users/krishna/greenhse.htm

I just constucted a greenhouse using this idea...straw bales for the back wall only...PVC arched pipe for the top and front wall, covered with clear plastic. As the straw begins to compost, heat is produced. I use it as a row cover. Works great!

I have not yet built my greenhouse *cause I cannot til we move which will be this summer Lord willing*, so I am reading and absorbing.
Does anyone use a circulating heated water system for their greenhouse? Perhaps where the water is heated by solar or wind generated power ? That is my ultimate goal. I am searching and gathering info. My aim is to eventually make teh cost of the greenhouse to be *free* by using renewable energy sources. Anyone else done/do/interested in this?

Kathie

I would like to find any info on solar power for a GH for winter heating as well as summer cooling (fans) and possibly lighting as well. I don't have a GH yet but would like to get one put up before winter hits (trying to find some plans for to build my own or possibly a kit).

Briggs

Hi Heidi,

Sorry I am a bit late for your question but can offer you my experience of different ways that I use to heat my greenhouse. Firstly, they get double glazed using bubble polythene - I reckon since using it I have halved my heating bills.

If the area needs to be kept just frost free (for raising early plants and over wintering half hardy things, etc.) I have a parafin (I think you might call it kerosine) heater; and no it doesnt stink the place out. You can even get them with thermostatic control. In the intermediate area I use a natural gas heater. The gas is piped for domestic appliances in the house and I have taken a feed off of that supply (quite legally !!). Its thermostaically controlled and is sensitive enough that the temperature only varies by 2 degrees each day. In the hot house (where the tropicals grow its a gas heater again, but backed up by soil warming cables to keep the roots warm as well. They work on the same principal as the heating strips Calalily mentioned (except these are buried 9 inches down in the border). And if it gets REALLY cold then I sometimes use Daves technique and get the old space heater (with blower) to augment the supply of heat.

Hope that helps.

El Tel

On the topic of compost heat, and sensible greenhouse design:

-it works, if one mixes a good "hot" pile...in addition, it would be sensible to develop, in a smaller house, some sort of chambered system, so that a relatively steady supply of heat could be maintained, by rotating fresh compost through the chambers.

-it can be extremely beneficial to plants, beyond the mere provision of heat: the composting process gives off CO2, and, if the compost itself is below the plants, this rises up to enter the stomata on the underside of leaves.

-VERY IMPORTANT: The composting process releases ammonia in concentrations high enough to damage plants, or stunt growth. Because of this, it is wise to use some sort of biofilter between the compost, and the plants....this isn't a complex thing, peat moss has been found to scrub ammonia just fine.

-In a small house, it would be difficult to have enough biomass to generate sufficient heat: what I have done is to create a box/plant table system which contains the compost in an insulated series of chambers, allowing heat and gases to escape upwards only: on top of this system is a layer of soil, and the plants sit on top of, or directly in, this. Thus the heat reaches the plant roots, and is used most efficiently.

-And finally, a truly sensible greenhouse will employ a number of passive and ecologically responsible techniques in combination: in my zone (zone 8), houses I have built combine a pit design with a straw bale back wall (for insulation: not for compost, though as previously discussed, bales will produce heat...I am presently growing some very fine watermelons directly from strawbales, inoculated with manure tea to get the bales heating up, and composting...this works well on rocky sites, and over time, the bales build up soil, if they are placed properly in natural hollows, and depressions. Anyhow, I have combined the pit structure with compost chambers, a back wall of plastic milk jugs filled with water, a stone floor, a south facing passive solar wall, and to a depth of four feet around the perimeter of the house, insulation to prevent radiant heat loss from the floor. All of this cost me exactly $150, the price of nails, and mostly, the cost of a roll of plastic: ribs were arching cedar limbs, walls were sod from the pit, cemented with a cob mix of straw, clay, and sand. Final trick I have seen used is a double layer of plastic, with an electric bathroom fan hooked up to an extension cord to inflate the space between layers...really jacks up the insulation value...but, of course, my thing is low-tech, no electricity, etc...

And, not to ramble on ad naseum, but much work has been done using greenhouse ponds to collect heat, and at the same time grow water plants, and raise fish, whose waste is used, in turn, to fertilize the greenhouse plants, and me next great experiment will use rabbits and chickens as supplemental sources of heat, fertilizer, and food.

Hope some of this helps: I'd be happy to direct interested folks to further info. on all of this...a home, or for that matter, a farm greenhouse need not be a black hole energy wise.

Regards,

David Hicks

I hope I am not repeting someone , but if you can find a free standing propane heater , like a warm morning type with a mechanical thermostat , it will still come on if the power goes off just no blower , the one we had was vented. worked great . Most of the newer types have an electronic ignition and will not come on with out electricity .:) Gin

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