How To Heat A Greenhouse Without Electricity
There are two main concepts concerning heating a greenhouse without electricity.
The first is by collecting the sun’s warmth as sunlight hits upon a dense material called thermal mass, such as rock and water. Thermal mass will absorb a lot of heat throughout the day and release that heat when temperatures drop at night. Utilizing thermal mass in a greenhouse is easy since it already receives much sunlight.
The second concept is with composting, since compost piles produce heat as the microorganisms within them break down the organic materials into compost.
MATERIALS NEEDED:
small stones or gravel
white paint
black paint
paint brushes
cinder blocks
water container(s)
ceramic pots
wire mesh
organic materials (leaves, twigs, etc.)
Step 1:
Put down a layer of small stones or gravel in your greenhouse. This creates a layer of thermal mass that will remain dry and clean.
Step 2:
Paint all the surfaces in your greenhouse that you want to reflect light, with white paint.
Step 3:
Arrange your cinder blocks in the way you want them as support for water containers or to make benches or table supports. The cinder blocks will absorb heat from any sunlight that touches them.
Step 4:
Paint the cinder blocks black. This will increase the efficiency of their absorbing heat.
Step 5:
Put one or more water containers in your greenhouse where you want them to absorb and release heat, and fill them up with water.
You may want to paint these water containers black as well.
Step 6:
Use ceramic pots, they will absorb and release heat in the same way as cinder blocks.
Step 7:
Put a ring of wire mesh where you want your compost pile. A word of caution… compost piles are known to create immense amounts of heat, especially large ones… compost piles can spontaneously combust into flames, so just be aware of what you are doing if you have a large compost pile in your greenhouse especially if it is attached to your house!
Step 8:
Add compostable material to your compost bin, such as any plant clippings, fallen leaves, and weeds, and keep it moist.
Step 9:
Enjoy an increase in your greenhouse temperature without raising your electricity bill!
About Troy Boylan
Ecoculture Village Founder & President; Anthropology BA, Interdisciplinary Studies: Ethnobotany BS. Two things I think are worth anything at all… all things wilderness and ecoculture.
Use the Jean Pane method. You can make hot water and and hot air. Several articles on Youtube. Place compose pile outside of greenhouse. Run water pipe and air pipe underground to greenhouse. Can run these fans and water pump off small solar panels. all these methods do not get your greenhouse temps up to 60 or 70 but can get the greenhouse in the mid 40s. You can grow cold weather crops.
You can also build what they call a Chinese greenhouse. Several videos on Youtube.
No! I’ve tried the compost heap heating system It heated the greenhouse fine, but made the air toxic with fungal spores. Compost heaps emit Aspergillus, which breathed in can cause Farmer’s lung or in many people (including me) sparking off an inflammatory response. Dangerous.
You need to be careful handling compost, especially indoors. Wear a mask. If I wear a mask, I get no reaction. If I don’t wear a mask, I’m gasping and coughing within a minute. You may not n=be as sensitive as me, but you can still get long term diseases like Farmer’s lung.
Don’t follow this recommendation! (BTW, I do have a degree in microbiology, this isn’t some paranoid panic.) Look it up yourselves.
Compost bins will require careful attention to C:N ratios, and probably should be kept at higher C ratios. An excess of N will create ammonia, good for roots, but not for leaves. They will not provide much heat.
Some time ago I read about a chicken greenhouse — bottom floor raising chickens, top floor green house. Chickens provided heat. The ammonia from the manure (lots more with chicken manure) killed the plants.
If you have an ammonia problem, put in a ‘water feature’ A very small micro sprayer (5-10 gph) spraying down into a container will absorb ammonia from the air. You can use this to water the plants.
Don’t waste sunny space on compost piles.
45 gallon barrels are about 3 feet x 2 feet, but both dimensions vary somewhat. Try to create matched sets. They are the right height to use as bench supports. A single row can support a 30″ shelf which holds 3 20×10 standard nursery trays sideways. A double row supports a string of pallets . Needs access from both sides.
Study done at U. of Missouri found that:
* Painting the barrels black didn’t make a noticeable difference, and they were using an entire back wall of them solid.
* Plastic vs metal barrels made no difference.
The optimum solar green house runs east west, or ENE to WSW (Oriented to winter sunrise somewhat) and is 2-3 times as long as it is wide. If shorter than than this, you lose too much from the ends. If it’s longer than this, it could be wider with very little difference in heat loss.
An insulated north wall is a good thing. Or cut it into a hillside, and only insulate the top 4 feet of wall.
What is healling in and how do you do it?
Ins’nt runoff compose piles a good source for fertilizer and irrigation?Thank you…………
Carl,
I guess that depends on what’s in the compost but I’m guessing it would be a good fertilizer but not enough to sustain container grown plants. Heeling in? See this; https://mikesbackyardnursery.com/2016/04/heeling-in-japanese-maple-trees-rooted-cuttings-and-other-plants/
Compost heating will work anywhere IF the pile is big enough and insulated well enough that rotting will continue. Read and reread Jean Pain’s work in France! However, for those indoor situations where the greenhouse is sealed very tightly, just remember the rotting action making the compost gives off gasses. I think it even depends on what materials are being composted as to what some of the off-gas are. Of course there’s co2, but there can be other things too.
Yes, I was concerned about this too. Well, my first thought was will the compost be active in WI in he winter? Second thought was if it is active won’t it smell aweful enclosed? Anyone know? Good ideas though ! Thanks
Kate,
I don’t think the compost will smell much as long as it’s not disturbed. Just my thoughts.
I agree, especially outdoors. I doubt if the smell would be very much. especially indoors. Sizeof “room” would probabvly be a factor??
My compost does not smell bad unless I add fresh horse manure, and then the smell goes away in a day or so. Do not add meat, fat or bones. Those will stink and attract pesky animals.
The smell of properly compiled compost won’t be objectionable. If it is, it either doesn’t have enough brown (dry) material, or it needs mixing.
Compost will function in the dead of winter even in very cold places. Aerobic compost piles have a nice earthy smell. Research a bit. Composting is great!
Most achieve the aerobic pile by turning it over with a pitch fork which requires some work but you can also blow air into the pile and it achieves the same outcome. Puts air into the pile.
Ok have had a ,new gas furnace installed. He ran the “exhaust” pipe to vent outside of the house. There is nice hot steam coming out of this. Thinking of mounting a (small) plastic greenhouse over this. Looked at your hints and ideas here. Maybe I can extend that pipe to send that hot air over the top of a water-filled ceramic (big) urn that I have, will also put down a gravel bed. This is also south facing (but at the front of my house, in my flower bed, LOL, Just another thought for you out there.
Susan,
That pipe is pushing out dangerous amounts of DEADLY, carbon monoxide gas. It should not be trapped or even restricted in any way or it could back up into the house creating a fire hazard as well as dangerous levels of carbon monoxide.
ok, that was the next thing I was going to check into. Wasn’t sure if it was carbon monoxide or carbon dioxide. Maybe I can just extend the (hot) pipe to run straight thru the greenhouse, leaving it to vent out the other side – will have to test how warm the pipe gets, I guess. It’s PVC so probably doesn’t get not enough. Thanks Mike.
Susan,
This is a high efficiency furnace. If you mess with that venting process it’s likely to shut down the furnace. And the gases really are not that warm. Actually so cool that they have to be force vented. I wouldn’t play with it.
Susan, you could put the pipe under some gravel on floor of greenhouse. Rock stove is what they are called, no worry of a hot pipe being touched as its under the gravel and still gives off heat.
Mike is right about the gases coming from the vent , but it may be possible to use at least some of the heat , while letting the deadly gases vent outside. In order to do this safely you would have to extend the pipe so it runs through the greenhouse (preferably the floor , but it must be run at an upward angle (pipe has to be pitched up to vent properly , and it would need to extend upward after exiting greenhouse and vent in to a safe outdoor space (don’t let it end under any windows or any openings into house . For more information ask your HVAC man for his advise on the matter!
Thanks,
Alex
I disagree.The pipe should b slanting DOWNWARD.
Condensate will accumulate at the lowest point,and restrict the air flow.If you are making a long run,over 20 ft from furnace ,you will need to increase to the next pipe size.The furnace will sense excessive back pressure and shut down.As previously stated,by the time the air reaches the end of the pipe,it will ambient temperature,and actually remove heat from the greenhouse.
Thermal mass and reflective foam insulation sheets on the inside walls is the best way to go..This is the type sheets they place beneath vinyl siding,available at your local building supplier.
You could make these sheets removable for summer if desired.
A row of water filled barrels will absorb a lot of heat.
Rabbits are also a good source of heat.The have a very high metabolism.
I had a friend that placed his plants on shelves above the rabbit pens.He fed them his waste greenery and sold them at Easter every year and started with another batch of rabbits.He used the rabbit droppings as fertilizer for his plants.He was also allowed to collect outdated produce from his local supermarket as rabbit feed.
Fix it up!,Make it work!,Reuse!Recycle.
DO NOT Mess with your high efficiency outflow pipes!!! A very small change (pipe elbows/lengthening the run of pipe) can shut your furnace down. You will NOT get any significant heat. Only one added elbow (An admitted mistake by the installers!) created enough frost, in the pipe to shut down the furnace. Luckily, we were home at the time and the company was reputable enough to do an emergency visit to fix it, at no charge.
I’ve seen this idea before somewhere – and the subject of mice came up because of sticks and leaves. We do see mice in our compost piles, and sometimes in the manure piles, it’s aged manure. At any rate – it is something to consider along with the fire part. Although I’m not sure there’s be much of a fire if it’s kept damp. Depends on how big you make them – maybe making several small ones would be better than one big one. The bigger they are, the harder to control the temperature inside the center which is where it gets so hot.
Oddly, our wood chip piles were cool last summer but steam was coming out of them – I couldn’t figure that out.
Cathy,
A compost pile would have to be quite large before it becomes a risk for fire. Rodents? They are everywhere, I wouldn’t be concerned, easy enough to deal with.
We inherited feral cats when the farm was bought My sonnj uses them to keep the mouse count down, but you have to make pets of those whose mother abandons them!!!!!! : )
Mice hate peppermint scent. Sprinkle some wherever they might enter. We kept our open garage clear of them.
In England they use large compost piles to provide hot water year round.They put copper coils in the center of the pile and circulate water through it.It can get over 160F inside a large pile of compost.Chicken house dropping are excellent for this.
Wet the pile and cover it with black plastic to get it going quickly.
I left a bale of hay in the back of my Wagoneer one winter,and all of the vehicle windshields frosted up in the mornings, except for the Jeep.
The hay gave off enough heat to keep the windshield above freezing.
A few bales of hay in the greenhouse is not a bad idea.
CT, I’ve often wondered about this, using compost to make heat to provide bottom heat for rooting cuttings with heat coils as you describe here. Interesting.
Don’t use hay, use straw. Hay can burn your place down because of the nitrogen content but straw is made up of carbon content and will heat but has a higher flashpoint.
Don’t put a cover over the exhaust vent to capture any heat. I did a small shed like attachment to the greenhouse and had the gas heater exhaust go into it. Even though I vented it somewhat the Carbon monoxide fumes pretty much killed any plants I had put in there.
Not to mention how deadly those fumes could be for you. There are ways to capture that heat without getting any fumes into the greenhouse using some kind of heat ex changer.
The exhaust is cool, that is why they can use PVC pipe. . The “steam” you see is condensing water vapor from the combustion process. When the exhaust hits the cold air out side, it condenses and forms the visible water droplets that you see. If you extend the pipe too far that happens inside the pipe and it can fill a low spot with the condensed water and smother your furnace flame.
That pipe would have to go through the greenhouse and out the other side. That way you’ll get a warm pipe, but no exhaust pumped in.
I’m working on building a simple greenhouse with a rocket mass heater right now. The rocket mass heater is very economical to heat and it heats the cob bench. It’ll give bottom heat for starting seeds, too. When it isn’t so cold, the sun will heat the mass and still keep it warm for the plants. I’m working on my idea to ventilate it really well in the summer so it doesn’t get too hot. I live in TN so I think it’ll work really well for us.
Serena, I hope you are still a member to reply to this. Can you tell me more about the size of ghouse and of the heater? How has it worked. And did you come up with your own g house plans or kit? Thank you!
This concept also works well in microcosm. A coffee-table sized “cold frame” like you show as a cutting-or-seed starter is called that to differentiate it from a “hot” frame, which is the same but built over a “compost” pile filled with material that is appropriate to keep on cooking undisturbed for a long time (think Grade A Manure.) With a layer or two of glass on top, and sealed against a draft, these are good to go most any zone. They age cheese in manure piles in Sweden because of the predicable heat. When you see a manure pile steaming in the snow, it’s not because cows are warm :). The big commercial/municipal compost operations up in Canada are usually self-heating.
The old timers in our part of the clan called a “cold frame,” a simple in-the-earth bed with wooden sides as high as the anticipated crop, and a glass or clear plastic lid to help retain moisture, heat, and for its “hothouse” effect.. Used for seed-starting or small crops in cold weather — especially winter greens , They called “green manure” fresh-from-the animal material of any sort whereas now we usualy mean grass clippings, and, interestingly either works as a compost-heating feed in a “hot frame” that is like a cold frame but with planting soil on top: heat was regulated by the amount of moisture you kept in the compost. Pure manure, esp. fowl or porcine, would indeed generate ammonia. Rabbit was considered ideal, and we used to use it as fresh top dressing, uncomposted. As an aside,expreiments in Colorado found that wild grassland vegitation could contain up to 4 pounds of nitrate per ton of vegitation — even morer if the vegitation had been stressed by weather, drought, etc. Not surprising that grass clippings make such good “green manure”when you consider that composition wise it is just cow poo with the milk still in it. : }
Donald,
Great info, thanks for sharing it. I think people truly don’t understand or underestimate the value of the heat from the ground. With a frame as you describe sunk into the soil the ground heat affect is amazing. I’ve used it alot https://mikesbackyardnursery.com/2020/01/a-simple-way-to-build-an-underground-root-cellar/ and https://mikesbackyardnursery.com/2020/12/storing-bare-root-trees-plants-over-the-winter/
Over this coming winter, I want to store dormant plants growing in various sizes pots under our raised back porch. It is a bit over 3 ft off the ground, and is in the South side of our house. We are in zone 6. If these plants were not newly grown without much of a root system, I would put them in the ground as they are all perrinals, but our’s is a new home site and little to no top soil was left in the clearing of our very wooded property(if we plànted in the trees, all would be great, but I want my flowers around our house, NOT in the trees! ) . Next year, I will have plants large enough to put in the ground, so hopefully I won’t need as many stored next year, but I will have several large plants in large pots. My worry is keeping the roots from freezing this coming winter here in South central Missouri. We plan to put fiber glass panels under the covered porch floor, and then behind lattice panels on all 3 sides , the back being the concrete foundation. That whole side of the house is in the sun during the coldest months, but I need a way to gather some heat for those single digit days and especially, nights. Any and all suggestions for our problem will be appreciated. I must add, though, that we are a retired couple, so funds are a BIG item to consider. Thanks to anyone who can give us ideas
Gramms,
I’m concerned that it will be too dry under that deck. Be sure to water them about every 2 weeks.
block the East and put clear plastic material in the south and west. The earth will have residual heat from summer and collect more thru the plastic. You can make a polystyrene panel to use as a cover for those real cold nights. You could also use old rug on plywood as a night cover.
Dig into ground and plant the whole planter pot with plant into the ground. This will simulate the same a planting them with less root freeze. Also cover the area, including on top of pot with a mulch of straw or …. to help insulate. Do make sure there is enough snow on them to keep them watered on thawing days. Then in spring you are digging up whole potted plants to place into their permanent home.
Dig into ground and plant the whole planter pot with plant into the ground. This will simulate the same a planting them with less root freeze. Also cover the area, including on top of pot with a mulch of straw or …. to help insulate. Do make sure there is enough snow on them to keep them watered on thawing days. Then in spring you are digging up whole potted plants to place into their permanent home.
Hi, The water mass system will work like Mike suggested if the water containers are in bright sunlight and a dark color to adsorb sunlight The formula for this method is 2 gallons of water per square foot of greenhouse space You can also use heat from the ground if you can excavate the greenhouse partially into the ground There are also active systems that circulate air or water through the soil under the plants A swimming pool heater (which has a coil containing water ) can be used with pipes passing through the soil , rocks , or water in the greenhouse will provide more heat than usual and reduce the amount of thermal mass needed !
Will this work in my Area 4b , some Times it Will drop to -25c during the night?
Thank you
Josee,
More than likely it will not work in your cold zone. Although this method can work, the climate would have to be warmer than you and I know.
My greenhouse is an 18×21 carport with 4 poly panels to let the sun in. We put screen on the front and back and when the weather gets cold we add plastic [clear shower curtains]. I planted cold hardy veggies for the first time and they are huge. The only thermal mass I have is 2 liter soda bottles filled with water.
I also bought two 5×5 plastic greenhouses on sale at the end of the season cheap. I put them inside the carport greenhouse. I keep my avocado tree and seedlings in those. Being in zone 7 central US, so far this winter I’m having to watch close because the temp is too high. The nights when it dropped and I used some brooder lights.
I believe 2016 is going to be a great year for gardening.
For those that have a std house shaped greenhouse. No sun comes thru the north top half to the ground. It isn’t pretty but for the price it works. Pick up old rugs and pads on trash day. Lay them on the north half of the roof and down the north wall.You can tie ropes thru holes and bring them over the south side to the ground. If you have extra $ you can place polystyrene panels under the rugs. Big Bx Store item
The assumption is your RIDGE runs some what East West. Here in Md. on the Chesapeake Bay the sun casts a 3′ shadow for every foot of height. So no sun can hit a North sloping roof. Place an object one foot high and measure the shadow on the ground.
There are double wall plastic.panels made especially for greenhouses. Not that much more expensive, and a lot more efficient.
Hi all,
Here are some other great resources for heating with compost::
http://www.compostpower.org/
These people special in larger projects with a kind of industrial approach to recuperating compost heat., but I’ve worked with them in making a design for heating a small greenhouse all winter in a zone 4. area.
Also the University of Vermont used to have an experimental greenhouse with a very sophisticated setup for heating with compost at their “Hort Farm”. I don’t know if it’s still there but we visited it on a very cold gray day in February a couple of years ago and it was around 70 degrees inside.
You need a lot of compost with a very slow heat release formula to make this work, mostly a mix of wood chips and sawdust; the greenhouse to compost ratio might be 4:1 ro 3:1 so the design has to allow for easy recreation of the compost pile every fall..
It’s all really fascinating stuff.
Elliot
Thanks Elliot, pretty interesting.
I have done this and it works in adding heat. dig a 6″ deep trench under the bed. place a piece of polystyrene on the bottom take a length of 4″ dia. PVC drain pipe on the poly. place an elbow on each end with a stack going to the ceiling on one end a just out of the ground on the other Fill with dirt 2″ over the pipe. Place a computer fan on the ceiling pipe and blow the hot air down into the ground and warm the earth each day. cover the trench area with plastic so water does not drain the heat. Big Bx for pipe and poly, Ebay for LOW amp fan and a plug in timer.
On 12/22 I got 8.5 hrs of daylight. For over 6 hrs I blew heat into the ground.
Interesting. Thanks for sharing that Ed.
Ed would love pictures and details of what fan you purchased etc.
Glad you posted this Elliot! I was looking at the little wire cage in the article thinking ‘no way will this create any amount of heat’! People need to realize just how INefficient a greenhouse is at retaining heat. So if you are in a moderate zone where you only need a little bit of heat, say, to tip the balance when it gets down to 25 degrees at night, that small pile might help.
But with a sizable greenhouse, and in a colder climate, where it gets below zero in winter, you need a LOT of compost, and it needs to be constantly creating heat. As you point out, it works best with something like wood chips (spent brewery grains are even better if you can get them), not the typical veggies scraps and grass clippings many people think of. You are going to lose at least 1/3 if not 1/2 of the greenhouse space to this compost pile for it to work effectively. It also helps dramatically if you can cover the greenhouse with a layer of insulation at night.
Compost power no longer available
One of the problems with smaller greenhouses is that they overheat when the sun is shining and then freeze at night. There is a huge temperature fluctuation, which is hard on most plants. So what you grow is also important. I grow leaf vegetables (lettuce and spinich), radishes, carrots, and turnips. All these grow close to the ground so they usually don’t get burned by the high temps of the day and are close enough to the ground that they don’t freeze. Between each row, I bury rows of plastic soda and/or juice bottles; the big two quart (or two liter) bottles. Three quarters of the bottle is below ground. I prefer to use clear bottles because I want the sunlight to penetrate the bottle, and the water they contain, to hit the dark colored soil. The sunlight warms bot the soil and the water, creating a huge amount of thermals mass. This warmth is right where I want it, down in the soil and between my plants. I don’t even try to heat the air, which has no thermal mass anyway.If it will be especially cold that night, I’ll lay a light cover over top of the plants so the ground warmth stays where it is. I have never had a plant freeze and used this technique in Pennsylvania and The Netherlands, which is as far north as Quebec.
Bill,
Interesting concept, thanks for sharing this.
So do you use raised beds to grow in the greenhouse? Or do you just plant in the ground? If I plant in a 3×3 raised bed how many soda bottles do I need?
Thank you,
Cris,
This is not article that I wrote, it was written by one of our contributors. It really depends on where you live. Trying to keep a greenhouse above freezing here in northern Ohio would be impossible without a strong heat source. I don’t do greenhouses, all of my plants are rooted outside in winter and summer. A raised bench in a greenhouse would need more heat than a bench on the ground. So it really depends on what you are growing, what you are trying to use a greenhouse for. I had one years ago, didn’t like it, spent all winter worrying about it and the plants inside. Never heated it up again.
If you use a raised bed then make a black painted cinder block wall from the ground to the bottom of the bed. This will help SOME The trick is to keep the heat in at night or supply extra.
I know this answer is late but maybe it will help someone. A 3×3 bed takes up 9 square feet of space and would require 18 gallons of water (2x 9 = 18 ) or 68 liters or 34 2 liter bottles of water , you can dig a hole under bed and place the bottles under the plants and use dark colored soil to help heat from sun during the day , or make a space behind the bed to pile up the water bottles painted black to adsorb heat during the day . If you are in a very cold climate you may need to use 3 gallons of water per square foot of greenhouse space !
I’m in SE PA, really expanding my garden and technique this year. I have a poly/pvc greenhouse that is portable. I’m going to take down a raised bed this fall and try your buried bottle concept. Currently I’m using gallons wrapped in black material, black outdoor carpeting and a dairy barn heater set to about 50 . I hate the idea of running a heater. I’m going to also try a compost trough and place flats on a grate *over* the compost. I’m almost wishing for Fall! Wait…maybe spring first. Thanks!!
Judy,
Bear in mind, I have no greenhouse, no hoop houses in my nursery and we root cuttings from June 1st through mid to end of March. See this https://mikesbackyardnursery.com/2015/01/easy-summertime-plant-propagation-techniques-can-home/
can I ask what zone you are in?
Mary,
That’s a good question. I did not write this article and in my zone 5, I don’t think it would work for me.
As you mentioned the Netherlands i thought of the temperatures they experience there wich are not nearly as lowe as Quebec Canada
Another use for solar panels is to heat water. The warm water can be run through pipes under the potting bench with a small pump, then returned to the solar heater. Maybe the pump could be battery operated.
Hi , Yes this can work and you can use a solar PV panel without a timer to run the pump (it will automatically shut off at night ! One thing to bear in mind is to use an insulated greenhouse with either 2 layers of glass or double poly with an inflation fan to keep the two layers from touching. Also when using water for thermal mass (heat storage ) it is recommended to use 2 gallons of water per square foot of greenhouse area.
Thanks,
Alex
Another option would be a rocket stove with cob mass benches. It uses little fuel, remains warm for hours and costs very little. I’m toying with the idea of a trench greenhouse utilizing earth beds and rocket stove heating built into the beds.
Megan,
Interesting concept.
One question, you said to put down white stones in the greenhouse. Are you talking about in the walkways or all over or what? Thanks.
Great article. Heating greenhouses is of special interest to me so I loved this article.
We have built several greenhouses. The best situation I had was in Southern Idaho (zone 6) and lots of high-desert sun. Six by twelve greenhouse on the south side of the house, enclosing a basement window and a window into a half-bath on floor one. Greenhouse was double glazes and I mounted a fan in the basement window to circulate air. Thermostats were set up to exhaust air during the day and gently add heat at night. It worked beautifully all winter long. This was quite a while ago, but I estimated at the time that heat gain and loss in our home probably balanced out.
Thanks Charlie! Real world experience always out weighs theory. Interesting approach to greenhouse gardening.
I did a similar project but did not have double glass.. I made a roll up rug shade and lowered it after the sun went down.. Up in the morning before work. My homes oil furnace was not needed on sunny days. I had a night blooming siris bloom in there..
I had a greenhouse that the previous owner built on the back of a house in Colorado. It was designed to draw cool air out of the upstairs, warm it by the solar gain in the greenhouse, and force it into a basement window. It used 6 or 8 black 55gal drums full of water as the heat sink. It worked amazingly well. It was glass patio doors and was a great DIY greenhouse.
One of the best things you can use to build your own greenhouse comes from Habitat for Humanity or any recycle shop or from window replacement companies in your area. Any home that has a sliding patio door that is going to be resold through FHA or VA will require that double pane windows or doors that have developed a small leak and allowed moisture between the panes.be replaced. It isn’t economical to replace only the double pane glass, so most people and companies replace the entire door. These make fantastic greenhouse walls and roofs. The moisture in between the panes is fine since you may need to paint your glass house with white paint if the sun is so strong it burns the plants inside. There is no commercial use for these doors or windows. You can pick them up for $20 or so from the salvage places and possibly for free from the company that replaces them. A side bonus is that they can be opened in hot weather to keep things from overheating. If you are going to the trouble of building a greenhouse, this makes it upscale and you never have to worry about ripped plastic walls.
Interesting, thanks for sharing!
It will need a electric blower to force air into soil below plants.
Mike, I have loved watching your videos over and over; reading and poring over all your info. Yes, I am Still interested in Plants. (to answer one of your recent e-mails)
The day before I broke my leg at work last October, I was hauling around cinder blocks, planning locations for baby citrus trees (we live in San Antonio, so we can grow a lot of stuff if we get enough water). Now two surgeries later, I am just puttering around in a wheel chair and a walker watering and trimming my tropicals we brought inside.
Even though I knit and crochet and can do sedentary stuff, I know it sounds crazy, but I soooo miss mowing the yard.
I dream of selling plants, since I do propagate as many as I can, But I usually end up sharing and swapping. Many of my neighbors are military wives from the Philippines or Korea and they have taught me about many edibles. I swap my pears and figs for citrus
Our 4 kids are grown and gone and the back south facing bedroom is now the Good Fairy Grandmother Garden Guest room. I have one of those beautiful anion humidifiers in a hanging bowl and fluorescent grow lights and a steel case desk top full of African Violet slips that will sprout babies even on their stems in that environment. I have a zippered plastic greenhouse that has 8 shelf units for seed starting that I’m thinking about setting up inside while I am so limited. My friends and I are poring over the seed catalogs for a joint order.
Tomorrow I get my first formal physical therapy and I will be working hard to get back to my previous activities
Maybe by this spring I’ll be behind my self-propelled mower again and digging and delving and shooting baskets at the nearby basket ball courts. In the meantime, Mike, I enjoy gardening vicariously learning everything I can from my favorite adopted brother in bib overalls. Keep up the good work and stay safe and well. temporarily grounded Good Fairy Grandmother Dorothy
Hang in there Dorothy. Plants and Eye Candy flowers give both physical and mental therapy, Mike and friends provide visions of pleasure to be had. Laugh in the face of adversity and pass it bye.
Dorothy,
Right now I am desperately missing mowing, weeding, potting and all of those things that I like to do when it’s warm. It so nice to hear from you and thank you for your kind words. Your brother in bib overalls!
I should have been clear on the white paint, you may have to paint the actual glass or use a sunshade. The moisture provides a slight shade on it’s own.
I just read this post….I can just imagine how you must feel!! but your words are so descriptive that I feel like I pictured every you wrote about. I hope you’re on your feet soon, and get your hands dirty again. I love my gardens, and to putter, etc….and this Mike guy is such a big help to us novice gardeners!!! thanks for sharing. and good luck!!!
Angela from NJ
Dear Dorothy,
Been there, done that. I am 83 and just finished mowing my California back lawn. The physical therapy will make a huge difference. Take an Advil before you go, it will probably hurt at first. My daughters bought me a 3 wheel bike for Christmas, and I am looking forward to pedaling around the block soon. After 3 years of drought, we are having an El Nino winter! Rain, rain and more rain. The weed are doing great!!
here is a list to think about and you don’t have to Email if you rather not
1 Glazing on three sides NOT the roof
2 Metal roof is easiest
3 Use standard size material
4 Use flat black paint on solar heat collectors
5 Consider ceramic floor tiles upside down painted on the beds
6 Water and electric
7 How to insulate the roof
8 Air flow into the house
9 Air from the far end of the house into the GH
10 shape of GH
11 Roof pitch , overhang tie down
12 Consider half a hoop house. Easily expandable
13 Reflective interior
14 How to vent heat in summer
15 Do I need to not attach to the house for tax purposes
16 Not attached but appears to be
17 footing. Treat. Set on pad 5 per leg, poured cement. Freeze line
18 stainless vs. galvanized. treated vs. plain
19 computer fan
20 glass sliding doors, storm windows, old replaced windows
21 Double lap poly panels. Cuts drafts. Use foam supports.
22 Use vinyl trim and foam filled materials to seal edges. J channel
23 Use storm door entrance Screen and removable glass for summer
24 Fluorescent grow light if you want longer daylight.
25 plastic sheeting under plants to hold water. Make trough
26 I use Gal. pots filled with wood mulch and slow release 14.
27 I have 175 pots In a 8×10. bed in front and west end.
28 how high is your bed.
29 hanging baskets
30 roll down shade . Closed cell foam, rug.
31 sun shadow 3 to 1 Take some measurements
32 Put a thermometer on sout side were GH is going.
33 Floor insulation and waterproofing if raised floor.
34 Manure to start compost bed. Wire and plastic sheet.
35 Green manure to start plants
36 Insulate non glazed walls
First determine what you want the greenhouse to do for you. Most people do not need a standard GH. Starting the season earlier is the main goal for most of us. The best location is attached to your house on the south wall. There is no sun on the North side of your home. Wind is your enemy and if they are out of the south they tend to be warmer. A North wind sucks your heat out. Now what do you want to use as glazing.(glass,polycarbonate, sheet plastic.) I have used all three. Now do you want a front and rear table. This determines the depth and size of your material. I have experimented with several solar heat collectors. I am in NJ across from Phila. so I needed free heat.
Ed
I have a polycarbonate ‘hobby’ greenhouse….its doing OK since I erected it in 2006….it withstood Sandy!!! right now I can’t really get to it, cause of the recent snowstorm here in NJ (down the shore!!) but I already started a small compost pile. I do light small tealight candles in aluminum enclosed (with holes punched on the top) containers….that helps a bit. but mainly my little greenhouse is a shelter for my outside cat…I leave the bottom ‘window’ open for him to come and go…and I’m also gonna try the water container…I did that once before in a plastic spackle type container, but the water froze. try try again. all good tips, for sure!!!
Angela from NJ
There is a double wall sheet plastic on the market. It has a corrigated inner layer to give it rigidity and some insulation, and it is slightly opaque to screen sunlight. Not cheap, but well worth the investment.
Thank you mr. mcgroarty! thank you so much for emailing me all of this wonderful information! I always look forward to hearing from you! you are a great guy! I LOVE the article you just sent me on heating a greenhouse without electricity! That just hit home with my situation! That is an answered request of mine. i look forward to trying out your ideas! Once again i thank you so much!
Incredible info thanks so much!!! From a rooky gardner who has had success in my gardens.but i am realizing so much to learn you are a godsend its plain to see.cant wait to build my greenhouseon our land.
I am in Minnesota. Last night it was -11 degrees F. We do have several days at a time when the daytime temps are -10 degrees F & night temps can plunge to a artic blast of – 25 degrees F or colder. Much of the winter we also have a wind chill factor. My questions are:
1) Will this compost heating method work in the Northern States where our night temps are usually in the single digits or colder ?
2) What about when it is cloudy for several days in a row ? No sun cuts down on passive solar heating so would the compost heating method be sufficient during cloudy spells & really cold (minus zero) periods ?
3) Will winds decrease your greenhouse indoor temps ? Would greenhouse need some caulking, insulation, etc. just like your house to keep out the cold & keep in the heat ?
4) Would snow on the greenhouse roof need to be removed to promote [passive solar heating ?
5) does this compost heating method work for the portable plastic greenhouses ? On only for the more permanent structures ?
I am wanting to construct a greenhouse on my new (old) single family house that is attached to the back of the garage. Access is only from the outside or yard & there is no electric service in that pert of the backyard. I have been wanting to know about some inexpensive & sustainable way to keep the greenhouse interior warm. This sounds like just the thing if it will work in our climate.
Thanks for your thoughts on this.
C.Dorr, a Northern Gardner.
Catherine,
It really depends on how warm you expect the greenhouse to be, but for the most part, in your climate I would consider it challenging at best. Any greenhouse that is built to be heated should be sealed, caulked and plastic covered greenhouses are usually built with two layers of plastic then a fan that blows air between the two layers for insulation.
In my nursery I have no greenhouse at all. I do everything without the use of a greenhouse. Mostly because I don’t like having to worry about plants in a greenhouse. Should I lose my height I would lose all of my plants.
But by not having a greenhouse my plants are all dormant, outside in the cold and come spring they’ll be just fine. Sure we lose a few, it’s bound to happen. But most of what I grow does just fine doing it the way I do it.
Mike,
For those of us in the far north, I would encourage folks to check out the WiseWay Pellet stove which requires no electricity. and can have a water heater attached to it. We have a customer in New Hampshire with an aquaponics greenhouse being heated in the extreme cold months by the WiseWay Pellet Stove and no electricity is needed to run it.
Dee
You’re welcome for the free plug.
I’m thankful for the free plug. I’m looking for something like that.
There is a university in Minnesota that is working in this very thing. They call it a winter green house for cold climates. I’m in alaska so I started looking into winter greenhouses…. Anyways. They have lots of info and can be found in a quick google search.
Wind Chill Factors do not apply to inanimate objects, only to living beings.
If anyone wants to seriously explore methods of heating with compost, he should read a book that came out in the 70s, called “Another Kind of Garden – The Methods of Jean Pain”. Here’s a link: https://archive.org/details/Another_Kind_of_Garden-The_Methods_of_Jean_Pain. He used compost to heat his house, and powered his vehicles and ran his kitchen stove on methane made from compost.
If you measure the square feet of glass (glazing) in your greenhouse and multiply by 2.5, that’s the number of gallons of water you need for thermal mass to stay above freezing. I use plastic 55 gallon containers (about $ 10- $ 15 each on Craigslist, or maybe free from a dairy). You’ll still need supplemental heat if the days are cloudy.
Thank you Mike! Our light bill this month was $403.00! We have two smallish greenhouses we heat because I have citrus and other tropical in them. This will be our next project. The greenhouses are warmer than our house.
Back in England in Victorian days, when horses were the usual mode of transport, there was so much manure available that masses of it was placed in greenhouses in the same way you describe, only in very large beds which were used to grow Pineapples. At this time, unlikely as it seems, England actually exported them. I have a copy of “Beeton’s dictionary of Everyday Gardening”, published in 1896 which describes imported ‘Pines’ as being sometimes little better than a sweet turnip, there being no comparison between these and a well ripened English grown Pine. Much of this difference would be occasioned by the time it took for foreign Pines to reach London versus a good ripe fruit from on your doorstep. The Beds were of four feet deep composting manure and the Pines were planted in pots which were sunk into them. Interesting I thought.
Gordon,
Interesting indeed!
Hmm, I have a horse that makes lots of manure. Might just try something like this.
I have a small green house with a considerable in ground water reservoir. I have compared the low temperature in the greenhouse to outside temp overnight and have found no overall difference. However humidity is much higher in the greenhouse and perhaps it is the,high percentage of water molecules in the air that insulate and protect plants.
THE ALMIGHTY MADE ALL PERFECT,GREEN COLOR ABSORBS THE MAXIMUM HEAT -MORE THAN BLACK-FROM EXPERIENCE IN UNIVERSITY
If you look at really old British greenhouses, you’ll see pull-out bins in the wall – about 3 feet high, than are opened from outside the greenhouse. These hoppers are for holding fresh manure or maybe plant compost – which gives off warmth as it decomposes, warming the greenhouse.
Ac,
That’s pretty interesting. In this article I discuss using manure to create bottom heat. http://www.freeplants.com/bottomheat.htm
I worked in the Horticulture sector and in winter the heat and warmth coming from farm manure bags was so relaxing as we were packing them on a cold and chilly day but least we was warm
Mike,
Thank you for the thorough reply – it has set me rethinking my whole greenhouse project.
Edward
Does this really work in Zone 5 or colder ?
Edward,
I think it really depends on what you intend to use the greenhouse for at at what time of the year. In the dead of winter in zone 5? I’m pretty sure the thermal mass will not hold enough heat to keep the greenhouse from freezing. And I would think that thermal mass works two ways, just like a thermos. A thermos can keep things hot or cold. Once all of that thermal mass gets really cold, it’s going to stay that way until the sun shines and heats up the air space again.
In my nursery I have zero greenhouses. Everything I do, all of my plant propagation is out in the open and left uncovered for the winter and I’m in zone 5. Right now it’s about 15 degrees, all of the cuttings that I rooted this summer, over 20,000 of them, are outside, uncovered but covered with snow. The sand they are in is frozen solid.
I should also add, that trying to heat a greenhouse all winter in zone 5 is no easy task. It can be done, but if the heat goes out for just a few hours you can lose everything in the greenhouse. Which is why I don’t have one. One less thing to worry about.
Many people use a greenhouse to extend their growing season a bit. In that case, either at the end of winter or the beginning of winter, using this thermal mass system should work just fine.
I planted in my greenhouse in zone 5a, mid july for a hopeful late fall harvest, Stuff that need 110 days….
the growing just slowed down ALOT in october and eventually I just gave up before wasting too much electric.
So the moral of the story….plant sooner for fall harvest
I have a nice barrel all set for composting, so will move that in to the green house and see if I can get a march 15 start on pre-plant into cups.
Already got 50 cinder block….they really do help even out the temperatures.
There is an active greenhouse in Chicago that is heated entirely by compost. They are also doing aquaponics with a large tilapia tank feeding many elevated grow beds. I think the only thing they need power for is to run the pumps to circulate water from the tanks to the beds.
David,
That would be an interesting place to visit. I”m curious how warm they can get it in the dead of Chicago winter.
I bet you could run the pumps with electricity generated by a solar panel.
AN easier way is to redirect more sun in your greenhouse Like I due with my solar panels . Use mirrors or aluminum foil wrapped around cardboard redirecting the sun to hit an area more then once. On a summer day in GA I took a wooden box painted the inside flat black used insulation around the box. then put a single pain glass over it. used a checker board covered it with the foil angled it sow the box was getting 4 times the amount of sun within 4.5 hours I was over 300 degrees inside the box. Yes you can cook a meal with the sun and it will never burn John
Yes, I did it in our zone 4 and it worked fantastic. I planted in February and it took the edge off until the end of March. There were no hard frosts in the greenhouse. But I made a huge compost pile (hotbed), put my seeds in dirt filled cardboard boxes, and moved the boxes out of the greenhouse as the outside temperatures became warm enough.