Anyone heating their greenhouse with 55-gallon barrels

Hi everyone,
I did a search for this and didn't find much (might not have done it right) so here it goes....What do you think?

I am in the middle of building this greenhouse with a few modifications of my own. https://www.youtube.com/watch?v=-DKlXs8iov0
I am using actual greenhouse 6m film to cover. It will have a regular screen door (like from a house on the east side) as the door and a regular storm window for the window on the west side.

I have purchased 4) 55-gallon blue barrels so I can hopefully extend my growing season.
I was originally thinking of putting the barrels filled with water on the Back north long wall to absorb the suns heat.

But I started thinking wouldn't it be better to have them up front, on the South long wall to catch as much sun as possible?

I live in an area where we get the least amount of sun thru winter.
Do you think this barrel system would work to keep the cool season plants growing for awhile?
I will have a couple 2x4's on top of them with my seed/plant trays.

I am not planning on growing through the winter months as I would need to add some sort of a heating unit using power which is not an option right now.

Thanks Lisa

I'm doing something similar, but on a much smaller scale. I have 1 gallon and 1/2 gallon milk jugs in my cold frame spray painted with flat black spray paint. They line the north end of my cold frame (which is up against the south exterior wall of our house). I put them on the north end so they absorb the sun and don't shade the plants (you probably wouldn't have that problem). I did the same thing last year but with clear jugs--the black color has made a drastic difference.

How warm it keeps the cold frame at night is highly variable, depending upon the amount of sunshine the previous day (probably due to small volume of water). I've had nights in the upper single digits earlier in March, and if the night before was sunny, the cold frame would stay in the lower/middle 30s. Nights in the 20s easily are staying in the 40s in the cold frame. If there wasn't sun the day before things usually stay above freezing as long as the temps don't dip below the 20s. I had one night where it was cloudy the previous day and then dipped to around 13 or 14 and the cold frame was 25 that morning (plants were in the basement).

I've read about people with greenhouses using smaller containers than 55 gallon drums because of the stratification that can occur in the large volumes of water (cold water stays in the bottom and warm water stays on top) which decreases efficiency, but my scale is too small to have those concerns, maybe others can comment.

Hope something in there helps!

I'm thinking of doing this next fall. We're in an area that drops at the most to low 20s off and on for about 6 weeks in the winter (Zone 8a) and gets a lot of sunshine. We're going to purchase a greenhouse that's a heavy plastic covered pole tent style that got really good durability and function reviews at Home Depot and Lowe's. With a couple of black trash cans filled with water I think we should be set for our winter.

I'll follow this thread with interest to hear anyone that has actual experience

Hi jmsieglaff, Thanks for the tour of your cold frame that was very helpful. I haven't heard about the stratification part before but it does make sense. I am keeping my fingers crossed for this to work. I am just looking to extend my season just a tad bit. It would be nice to have some garden fresh greens for Thanksgiving or maybe Christmas. But we'll see how it goes.


Hi audrey, Sounds like this would work great for the area you are in. Love the trash can idea too. I guess this is going to be one big experiment. lol.

You guys have got me thinking .
About putting a lidded plastic coffin type box 4 foot long x 18 " high x 2 foot wide under the propagation grow bench and using a matt black home made solar panel inside the greehouse to heat salt water( cheap not so toxic antifreeze ) in the coffin, perhaps the circulation could driven by a cheapie solar pond pump in a fully vented system .
I'll have to sleep on it and let my single brain cell come up with the answer whilst I'm in the land of nod .

Ooooh....Sounds interesting.

Hi there
I really enjoyed the video you posted. I have built a cattle panel greenhouse before, in a previous local.

There we were zone 8 and I grew for the winter. Now I am in zone 5 and have another greenhouse, we built from a kit, and cedar greenhouse.
But I have been experimenting with those 5 gallon water jugs that people buy water in. Here they throw them away (we are in a tourist area), so I have about 50 of them from the bottle depot.
I used 6 of them in the greenhouse this last winter, and I did not find that they made much of a difference. Perhaps if I had used more of them I might have?..
We will see next year.

Morning everyone,

GWN love your green house. I took a guess that your GH is approx 7x12=84sqft 84sqftx2.5=210 gallons needed
210./. 5 gallon jugs = 42
so you would need 42- 5gallon jugs to make a difference. let me know how it works out for you.

I have found some calculations on how to determine the amount of water/barrels needed to heat/warm the greenhouse.
They say you need 2.5 gallons of water per square foot.

width X length = sqft example: mine is 7' X 8' = 56sqft
56 X 2.5gallons = 140 total gallons needed
140 ./. 55 gallon barrels = 2.5 barrels needed

Well I do have room for 4 barrels across the front/back Sounds like I should be good. In theory anyway.

I also am thinking of bringing in some composting materials and placing them along the back/north wall. I would mix them when it becomes the colder part of the season to help with heat/warmth.

It is and will be raining/snowing/sleeting here for the next few days. I have WAY too much time to think....lol

thanks... I guess I thought I did not have enough water.... will see if I can lower the electricity bill next year with more barrels of water.

Elliot Coleman says you can gain 5-8 degrees just by placing a 'greenhouse' inside a greenhouse. You could benefit by putting your barrels and plants inside a smaller enclosure inside your greenhouse.

I saw some posts from last year where someone on the West coast was trying barrels inside a greenhouse. Sorry, I don't remember who it was.

with my cattle panel greenhouse I was trying to achieve what Coleman explained and so what I did was to have another cattle panel hoop over the beds... inside the greenhouse It seemed to work. well, we just hinged the one over the beds.

Hi,
That sounds like a great idea. Greenhouse inside a greenhouse.

I could drape another bit of plastic over the plants and the barrels to keep the warmth in. They would be toasty.. perfect.

My DH put his foot down and said no to electricity in the GH. Darn.

I should be able to extend my spring and fall just enough (fingers crossed) to be able to put some extra veggies away for the winter months.

plantoid wrote:You guys have got me thinking .
About putting a lidded plastic coffin type box 4 foot long x 18 " high x 2 foot wide under the propagation grow bench and using a matt black home made solar panel inside the greehouse to heat salt water( cheap not so toxic antifreeze ) in the coffin, perhaps the circulation could driven by a cheapie solar pond pump in a fully vented system .
I'll have to sleep on it and let my single brain cell come up with the answer whilst I'm in the land of nod .

Are you still thinking?

The concept you folks are discussing is the use of a "thermal mass" to store heat energy from the day's sunshine and release it at night to reduce the temperature in the micro-climate at night.

Water, properly used, CAN be a good thermal storage device, but it is not as simple as using barrels.... There are many additional variables to consider... I've done some thermal design, but don't have the time right now to go into it in any detail.

You might consider researching thermal mass and passive solar...

Bottom line you want the following:

...a thermal mass design that will:

1) easily uptake heat energy during the daytime,
2) of sufficient size to store the AMOUNT of energy you need, and
3) of proper design to RELEASE the energy at night.

Movement of heat energy around is a huge area of study, and lots of folks make a lot of money engineering for just this purpose...

I am still not sure if I should put the barrels up front and personal with the south/sun wall........or back north wall.

everybody puts the barrels on the back wall because then the plants would be up close to the sun/south wall, plus the barrels would be out of the way.

But can I dare to be different?

I am leaning toward putting them on the south wall.
Then I would be able to use the barrels for a shelf as well.
plants would still be up close and personal with the sun.

Ok I am thinking toooooo much.


Hi cautery,

...a thermal mass design that will:

1) easily uptake heat energy during the daytime,
2) of sufficient size to store the AMOUNT of energy you need, and
3) of proper design to RELEASE the energy at night.

Movement of heat energy around is a huge area of study, and lots of folks make a lot of money engineering for just this purpose...

So this is what i have right now....
A) 7x8' GH.. single layer GH 6m film... (wanting to insulate East,West & North walls. With double film and ? bubble wrap or shove something in between the layers. not sure what yet....moving the barrels from the back/north wall to the south wall with plants on top with another mini GH plastic over the barrels and the plants

1) 55 gallon barrels painted Flat black plus possible compost pile started when it gets colder.
2)4- 55 gallon barrels (filled with water) for this size GH. Some say to use 2.5 to 5 gallons per sqft glazing. the 4 barrels will give me 220 gallons. I think I am close. not sure though.
3)Adding a mini GH on top of and including the Barrels. to localize the heat.
I tried to find info on the web that would be do able for my small GH.
what do you think am I close? I am not trying to grow warm season plants all winter just to extend my season a bit to like Thanksgiving or even Christmas.

I have three drums of water in my greenhouse. They help keep from overheating during the day, and warm the greenhouse at night.

I've thought about setting up a system with a separate solar water heater, and then circulating the water through the greenhouse, but then it gets complicated. I don't want to increase the risk of overheating during the daytime. So I guess I'd need some kind of insulated tank to keep the hot water, then to pump it only at night.

I dunno; I like to keep it simple. What I have now is adequate for now.

omg. I have a greenhouse that is fiberglass, at least 20 years old, and very opaque fiberglass. It is an oven!!! for most of the year here in central Texas so I have only used it for storage of gardening equipment. I do not have electricity to it so cannot use it for starting seedlings. Dear Hubby and I will put a clear window in its roof soon and will use it to have winter lettuce/kales going and to help me start my tomatoes and "spring" veggies going earlier. The lettuces/kales will be SFG for sure. Garlic and super sweet Texas onions are soooo expensive I need to work on getting these SFG in the greenhouse too.

I just ran an electric cord to the greenhouse and plugged in a space heater.... to heat it.

Hi plantoid ,
This is getting good.

Hi Pollinator,
I know simple is good....my head hurts.

Hi hillcountryhick,
Sounds like you have a plan of attack going. good job.

Hi GWN,
That works too...
I just might have to bury an extension cord so DH won't see it...lol

Man... I'm sick at my stomach....

I just spent over an hour writing a complete Analysis/Recommendation for the thermal mass and structure design for this thread covering the principles of heat exchange, heat conservation, coolants, containers, heat exchangers, insulation, et al... With the cheap way to do it and with all the "upgraded" ways to do it to include circulation systems, radiators, et al...

I absolutely KNOW that I hit submit.... and it is NOT showing up...

I'm sorry, but I don't have the time or the will to recreate it right now...

To the OP:

1) Switch to steel drums, prep and paint them with flat black corrosion inhibiting paint. Alternatively, use "jerry-cans" or similar blocky type containers of metal and build a floor to ceiling wall with a supporting structure of wood/angle iron as an upgrade.

2) Use FRESH water treated with bleach prior to closing. Salt water ain't worth the corrosion and contamination risks for the benefit it would give you.

3) ABSOLUTELY place the thermal mass on the North end of the structure, possibly wrapping around the West and thence the East side as long as you don't let it block light entry.

4) Get thermal mass up off the ground by at least 2-4" in winter to conserve heat. Floor should be insulated in winter... "mulch the floor".

5) Air gap on all walls and roof... North and areas where sun won't shine through directly, can be opaque and built with insulated stick frame. Translucent areas... cheapest is double film, with outer film as thin as durability will allow, and inner as thin/clear as you can... minimize reduction of light transmission.

6) Ventilation: Make structure AIR TIGHT. moving air is death to heat conservation, BUT add adjustable vents at minimum at/near floor in North end, and at eave/ridge in South. Used ceiling fan for winter air movement. Natural convection and/or exhaust fan at south vent for summer air exchange.

7) Summer shroud of Mylar bubble wrap around thermal mass with intake oriented North, and terminating shroud to a duct that exhausts cool air into structure... ducting can be tweaked for max effectiveness...

Man, I hate that I lost the complete version of this....

Ooooh Clay,

I am so sorry you went through all that work and it's gone.
Do you think you hit the draft button? if so it would be in your profile.
might be worth checking.

Clay,
What frost protection will the bleach give you or do you have to drain it off each winter because of prolonged low temp frosts ?

For my idea I said salt ( for plastic food barrels & a fibre glass coffing tank ) for I know it will give protection when the glass is down to about 18 o F. I'd be using use high temp plastic piping and connectors such as the acorn pipe range so no corrosion problems .

WI FarmChick wrote:Ooooh Clay,

I am so sorry you went through all that work and it's gone.
Do you think you hit the draft button? if so it would be in your profile.
might be worth checking.

Nope, I checked everything I knew how to check... it's gone.

plantoid wrote:Clay,
What frost protection will the bleach give you or do you have to drain it off each winter because of prolonged low temp frosts ?

For my idea I said salt ( for plastic food barrels & a fibre glass coffing tank ) for I know it will give protection when the glass is down to about 18 o F. I'd be using use high temp plastic piping and connectors such as the acorn pipe range so no corrosion problems .

The bleach isn't for frost protection... I didn't address "frost protection" at all... The bleach was to inhibit micro-organism growth in the closed containers.

If the system/structure are put together properly, there shouldn't be any need to worry about freezing of the coolant.... She stated she was looking for season extension, not a year-round solution.

IF you are using completely non-corrosive materials EVERYWHERE, then using a brine coolant would offer some additional freeze protection. But, as someone who has worked around brine a LOT in the gas fields of Texas, it is very nasty stuff to deal with, and it will somehow, someday find its way OUT of the system.

And brine contamination of the soil usually means death to the soil it falls on for... well, practically forever. AND depending on the circumstances, you could find the EPA and State officials up your wazoo with questions and fines if you should ever have a spill.... Just speaking from experience.

You are looking at a totally different type of system from the OP... If you are going to use a circ system and heat exchangers, then your coolant tanks and piping would be better off NON-conductive and insulated... letting all the heat exchange happen at the radiators.... Which I would use a dual-set with a valving manifold for flow control...

I LOVE thermal design... no matter the application... from water cooling electronics, to thermoelectric coolers, to thermal control for entire buildings....