I hope someone can help me! I used our dog kennel to make a cold frame last year, which I've described on another thread:
The thread "My Dog Kennel Greenhouse!" in Greenhouses forum

I'd love to heat it this winter, and see that using drums or barrels of water is a good way to go about doing that. I'd like to use 30 to 50 gallon drums. I was told that painting them black will make them heat up even more, which is great, but I have NO idea how many barrels or drums I'd need to help keep the green house a little warmer during the winter. It's 6 feet wide by 10 feet long, and about 8 feet tall. I'd prefer to use 30 gallon drums because they would take up a lot less room on the ground.

Anyone know how many I should use? Also, do the drums need to be covered with a lid? I was hoping to set boards across the top to use as a table to hold more plants. Would that be enough of a cover or should they be sealed shut? I don't want it super hot in there, but a little heat would be great. Thanks for any help!

Natalie, My husband built my greenhouse a couple of years ago (15 x 30). It is timber frame, and he used polycarbonate for the walls and roof. Along the back wall, which is cinderblock and butts a hillside, we have put 55-gallon barrels all across the back wall, and they are double-stacked. The entire back wall has barrels. I think there are at least 10 on each side, but in the middle is a fish pool. They have lids, of course - since they are doublestacked, there is no way to use them. The barrels are painted black. We have had success with this method. It does add warmth to the greenhouse in the winter and, in fact, it keeps the greenhouse cooler in the summer. If you have more "technical" questions, please feel free to ask me, and I will ask my husband for the answers. I can also give you the names of a couple of books he used.

Dottie, thanks so much for the information! Your greenhouse is totally different than mine is, but I think the heating part would work the same. I had given up hope that someone would come along and answer, so I really appreciate your input! I never thought about the water barrels keeping it cooler in the summer, so that is an added bonus!

Natalie, I forgot to mention that the more water you have in there, the better it is supposed to work, so that is why we have double decker barrels. It is not attractive in the least, but it works and saves money. Also, there is space on top but not enough for more barrels, so whenever I have a cat litter plastic containers (scoopable kind of litter) empty, I fill themt with water and put them on top, too. If you have any questions, I'm glad to help. I have seen this used in other types of greenhouses, too.

I'm really short on space in my greenhouse, since it's very small. It's made out of our chain link dog kennel that wasn't getting used, and is wrapped in plastic. I'm planning on putting the barrels on the outside of the kennel, and then wrapping the plastic over them. Otherwise, I'd have no room for the plants! I can put the barrels on two sides, since those are the sides that will get all the sun.

I heard about using milk jugs before, and I'm going to put some of those inside. I'll wrap them in black garbage bags, since I heard that helps.

Thanks again for your help!

If Natai is short of space then she can use the stones to heat the place, stones will absorbs the heat in day light, and heat will be release at night.
May we join each other for further discussion on skype my ID is mentioned below
faisal.kaps

Dear Dottie
I would love to go for the helping books too those are consulted by your husband.
Because i am working on passive heating for my greenhouse in Pakistan size of 30 x 120 feets.
As far as my knowledge is concern may be 4 gallon water is recommended for 1 sft.
Regards

I will be glad to list the books for you and will do it today. If you have any questions at all, I will be happy to get my husband to answer them.

Faisal,

Here are two books my husband used as references when building my greenhouse. He informed me today that most of what he did came out of his head and/or from hearing about it from others. If you want to "pick his brain," I'll be happy to ask him questons for you.

The Solar Greenhouse Book, Edited by James C. McCullagh, published by Rodale Press
Greenhouse Basics: Building Your Own Greenhouse by Mark Freeman, published by Stackpole Books

Faisal, thanks for the information on gallons of water per square foot. Until now, I had no idea what the ratio should be. That gives me a much better understanding of what sized water barrels I'll need to use.

Stone are also a good idea, and I have lots of them, but I'm not sure that they could absorb enough heat through the plastic to keep the inside warm at night. It gets very cold here in the winter. It's a great suggestion though

If thee is any way to keep it dry, "drywall" or gypsum sheets are very good insulators, especially if taped together to prevent drafts.

I thin k that, if your water barrels are not INSIDE your greenhouse, you wnat as much insulation as possible surrounding the barrels on the outside, so that they "thermally INside" the greenhouse as much as possible. Otherwise they will give up their heat to the atmposphere and not help your plants.

You do want lids, or water will evaporate and chill the barells, producing humidity instead of raised temperatures.

Allow as much air circulation as possible, to get the heyat out of the barrels and into the air.

If the greenhouse is v ery well insulated everywhere the sun doesn't shine on plants, it MAY hold heat well enough for you to run an elctric heater affordably on a thermostat to provide just 10-15 degrees rise, if that's enough.

I use 2ltr soda bottles painted black and filled with water for passive solar heating .. they collect heat in the daytime and release it at night .. I also heat both my GH's using a milk house heater on a portable thermostat and a fan at the other end of the GH for air circulation .. system works out really well.








Here is a link for the portable thermostat:

http://www.kkontrols.com/

I am curious to hear what has been going on with these or other passive heat systems since this discussion started.

The past couple winters, I've used an electric hot oil heater, which heats well, but the heat is lost so quickly, it has trouble keeping the temp more than 10° higher than outside. That was enough the past couple winters, with the season low in the mid-20's, but if a really cold night hits, probably night. This season, I'm going to build a wall of water bottles painted black around the 3 sides in the sun and will report back here about the progress and the results.

I chose this material because we have these bottles in abundance (once I stopped taking them to the recycle bin, which I will do with these once they have performed a re-use first.) I plan to lay them flat on the ground, and stack them up between stacks of bricks at the ends to hold them in place. I don't expect this to heat the GH because it will be on the outside, but to help reduce the speed at which the heat is lost, more like insulation.

I am planning to build a solar heat collector for heating water for my 55 gallon drums rather than just relying on passive heating. I have started to gather what I will need even though I probably won't get to building it until the Spring for next Winter. I plan on building a solar collector with absorber fins that have 1/2" channels to run pex tubing. It will all get enclosed in an insulated box painted black with a plexiglass front. I am going to use a solar powered pump to pump the water from my barrels through the collector and back to the barrels. At this point, I plan to locate the collector within the greenhouse to prevent freezing in the collector on cold nights, but if I can't get the heat gain I am looking for, I'll build it larger and locate it outside the greenhouse. In that case, I will have to go with a closed glycol system and heat exchanger.

I think the effort I made with the water bottles was worth it. It took a LOT longer than I'd anticipated to fill and stack water bottles in 3 stacks, 2 on the south side on either side of the door, and one on the west side, and I learned that about 8 bottles high is the limit, and to alternate which way the caps are (facing in vs. facing out) or the stability is lost.

I ended up covering the stacks with black garbage bags to absorb heat instead of trying to paint anything. These stacks seemed to have helped insulate & block the wind from being able to go through as easily because this has been my only change vs. last year but the difference in temp inside GH has been noticeable.

It has been nice and warm every time I've checked, at least 45° in there, and nothing seems to have suffered any damage from what was an unusual cold spell for this area - over a dozen nights in a row below freezing and 2 days in a row of mid-30's for highs, ice did not melt & caused 2-3 days of school being closed in the area. No nervous moments like previous years when the temp inside could only be counted on for about a 10° increase vs. the outside temp.

SOOO glad I did this, using nothing but "trash," some time, and water.

That sounds great! I like that you used black garbage bags rather than messing with paint...smart! What size water bottles did you use?

I just finished buying all the supplies today and plan to start building my solar powered hot water storage system...hopefully tomorrow. It will probably take a number of afternoons to get everything done. I'll report back and post pics.

Jim

Thanks! I used 16 oz. clear single-serve water bottles. Very flimsy. More sturdy &/or bigger bottles could stack a lot higher. I used these because they are what we had in abundance. My husband drinks one very occasionally but otherwise, we don't buy or drink soda.

I can't wait to see your project, Jim!