Heating and Cooling Larger Greenhouses

[Brent Kliesen]

Hello everyone, I live on the plains in NE Colorado and have recently decided to construct a large greenhouse (30' x 168') to start my dream of becoming an aquaponic farmer. Where I live, in the winter it can get down to -15F and in the summer above 100F. I was wondering if anyone had any ideas on how to cost effectively heat and cool the greenhouse the least amount of fossil fuels as possible. Thanks!

[NG Sutt]

I can relate to the -15 F temps!  Based in Wisconsin.  I've been to a few greenhouses that burn wood, but also have propane/natural gas as a backup system.  Lots of good ideas out there, however few that work during January/February here in the upper Midwest!  While I'm all for sustainable approaches to heating, the least risky (and arguably least costly) is still propane/natural gas.  At least for 2-3 months of the year.  Half the year we don't need the added heat anyway.

[Anthony Payne]

Hello I was reading some of what people talked about. I thought of geothermal? If you find the depth of the constant temp of the ground then you can put in pipes. Some can be filled with water or big enough to blow air through back up to the greenhouse this would make a more even temp. I have been kicking this around for my greenhouse. I think I can run pipe to cool my trout tanks and keep the water around 50F. If I run air ducting I will reduce the heating and cooling cost. That is if my space can hold the amount of pipe. I have read about drilling deep shafts to save space and it is costly on the front end. You may want to take a look at it, I find it fascinating. Good luck with the dream!

[FriendlyAquaponics]

Aloha Brent

Whole series of articles on energy efficient greenhouses you can build yourself starting with #135 here: (http://www.friendlyaquaponics.com/support/newsletter-back-issues/). Let me know if you have any questions after you read it ALL (you'll know as much as we do then!). Aloha, Tim Mann, "The Friendlies" in Hawaii

[Steve R]

Rocket mass heaters are great as well as solar oven designs depending on your wood requirements. You can hook up multiple solar heaters to heating coils and circulate the water inside to coils in your floor in the green house.  iv never seen it done on a large scale but i see no reason why it wouldn't scale up if you just did it in sections.

[Jason N]

I have a similar dream of yours but I live in Minnesota, I am in the process of designing a passive solar green house on the South side of a building that I will feed beef cows aquaponic fodder too in the winter. I or may enclose the cows and the system under a very large hoop house. I am hoping that the cow waste composting will throw off enough heat and on the coldest days the body heat from the cows will also add heat the system.

[Joe Bifano]

After going through a few winters now in my 1500 sqft greenhouse I have tried several things to heat it. My greenhouse has a r24 North wall with 1/2 the East and west wall the same. I had about 5000 gallons of water in the greenhouse last year and switched to less becasue I am growing tomatoes rather than lettuce/herbs/greens. I had a wood stove set up and now use propane. I am realizing that the heat source does not matter and having something like wood has its advantages but the disadvantages of having to go out and keep it going every few hours sucks. If I could afford a wood boiler,10k, where I can burn to a large water tank or a pellet boiler where it just comes on when it needs too would be the best.

Having tomatoes I can't get away with just having my roots at 70 I need the whole greenhouse at 68 to 70 all night long if I want tomatoes to grow all winter and that is just to much to do. I can have it on through December maybe but the costs or the work involved is way to much. When I had just the greens then having the roots at 65-70 was perfect. Every once in a while the plants froze and I lost some but I could grow winter crops okay.

I think that the bottom line is what is the r factor in the roof plastic and southern side. You can get single poly , double and go all the way to the best polycarb you can afford but there is not much of a difference in them all. When I had the 5000 gallons or what I have now, when the sun goes down so does the temperature in my greenhouse. It does not take long and it is cold out there.

What we need to figure out is a new way to have a clear plastic roof that can have some kind of way to up the r factor at night so what ever heat source you use it stays in the greenhouse longer. So having a r 1 or 2 is just not going to do this. It needs to be an r 20 or more. A thermal curtain that can be automatically put up and down at night and the morning with a high r factor has to be what we need to figure out.

And yes they tried the soap bubble idea and no one has done anymore with it since it was invented and we need something else.

The rocket mass heater is great but it needs to be automated with a high r factor roof and sides.

If we could get a high r factor roof then we can save money and grow a lot more in winter.

[Rob Nash]

we don't heat our 30 x 72ft greenhouses... just heating the water in the fish tanks with electric elements, has kept our greenhouse above freezing.. I used propane in the past and was always pleased that I could keep the greenhouse above 50 degrees. one night I forgot to turn on the heater and was surprised to find the temps in the 40s.. from then on I decided to see how long I could go without running LP heaters.... so far weve gone down to the 20s and been ok...
FTR- running four 5500 watt 240v heaters in about 7500 gallons of tanks and rafts.

[Joe Bifano]

With 22,000 watts running what has your electric bill been for the months in winter?

Rob Nash said:

we don't heat our 30 x 72ft greenhouses... just heating the water in the fish tanks with electric elements, has kept our greenhouse above freezing.. I used propane in the past and was always pleased that I could keep the greenhouse above 50 degrees. one night I forgot to turn on the heater and was surprised to find the temps in the 40s.. from then on I decided to see how long I could go without running LP heaters.... so far weve gone down to the 20s and been ok...
FTR- running four 5500 watt 240v heaters in about 7500 gallons of tanks and rafts.

[Alex Veidel]

'Tis better to heat the root zone than heat the surrounding air...

Rob Nash said:

we don't heat our 30 x 72ft greenhouses... just heating the water in the fish tanks with electric elements, has kept our greenhouse above freezing.. I used propane in the past and was always pleased that I could keep the greenhouse above 50 degrees. one night I forgot to turn on the heater and was surprised to find the temps in the 40s.. from then on I decided to see how long I could go without running LP heaters.... so far weve gone down to the 20s and been ok...
FTR- running four 5500 watt 240v heaters in about 7500 gallons of tanks and rafts.

[Joe Bifano]

You can heat the root zone for most leafy greens but tomatoes freeze. I have had 70 degree root zone temps but still froze my tomatoes so for fruiting plants that statement is not accurate.

[Alex Veidel]

I said it's better... not a cure-all for temperature problems. If you have warm air and a cold root zone, your plants are more likely to die.

And yep, tomatoes are summer lovin' plants, so cold temps will definitely kill them off.

Joe Bifano said:

You can heat the root zone for most leafy greens but tomatoes freeze. I have had 70 degree root zone temps but still froze my tomatoes so for fruiting plants that statement is not accurate.

[Layne allen]

I am also in a northern climate and have been researching methane production thru anaerobic composting for a fuel source. My hope would be to generate enough methane to heat a greenhouse through the winter. I am still working my way through the theory but I thought I'd throw it into the discussion. Please let me know if it is one of those looks great but don't work ideas.