greenhouse heating system design input needed and appreciated!

[tyler gaudet]

Hello,

My partner and I have run a small  3 season aquaponic greenhouse for two years while selling to local markets and restaurants. We now feel that we are ready to take the next step and setup a commercial scale greenhouse. We purchased a 100 ft greenhouse and plan to use a raft hydro system. We are thinking 2 rafts that run the length of the greenhouse. We are using tilapia so the water would need to stay warm throughout the maine winter. 

We are thinking of using an on demand boiler with radiant heat under the plant rafts. Does anyone have any experience in this? Has anyone done this or could point me in the right direction for info.

Or would anyone have any other suggestions for economical heat for a greenhouse of this type?

[George Schreiber]

Hi,

Gönczi Péter has created a passive greenhouse project (place thermal mass and solar collector in your south-facing greenhouse in such a way that it is exposed only to winter sun (or cover from summer sun, depending on how you can adopt idea to existing greenhouse)) a year ago, you might want to check with him for details.

BR,

George

[Jonathan Kadish NYC AA Chair]

Nelson & Pade have a gas boiler for heating their raft area so it can be done. They also have gas heaters for the greenhouse... It is economical from a standpoint of paying for all those BTUs? I haven't done the math on that. You might consider changing species to a cold water fish which will save you a lot of BTUs.

[Rob Torcellini]

I agree with Jonathan.  The first thing you should do is figure out how much it's going to cost to heat a building of this size vs the amount of food you'll produce.  You'll most likely need artificial lighting too from December through February.

[Kathryn Cope]

If you dome over your growing beds you will be creating a smaller area to heat inside the green house - of course ventilation/air movement are still critical to the health of plants.  Keep in mind gas/propane units will add to moisure content if running inside the greenhouse.  Have you read the 4-Seasons Growing book?  Seems like a lot of his ideas can be adapted to aquaponics. Can you run the water thru a solar preheater system? Maybe a series of of tubing placed on a black surface. Just some ideas to bounce around.

[wes]

The Friendlys have a solar greenhouse that uses a low cost heat exchanger to keep the greenhouse cool in the summer and a even temp in the winter using some deeply layed piping in the ground for the constant earth temp. Just a thought check them out. Google them and read up.

[tyler gaudet]

this is all great info, thank you