Greenhouse root heating

Robert O'Connor_5

I have a potential customer who inquired about heating his greenhouse with radiant root zone heating in the soil. He will be growing tomatoes directly in the soil. Was wondering if anybody has experience with this kind of method. This would not be in a slab, but directly in the soil above insulation. Probably 6" deep.

Ken_8

I have such a customer...

He went to a special class @ Rutgers for root heating and has turned it into a huge success.

He runs micro-tubing off simple manifolds and keeps 90-110° water circulating from a condensing boiler and does not heat the greenhouse - but rather the growing pots which he places directly on top of the micro tubes.

Reduced his winter greenhouse fuel bill by more than one-half and incesed growth and plant health measurably!

Two other greenhouses have radiant in soil and he uses plain jane black pipe as the buried source - about 6 inches below the surface.

Sadly, he did not put rigid insulation under the soil but still grows year round in Jersey, when outdoor temps can stay at 10 above for a few days straight. The growth of plants in that situation is excellent, but the energy costs are stiff.

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Robert O'Connor_5

Ken,
I've seen the radiant with the pots before. This guy wants to do the radiant in the soil as you indicated a couple of your clients have done. I told him we would insulate the base and sides with 2" blue. I'm curious as to the heat calc. of direct soil heating. I wonder if it is calculated as a concrete pad and then converted with some demand factor? I had seen in my research that guys do use the polybutylene tubing. PB has a thicker wall for sure which would be more conducive to direct burial than pex (and cheaper). Most greenhouses are heated with unit heaters in our area. Radiant would definately be more economical in the long run. He would be heating with an outdoor furnace with skids. Matt

Troy_3

Greenhouse radiant

Matt: I designed a job in the early 80s that is still going strong. 30,000 sq.ft. It was done this way- 2" polystyrene on the ground with 5/8" pex on 9" centers, then covered with 4" of sand and 2" of gravel. This grower grows mainly flowers in pots. Works great. When the place is full there is barely room to place one foot in front of the other to get down the rows of pots. That is great space utilization. The lower air temp. helps keep down disease and the utility bill. We are in Buffalo NY so hot air unit heaters are also in place for heavy snows. When it is important to melt the roof.

Robert O'Connor_5

Troy,
That's what I'm looking to do except instead of sand/gravel it would be all soil media. The one thing I'm concerned about is water drainage with the blue underneath. I guess I could put a water barrier on top of the blue styro and have the pad sloped to accomodate drainage. Did you do your design tube layout/flow rates based on a concrete floor parameters? Matt

Troy_3

Design

I can't remember anymore. I know Wirsbo helped me with it way back when. I know it works. The only other down side I can report is during watering they say it will fog up the place during high heat demand. Air circulation is critical to a healthy environment I'm told. It is interesting the parallels of human comfort and what the plants like. You can see the fluctuation in growth if a loop becomes air locked. We also have provided tempered water for the plants in most of the local greenhouses. They claim 30% more growth after tempering the water. The plant actually goes dormant so to speak when shocking it with cold water. Until the roots warm back up no growth happens. I think it explains why our radiant floor customers are so happy when they experience comfort for the first time. Their roots are warm. sorry I think this holiday is gettin to me.

Mike T., Swampeast MO

How about a layer of Inca drain covered by a soil-proof landscaping fabric on top of the rigid insulation?

Tim Doran_2

Call

Call us if you like, we have plenty of experience with root zone conditioning. 1-800-321-4739

Tim D.