Greenhouse Heating

Missing Link

Wondering if anyone has experience in utilizing bare element under the benches that the plants set on. They tell me that heating under the plants gives them another growing season. Putting the tubing in the soil is not an option on this particular job. Wondering how far below the shelves to hang the element so that it does not heat in just a concentrated area. The benches are made of treated lumber and the plants sit on heavy wire. The lower the element, the better the dispersal of heat I imagine. If anyone has done this I need to know how well it worked and if the greenhouse owners were pleased with the results. I don't want to re-create the wheel here. Thanks for the help.

Mark A. Custis

I do a few

green houses. I want to know what type of eliment you are talking about.

Quick fix is a DHW tank loaded with glycol and run a bunch a pex aroud under the plants.

The DHW tank won't care what kind of return temps it sees, and for what they cost I would consider them to be dispossable. A manual three way valve and you will have plenty of warm plant feets.

Mark

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Missing Link

Element I was thinking of utilizing is copper finned, one inch.

[Deleted User]

try here...

found on google.com with Radiant Greenhouse Heating.

http://www.radiantroots.com/left.html

I'm not sure that convectors is what you really want. THey would heat the air, and hot air rises, right past the plants to the ceiling. If you used, say an extruded heat tranmission plate connected to either plastic tubing or copper, you would heat the plants radiantly, thereby cutting the fuel bills by say 50%.

ME

Luke Lefever

We have a customer that grows orchids...

apparently orchids are more temperamental than most other flowers. Anyway, he has a fairly small greenhouse (approximately 25x8) heated by a small cast iron boiler. The radiation is bare fin tube about 8 inches below the trays. I don't know what temperature he runs in the water- on sunny days, he doesn't need to add any heat, on cloudy days he does (we are in Northern Indiana, 100 miles east of Chicago and 5 miles south of Michigan). Most recent challenge was programmable thermostat with remote sensor. He read somewhere that orchids grow best at 70 daytime and 58 at night. Tekmar thermostats are sooo sweet. After I installed it for him- I had to order one for my house. Anyway, hope this helps. Luke Lefever, Lefever Plumbing and Heating, Inc. Elkhart, Indiana

Mark A. Custis

My guy here in northern Ohio

wants to bury the pex in the floor, not just under the benches. I think Mark has a great idea with using staple up plates under the wire mesh. The down side is air flow. My guy grows stuff up for the retail diy garden trade and has "tropicals" he heats all winter. One of his concerns is air flow and we have circ fans tied to a temp RH switching set up. I think you need to see if air flow is a concern to your customer. If not get some plates and some pex and go. If air flow is a problem then just string a bunch of pex under the mesh. You may need to fool with output temps to the pex so include a mixing valve in your up front pricing. You don't want to kill the boiler by condensing.

Mark

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

George Peteya

Pex and UV

Pex does not stand up well under ultraviolet, and a greenhouse is Ultraviolet City. I don't sell it, but if I were going to have hydronic tube exposed, either in a greenhouse or as roof/gutter melting, I'd use Onix. The carbon black in the rubber acts as a UV stabilizer. Am I on track, Watts/Heatway?

Missing Link

Neat Ideas

I'll be at the job tomorrow to seek the customer's thoughts on your ideas. I appreciate all of the help. We should be able to come up with a game plan for him now.

Dave Palmer

if..

they dont already do it see if the houses are covered with plastic. I supply fuel and service to a large greenhouse (6 unit)They wrap the roof with poly and run a litle fan from inside, between the poly and glass to make a air bubble.Works great,the air adds like a layer of insulation.

Missing Link

They do run a fan between the plastic which does create a decect r value. Not cocerned about heating the greenhouse,more concerned about warming the roots to make the plants flourish. I was going to use non-barrier tubing and a heat exchanger with a bronze pump as it would not be worth spending the money on barrier tubing when the U V rays would deplete it anyways. Yes?

Dave Palmer

the

fan is run between the poly and glass to make the bubble.What if you used tubing under the tables out of the sun (sandwiched between duro-roc and foil bubble wrap)?Just a thought,good luck Dave

Troy_3

Greenhouse heat

We've done a lot of greenhouse work. We designed copper fin tube hanging about 18" below the rolling benches and skirting the benches back in the early 80's. It worked well. We've used thin wall 2" steel in the same manner. The latest jobs have been installed in the floor. We installed 30,000' on greenhouse this way- 2" polystyrene oner gravel, then tubed with 5/8" wirsbo, covered with 4" of sand,and then 2" of stone. They grow the flowers on the ground. the heat is amazing. If the roots are warm the plant will grow . With cooler air temp. it helps keep disease down and the bills down too. The design depends on the crop and the layout. If benches are used you need a different approach. Greenhouses see fast fluctuations in temp. You really benefit from constant circulation in a greenhouse. The plant growth will tell you if you have a cold spot. The growth will be uneven if the heat is too far apart. The extremes of a greenhouse can teach us a lot about creature comfort. Or is that plant comfort? And are they really so different? Years ago my first greenhouse jobs were done with 1/2" pvc sch. 40 on the rolling bench tops connected with hose at the end of the benches. Pvc and pex really should never be left exposed in a greenhouse. Way too much UV. If I can be of any help call me at 716-913-4166. Troy

Mark A. Custis

I like the HX idea

I am not sure of the saving on non-barrier pipe.

Post a before and after photo if you can.

Mark

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"