Building heated propagation tables

I have been thinking of the best way to heat and at the same time water some shelf's in my new greenhouse. I have 10 - 100 foot heating cables and the shelf's are around 9 inches to 12 inches on top of each other. I have been trying to think of a way to lay the heating cables down on the shelf's so that the heat is reflected up and onto the plants. I have thought about putting 1/2 inch Styrofoam type insulation down with the aluminum side up and the wires attached to this.
The the watering I have been thinking of a few different approaches. One to lay plastic or pond liner on top of the insulation and heat cables. The pond liner would then have a capillary mat over it to keep the unleveled areas damp and humidity up. My last thought was to have each shelf with the pond liner holding a small amount of water and in on each end of the shelf's to put a hole so that the water drips down to the lower shelf and then is recycled back to the top from a bottom reservoir.
I am open to any suggestions and if their are draw backs to my original design. One that I have been thinking about is on the flowing water system if it is heated would this be a good thing for the plants or a bad thing. As I have heard in hydroponics that heated water can cause root problems on many plants?

I have also thought about just laying the heat cable on the metal shelfing frames and adding a timer mist system on the under side of each shelf?
Here is a picture of the new greenhouse I just moved and set up. The shelfing is around 30 feet long and each shelf is around 2 feet wide or 4 feet from one side to the other. This was before the move.

There was a wonderful nursery here for many years and the owner was a great guy who took pride in his greenhouses. He set up trays with bottom drainage and heat cables topped with a couple of inches of sand. The sand was kept slightly damp and kept the warmth of the heat cable evenly spread so no "hot spots" it was also great for the plants because excess water would drain from the pots into the sand and keep the humidity up without being excessive. He also started cuttings and things in a similar setup that he had hooked up with a misting system and simply covered with lightweight plastic (like painters plastic that comes in rolls) to keep extra humid. Seemed to work very well for him.

I have thought about using the sand but it is extremely heavy. If I could find something that would work similar but weight much less I would use it. I have a propagation wooden box with the sand and heat cables made. I hope to have something similar for these shelf's

Adding a plastic cover over the shelf's will be something to look into adding. It will be good for seeds and seedlings.

Hi:
I believe the sand aproach would be the best way to go. I am not sure how well the sheet foam will spread the heat out. You are faced with one of the oldest issues we all have to deal with. How much weight will a shelf hold. You might try even an inch of sand would be useful and I don't think it would be too much for the shelves you show. You might try one shelf and see how it does. Congratulations on the new green house. Please keep me posted on how its coming.
Dave

I have been wondering if their is a way to use the cables to actually heat up the metal on these benches rather than put anything down?

It should transfer some heat to the benches. In the greenhouse at oklahoma state they have a comercial version of radiant heat on their tables. They use a wire mesh over the tubes that recirculate through a water heater and heat exchanger. I will talk to my grandfather to get some hints on this as he built large heat exchanger for his carpet cleaning companies. I think he used 2" Galvanized pipe and a little giant water pump. I would thing a smaller pump should be used instead of galvanized pipe.
How big are the heating cables (diameter)?

Dave

Guys, have you thought about using 3/4 minus gravel? It is a great heat conducter, sand doesn't really work all that well. the 3/4 locks together and spreads the heat out evenly. I have a 1 to 1 1/2inch layer. I can put my hand on the bed and feel the warmth. I set whatever I'm doing on top in flats or trays. cuttings, seeds, etc I have a unheated greenhouse and I also over winter tender plant material on the beds. it's a nice, microclimate. Jim

Jim It sounds like you have a great answer to the problem. I will use your idea and do the same I think it might solve my problem with non heated green house . I know I had a lot of damage from the last week of cold it was extreamly cold single digits with a below 0 wind chill brrr.
Dave

Ok I am jumping in . Jim ,could you tell me what this 3/4 minus gravel thing is?

Hey Dave I got my green house today WOOOO HOOOO.

What about perlite instead of sand, prefectly light weight but would have more spaces for heat to escape than the sand.

You all gave me an idea of a lightweight permanant solution. My first thought was pour a thin layer of concrete over the heat cables but since weight is a huge concern that would never work. But in my faux rock projects I use perlite a lot as part of my mix- it takes very little portland cement to bond together perlite. You could pour a thin layer of a cement/perlite mix over the cables, it would be permanent and fairly light weight.

azreno, don't do it, you won't like it. Flowerfancy, 3/4 minus is available in sand and gravel places. they sell pea gravel, and sand and 3/4 minus etc. you can call them and they'll most likely tell you they have it. you won't need more that a 5 gal bucket of it. or they might have bags of it. it's a dense gravel that locks together making a nice heat conductive bed to radiate the heat evenly and also it make for a micro climate in the greenhouse. trust me, I go this from a local commercial nursery that has been in business for 50 years. good luck all of you. Jim

Thanks Jim, When the holidays are over I will call the place we have here in town that carries this kind of stuff and see if I can get some cause I want to try the heat cables and if this works good enough I will use it.

FF, you won't believe all the propagating you can do, when you get the bottom heat. it comes under the catagory of " things your nursery won't tell you " at 1st, when I started using the bottom heat I would ask questions. and they wouldn't answer them. after I figured it out, they'd say. oh, we've been doing that for years. Jim

Yeah the question thing is kind of hard to get answers to. Everybody has their own opinion and it makes it hard to figure out which to use. I even saw a few discussions on here that has gotten a little heated as to whats right and whats wrong LOL.
I really do want to try the bottom heat and seen if I can get better results than just trying to propogate with out much of anything. I also want to try a bubbler system. I have everything for that but the container,and I have just been to lazy to go get one, besides it's Christmas.

You won't believe the difference bottom heat makes, flowerfantasy! My seed germination rate jumped from the mid 50% range to the mid 90% range. Cuttings went from 60%-70% success to over 95%. I just have a simple rubber heat mat plugged into a thermostat (so I can change the heat level of the mat). I set the thermostat for 72 degrees because that seemed like a good temp for most seeds. Haven't changed it in 5 years. That temp seems to work fine for cool and warm weather crops.

StonoRiver,
You say you have just a simple rubber heat mat? Is that one that you buy for that particular purpose? I have a GH and we aren't going to be able to get it up anyways soon and I have some seed I really need to get started,but I am going to need something to help me along.

I have started to buy the supplies for the shelves. I figure I will start by putting down the foam insulation on the bottom shelf with the aluminum side facing up. After this the heating cable will be added with aluminum tape and topped off with capillary matting. The misting system will added under each shelf for over head watering. If this works well and reflects the heat I will be adding it to the others all the way up. If not I will just be adding the heating wires directly to the metal shelves. After this is done I plan to add plastic to curtains to keep the shelves very high in humidity. I am still trying to figure out the easiest way to construct the curtains. I have plenty of greenhouse plastic but I will need it to be easily opened to retrieve trays and easily closed. Any Ideas?

StoneRiver, I have the mats inside for germinating my Hosta seeds. I make individual boxes that the mats sit in them I set the trays with the seed on top. yes, you are absolutely right about the germination rate. it goes way up with the bottom heat. plus there's less problems with fungus, and molds, Jim

I want so bad to try the bottom heat but I guess I am going to have to wait for awhile. $$$$$ shortage right now Grrrrr!!!

FF if you c an get to use the bottom heat your desire to use the bubbler will go away. I feel this because of the ease of prop with bottom heat. it should be faster and higher success rate. Jim is on the right track with the benches.
Dave

I figure thats what will happen but I may have to go with the bubbler for awhile til I can get the $$$$ built up again

There is an open ended ( no end date set) coop going on right now in the coop section of DG for heat mats. You might want to look into it. The price is not bad and shipping is free.

And you can use other methods of warmth - on top of stoves, refrigerators, anything that creates a constant warmth. The fine print on electric blankets and heating pads is that they a) aren't waterproof and b) aren't necessarily meant to run for days at a time and could be a fire risk, so I wouldn't suggest those, but I bet there's other things around.....

I had a small commercial grower suggest the fine(r) gravel instead of sand, too ....

One of the best things to use is deicer cables. They are used up north on the roofs of homes to keep ice out of gutters. The wire is thick and comes in many sizes usually 50, 100, 150 and 200 and usually coast around 20 to 65.00. The wire heats up to 90f automatically and they can be left on for weeks or months. You have to be sure not to cross the wires this is were the fire hazards happen.

Just a thought.

I have several discarded hot water bed heaters that I use under mats. Perhaps there is a way to plug the deicer cables into the thermostat from the water bed. They all have a probe you could stick in the soil close to the cable that would keep the temp constant at what ever you set it.

I had a friend who owns a nursery order me two 5 ft. heating mats with a thermostat as you said. What a world of difference a heating mat makes with any kind of propagation........cuttings, seeds, etc. They aren't that expensive and as was mentioned.....there is a co-op going on right now, too.

Happy New Year y'all

You really stayed up last night, flowerfantasy! Happy New Year back to all of you.

Yea I stayed up and watched the new year come in, in spite of not doing anything. I am getting to old to go out and party anymore LOL.

At 67 I promise you I am not partying anywhere past 9 in the evening!

Well I am not all that far behind you so I know the feeling. I do stay up late ,but thats only because I am kind of a nite owl anymore. More likely it's because if I get sleepy during the day I take a nap LOL.

gessiegail, 2 5ft mats, that will give you plenty of room to do most anything. mine are almost always full. this time of year especially. I just check on some cuttings I did late, Golden Curly Willow, Golden Uonymous. I stuck them in Nov. and they have roots already. Jim

I used those mats all the time when I had a cutting garden .........then I switched to all gro light stands inside the house 2 years ago and I grow my seeds and cuttings inside now. I had those mats with gro lights built on top of them and plugged all of it in on the covered front porch..........
If they weren't so heavy I would help someone out. They are sitting in my storage building right now.

I just ansered my own Q, on the other tread. Always late and a dollar short. LOL Glad I was lurking.
Thanks Jim, (wished I looked at yours closer) I know what I'm going to do now when I get my GH extended this year. I have been toying with how to do it. The small gravel with heat tape will work, the same as it works on pipes here, I have all my pipes wraped with it. I have a cold GH the only way I can heat it now is with heat lights (spot lights) Which is okay but not for seedlings. I like your GH bwillaims. But I will have to make wood benches. What is the best way to keep them from rotting in time.
Happy 2009

Tilly buy treated lumber..and then use something like thompson water sealer on them.

I noticed some heat cables on amazon.com (see picture) It looks like there is a dial which might be a thermostat. Has anyone ever used something like this? They come in 9 foot to 100 foot lengths. The 9 foot one is only $17. Someone said these run at 90 degrees which is too hot. If this one can be turned down, it is a good deal.

I don't know if anyone has tire this before or not, but my father in law is a plummer and he installed a second water heater in his new home with a very small pump connected to 3/4 inch pvc pipe which is run under his steep driveway. When it snows, he just turns on the pump and the circulating warm (anitfreeze/water mix) keeps all the snow off. I wonder if it would be cost efficient to use a similar system to heat the growing beds in a green house. We use a simiar system under the floor in our cabin. It is tied into a boiler which works off the room thermostats.

Shouldn't the heat rise without the insulation anyway, if you installed the cables on the bottom side of the shelves? Misters should be easy to set up on those shelves. The Dramm Misty-mist nozzles would probably work well. if there's enough clearance. I'd be worried about the capillary matting because it quickly gets algae on it and with that comes fungus gnats.
One of my friends set up heated benches on his greenhouse with metal pipe and a water heater and a circulating pump. It was really nice until a windstorm took out that greenhouse.
I still want that greenhouse. We got another one, but the weather has been too cold to think about putting it up yet.

Bill: A lot of comercial growers use the water heater to pump warm water under the benches and they work great.
Dave

Dave, I'm sure that's the way they did it before the heated cables were invented and they are still doing it like you said. I'll be all the greenhouses in Iceland are that way. but the cables are by far the cheapest way to go for the hobbiest. what did it cost me? about $50 for all the materials. Jim