Did you put trash bags in your trash cans then fill them with water and tie a knot in the top?

The evaporation heat loss is a killer when using trash cans.

No I did not just put the lids that came with them. These are fairly secure. I do have a recycled 40 gal storage bin underneath a bench of the southwest side that I just layed some spare plexiglass over it because it didn't have a lid for it. I also sterilize old pots for people and put them back in use. I use what is free first, what is cheap and available second and more costly measures as needed.
With the storage bin should I water plants and refill a large trash inside the bin and twist tie it up? I can see the black bag conducting more heat into it but am not real clear on the evaporative heatloss part. I know you want as much heat gain as possible during the day and as slow of a release at night as possible. If this is what happens even if I don't understand the science fully I will gladly take into account this with all I do in the future.
Question: Do you think additional black trash cans closer the the radiant heater (located on NW side) would be of enough benefit to warrant the cost of the containers. I have the heat sinks so far mostly on the south wall and the one bin on the southwest wall(solar gain)? I probably will use most of the usable space on the west wall floor and benchs space for continued potting up of material through out this month. Shift some pots as needed as I get into the seeding process later this month and in January. I still will have some dead space on the floor under the center bench area on the east side of it that I may consider more under 30" heat sinks (not much solar gain there) but again to hold more heat lower down from the electric heaters located under the benchs on either side of the double center benchs. I do expect by mid- January to be almost maxed out for any more growing space so will have to be judicious with heat sink investment (I will be looking at it for summer slowing of heat gain as well).
Thanks for the response Chris and I appreciate your input and thoughts!
Happy Growing David

You should look into putting the infared (IR) plastic for the inner layer of your inflated poly. They say it really cuts the heat bill. I'm going to put it on my greenhouses for the inner layer when the plastic needs replacing next time.
It might pay to go ahead and put that plastic double top on now, then put your overwinter poly on top like a shade cloth. Wire it on separately and when it gets warmer, take it off.

I am trying to evaluate the various poly for the double layering but want to figure out the winter and summer cover issues as a single answer and project to complete. Winter is a tough time to put on poly but there are several days at a time that will allow for it. I will just need to decide on material, get it onsite and be patient for the weather to turn calm and warm enough for the install. klerkusa.com has a k-50 4 year poly that is suppose to be good for its IR and with a good anti-condensate incorporated into the poly not just surface treated so it is supposed to last past the first year much better than the industry average as far as greenhouse poly goes. I am looking to get around 70 percent useable light with the double poly. I may have to resort to shadecloth for the May-Sept time period like all the others in the area but there just seems like there has got to be better and more effective ways to allow good light in the winter but not burn up in the summer with out using shade cloth. May be I am asking too much of technology still.
Happy Growing David

I still have to use shade cloth here in Indiana in the summer, just too intense. I have to put it on by the end of June.
One thing that helps, I use the aluminum channel type of wire lock and the "wiggle wires" inside of that. I've found that I can pull the shade cloth right over the top of the inflated poly leave the wires holding on the poly, put another wire in the channel over the top to hook the shade cloth on with, and then in the fall, just take off the shade cloth and the extra wires for winter. You can get about three sets of wires to hold well in that channel.
I talked to some other people on a high tunnel forum that are doing that, and it seems to make the poly last an additional year or so also.

[quote]I may have to resort to shadecloth for the May-Sept time period like all the others in the area but there just seems like there has got to be better and more effective ways to allow good light in the winter but not burn up in the summer with out using shade cloth. May be I am asking too much of technology still.[/quote]

Geometry can do the trick for you. The sun arcs higher overhead in the summer than in the winter. Give me your latitude and the length of your walls, and I can describe an awning that would only let in full midday sun in the winter.

If you're looking for a glazing material that alone does this, however, that's not going to happen any time soon, I'm afraid. You'd need a material that can repeatedly fog and unfog, with the fogging action based on solar exposure or temperature. Seems a tall order to me.

Actually, come to think of it, there are photochromic chemicals which become opaque when exposed to UV. For example oxazine. There are two challenges that I can think of, however. One, they would need to not react *at all* to low levels of UV, but react strongly to high levels. I suppose that this would be possible if the rate of relaxing to the ground state tended to exceed the rate of ring excitement from UV under weak light conditions, but not bright light conditions. Also, photochromic chemicals tend to degrade over time when in their activated state, so you'd need some particularly long-lived ones. I don't think there are any out there that can withstand thousands of hours of sun exposure -- somebody correct me if I'm wrong. :)

I don't think UV should be the driver - it is very variable compared to PAR and heating light. probably more effective would be to use heat changing films such as some LCDs, and better still, integrating measures - things which darked progressively based on their own darkness and the sun's brightness would probably work (giving classic exponential IIR response). I'm sure it is withing current tech, just not interesting enough to be studied.

There are already electrochromic films which can change density given an electric field or current.
http://www.toolbase.org/Technology-Inventory/Windows/switchable-glazing-windows
http://en.wikipedia.org/wiki/Electrochromism

Bet they cost a bundle though.

Sounds like the concept is possible just not yet economically practical. I will have to stay with more conventional means for the time being and accept it for the task at hand. I do want to be able to make money for the company and continue to build on the success of this year. Also I need to save the more unconventional for personal space not my work space. Thanks to all for your input. If I come up with something more worth discussing I will post it. I will have to play around with the extra wiggle wire and see if it looks reasonable to use the same channel for two more layers (poly now and shade cloth come May). I was curious whether or nor regular channel will support 3 layers. I guess from Sandy's reply that yes it is and can be done. Thanks to all for your thoughts and
Happy Growing David

The reason I say put trashbags in the containers is last season (march-may) several of my trashcans had only a few inches of water in them when I took down my benches. I checked for leaks (you put the trashcan over your head in the yard on a sunny day, yep now you know I am nuts)

My benches are 4x8 plywood on top of 6 trash cans as legs. Plastic sheet on top of the trashcans to seal them, then the ply. As I took more benches down it was obvious that the south cans had a lot less water in them. Instead of storing heat during the day and releasing it at night it seems I was just evaporating water!

Remember when you have a greenhouse, next year will be better!

:)

Chris, Since my cans are not under the bench I can check them and see what I am getting for evaporation. I am still curious about putting a few cans close to the radiant heater to see if I can store more heat longer and not just warm air. I was really impressed with the biotherm tube concept and heating the root ball mass seems to be so much more effective as a way to heat the plants not so much the air. I do worry a lot about cool temps and condesation on the leaves leading to fungal problems. Heat rising up thru the canopy of the plant seems to be helpful. I hate the idea of having to use fungicide seeing as most them are not friendly to the environment. Lots of humidity in the air (fog) today and so plants are going to stay wet for long periods over the next several days. Just one more area of the GH environment to be concerned with as a grower.
Happy Growing David

Check into heated benches, for the future, too. One of my friends has heated benches with the tubes and boiler in his propagation house. I wish I had the money to throw at that right now! His stuff grows like crazy because the roots are warm, and he can reduce the ambient heat by 15 degrees or more. It's a terrific advantage...
If you try the wiggle wire and poly with the shade cloth or white cover over the top, you'll love it. After you get your initial clear poly down, you can add the shade cloth or white poly even if you have a little wind as long as you have plenty of helpers to assist. We get a ton of high winds here because we live in front of a corn field, and it got to 50 mph last week and it held up. It also held up fine last spring in the high winds with the shade cloth.
Did you see that Farmtek also has solar water bags now for greenhouses? They have them in wall units and lay flat too. I'd like to try that, maybe next year. This is the most expensive time of the year, trying to get everything started and all the supplies in with no sales money coming in...
Happy Holidays
Sandy

Yes, I have seen the solar greenhouses from farmtek I get their mag every quarter or so. A nursery I used to work at used them fairly regular so I got on their mail list to keep up with new ideas as best as I could. I will continue to look for bottom heating as viable and cost-effective way to reduce air-heating and still get get good growth and lower fungal spore formation. I also use seaweed as a foliar feed to help with overall health, disease resistance and quality growth.
The channel I have for the wiggle wire looks too shallow for a double layer but it might work. The shade cloth will I think need to be tied down without the use of the wiggle wire or I will need a deeper channel. That's the way it looks for now. Too bad when they installed the white poly they cut it too close and will make it hard to put back on. It did work fairly well for the summer without shade cloth. I figure only if I go more than 55%PAR (say 70%PAR) will I need to consider a shade cloth. The problem is with this (55% I am not getting enough quality light for the Nov-Feb time period. It seems OK for the Mar-Oct time frame. Still mulling options. Thanks for all the thoughts and feedback to all.
Happy Growing David
I am lucky being here in Central Texas because there is some sales albeit not a lot. I am working on the premise of covering my labor cost as being good enough between now and Mid- Feb.