Earthtainer Greenhouse????

[rnewste]

Free Ticket in the mail to you if you come out to San Jose, and build a few for me.

Raybo

[dfollett]

It would be worth it for the opportunity to pick your brain - save me some of the inevitable trial and error.

[JamesL]

DF,
This is good stuff.
I have more questions. (big surprise) So you are only getting a 6.5 degree bump on average with the heater and wrap use? Was that an average differential for the entire nine days?
You running the heater over night? What was the temp difference last night for example when it was 7 degrees out?
Is that thermometer giving you an air temp reading inside the tainer as well as a soil reading? What kind of numbers are you getting at night?

[dfollett]

Temperature differential - There are a million ways to calculate things (you can prove anything with numbers). The numbers that I cared about were the lowest air temperature inside the tainer (air temp above the soil) and the lowest temperature outside the tainer (what Mother Nature gives me). Over the time I have numbers, the average difference between those two readings was the 6.3 degrees (I rechecked my calculations and edited the original post to make a minor correction). The range was from 5.5 to 7.1 degrees, with each night in that range.

At any given time, I’ve seen the temperature differential as low as 3 degrees. The temperature inside the tainer drops steadily throughout the night, while the outside temp bounces down like a stock market – not steadily at all. It fluctuates much more than I realized it does (my monitors take readings at 5 minute intervals), so when it bounces up 4-5 degrees during the night before it goes back down, it can be fairly close to the tainer air temperatures. Again, what I am concerned about are the actual lows and the temperature gain inside the tainer.

The heater was on continuously, although during the day, it turned itself off before mid-day (I have them connected to a watt meter so I can see if they are actually heating). By the middle of the day, the water temp reaches the temperature where their internal thermostat turns them off. I have temperature probes inside both tainers, in the soil of one, in the water of one and outside. Yesterday’s temperature ranges were:

• Outside air – High – 45 : Low – 7
• Water temp – High – 77 : Low – 62
• Soil temp – High – 72 : Low – 43
• Air in Tainer – High – 90* : Low – 14 (both within 0.1 degree)
o *Left the lid on.

It doesn’t appear to radiate as much heat into the top of the tainer as I thought it would (or it doesn’t insulate as much as I hoped it would), but if I can count on a consistent 6+ degrees of gain above the ambient low, I can get at least an additional month of growing season. What I’m after is a way to plant early without having to cover or move things every night. If I can get a month and only have to do something extraordinary one or two nights, it might be worth it. I can put one early season tomato and one mid-season heirloom in a tainer and have something ripe 4-6 weeks earlier than normal and have an heirloom that wouldn’t normally ripen.

Like I said, we’ll see.

[JamesL]

Thanks for posting the numbers. I would have thought there would be more radiant heat as well. The low temp difference between soil and air in tainer is a little surprising.

[dfollett]

That'd be a great name for a movie!

I'll start with the ugly: I jumped to conclusions way too soon! What happens when the temperature drops from 35 on a sunny day to 10 at night is different from when the temperature drops from 35 & cloudy to 25 at night. In the latter case, the temperature gain is as little as 2.5-3 degrees. Raybo was right.

[QUOTE=rnewste;327229] The fish tank heaters proved of limited success here in California (the heating of the sidewalls from the Sun proved equally effective). /QUOTE]

Apparently the soil does not radiate heat to the top consistently enough under different conditions.

Now, the Bad: One of the fishtank heaters has already stopped working and it can't be changed. Oh well, they were cheap ones (maybe that's why it quit working).

Finally, the Good: I've learned you can't get heat from the water to the top of the 'Tainer consistently enough to help at night - even with 100 watts going full-out. (Folks who have greenhouses or experience with cold-frames probably already know this stuff I'm just learning). That means I'll have to introduce heat directly into the top.

I'm playing with several ways of doing that, some of which look like they'll work. I think I only need 15-35 watts of heat into the top of the 'Tainer with the lid on. It appears (I'm not going to jump to conclusions too soon this time) I get about 1/2 a degree per watt. I've tried 16 watts and 22 watts. The first few days have been relatively consistent. I'm trying 32 watts tonight.

I have a couple of objectives:

• Pick a ripe tomato, grown outside in one of the Earthtainers, by my normal frost-free date - 1st week of June.
• Set up something that works automatically except for adding water, putting on the lid at night and taking it off in the morning. No wheeling them inside or covering them with blankets, etc. Nothing that takes too much effort (other than the initial setup).

If this works like I hope it will, I'm going to plant a couple before the end of March. I'm thinking of planting one with 1 Sophie's Choice (I've seen a lot of good comments) and 1 Siberian (It claims the shortest maturity) and a second with Sophie's Choice (to compare with and without the water heater) and 1 Sasha Altai. I haven't grown the Sophie's choice or Sasha Altai before. I want something that won't outgrow the top or the 'Tainer, as I will need to put the lid on for at least 2 months.

If anyone has suggestions for better varieties to plant, I'm open. The varieties I have to work with that are small and determinate are Sophie's Choice, Silvery Fir Tree, Beaverlodge Slicer, Bushsteak Hybrid, New Yorker, Siberian and New Big Dwarf.

Will post again when I know more.

[rnewste]

One of the devices I looked at to keep the above ground environment at a warmer temperature in the spring, were reptile heaters. I didn't follow through on trying them, but you may want to research them.

Raybo

[Redbaron]

Will this help?

http://www.toolfetch.com/greenhouse-...FQKoPAodRG0A-w

[dfollett]

Thanks for the suggestions. The 16 watt heater I've bee testing is a seedling heat mat attached to a piece of Masonite and zip tied to the inside side of the cage. It seems to work well, but I think I will need a little more wattage. The reptile heat mats are similar, but with more variations on size and wattage. My 30 watt trial right now is the seedling heater and a 14 watt candle warmer in the same cage. We'll see what that does.

[JamesL]

DF,
That is a real bummer about the tank heaters. I was really pulling for that to work.

[dfollett]

Baron - I'm afraid the soil cable won't address the core issue. The soil seems to warm up fine. The soil gets nearly as warm in the 'Tainer without the heater in the bottom as it does in the one with. The problem appears to be that that heat does not make its way from the soil into the air above fast enough. I've concluded that the answer is to find a consistent, simple, safe way to inject heat directly into the air above the soil.

I think the heat in the water mostly migrates out directly through the wall to the outside when its cold (when it is needed above). Hmmm, if there was an easy way to insulate the bottom to keep the heat inside..........?

[rnewste]

Find an insulating "blanket" of some type to wrap the Rubbermain in. Also, look into infra-red reptile heater lamps to maintain heat inside the clear wrap area.

Raybo

[dfollett]

Wouldn't an infrared heat lamp affect the plant growth if it was used at night? I like the notion of the reptile heat mat or pad. They appear to be a better version of what I am currently playing with. I'm just waiting to figure what wattage I want to get. They are fairly pricey.

[dfollett]

Spring fever got the better of me. I'm actually a couple of weeks earlier than I originally planned on setting plants out. My previous experience with setting out early - whether with walls of water or any other scheme I've tried - is that, while I may be able to keep them from freezing, they usually don't grow much. The ones I plant in June usually ripen within a week of the ones that were planted in WOWs 4-6 weeks earlier. We'll see if this will turn out differently. Hopefully, the weather has turned. Three nights ago, it reached 14 for a low - 24 last night. The low in the 7-day forecast is 30, with 62 as the high.

I decided against using the reptile heaters and seedling heat mats for several reasons . 1)- I'm afraid they will generate too much heat during the day. Even turned off, they are large and opaque and get really warm in the sunshine. They radiate a lot of heat into the inside of the 'Tainer top during the day. 2)- They're kind of pricey. 3)- I found something inexpensive and flexible that seems to work.

I'm using candle warmers. Walmart sells a 13w candle warmer for $5.

(Disclaimer!!!! - These candle warmers say they are for 'indoor use only'. They also say not to leave them on unattended. I am using them in a way contrary to the manufacturer's recommendations. I DO NOT recommend that anyone use them this way. I have my 'Tainer greenhouses on a south facing patio under a covered deck. They are protected from most rain and storm.)

Four of these warmers - one in each corner - consistently keeps the inside of the 'Tainer 10-15 degrees higher than the outside temps during cold nights. With four of them, as the season warms, I can unplug them one at a time if needed. No aquarium heater in this one.

I planted one Siberian and one Early Girl. I am planning on planting one more 'Tainer each week for the next three weeks. That's the extent of the trial. I may not have hardened them off enough. I've not been able to set them out before leaving for work in the mornings - it hasn't been getting above freezing until after 10 am. They've been in a window and going outside Wednesday, Saturday and Sunday - the only days I'm around. One of my fears is they will not take the warmth during the day.

Early Girl on left - Siberian on right.

[rwsacto]

Thanks for the update. I like your project.

Interesting that hardly any heat from the reservoir transmits upward through the media. I recently tried one earthtainer on lite insulation and a seed starting mat (17 watts) outdoors. No difference in media temperature. Previously, I got better media heating when I bottom heated AND wrapped the earthtainer with part of a water heater blanket (fiberglass insulation)

Looking at your set up with the candle warmers makes me ask, what if you used small (13-23 watt) CFL lights instead? You would get the same amount of heat plus supplemental lighting. I am thinking something like an aquarium light fixture with small reflector, shop lights or small desk lamps. More permanent would be outdoor light fixtures.

I use CFLs for seed starting and used them successfully for overwintering a few container tomatoes.

Good luck,

Rick