How to prevent evaporation

[Jeremiah Robinson]

I've been growing using aquaponics in the cold for a little over a year now, and it seems to me that one of the biggest energy suckers is evaporation from my grow beds.  I know that when water evaporates it absorbs a lot of energy, and especially in flood-drain beds the filling-expelling action can cause a lot of evaporation.

I wonder if anyone has ideas for how to best prevent water from evaporating from your grow beds?

Are DWC beds better for this issue?

[Max Gfx]

If you look at the actual science behind evaporation, you will find your answer. Just out of curiosity, what is the average temperature and relative humidity in your grow area?

[Jeremiah Robinson]

Hi Max, 

I'm in Wisconsin.  It's pretty dry in the winter and pretty wet in the summer.  I know that I'm getting a lot of evaporation in winter especially because of the crust of ice that forms on the greenhouse plastic every night.

[Max Gfx]

I think you just answered your own question. Look at the way that any refrigeration device, dehumidifier or swamp cooler works. Better yet, look at what happens when you take a cold drink outside in the summer. Is the glass really sweating, or is all the warm humidity in the air actually being attracted to the dry cold surface of the drink container? The only real way to combat the problem in the winter is to use glazing with better insulative qualities, such as triple wall Lexan or double wall polyethylene on a tunnel with air between the layers (requires a blower/inflator to run full time).

[Jack Dunbar]

Hi you guys. I live in New Hampshire and we have some pretty cold winters and as I get older, I think they get longer. I don't know to much about this subject but I have an indoor flood and drain and it is in the same room as my woodstove so my room is really toasty. The water doesn't get to hot even though it is near my stove and I lose a lot of water from my system. Is it possible to maybe do a greenhouse within a greenhouse. Probably if you are in the process of building a new greenhouse , then if would be worth doing the triple glaze covering. I have an old Cover-it car shelter that the covering is full of holes . I'm thinking of replacing the cover with 6 mil greenhouse film. They don't give it away. I need a piece that is 28' wide and 24' long at a cost of approx. 90.00. I'm not sure how to attach it to the frame , so that's more money.This will still only give me single layer. Farmtek has different  greenhouse films.I do know a gentleman who is into Hydroponics who has built foil faced foam boxes in his greenhouse. they are just big enough to cover his plants and then he puts small space heaters ,fans etc in those enclosures. This extends his growing season to all year except I think he said 2 Months.   

[Jim Fisk]

Jack, first of all check out your local greenhouse operations for what they consider "scrap" after they replace their aging covers. What you need, they throw away as trimmings. I pu a 25 x 50 ft brand new scrap locally for 25.00. Nuff said. Oh, and wood heat rules! Right on!

Now as to GH design for cold climates we need to look back say 40 yrs. to the typical "Mother Earth News" plans that have an INSULATED north wall. What is up with all these "tunnel" greenhouses? They are anything but "green". In AP the insulated N wall style makes even more sense as the N side can be separated from the "hothouse" side and that is where the "fish room" should be. I certainly hope that folks in the "cold" climates are not enamored with the idea of raising Tilapia when you are in the perfect places to raise far more "healthy" and tasty fish like Trout or Salmon, etc. Those species LOVE the cold so right away you are at an ADVANTAGE over say Florida, etc. They would give up their left you know what to be able to raise Trout. My GH and system 2 family design was created, by me, to take advantage of our cold climates.

I may be in TN but we hit 20F BELOW ZERO twice last Winter and due to green firewood problems and we hit 16F by morning twice INSIDE the GH with NO double insulation (YET) and everything did fine. Not one loss. By next Winter we will be properly enclosed and insulated (still have tarps enclosing the "fish room" and our cats can still literally walk in and out at will) but the point is even with these horrific conditions we came thru in style. I can't even begin to describe the feeling in my stomach when I walked in and found every veggie frozen solid, leaves shatterable, (hey I coined a word! at least Google, my spell checker, thinks so) and yet everything thawed and no damage at all. SO, be of good heart, design and build a GH for your climate, and appreciate and work with what you have.

I will go into more detail on our GH design when time allows. Right now I have to go out and feed some very hungry Trout.
And Jeremiah, I love your topic here. I am living it and loving it.
Jack Dunbar said:

Hi you guys. I live in New Hampshire and we have some pretty cold winters and as I get older, I think they get longer. I don't know to much about this subject but I have an indoor flood and drain and it is in the same room as my woodstove so my room is really toasty. The water doesn't get to hot even though it is near my stove and I lose a lot of water from my system. Is it possible to maybe do a greenhouse within a greenhouse. Probably if you are in the process of building a new greenhouse , then if would be worth doing the triple glaze covering. I have an old Cover-it car shelter that the covering is full of holes . I'm thinking of replacing the cover with 6 mil greenhouse film. They don't give it away. I need a piece that is 28' wide and 24' long at a cost of approx. 90.00. I'm not sure how to attach it to the frame , so that's more money.This will still only give me single layer. Farmtek has different  greenhouse films.I do know a gentleman who is into Hydroponics who has built foil faced foam boxes in his greenhouse. they are just big enough to cover his plants and then he puts small space heaters ,fans etc in those enclosures. This extends his growing season to all year except I think he said 2 Months.   

[Jim Fisk]

Just noticed our GH system layout is not among my pics so here are the basics:

[Jack Dunbar]

Hi Jim. Do you grow year round? What kind of crops do you grow?

[Jeremiah Robinson]

Jim,

I'm so jealous of your greenhouse!  It looks awesome!  Do you do anything special for thermal mass?  If you're interested in writing a guest blog post for me I'd be thrilled.

I'd love to make mine into one like that but I built my "temporary" hoop house too close to the lot line and making it permanent would take me from zoning "grey area" to zoning "clear violation."

For those like me with a crappy hoop house, using a pool cover folded over itself or making a cover out of bubble wrap can help.  That's my plan for the next winter.  

I hear the strategy of making a better greenhouse so that less water condenses (which will keep humidity up inside the greenhouse and drive less evaporation).  

I'll definitely pursue that, but I also wonder if there isn't more you can do to the system itself to keep water in the beds and tanks, and prevent it from evaporating into the greenhouse (or living room, in Jack's case) air to begin with (even if the greenhouse air is dry)?

Would running a humidifier in the greenhouse help?  It would cool the air, but might prevent some evaporation.

[Jeff S]

OK I'm no evaporation expert but I have a large 30'x60' indoor pool and hot tub. I struggled for years trying to stop the rainfall from the ceiling. As it's been said already it takes more insulation and that solved the rain problem. However, That doesn't stop the evaporation. When you have warm water you'll have evaporation but the warmer the surrounding air the more moisture it will hold and you won't get a much visible sweating except from cold surfaces. The only way I know to slow down evaporation is to cover your tanks. I covered mine with some scrap Lexan that I had. When I remove a one foot section for feeding I shake the water drops off so I can see I'm eliminating a lot of loss. Next winter I plan to box in my GB  with the grow light inside and vent as needed. That will add heat to the water and then I can lower the temp in the GH. I'll also thoroughly insulate the FT and GB. I also plan to try some solar heating.

[Jeremiah Robinson]

Jeff, I'm having a hard time picturing what you're describing.  Do you grow indoors, or in a greenhouse?

When you say "box in my GB with the grow light inside" are you thinking of making something like a cold frame with a clear glazing over the top?

[Jack Dunbar]

Hey Jim, I'm envious of your GH. A thought that I had was; I built my split level ranch back in the late 80s and what I did was 2x6 construction and 1/2 foil faced foam on all exterior walls and I taped all seams. I can't remember what I used in the attic other than it was overkill. My house is very well insulated. I then got a woodstove that will take a 22" log, erected an outside chimney and burn wood. A couple of years later I built a hot water coil for the outside of my woodstove. the coil contains 60' of copper. using a circulator and a 40 gal tank, it circulates 24/7. From that tank it goes to my regular hot water heater. I have to run my electric hot water during the summer months and then when cold gets here and my woodstove is up and running, I can shut my electric off. I can produce approx. between 80-100 gal hot water a day. My woodstove and chimney are on a south facing wall so I thought of putting a greenhouse on that side of my house using triple glaze lexan etc approx. dim. of 20'( the width of my house there is 22') and maybe go out another 15-20'.Then I was going to put auto vents with sensors that would open when needed and heat from my woodstove could heat my GH and if the GH got to warm, have it heat my house Part of my chimney would also be within the GH. I go through less than 5 cord now and I do have a wood lot 5 miles away that has plenty of wood if I need it. I buy my wood 'cause I get it for 180/cord cut/split/delivered. I feel like I have a plan. Anybody got any suggestions? I love this site. You guys give me so many ideas and I love to experiment. My wife told me tonight NO chickens. I tried telling her that they will eat woodticks. I have them bad this year.   

[Jeff S]

Jeremiah Robinson said:

Jeff, I'm having a hard time picturing what you're describing.  Do you grow indoors, or in a greenhouse?

When you say "box in my GB with the grow light inside" are you thinking of making something like a cold frame with a clear glazing over the top?

 

I have an 8x10 GH for aquaponics. The pool is in my business. Was just using that as an example of evaporation and condensation. Right now I'm only doing a single IBC setup so enclosing the GB isn't a big project. Since we are lacking for sun in the winter I would probably go with an insulating cover material and preserve the heat. I am expanding just outside the GH this summer and may enclose that if it seems practical. I don't have a production plan at this time. Still trying to get veggies to produce. The Tilapia produce endlessly.