greenhouses worth it

[Ravnis]

Hi, just kind of wondering about a greenhouse. A friend of mine is wanting to build a system on his land as a joint venture. We could easilly extend from one of his sheds, but was wondering if it would be more cost effective to insulate and grow with lights or to build a green house. I figure the greenhouse will be a huge heatloss in the winter. Texas winters here stay around 40f and our summers bust 115f sometimes higher. We do have freezing snaps that last a few days to as much as 2 weeks at a time.

I'm a total greenhorn when it comes to greenhouses, and most of my gardening experience was with my dad telling me to hoe this row or pull those weeds or plant this here.... and that was 30+ years ago :D

Just wondering if anyone had any experience in this matter.

[Murray]

Hi,
A green house will be better. A well designed greenhouse will gather radiant heat in the winter if you have sunny days even though the air temp is down.
It would cost a small fortune to buy and run lights for the shed. A problem for indoor hydroponics.
Greenhouses are not all that expensive really in the overall scheme of things

[djs-sa]

go indoors way easier with CF 100w globes= 400w hps, aint that dear these days Murray

[Murray]

Most folk are trying to cut down on electricity use especially in commercial applications. There are Gov incentives to go as green as possible.

[Jason Palenske]

Well having been to Texas in the winter I would say go with the greenhouse. Electricity expenses being what they are in the States it will be cheaper in the long run even if you supplement it with a heater in the winter. If you have enough room you could even set up a wind turbine for your power.

[Hamish]

I have seen people using recycled bubble wrap attached to the glass of a greenhouse to help insulate it - might ba a cheap option to let the light in and keep some heat in.

[Finn]

You can also get 2 and 3 paned greenhouse glass that insulates quite well. It is pricey, but worth it in the long run. We use suplimental lighting in the winter because of the short days and this helps keep the greenhouse warm.

Finn

[djs-sa]

Hi Finn
what lights do you use in your greenhouse

[Finn]

DJS

I moved so I don't have the greenhouse anymore.(Have to build a new one in the spring.) I used 600w HPS lights as we were growing flowering plants and the light spectrum suited better. The 600s were the most efficient lumen to watt ratio at the time. There has been alot of advances in bulbs and electronic ballasts in the last couple of years and I am a little out of touch in what is best now.

The nursery here uses 1000W MH bulbs in a poly greenhouse, no insulation. They just brush the snow off so it doesn't collapse and run a propane heater/CO2 emitter. At least that is what the lady behind the counter told me it was.

Finn

[jack@badflas]

Greenhouses, especially in the south, are far more efficient that lights. If you build from scratch you can also take advantage of geo-thermal heat storage and pay almost nothing for heat.

Before building the greenhouse you dig a "basement" about 6' deep. you burry plasic 55 gallon barrels on opposite sides of the greenhouse every 4 feet. These are inter-connected with perferated drainage pipes at the bottom, middle and top and soild or gravel is back-filled to cover it. Headers go from the barrels to the surface and fans blow hot air from the top of the greenhouse into one side. Moist hot air condenses in the cooler soil and come out much cooler. This keeps the greenhouse cool during the day. At night cooler air is warmed from the heat stored in the ground. The only cost is the small amount of power needed to run the fans.

[GaryD]

Hi Jack,

That's the best explanation I've heard, so far, of how a geothermal system is built and how it works.

What sort of temperature impact would a geothermal system have?

Gary

[Hamish]

Hi Jack - any chance of a drawing or photos of such a system. I think I understand the concept but im more a visual person :(

[Ravnis]

THanks for the post Jack,

after reading your post I searched for greenhouse geothermal heating and found this link. Looks like a similar version of your idea works in Nebraska even which is a much colder climate than north texas. The gravel that you said to fill with would be much greater thermal mass and surface area.

http://www.earthtoys.com/emagazine.php?issue_number=03.08.01&article=finch

I remember reading about a greenhouse that used lots of 1 gallon milk jugs to act as heat buffers, absorb heat when ambient temp is higher, release when its colder. Suspect that fish tanks will perform the same function.

[MarkEinOz]

G'day Folks,

Actually I have seen such a system built. There is a "self-sufficiency" series from the UK called "It aint easy being green"http://www.itsnoteasybeinggreen.org/ where this crazy but completely hilarious hippy family, where the Dad [Cmdr. **** Strawbridge] is a ex Army Engineer (and a genius).

They became smallholders in Cornwall I think (ala like River Cottage), and built a glasshouse with passive thermal system based on crushed glass bottles in a pit. Worked like a dream. I'm in NZ working until tomorrow, but give me a couple of days to find the episode and I'll splice up the video concerned with this project, and post a link.

Very cool thing indeed.

[Hamish]

Hi Mark - that guy **** Strawbridge is great - he is a regular on scrapheap challenge and he is also on another similar show making stuff out of junk.

[Hamish]

That other show is called Planet Mechanics - heaps of videos on youtube.

[jack@badflas]

If you have enough thermal mass, like 6' below the greenhouse and the entire footprint, it can lower daytime temps by 20 degrees F and raise night time temps about the same. Instead of 115F in stays closer to 85 in the day, and rather than dropping into the 50's it stays closer to 70-75F at night.

The underground pipes with their perforations allow the condensed moiture to drain away. Consensing or evaporating water moves loads of heat.

In Texas, you would rarely need to spend money on anything but the circulating fans.


Hi Jack,

That's the best explanation I've heard, so far, of how a geothermal system is built and how it works.

What sort of temperature impact would a geothermal system have?

Gary

[echidna]

Quite a bit on information in these two links.

http://www.sunnyjohn.com/indexpages/shcs_greenhouses.htm

http://www.earth-house.com/Going_Organic/Greenhouses/Pit_Greenhouse/pit_greenhouse.html

Also google "solar greenhouse" and "bubble greenhouse".

[jack@badflas]

"Slideshow of latest SHCS Install" at the sunnyjohn link has a nice slideshow. It shows the barrel system I discussed. Sunnyjohns also has a calculator for figuring out what you need. This is the system I plan to build.

[Hamish]

Also google "solar greenhouse" and "bubble greenhouse".
http://www.tdc.ca/livelyupprinciples.pdf

[Ravnis]

forgive my crude drawing skill, here is a layout im thinking about.

fans will push air from pipes in the center of the ceiling down into the water where the heat will be absorbed by the sump. The sump will be 18ft long x 4ft wide x 3 feet deep should hold 1600 gallons(~6k liters). to make the most of space, the growbeds will go ontop of the sumps where they drain into it by gravity. The submerged pump will pump up to the 4" diameter pvc pipe to be a return line to the fish tank, the pvc pipe will double as nft grow line,(great idea, Hamish). I can probably rig up a 24 volt solar arrangement with marine batteries to run the fans 24/7. The property is already on a slope and has 18 inches of gravel and then clay for a lot of thermal mass. The sump will be just a hole dug with pvc pond liner to contain it. Anyone see any major flaws in this design?
FYI the copyright is just so I don't get sued for using a design I made(happened more than once). Here in the states everyone is lawsuit crazy.

The level building is an existing farm shed.

[jack@badflas]

The sump would need to be covered to prevent evaporation. The other issue is blowing air directly into water. This taks a great deal of energy and regular fans can't do it. Most fans only make enough pressure to go into 2" of water.

This is why the drainage pipe system is recommended. Very low pressure can move the air through the system and the ground absorbs and releases the heat.