Rethinking the greenhouse concept - advice & thoughts welcomed
 

I'm zone 7 Arkansas and on my second greenhouse that i built last fall. It's wood frame, 2x4 wire and plastic, 8' wide x 28' long.

This past winter was one of our coldest ever. I had various temperate plants plus bananas in there with zero heat / zero water for heat sink. I had 13 basjoo in containers that came back just fine, but i lost all my tropicals.

This fall, I'm planning to section off a 8' x 16' portion of the greenhouse and install permanent, solid styrofoam walls, leaving the top as the only light source. I'll also have 2x4s on the walls at about 6' height (top of greenhouse is 7ish) and I'll have 8 foot Styrofoam panels that i can slide over the top at night-time and run a small electric heater intending to keep temps just above 45 degrees.

I'm semi-retired and have time to move the ceiling panels evening and morning. I think that will be an improvement and allow me to keep some tropicals without having much heat expense.

Since i am partially retired ... I'm planning yet another greenhouse / grow area ... not entirely sure what i would like. This one will be in-ground plants where the other is containers.

I've read accounts of folks in Mediterranean Climates that favor greenhouses to prevent wind damage (even though temps don't get low enough to kill plants) ... so I'm taking wind damage prevention into account. Plus i want a 12' or higher height (or i think i want that extra height).

Of course, when you double the height, you double the area needed to heat, and double the expense to heat.

I'm leaning towards it might be more practical to make this next greenhouse the higher 12 to 15' high with solid styrofoam walls again, up to 8' high and make my removable styro ceiling at the 8 ft level and just cut plants back to that size each fall.

Options are pools of water for heat sinks, etc.

Your thoughts?

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

I am seriously considering putting some bananas in a greenhouse, of course it rarely freezes where I live, but I would cut out the wind and be able to protect my plants when it does get cold.

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

Use the sun for solar heat

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

I have used water in cold weather and it works well. I don't have anything close to your weather to fight but one idea was to make a solar water heater from a grid of copper pipe and possibly a solar powered pump to move the water into and out of 55g barrels. The barrels could be in an insulated box and pumped into place or uncovered at nightfall or whenever your temps get too low. I have also used catalytic propane heaters that are rather small and can be placed all over. I gave up on the cold stuff many years ago and moved to smoldering heat. It was 91F at 6:30 am in my yard today and 105F at 11am, it will be around 115F for the high. My house is 82 and feels cool when I come in.

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

I would look @ Greenfins threads to see if that might help. He is in Kansas and does pretty good.. I grow bananas in S. Ark in the ground protected w/ heat-tapes & frost cloth.. Orinoco only gets frost cloth.. :v)

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

Burris, I would consider using bubble wrap as an added insulation layer to your greenhouse film. Obviously there is some light loss but you don't need as much in the winter.

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

Good comments all - thanks for sharing :)

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

A) Build it Solar - Solar Sunspaces and Greenhouses B) Permaculture Greenhouse - http://www.midwestpermaculture.com/G...escription.php
C) Calculations - http://numsum.com/tag/show/greenhouse
D) SunnyJohn - interesting array of info - Subterranean Heating and Cooling System Explained


Author Comment

Ingevald

Avatar / Picture

Registered: 01/20/08
Posts: 273
Posted 10/29/08 #1
This is a followup note to my original posting Fresh figs grown for market in Missouri regarding the growing of fresh figs for market in Missouri. I have not had time to process all of the information from the visit nor have I yet had time to research the topic in great depth. I will do my best to explain my observations from my short but impressive visit. (This is also posted on G.W.)
The first of his two 30’x100’ greenhouses is filled with figs. It is heated with vegetable oil and is cooled by the raising of a curtain on both sides of the greenhouse (cross ventilation) with an electric motor that runs off of a battery that is charged by a solar panel. The motor drives a worm gear that pulls a cable and pulley system that raises the side curtains (both sides) of the greenhouse, allowing for cross ventilation. It cools down adequately on hot days.
His "solar geothermal" hoophouse contains about %25 figs and the rest are vegetables and strawberries. This house is cooled and heated by taking advantage of the thermal mass under the greenhouse - a subterranean heating and cooling system. The earth under the greenhouse was excavated to install two heat exchange systems - two is needed to maintain maximum efficiency. Each system is composed of 16 rows of 4" flexible perforated tubes, spaced 1 foot apart. The 4” pipes connect to a larger pipe (15”??). The two larger pipes connect to a 20” vertical pipe for input and output. (see my basic drawing "Photo 15 link)

Air is blown down one 20” pipe and comes out the opposite corner. During the day the fans run, pushing the the warm and humid air through the pipes. Mold, fungus, and mildew does not form in the tubes because it is an aerobic system. The nearly continuous air flow plus the perforated pipes contribute to the health of the system. The perforated drainage pipe allows moisture and heat to transfer between the soil and the pipe. This also warms up the soil which is good for the roots, especially when front and back end seasonal temperatures are cold. (He planted some fig cuttings this spring and they are already making figs on their 5-6' stems! See the photo below)
At nighttime the fans can run and the heat that was stored in the ground becomes available to warm the greenhouse. Warm moist air is produced by the system at night.
There is also a thermostatically controlled exhaust fan mounted on the back wall to pull out excessive heat during the day. The fans that blow air through the underground grid are also controlled by a thermostat. I am not sure of the exact temperature levels that are set for day and night time running cycles. (He has a goal to someday run these fans off of solar electricity if I remember correctly)
The coldest that it got last winter was about 2 below zero F. The geothermal system kept the greenhouse around 43 deg during this coldest time. That is what really impressed me! It is like having a Mediterranean microclimate all year.
The outside of the greenhouse has a thick blue styrofoam insulation skirt that extends about 2 feet outward on the ground level, then extends about 5 feet into the ground. This is more important in the winter time, keeping the frozen ground at some distance from the edge of the greenhouse. He has a double layer of plastic that is inflated, especially in the winter months. This adds some insulation value.
The minimum sized greenhouse that will will function this way is 1000 sq feet. Small houses end up with more exposed surface area relative to the amount of underground heat storage.
If you are serious about this type of greenhouse - shop around. There are huge differences in price with little difference in quality in some cases. Also, thoroughly research your plan. Fossil fuel heated greenhouses are wasteful and expensive to run - this alternative design really saves a lot of money and energy in the long term.
Here are some photo descriptions (probably are not in order of the uploads)
This first photo shows the dense fig tree growth in his first greenhouse.

The second photo shows the outside of the first greenhouse with the movable curtain to allow ventilation.

The third photo shows one of two exit vents from the underground system Clean dry fresh air!

The fourth photo show an input fan next to a bed of strawberries.

The fifth photo shows the first years growth from cuttings - now five to seven feet tall and ripening figs. The warm soil makes them grow fast.

The last photo shows the outside of the first greenhouse with the ventilation curtain open. There is a forest of Brunswicks growing outside.


A) Build it Solar - Solar Sunspaces and Greenhouses B) Permaculture Greenhouse - http://www.midwestpermaculture.com/G...escription.php
C) Calculations - http://numsum.com/tag/show/greenhouse
D) SunnyJohn - interesting array of info - Subterranean Heating and Cooling System Explained
E) Columbia Tribune - another article about Ivan’s greenhouses - http://columbiatribune.com/2008/Sep/20080912Busi009.asp

By placing your curser over the photos below, the title will likely make an appearance.

Ingevald

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

If you are interested you can look at my experience here:

Mango in central Italy: an experiment.

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

I live in a warmer state then you but my I suggest the Harbor freight 6-8ft greenhouse. I love it,plus it's on sale now and you can use a coupon towards if as well. I customized mine a bit an even with the hurricanes we get here at thd coast it has been fine. I bubble wrap the inside during the winter and keep a thermostated heater on 50 degrees an never any issues. Reviews for the most part suck about the greenhouse instructions for the most part. When you open it up make sure all parts are counted for. 9 months I had the greenhouse an got around to opening it and four little parts were missing. Went to the store and they gave me the parts for Free out if the box.

Re: Rethinking the greenhouse concept - advice & thoughts welcomed
 

I usually make hoop greenhouses. lay 2 posts about 10 feet apart parallel and spike them in the ground. drill holes every 16 inches and bend pvc pipe to make a upside down U.
pvc pipe will eat the plastic so I cover all the areas that make contact with duct tape