Market Farming

[Joshua Bryceson <turniprock AT gmail.com>]

I'm installing a system like this, only in the floor with the pex buried in sand and 2" polystyrene under that. Ive tried it with just the benches and pex under benches, and you need something to hold and radiate the heat, or you only get good growth on the areas where the tubing is near the growing flat. Radiant heat also radiates down as well as up, so you need something under that to keep it going up and not sapping into the cold ground or through the plastic sheeting. We are using sand because it wont hold water, but water will help it become more conductive (fill in the air pockets).  We will be using landscaping fabric on top of the sand and pallets on top of the fabric to keep the flats out of any pools of water that might show up. The key for laying the polystyrene is to have a FLAT ground surface as you can imagine. We had the ground graded before we put up the house (after a few attempts of just throwing it up without grading)

Pex is spaced at 1 ft apart, but 6" apart on the outside edges because you will loose heat to the outside if not adequately insulated. loops aren't longer than 250' 

I've seen some places build sand box benches (put don't tell your cat about them), I think the more mass you can put in the house the better.

We will be using a heat exchanger on the exhaust to capture a little heat to throw in the air. I know some people even have a seperate air heater to keep the air temp above freezing (set at 40 or 50) but the root zone and plant zone is 60-70 plus. 

the heater is a high eff. micro boiler LP, i think it goes up to 180k BTU, but it will only radiate as much heat as you have surface area (pipe) exposed to radiate the heat it produces... 

this is just what i've gleaned from other farmers doing this and what i've learned trying it with less than that. In my opinon if you don't have the resources to do it well, save yourself the time and wait until you do have the oppotunity to do it right. We had a complete freeze up the first year as well as a boiler break down, some people just use a 40-50 gal hot water heater. there are some plans out on the internet. I can send you some if you'd like to see them. 

I'll be documenting my installation as much as i can remember, so I can send pictures of that too. 

good luck, and I am excited to hear about anyone elses experience as well.

Josh  Zone 4 WI

On Wed, Jan 26, 2011 at 8:39 AM, MAsteveINE <MAsteveINE AT 207me.com> wrote:

 

To heat the soil blocks and plants in my large double poly greenhouse (3000 sq) , I am thinking of hooking up an on demand propane fired Bosch water heater to some pex tubing and running it on 9" spacing looped under my benches.

Anybody else try this?

Thanks J

00000000000000000000000000000000000000000000000000000000000000000000000000000000000

 

What is the heating system for this greenhouse?

 

 Huge reading with a google search "greenhouse under-bench heat".

 

Consider puting in a back flow preventer and a boiler feed which would reduce water presure to 10 lbs;

then run the system with a high % of  pink RV anti freeze.

 

My experience is that if  I was  not planning to run water temps over 150F it would be cost effective to use

common black plastic water pipe in stead of pex.

 

Before going with all that pex compare the price of a couple runs of 3/4" copper fin pipe (the tubing with

aluminum fins that in the houshold HWBB.)

 

MAsteveINE

 

 

 

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Turnip Rock CSA
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