Evan was kind enough to pass on his notes that he used to source for specific materials and data for building his greenhouse. We’ll include them here so you can check them out, and hopefully they will be of use to you as well:
My greenhouse is approx 14'x11'x9'
=1386 ft3 (cu ft)
Using the formulas given by Sunny John, i estimated that I needed approx 225 linear ft of subterranean tubing.
So, take 15-20 percent of the cu ft number, and that is how many feet of tubing you ideally want underground.
*Note, all tubing lengths used should be equal in length to ensure an even amount of airflow..
In my greenhouse there is an approximate total of (only) 120 linear ft of tubing.
The tubing is in 3 flat rows of 4 10-ft lengths that are spaced approximately 12 inches apart on all sides.
In regards to air movement, you want to move a minimum of 128 cubic feet per minute (CFM) with my 1386 ft3 greenhouse.
So, take approx. 10 percent (or a little less) of the cu ft number, and that is the CFM fan you want to use.
The fan I used is an (8”) corded in-line air duct booster fan by Suncourt with a Suncourt variable speed controller ($45) ($30)
I used 8” galvanized ductwork ($50)
For plenums I used taped buckets, but I did it again for a similar room I would use 55-gallon plastic drums on either end. (free to $150)
2 Thermostats (1 for low temperature threshold and 1 for high temperature threshold), used something like: “JOHNSON CONTROLS
Line Volt Mechanical Tstat for Heating and Cooling, 120 to 277VAC” (cheaper then but now $210 for 2)
Roofing top layer: Used 9 Sequentia Super 600 Residential Fiberglass Panels ($325)
For underground tubing: 4” corrugated and perforated ADS pipe ($150 for 200 linear ft)
*Drain sleeve optional – did not use
(WHOLE GREENHOUSE WAS BUILT FOR APPROX $875 + Lumber = No more than $2K total)
(SUBTERRANEAN HEATING AND COOLING SYSTEM WAS BUILT FOR APPROX $700)
Subterranean heating items:
8” (x 60”) duct - http://www.lowes.com/pd_82361-85334-GVL0023_0__?productId=3135349&Ntt=8-in+galvanized+duct&pl=1¤tURL=%3FNtt%3D8-in%2Bgalvanized%2Bduct&facetInfo=
And a 24” for a little added height if needed - http://www.lowes.com/pd_36398-85334-GV1336_0__?productId=3134339&Ntt=imperial+8-in+duct&pl=1¤tURL=%3FNtt%3Dimperial%2B8-in%2Bduct&facetInfo=
8” elbow/end - http://www.lowes.com/pd_607437-85334-GVL0280_0__?productId=50260707&Ntt=8-in+galvanized+duct&pl=1¤tURL=%3FNtt%3D8-in%2Bgalvanized%2Bduct&facetInfo=
8” inline fan - http://www.homedepot.com/p/Suncourt-Corded-8-in-In-Line-Duct-Fan-DB208-CRD/203227165
Variable speed controller for fan - http://www.smarthome.com/suncourt-vs200-plug-in-variable-speed-fan-controller.html
ADS Pipe (Lowe’s cheapest – 100ft):
Snap-in ends to screen?: SHOULDN’T NEED
Drain sleeve (100ft):SHOULDN’T NEED
Possible solutions for thermostat: (call them) http://www.littlegreenhouse.com/accessory/controls.shtml
Sunny John recommends this (don’t know how it works): http://www.grainger.com/product/JOHNSON-CONTROLS-Line-Volt-Mechanical-Tstat-4E047
Steel 55 gallon drums (Lafayette - $10 ea):
Mathematics of layout:
Approx 225 linear ft of tubing
Approx 128 minimum CFM fan
A great example showing a clever design with reflective panels concentrating the winter sunlight into an above ground pond to heat the greenhouse at night.
and more from the same manuf., as well as solar “central air” system:
CO supplier of Lexan and acrylic
Underground greenhouse and heating
The good heavy duty corrugated fiberglass panels are Super 600. Eplastics.com and others
Solar cooling and heating system, everything needed $3,450:
Corrugated (Perforated) irrigation tube
Christmas lights (i.e. 25 Bulb C9 Incandescent Transparent Light Set – Clear)
Tubular heaters? Find out wattage
Lean to recycled greenhouse with outline of process:
Calculated that 112 cfm or a little over 100 cfm is needed. Verify again before purchasing fan but here is link for appropriately powered fans: