Passive Solar Greenhouses Materials
Need to Know
- Size-ratio of 2:1:1
- Length, Width, Height
- 24 ft x 12 ft x 12 ft
- Latitude plus 10° (Central Missouri:
38.9 + 10= 49°)
- Black 55 gallon barrels filled with water.
- Rule of Thumb: 2.5 gallons/ft² of glazing for season extension or 5 gallons/ft² for all season.
- How much do we need then?
- 12 ft x 24 ft = 288 ft²
- 288 x 2.5 = 720 gallons
- 288 x 5 = 1440 gallons
- We have 20 x 55 = 1100 gallons
- 1100 gallons of water weighs 9,130 lbs.
- For each degree of drop at night, 9,130 BTUs are released.
- At the Southwest Center, approximately 8 to 9 degree change is occuring so there would be 73,000 – 82,000 BTUs released. Temperature Over Time
Heat Saving Ideas
- Double layer of plastic glazing
- 6 mil four-year-plastic
- Should add about 10 degrees to the inside on a cold day.
- 60 cfm squirrel cage fan – outside air!
- Walls and Insulation
- 6-inch walls
- Wrapped in plastic
- R19 insulation
- Interior Wall Material
- Needs to be reflective.
- Bathroom material that is glazed on the outside.
Keeping It Cool
- Exhaust fan
- Rule of Thumb for CFM required – ft2 x peak height or 24 x 12 x 12 = 3,456 cfm.
- Standard sizes are sold. (Bradford’s is 3,200 cfm.)
- Also need an inlet shutter that matches the exhaust fan. (Bradford’s is a 3,000 cfm, 27-inch fan.)
- Set temperature when exhaust fan comes on.
- Be careful not to keep it too cool.
- South wall plastic being able to be rolled up and down.
- Allow for cooling in the warmer weather.
- Can be raised or lowered each day.
- Sealed down during the winter.
- Roll up side
- Allows for year around use.
- Sun does not directly shine into the greenhouse therefore it stays within reason in the summer with the roll up side.
Building a Passive Solar Greenhouse
- The first thing to do was to lay out the foundation. We used 4 x 6 inch treated lumber setting on two foot concrete piers at the corners and in the middle of each post. Each post was wrapped in plastic.
- Two x six walls were used throughout.
- The entire greenhouse was wrapped in plastic.
- 6-inch insulation was used in the walls.
- Cutting the right angles was extremely important.
- Metal siding was applied to the outside.
- Lumber, fasteners, hardware, door, insulation, etc. – $1,619
- Exhaust fan, shutter, thermostat, plastic, etc. – $786
- Concrete – $190
- Electric – $490
- Water – $190
- Total – $3,275