The Building Process
- Building a greenhouse is a wonderful way to learn a new skill if
you are not already a carpenter. When I began, I couldn’t read a blueprint
and had built nothing more complicated than a basic book shelf.
- The building process is a good way to engage your community. Many
neighbors and local high school students assisted at various times,
learning as they helped.
- Once completed, the greenhouse produces a lot of food year round,
enabling a family to eat good home-grown organic vegetables regardless
of weather conditions or grocery store availability.
Building the passive solar greenhouse
We began on a cold May morning by measuring the foot
print of the building, orienting for southern exposure, and putting up
the batter boards and string.
After the backhoe dug the perimeter trench, rebar was
laid and tied for the footing. Then the cement truck came and friends and
neighbors helped with the first pour.
Foam forms and rebar went together like a modern day
erector set, creating the insulated foundation. Here we are preparing for
the slab (for the rear straw bale wall and the water wall) and foundation
The foundation and slab are done, including rebar for
the first two courses of straw bales. Two of the six posts are in place
for the post and beam rear straw bale wall. The large black object is the
1,225 gallon cistern.
Here we are tarring the plastic vapor-barrier where it
pokes through the rebar, prior to the placement of the first row of straw
The sills or bottom plates are attached to the foundation
with anchor bolts, the south knee wall has been built, and now we are erecting
the south glazing wall. This was done in two sections and held in place
Next the east and west end walls were built, with cut-outs
for vents and the fan. These side walls were attached to the rear post
and beam wall. The straw bale wall was kept covered to keep it dry.
The south glazing wall frame is visible here with its
purlins (the cross pieces) for fastening the polycarbonate (a type of tough,
durable, light weight, transparent plastic). You can see one of the many
collar ties, rafters, the first row of decking, and the outside wall (3/4
inch CDX plywood). Also, there is one of the door openings framed in and
we are working on where the ventilation fan will be mounted.
This is a view of the rear of the greenhouse. We have
finished the roof decking and are measuring our 15 pound roofing paper.
Here we are finishing the foundation for the cistern;
which will collect water off the roof via gutters, and deliver the water
to the plants by way of soaker hoses and drip irrigation.
Local young adults are learning how to stucco as they
put on the first coat of cement on the straw bale wall (inside and outside).
They also put the first coat of wood sealer on the south glazing wall frame
and the plywood on the east and west end walls.
We’re in the home stretch! The polycarbonate is attached
to the frame, complete with flashing and metal stops, the west wall screen
door is hung, and one of the vents is in place. Later in the fall we installed
the top solar vent, hung the outer door, put guttering along the bottom
of the glazing wall, and dug in a stock tank to receive the water from
the glazing wall.
Here’s the east side, with the aluminum fan shutter in
place. Later in the fall we hung the outer door, made the lower vent, put
the solar panel on the roof, and installed and hooked up the solar fan.
• Insulated foundation: you can add or subtract from our two feet of
below grade insulated foundation to customize the greenhouse to fit
your USDA zone and average winter climate.
• Rear straw bale wall: uses the waste of barley farming to create an
inexpensive R-40 super insulated north wall.
• Polycarbonate glazing: a difficult to break, lightweight glass alternative
that is user-friendly, doesn’t burn the plants, and is guaranteed for
ten years against yellowing, even at high altitudes.
• Super-insulated side walls and roof: uses newer, less itchy fiberglass
and a foil/bubble wrap material that insulates (bounces back radiant
heat), serves as a vapor barrier, and reflects light back toward the
• A 1,225 gallon cistern: stores and recycles rainwater (plants preferred
water source), a must for rural areas that lack a (reliable) well and
a safeguard against drought and water rationing in these climatically
uncertain times. The size can be adjusted to fit the rainfall
pattern and amount in your locale.
• Passive solar water wall: 900 gallons of water in a combination of
recycled white plastic and new black metal five gallon buckets.
These store heat from the sun during the day (in winter) and release
the heat to the air a night. In summer, the water helps keep the
interior of the greenhouse cooler.
• Active solar fan and vent: uses the sun to run the ventilation system
(augmented by human operated vents). The size, placement, and
number of vents can be customized to fit your heat and humidity profile.
• Two growing beds: the interior of the greenhouse is about 35'4" long
by 10' wide, or approximately 353 square feet (not including the water
wall). The two beds are 4' wide and contain about 282.5 square
feet of useful growing space for plants.