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The National kit called for a kneewall 28" above
grade. I had decided on a wall-mounted greenhouse rather than one going
all the way to the ground for several reasons. One was that I feared
the effect lawnmowing and weedeating might have on polycarbonate glazing
near ground level. Also, I planned to use raised beds inside the greenhouse,
and finally, I like the look. There may be some thermal storage value
from the wall, but to maximize that, the cinder blocks should be filled
with concrete, and I had decided to fill them with insulation instead.
At last, some semblance of a building! But for a while
everything looked a MESS:
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In addition to filling the cinder blocks with insulation (below),
I also put styrofoam panels against the outside of the foundation.
Overkill? Perhaps. But during winter the floor of the greenhouse
will absorb heat from the air above it, and the insulation will
help keep that heat from being lost to the ground outside. The
black plastic pipe at the lower left is a conduit for the electric
line. Dirt will be backfilled to the level of the styrofoam,
and I plan to put in an asparagus bed along this side of the
greenhouse.
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The gravel seen inside lies over a 12"-deep drainage ditch dug
down the length of the greenhouse. Plastic drain pipe inside this
ditch leads out the back of the greenhouse and continues about another
25' beyond, where the ground slopes away. Our Virginia special red
clay (why are there so many brick houses in Virginia?) poses real
drainage challenges!
| The pourable insulating material shown below is called Zonolite
Masonry Insulation; it is really a form of fine vermiculite. I
panicked when I discovered that Zonolite used for attic insulation
in the 70's and 80's had been found to be contaminated with asbestos,
and that there were some class action suits pending, etc.! I made
it a point to get the MSDS (Material Safety Data Sheet), and was
reassured to find no trace of asbestos listed for this product.
It took about 24 bags of the stuff to do the job (at a cost of
$300), and I hope I recoup the cost with savings on my electric
heating bill. |
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Well, here is the kneewall, ready to receive the superstructure. The
inside is painted white, and it blends in with the white gravel on
the floor. I was upset to see dirt being tracked in on the pristine
gravel, hence the doormat at the entrance. The square opening to the
right of the door is for one of the two louvered air intakes; the
other one is around the corner on the left. The wooden structures
inside are the raised beds, which are shown in close-up on the next
page.
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