DEAR NEW FARM:
I have space to put up a gothic-style greenhouse, but it
will only be able to run north to south. Will I have any problems
with enough light coming in to grow cold-hardy crops in the
We asked our friend Darrell Frey, proprietor of Three Sisters
for some assistance with your question. Here’s what
Darrell had to offer:
“Assuming you mean a greenhouse glazed on all sides,
the orientation is not as critical as you may think. The
shape of your property, available level ground, drainage
and best orientation for the most sunlight (no trees or
buildings blocking light) all help determine placement.
The high tunnels at Penn State's High Tunnel Research Facility
all run north to south, with the roll-up sides facing east
and west. This allows for full ventilation by prevailing
winds when the sides are up.
At Three Sisters Farm we orient our 16-foot by 45-foot
high tunnels east to west, partly because the garden contour
lines run that way, and partly because our tunnels have
no roll-up sides and so are ventilated by the wind passing
through them lengthwise.
With either orientation, productivity is not affected if
light enters from all sides.
If you have a greenhouse that is only glazed on one side,
orientation north and south will greatly reduce productivity.
Variation to the east or west of solar south by 20 degrees
reduces solar gain by 5 percent. Variation by 30 degrees
reduces gain by 10 percent. The numbers seem small but can
become significant relative to heat gain and plant growth,
so any orientation over 30 degrees away from true south
is to be avoided. When a building is oriented 45 degrees
from true south, solar gain is reduced by more than 25 percent.
Certainly a north-south orientation would reduce light by
50 percent if one side is not glazed. Be sure to glaze the
south-facing endwall well. If you are also plagued by lake-effect
clouds, orientation away from full sunlight is especially
critical. In areas with plentiful winter sun, the difference
may not be as important.
Three Sisters Farm
us with comments, suggestions and questions.