August 2024 - 38

SGAFT
breath. Paying a higher price for the
two you need rather than burning all
that cash may be the better choice.
A once-in-a-career exception
to this logic happened during the
COVID pandemic when supply chain
shortages threw a monkey wrench
at us. Try not to be fooled into
stockpiling too many supplies as a
default position.
A GREENHOUSE IS STILL
MY HAPPY PLACE
In 2019, I built a research
greenhouse in my backyard, attached
to my basement (shown). My brother
and I had recently sold the family
property following the passing of our
parents. It was the first time since the
age of six that a greenhouse wasn't
part of my life.
One of several reasons for building
this house was to use it as a case
study in my research and education
work. A common theme in my work
evolved into the SGAFT project, and
early content will be focused on
examining energy use efficiency from
the small grower perspective.
This discussion relates to how
greenhouse geometry affects surface
area distribution to better understand
heating and cooling efficiency.
HOW INEFFICIENT IS A
SMALL GREENHOUSE?
Through the early months of the
year I worked with a good friend at
Prospiant, Keith Bemerer, on design
details that included systems to
purchase with the greenhouse and
others for later as funds allowed.
I knew I wanted more than I could
afford and having Keith's experience
on hand helped me create a staged,
long term vision for the house.
Everything arrived in August,
and by November, construction had
proceeded through site excavation,
driving side posts, raising hoops,
building end walls and covering the
roof before snow fell.
Inside work continued through the
winter to install propane lines and a
furnace, pour a concrete floor, run
electrical wiring and irrigation lines,
and install control systems. A pictorial
account of construction from start to
current state is ongoing at sgaft.com.
TIME FOR TABLES
Table 1 presents dimensions,
footprint area and surface area for my
24 x 40 foot structure compared to a
standard 100 foot house of the same
width, both with six foot sidewalls.
The last column compares the surface
area to footprint. The shorter, 40 foot
house has 16% more exposed surface
area for every square foot of floor
than the 100 foot house, meaning the
shorter house will be more expensive
to heat on a square foot basis.
Table 2 breaks the surface area
into its three components: end walls,
side walls and roof. The surface area
to footprint column from Table 1 is
repeated for reference, and columns
showing ends, sides and roof area for
both houses are presented as percent
of each house's total surface area.
The bottom row shows the difference
between the two houses. For purposes
of discussion, I'll call the shorter house
mine and the longer house yours.
The geometry and algebra show that
the big difference in comparing the
houses, both the same width but one
shorter than the other, is in the end
walls. My house has 23% of its surface
area tied up in the two end walls, yours
has only 11%. Our end walls have
exactly the same square footage, but
comparing mine to yours, my end walls
contribute double what yours do to the
house's total surface area.
Photo by
Peter Konjoian.
38
AUGUST 2024 GPNMAG.COM
http://www.sgaft.com http://www.GPNMAG.COM
August 2024

Table of Contents for the Digital Edition of August 2024
