Mechanical Engineering

BrightFarm’s rooftop greenhouses are carefully designed to provide water and steady temperatures without overloading the building’s structure.

Photos: courtesy of BrightFarms

greenhouse structures are not relatively heavy. Most roofs in the Northeast, for example, are already built to support a snow load of 40 pounds per square foot, roughly equivalent to that of a greenhouse. The school has an aggregate roof with multiple epoxy membrane layers, so BrightFarms peeled off and removed the membrane, leaving enough to overlap onto the greenhouse.

With the roof providing adequate overall structure, the concern shifts to point loading. The roof has girders, or I-beams, every 15 to 20 feet, but these didn’t match the spacing of the loads, mainly water tanks, in the greenhouse. So the company put in dunnage I-beams perpendicular to the girders for additional support and placed the loads over the girders as much as possible.

“Because we use rainwater catchment in our facilities, we want to store as much water as possible. That can be difficult,” Adams said. “You might need to come up with schemes for how to store the water. Store it at ground level and maybe pump up to a smaller tank at night when electricity’s cheaper and less in

A 50,000-square-foot
greenhouse will grow
about 500,000 pounds
of produce a year.

over very strong points in the roof, where girders intersect or where
there’s a dunnage stage or an elevator bulkhead.”
The school greenhouse has single-pane glass around the sides
and double-layer polycarbonate on the roof, which is actually the
opposite of how it would normally be done. Normal greenhouse
construction uses glass in the roof to get the most sun exposure.
You want the roof as clear as possible because that’s critical to plant
growth. However, school rules would’ve required safety glass with
wire in it to provide extra protection for students, and this would’ve
been extremely expensive. BrightFarms used glass for the walls
mainly so the students could see out better.

Adams said that the BrightFarms greenhouse grows food using
a fraction of the land and water of conventional methods and pro-
duces no agricultural runoff.
The company tries to use renewable energy sources and waste
energy from a host building. If an adjacent building gener-
ates waste heat from a process, that too can be piped into a
greenhouse.

The founder of BrightFarms, Ted Caplow, recalls how
he got started. “I visited a large-scale hydroponic vegetable
greenhouse in 2005, and I was immediately hooked,” Ca-
plow said. “To me, hydroponics represented a fusion of
engineering efficiency and grassroots food produc-
tion, and the challenge of applying these ideas to
the congested urban environment was immedi-
ately appealing.”
Born in New York City, Caplow has a B.A. in
sociology from Harvard, an M.S. in mechani-
cal and aerospace engineering from Princeton,
In 2006, Caplow founded New York Sun Works to
promote the use of hydroponic greenhouses for sustain-
able urban agriculture. In 2007, NYSW launched the Sci-