Greenhouse Shading Guidelines
Keeping the greenhouse
cool is accomplished by obtaining a balance of shading, ventilation and
humidity. Providing the proper amount of each is the secret to a cool
greenhouse. Here are some guidelines for shading:
Shading will be 40% more
effective when installed on the OUTSIDE of the greenhouse. Improve cooling
by suspending the fabric 4" to 9" above the glazing surface.
Shading installed INSIDE
the greenhouse will protect your plants from sunburn, but because of the
"greenhouse effect" the sun's energy will be trapped in the
greenhouse and overheating can result. Radiant/reflective shading recommended
for inside installation.
Choosing Shade Panel Size
Panel width should be at least 4 ft wider than the greenhouse, to hang
down 2 ft on both sides. Panel length should at least extend the length
of the greenhouse.
UV Protected Materials
Sunscreen is attractive and rolls up well. It has a life of 5-6
years as a roll shade, longer as a fixed panel.
polyethylene shade fabrics are popular because of their light
weight and easy handling. They do roll up easily and do not unravel when
cut to size. Life of the material is 5-10 years.
Charley's finished polyethylene
shade panels are very durable (lasting 8-15 years) and available
in a wide range of densities and sizes. See Knit
Lock 40%, Knit
Lock 50% and Knit
Lock 62%. This material does not roll up easily. Panels come hemmed
to prevent fraying and pre-grommeted for easy tie-down.
is recommended where exposure to sun and heat is very high. Life of 3-5
Liquid Shading Compounds
"paint" is popular where neat appearance is not a major
concern. The compound comes as a concentrate and can be thinned with water
to the desired shading density. The paint can be layered to increase shade
density and to allow different shade densities across the greenhouse.
A density number is the
percentage of light blocked by the shade. The following can be used as
a general guide:
30% - Snapdragons, Chrysanthemums,
45% - Lilies, Bedding Plants, Caladiums
50% - Azaleas, Begonias, Camellias, Gloxinias, African Violets, Poinsettias
55% - Pachysandra, Ivy, Orchids
60% - Diffenbachia, Stag Horn Fern, Rhododendron
70% - Fern, Anthurium, Dracaena, Philodendron
75% - Palms, Chinese Evergreen
Experience has shown that
40 to 60% density is satisfactory in temperate zones, with the higher
densities of 70 and 80%, and reflective shading, used in the Southern
states. Consider using a high-density shade on the roof, and a lower density
shade on the walls. A Light
Meter is a valuable tool in determining the proper amount of shading.
The easiest method is to
drape the shade over the greenhouse and secure it with lines through grommet
clips that snap onto the edges of the shade. If you have roof vents,
open the vents all of the way, then drape the shade over the greenhouse
and tie down with a small amount of slack. Anchor stakes can be twisted
into the ground or eye bolts can be twisted into the wood sill plate to
provide another place to attach the lines. A Tie-Down
Kit provides the line and 4 rope locks for easy adjustment of the
A Roll Shade System may
also be used to allow an easy way to let more light in when needed. For
an idea on how to build
a Roll Shade System click here.
If your greenhouse has cresting, simply place
a gooved piece of wood on top of the cresting, then drape your shade panel
over your greenhouse. This will prevent the cresting from poking holes
in your shade panel. Shade panel should be tied down loose enough for
your automatic roof vents to open and close.
Take down, dry, fold and put away for winter. Can clean with mild soap