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. Available in Brown 70%
and Charcoal 55%.
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. Available in Green 60%
and Mocha 80%. Charley's finished polyethylene shade panels are very durable
(lasting 8-15 years). This material does not roll up easily. Panels come
hemmed to prevent fraying and pre-grommeted for easy tie-down.
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, Anthodium, Dracaena, Philodendron
75% - Palms, Chinese Evergreen
It's important to know the light requirements of your plants. Many plants that flower in the spring will last much longer if kept shaded and cool. Seed sowings also often need shade.
Make the most of the micro climates inside your greenhouse. Shade lovers can go under bench level. Use the natural shade of taller plants to shade smaller plants. Plants needing full sun can go on shelves or in parts of the greenhouse left unshaded.
Experience has shown that
50 to 60% density is satisfactory in temperate zones, with the higher
densities of 70 and 80% 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 rope 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 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